Full text of "Main drainage works of the city of Boston (Massachusetts, U.S.A.)"

Plate XV I 




MAIN DRAINAGE WORKS 



OF THE 



CITY OF BOSTON 

{MASSACHUSETTS, U.S.A.) 



BY 

ELIOT C. CLAEKE 

Principal Assistant Engineer, in charge" 




BOSTON 
ROCKWELL AND CHURCHILL, CITY PRINTERS 

No. 39 Abch Street 

1885 



7 0\/. 



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in 2010 with funding from 

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PREFACE. 



This brief description of the Main Drainage Works, of Bos- 
ton, aims to record, for the benefit of engineers, an account of 
the engineering problems involved and the methods of construc- 
tion adopted. It also aims to give to the tax-payers and gen- 
eral public a descriptive account of why the large appropriation 
for "An Improved System of Sewerage " was needed, and how 
it has been spent. By attempting to accomplish both of these 
purposes it fulfils neither of them adequately ; since one class 
of readers will find it too technical, and the other too deficient 
in detail. It has been prepared amid pressing engagements, 
and to save time the writer has not hesitated to borrow freely 
from previous reports, by himself and others. Traces of such 
compilation will, doubtless, be noticed by the discerning. It is 
hoped that a fair idea of the works can be obtained from the 
illustrations ; and that the description, even by its defects, may 
encourage other engineers to publish, as they too seldom do, 
accounts of works with which they have been connected. 

E. C. C. 

Boston, April, 1885. 



TABLE OF CONTENTS. 



PAGE 

CHAPTER I. 
Early history of sewerage at Boston 7 



CHAPTER II. 
Character and defects of the old sewerage system . . . 12 

CHAPTER III. 
Movements for reform — Commission of 1875 16 

CHAPTER IV. 
Preliminary investigations 22 

CHAPTER V. 
Main sewer ............ 31 

CHAPTER VI. 
Intercepting sewers .......... 37 

CHAPTER VII. 
Pumping-station .53 

CHAPTER VIII. 
Outfall seweb . 62 

CHAPTER IX. 
Reservoir and outlet .......... 76 

CHAPTER X. 
Details of engineering and construction ..... 83 



CONTENTS. 



CHAPTER XI. 
Working of the new system 93 



APPENDIX A. 



Eecord of tests of cement made foe Boston Main Drainage 

Works 113 

APPENDIX B. 

List of officers connected with Boston Main Drainage Works, 140 



MAIN DRAINAGE WORKS. 



CHAPTER I. 

EAELY HISTORr OF SEWERAGE AT BOSTON. 

The conditions wliich necessitated a change in the system of 
sewage disposal at Boston, and the problems to be solved in 
making that change, can be better understood after a brief con- 
sideration of the early history of sewerage at that city and the 
manner in which the sewers were originally built. 

Boston was first settled in 1630. When the first sewer was 
built cannot now be determined, but it was earlier than the 
year 1700, for already, in 1701, the population being about 
8,000, a nuisance had been created by frequent digging up of 
streets to lay new sewers and to repair those previously built ; 
and in town meeting, September 22, 1701, it was ordered, 
" That no person shall henceforth dig up the Ground in any of 
the Streets, Lanes or High-wayes in this Town, for the laying or 
repairing any Drain, without the leave or approbation of two 
or more of the Selectmen." 

The way in which sewers were built at this time was, appar- 
ently, this. When some energetic householder on any street 
decided that a sewer was needed there, he persuaded such of 
his neighbors as he could to join him in building a street drain. 
Having obtained permission to open the street or perhaps 
neglected this preliminary, they built such a structure as they 
thought necessary, on the shortest line to tide-water. The ex- 
pense was divided between them, and they owned the drain 
absolutely. Should any new-comer, or any neighbor, who had 
at first declined to assist in the undertaking, subsequently desire 
to make use of the drain, he was made to pay for the privilege 



» MAIN DRAINAGE WORKS. 

what the proprietors saw fit to charge. Wheo a drain needed 
repairing all persons using it were expected to pay their share 
of the cost. 

As might have been expected, under such a system, great 
difficulty was experienced in distributing fairly the expenses 
and in collecting the sums due ; so that it became of sufficient 
importance to engage the attention of the Legislature, and in 
1709 an act was passed regulating these matters. It is entitled, 
" An Act — Passed by the Great and General Court or Assem- 
bly of Her Majesty's^ Province of the Massachusetts-Bay. For 
regulating of Drains and Common Shores.^ For preventing of 
Inconveniences and Dammages by frequent breaking up of 
High-Wayes .... and of Differences arising among 
Partners in such Drains or common Shores about their Propor- 
tion of the Charge for making and repairing the same." 

The act recites that no person may presume to break up the 
ground in any highway within any town for laying, repairing 
or amending any common shore, without the approbation of the 
selectmen, on pain of forfeiting 20 shillings to the use of the 
poor of said town ; that all such structures, for the draining of 
cellars, shall be "substantially done with brick or stock ;"^ 
that it shall be lawful for any inhabitant of any town to lay a 
common shore or main drain, for the benefit of themselves and 
others who shall think fit to join therein, and every person who 
shall afterwards enter his or her particular drain into such main 
drain, or by any more remote means receives benefit thereby, 
for the drainage of their cellars or lands, shall be obliged to 
pay unto the owner or owners a proportionate part of the charge 
of making or repairing the same, or of that part of it below 
where their particular drain enters. In case of dispute the 
selectmen decided how much each person should pay, and there 
was an appeal from their decision to the courts. 

For one hundred and fifteen years the sewers in Boston were 
built, repaired, and owned by private individuals under author- 
ity of this act. 

It may be doubted if most of them were " substantially done 
with brick or stock," and there certainly was much difficulty 

^Anne. ^ Sewers. ^ Stone. 



Plate I. 




EARLY HISTORY OF SEWERAGE AT BOSTON. 9 

about payments ; so that in 1763 the act of 1709 was amended, 
the amendment reciting that " Whereas it frequently happens 
that the main drains and common shores decay or fill up . 

and no particular provision is made by said act to com- 
pel! such persons as dwell below that part where said common 
shores are repaired, and have not sustained damage, to pay 
their proportionable share thereof, as shall be adjudged by the 
selectmen, which has already occasioned many disputes and 
controversies," therefore it was decreed that in future all per- 
sons benefited should pay for repairs. 

No further change was made till 1796, and then only to 
provide that persons who did not pay within ten days of notifi- 
cation should pay double, and that the sewers, besides being of 
brick or stone, might be built of such other material (probably 
wood) as should be approved by the selectmen. 

Under this act the greater part of Boston was sewered by 
private enterprise. The object for which the sewers were built 
was, as indicated "for the draining of cellars and lands." The 
contents of privy-vaults, of which every house had one, and 
even the leakage from them, were excluded ; but they received 
the waste from pumps, and kitchen sinks, and also rain-water 
from roofs and yards. 

That much refuse got into them is proved by their frequently 
being filled up, and as they had a very insufficient supply of 
water they were evidently sewers of deposit. That they 
served their purpose at all is due to the fact that the old town 
drained by them, as shown in Plate I., consisted of hills with 
good slopes on all sides to the water. Of this early method of 
building sewers Josiah Quincy, then Mayor, said, in 1824 : 
"No system could be more inconvenient to the public, or embar- 
rassing to private persons. The streets were opened with little 
care, the drains built according to the opinion of private in- 
terest or economy, and constant and interminalile vexatious 
occasions of dispute occurred between the owners of the drain 
and those who entered it, as to the degree of benefit and pro- 
portion of contribution." 

In 1823 Boston obtained a city charter, and one of the first 
acts of the city government was to assume control of all exist- 



10 MAIN DRAINAGE WORKS. 

ing sewers and of the building and care of new ones. The 
new sewers were built under the old legislative acts, and 
the whole expense, as before, was charged to the estates bene- 
fited, being divided with reference to their assessed valuation. 
A small, variable portion of the cost was, however, generally 
assumed by the city, in consideration of its use of the sewers 
for removing surplus rain-water from the public streets. 

The city ordinances regulating sewers required that, when 
practicable, they should be of sufiicient size to be entered for 
cleaning. Some supervision was exercised over connecting 
house-drains, and, if thought necessary, a strainer could be placed 
on each. Fecal matters were rigidly excluded until 1833, when 
it was ordered that, while there must be no such connection 
between privy-vaults and drains as would pass solids, the 
Mayor and Aldermen, at their discretion, might permit such 
a passage or connection as would admit fluids to the drain. 
This action was perhaps due to an advent of cholera during the 
previous year. To assist in flushing out deposits, it was pro- 
vided, in 1834, that any person might discharge rain-water from 
his roof into the sewers, without any charge for a permit. The 
same year control of the sewers and sewer-assessments was 
given to the City Marshal. He was especially to devote him- 
self to the collection of assessments, new and old, which were 
largely unpaid. The other duties of the marshal probably pre- 
vented him from devoting sufiicient energy to the accomplish- 
ment of this task ; for it appears that, while there had been 
expended by the city, for building sewers, from 1823 to 1837, 
the sum of $121,109.52, there had been collected of this sum 
but 126,431.31. 

That there might be some one to give his whole time to the 
financial and administrative duties connected with the sewer- 
age system, a " Superintendent of Sewers and Drains " was 
appointed in July, 1837. He was empowered to assess the 
whole cost of any new sewer upon the real estate, including 
buildings benefited by it. In 1838 the city decided to assume 
one-quarter of the gross cost; and in 1840, in obedience to a 
decision by the Supreme Court, it was ordered that the three- 
quarters of the cost of sewers which was to be paid by the 



EARLY HISTORY OF SEWERAGE AT BOSTON. 11 

abutters, should be assessed with reference to the value of 
the land only, without taking into consideration the value of 
buildings or other improvements, and such has been the prac- 
tice up to the present time. 

It is estimated that there are at the present time (1885) 
about 226 miles of sewers in Boston. In 1873 there were 
about 125 miles, and in 1869 about 100 miles. There are at 
present supposed to be more than 100,000 water-closets in use 
in the city ; in 1857 there were 6,500. 



12 MAIN DEAINAGE WORKS. 



CHAPTER II. 

CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 

Such changes have taken place in the contours of the city, 
through operations for reclaiming and filling tidal areas border- 
ing the old limits, that, from being a site easy to sewer, Boston 
became one presenting many obstacles to the construction of an 
efficient sewerage system. 

This will be understood from an examination of the plan of 
the city proper, Plate V. On this plan the shaded portion rep- 
resents the original area of the city, and very nearly its limits 
in 1823. The unshaded portion of the plan, indicating present 
limits, consists entirely of reclaimed land filled to level 
planes little above mean high water, the streets traversing such 
districts being seldom more than seven feet above that eleva- 
tion. A large proportion of the house basements and cellars 
in these regions are lower than high water, and many of them 
are but from five to seven feet above low-water mark, the mean 
rise and fall of the tide being ten feet. This lowness of land 
surface and of house cellars necessitates the placing of house- 
drains and sewers at still lower elevations. Most house-drains 
are under the cellar floors, and ftill in reaching the street sew- 
ers ; the latter must be still lower, and in their turn fall 
towards their outlets, which were rarely much, if at all, above 
low water. 

Moreover, as filling progressed on the borders of the city, it 
became necessary to extend the old sewers whose outlets would 
have been cut ofi". The old outlets being generally at a low 
elevation, even where the sewers themselves were sufiiciently 
hioh, the extensions had to be built still lower, and when of 
considerable length could have but little fall towards the new 
mouths. 

As a consequence, the contents of the sewers were damnaed 
back by the tide during the greater part of each twelve hours. 



CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 13 

To prevent the salt water flowing into them many of them 
were provided with tide-gates, which closed as the sea rose, and 
excluded it. These tide-gates also shut in the sewage, which 
accumulated behind them along the whole length of the sewer, 
as in a cesspool ; and, there being no current, deposits occurred. 
The sewers were, in general, inadequately ventilated, and 
the rise of sewage in them compressed the foul air which 
they contained and tended to force it into the house connec- 
tions. To afford storage room for the accumukited sewage, 
many of the sewers were built very much larger than would 
otherwise have been necessary, or than was conducive to a 
proper flow of the sewage ; and, as there would have been little 
advantage in curved inverts where there was to be no cur- 
rent, flat-bottomed and rectangular shapes were frequently 
adopted. 

Although at about the time of low water the tide-gates 
opened and the sewage escaped, the latter almost immediately 
met the incoming tide, and was brought back by it, to form 
deposits upon the flats and shores about the city. Of the large 
amount of sewage which flowed into Stony Brook and the Back 
Bay, and especially that which went into South Bay, between 
Boston proper and South Boston, hardly any was carried 
away from the vicinity of a dense population. 

The position of the principal sewer outlets and of the areas 
on which the sewage which caused most offence used to accu- 
mulate, is indicated on Plate V. From these places foul- 
smelling gases and vapors emanated, which were difflised to a 
greater or less distance, according to the state of the tempera- 
ture or of the atmosphere. Under certain conditions of the 
atmosphere, especially on summer evenings, a well-defined 
sewage odor would extend over the whole South and West 
Ends of the city proper. 

This evil was thus described by the City Board of Health in 
one of their annual reports : — 

Complaints of bad odors have been made more frequently during the 
past year than ever before. 

They have come from nearly all parts of the city, but esj)ecially and 
seriously fi'om the South and West Ends, 



14 MAIN DEAINAGE WORKS. 

Large territories have been at once, and frequently, enveloped in an 
atmosphere of stench so strong as to arouse the sleeping, terrify the weak, 
and nauseate and exasperate everj'body. 

It has been noticed more in the evening and by night than during the 
day; although there is no time in the whole day when it may not come. 

It visits the rich and the poor alike. It fills the sick-chamber and the 
office. Distance seems to lend but little protection. It travels in a belt 
half-way across the city, and at that distance seems to have lost none of its 
potency, and, although its sovirce is miles away, you feel sure it is directly 
at your feet 

The sewers and sewage flats in and about the city furnish nine-tenths of 
all the stenches comi^lained of. 

They are much worse each succeeding year ; they will be much worse 
next year than this. 

The accumulation of sewage upon the flats and about the city has been, 
and is, i-apidly increasing, until there is not probably a foot of mud in the 
river, in the basins, in the docks, or elsewhere in close proximity to the city, 
that is not fouled with sewage. 



Yarious palliative measures were adopted. The Back Bay, 
into which the waters of Stony Brook, and with them most of 
the sewage of Roxbury and Jamaica Plain, used to empty, was 
lately partly filled with gravel, forming the present Back-Bay 
Park. The brook was carried in a covered channel to Charles 
River, which somewhat lessened the nuisance caused by it, or at 
least transferred it to another locality. Owing to complaints 
from the physicians of the City Hospital and other residents in 
that neighborhood the city purchased and filled the upper por- 
tion of Old Roxbury Canal at the head of South Bay. The 
sewers emptying into it were extended, and the position of the 
nuisance caused by them was thus altered by a few hundred 
feet. In general terms it may be said that none of the old 
sewer outlets were in unobjectionable locations. 

There are no plans in detail of the sewers of Boston. Many 
of the older ones have no man-holes. In some streets several 
sewers exist side by side. Occasionally a sewer is found built 
directly above an older one. Probably one-half of the larger 
main sewers are wholly or partly built of wood and have flat 
bottoms. An unwise provision was inserted in the charters of 
some of the private corporations organized for the purpose of 
reclaiming and filling areas of flats, by which it was stipulated 









Fig. I Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig.6 





Fig. 11 Fig. 12 

COMMON TYPES 




FigJ3 



Fig. 15 



BOSTON CITY SEWERS. 

SCALE, 

iiiiT i f n f r [ ? ! r 



HOUSE DRAINS. 




ng.23 24 25 26 27 



o 

28 



Fig. 17 




ng.18 



Fig. 19 




Fig. 7 



Fig. 8 




Fig, 14 



Fig. 16 



29 





Fig. 20 



ng.2l 




ng. 22. 



CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 15 



that the corporations should themselves extend all sewers whose 
discharge would be obstructed by the filling. Such extensions 
were made without system, by building flat-bottomed wooden 
scow sewers, which were laid upon the soft surface of the flats 
before the filling was done. Cross-sections of various common 
forms of existing city sewers are shown on Plate II., Figs. 
1 to 22. Fig. 22 shows Stony-Brook culvert, which consti- 
tutes the lower mile of Stony Brook, and is that part of it which 
is covered and used as a sewer. 

One fact which increased the danger arising from the dam- 
ming up of the sewers, and the consequent compression of their 
gaseous contents, was that the house-drains connecting with 
these sewers were ill adapted to resisting this pressure. 
Most of them were built of brick or of wood, before the rise of 
modern ideas in regard to sanitary drainage ; and, as they were 
usually leaky, the gases forced into them found ready egress 
into the houses. Figs. 23 to 29 on Plate II. show common 
forms of these house-drains. 

The drains diflier greatly in size. Of 113 which were ob- 
served while building the intercepting sewers in 1878, — 

11 were about 4 inches in diameter. 



4 


5 


21 


6 


5 


« 7 


27 


8 


8 


9 


11 


10 


26 


12 



or more. 



113 



Of these 113 drains, 9 were level and 14 pitched the wrong 
way ; 45 had flat bottoms and 68 curved ones ; 38 were 
wholly or partly choked with sludge, and 75 were reasonably 
clean. At about the same time examinations made with 
peppermint, by the City Board of Health, of 351 house-drains 
in various sections of the city, showed that 193 of them, or 55 
per cent., were defective in regard to tightness. 



16 MAIN DEAINAGE WOEKS. 



CHAPTER III. 

MOVEMENTS FOE EEFOEM-COMMISSION OF 1875. 

Foe the ten years preceding 1875 the average annual death- 
rate of Boston was about 25 in 1,000. On April 14, 1870, the 
Consulting Physicians of the city addressed to the authorities a 
remonstrance as to the then existing sanitary condition of the 
city, in which they declared the urgent necessity of a better 
system of sewerage, stating that it would be a work of time, of 
great cost, and requiring the highest engineering skill. 

At about the same time, and in each of their Annual Reports 
thereafter, the State Board of Health referred to the matter, 
saying that the question of drainage for Boston and its immediate 
surroundings was of an importance which there was no danger 
of overstating. 

Of such great importance was the matter considered by the 
State Legislature that, in the special session of 1872, an act was 
passed authorizing the appointment of a commission, to be paid 
by the City of Boston, to investigate and report upon a compre- 
hensive plan for a thorough system of drainage for the metro- 
politan district. This was not accepted by Boston, on the 
ground that the expense should be shared by the neighboring 
cities and towns, and no commission was appointed. 

In a communication to the City Council (Dec. 28, 1874), up- 
on the necessity of improved sewerage, the City Board of 
Health pointed out clearly the evils of the existing system, and 
strongly urged that a radical change should be made. March 
1, 1875, an order passed the City Council authorizing the Mayor 
to appoint a commission, " consisting of two civil engineers of 
experience and one competent person skilled in the subject of 
sanitary science, to report upon the present sewerage of the 
city . . . . and to present a plan for outlets and main 
lines of sewers, for the future wants of the city." The Mayor 
thereupon appointed as members of the commission Messrs. E. 



MOVEMENTS FOR REFOEM-COMMISSION OF 1875. 17 

S. Chesbrough, C.E., Moses Lane, C.E., and Charles F. Fol- 
som, M.D,, and in December of the same year their report was 
submitted. 

As was to be expected from the professional attainments and 
reputation of these gentlemen, the report contained a compre- 
hensive and exhaustive statement of the defects in the existing 
system of sewerage, and of the causes which had produced such 
a condition of affairs, and finally recommended for adoption a 
well-considered plan for remedying present defects and for pro- 
viding for future needs. 

The commission stated, as essential conditions of efficient 
sewerage : first, that the sewage should start from the houses, 
and flow in a continuous current until it reached its destination, 
either in deep water or upon the land ; and, second, that the 
sewers should be ventilated so that the atmosphere in them 
should attain the highest possible degree of purity. To quote 
from the report : — 

The point which mitst be attended to, if we would get increased com- 
forts and luxuries in our hoiises, without doing so at cost of health and life, 
is to get our refuse out of the way, far beyond any possibility of harm 
before it becomes dangerous from putrefaction. In the heat of summer 
this time should not exceed twelve hours. We fail to do this now in three 
ways : — 

First. We cannot get our refuse always from our house-drains to our 
sewers, because the latter may not only be full themselves at high tide, but 
they may even force the sewage up our drains into our houses. 

Secofid. We do not empty our sewers promptly, because the tide or tide- 
gates prevent it. In such case the sewage being stagnant, a precipitate 
falls to the bottom, which the slow and gradual emptying of the sewers, as 
the tide falls, does not produce scour enough to remove. This deposit re- 
mains with little change in some places for many months. i 

Third. With our refuse, which is of an especially foul character, once 
at the outlets of the sewers, it is again delayed, there to decompose and 
contaminate the air. 

As a result of this failure to carry out the cardinal rule of sewerage, 
we are obliged to neglect the second rule, which is nearly as important, 
namely, ventilation of the sewers; for the gases are often so foul that we 
cannot allow them to escape without causing a nuisance ; and we compro- 
mise the matter by closing all the vents that we can, with the certainty of 
poisoning the air of our houses. 

'The catch- basins, too, in the course of the sewers, serve only to aggravate this evil, 
and should be filled as early as is practicable. 



18 MAIN DRAINAGE WORKS. 

In the opinion of the commission there are only two ways open to us. 
The first, raising more than one-half of the superficial area of the cit}- 
proper (excluding suburbs) is entirely out of the question, from the enor- 
mous outlay of money which would be required, — more than four times as 
much as would be needed for the plan which we propose, and which con- 
sists in intercepting sewers and pumping. 

There are in use now in various parts of the world three methods of 
disposing of the sewage of large cities, whei-e the water-carriage system 
is in use : — 

First. Precipitation of the solid parts, with a view to utilizing them as 
manure, and to purifying the streams. 

Second. Irrigation. 

Neither of these processes has proved remunerative, and the former only 
clarifies the sewage without purifying it ; but if the time comes, when, by 
■ the advance in our knowledge of agricultural chemistry, sewage can be 
profitably used as a fertilizer, or if it should now be deemed best to util- 
ize it, in spite of a pecuniary loss, it is thought that the point to which we 
propose carrying it will be as suitable as any which can be found near 
enough to the city, and at the same time far enough away fi'om it. 

The third way is that adopted the world over by large cities near deep 
water, and consists in carrying the sewage out so far that its point of 
discharge will be remote from dwellings, and beyond the possibility of 
doino- harm. It is the plan which your Commission recommend for 
Boston. 

On Plate III. is reproduced a portion of the plan accompany- 
in o- the report of the commission. The plan shows the routes 
of the main, intercepting, and outfall sewers recommended, and 
the proposed locations of the pumping-stations, reservoirs, and 
outlets. It will be seen that two main drainage systems were 
proposed, one for each side of the Charles River ; that on the 
south side having its outlet at Moon Island and that on the 
north side discharging at Shirley Gut. 

The former system was designed to collect and carry off the 
sewage from all of Boston south of Charles River and from 
Brookline ; the latter was to drain the Charlestown and East 
Boston districts, and also the neighboring cities of Cambridge, 
Somerville, and Chelsea. The two systems were identical in 
their general features. These were : intercepting sewers along 
the margins of the city to receive the flow from the already 
existing sewers ; main sewers into which the former were to 
empty and by which the sewage was to be conducted to pump- 
ing-stations ; pumping machinery to raise the sewage about 35 



Plate, III. 




MOVEMENTS FOR EEFORM-COMMISSION OF 1875. 19 

feet ; outfall sewers leading from the pumping-stations to reser- 
voirs near the points of discharge at the sea-coast, from which 
reservoirs the sewage, accumulated during the latter part of 
ebb and the whole of flood tide, was to be let out into the har- 
bor during the first two hours of ebb-tide. 

The cost of the proposed main drainage works, as estimated 
by the commission in its report, was : — 

For the territory south of Charles River . . $3,746,500 
north " . . 2,804,564 



Total $6,551,064 

The commissioners' recommendation met with very general 
acceptance. But, as was to be expected, a certain amount of 
opposition to it was encountered. 

One remonstrance against the adoption of the proposed plan, 
which was presented to the City Council by a number of esti- 
mable citizens, may be of sufficient interest to cite, because it is a 
type of the kind of objections which are often urged against 
plans for municipal improvement, however carefully considered 
by the most competent experts : — 

The undersigned respectfully remonstrate against the adoption of the 
system of sewerage proposed in Report No. 3 of this year. We believe if 
carried into execution it will prove not only ineffectual, but destructive to 

the health and prosperity of the city Of late years the cost 

of many, if not most, of the public works has greatly exceeded the esti- 
mates ; in some instances, it is said, two or three hundred per cent. 

Should this new system exceed the estimates to a like extent, the amount 
would be augmented to between fifteen and twenty millions of dollars. . . 

But we do not believe it (flushing) will, or even can, be made to per- 
form that end in an effective or satisfactory manner ; because we under- 
stand, by the report, that the inclinations of the sewers will aiford a flow at 
a minimum rate of only two miles an hour, so that it will be almost impos- 
sible to prevent the glutinous slime and putrefactions from constantly gath- 
ering and adhering more or less to the sides and bottoms of the sewers 
and drains, and as constantly exhaling the deadly gases on every side. 
. . . . It will likewise be borne in mind that the thick mass of liquid 
corruption within the sewers and drains nnist be drawn along to their up- 
hill or final ascent of thirty feet and over, and kept in motion and delivered 
at the distant outlets on the bay, by means of enormous pumps and ma- 
chinery worked by steam-engines, .... for a stoppage in the oper- 



20 MAIN DRAINAGE WORKS. 

ations of such an extensive system for only a day or two, along the low 
lands and other parts of the city, would almost inevitably result in serious 

maladies and other evil consequences Will not the exhalation 

and odor (from the stoi'age reservoirs) blown by evei'y changing wind here 
and there along the wharves, upon the shipping and back uj)on the land, 
create a nuisance so offensive and unhealthf ul as to become intolerable ? No 
provision seems to be devised to prevent such emanations or their baleful 
consequences. In these noisome reservoirs the contents must ever be ex- 
posed to the sun, the storms, and the inclemency of the weather. 

In the severity of winter they must become as frozen as the water in 
the bay or along the shores ; and as often as they ai-e converted into ice 
there must be an entire stojDpage of the woi'ks. . . . Such i-esei-voirs and 
outlets might be reduced to ruins in any future day of hostilities — either 
foreign or domestic — should such hostilities ever occur, the effect of which 
ruins would be the fatalities of the plague 

There is now but a single system before the authorities, although there 
are not less than five different systems in Europe alone. . . . It is hereby 
requested that the same be postponed, and that a reward be offered for the 
best plan for sewerage relief .... and that such plans be referred to 
a commission of citizens .... with power to give the reward for the 
best plan. 

Other remonstrants thought that city sewage had a great 
manurial value, and should be so utilized as to be a source of 
revenue ; still others considered the proposed scheme extrava- 
gant, and advised temporary palliative measures. 

What prevented these remonstrances from having much 
weight, was that while criticising the proposed scheme, they 
either suggested no alternative plan, or else failed to show that 
the method which they themselves recommended would remedy 
the existing evils. 

As a compromise the City Council inclined to adopt the 
recommendations of the commission in so far as they referred 
to the territory South of Charles River, which included those 
portions of the city which suifered most from ineffective sewer- 
age. Application was made to the Legislature for authority to 
construct works in general accordance with the recommendations 
of the Commissioners, and an act, approved April 11, 1876, 
entitled " An Act to empower the City of Boston to lay and 
maintain a main sewer discharging at Moon Island in Boston 
Harbor, and for other purposes," was passed. 

The subject had been referred by the City Council to a Joint 



MOVEMENTS FOR REFORM COMMISSION OF 1875. 21 

Special Committee on Improved Sewerage, and in June, 1876, 
tliis committee reported, recommending the adoption of the 
system devised by the commission, and that surveys and esti- 
mates be made for the worlc, and also that the feasibility of an 
outlet at Castle Island be considered. 

By an order approved July 17, 1876, the sum of $40,000 was 
appropriated for the purpose of making surveys and of procur- 
ing estimates for an improved system of sewerage for the City 
of Boston, on a line from Tremont Street to Moon Island, and 
also on a line from said street to deep water east of Castle 
Island. 

A few days later the City Engineer, Mr. Joseph P. Davis, 
appointed the writer principal assistant, in immediate charge 
of the survey and investigations, which were at once begun. 



22 MAIN DRAINAGE WORKS. 



CHAPTER IV. 



PRELIMINARY INVESTIGATIONS. 



By a liberal interpretation of the order in compliance with 
which the survey w^as carried on, it was assumed that any 
information was desired which mio-ht be of use in desiscning 
main drainage works, in general accordance with the plan 
recommended by the commission. 

As the location of the outlet would aifect materially the 
whole scheme its consideration received the earliest attention. 
It was necessary that the discharge should be into favorable 
currents, and also near a practicable site for a reservoir which 
could be reached by the outfall sewer from the city. A party 
for hydrographic work was organized, consisting of one assist- 
ant engineer, one additional observer, two sailing-masters, 
and two boatmen. Their outfit included a small yacht and two 
tenders. 

A projection of the harbor was first made, and the triangula- 
tion points given by U.S. Coast Survey were plotted upon it, 
together with others obtained by ourselves from these, by 
means of the plane table ; the shore line being taken from a 
chart belonging to the Harbor Commissioners. A sufiicient num- 
ber of prominent points having been determined in this way, it 
was easy at any time to locate the position of a float by the sex- 
tant. At night, when other objects could not be seen, the har- 
bor lights furnished points for observation. 

Some difficulty was experienced in deciding upon the best 
form of float. That first adopted consisted of four radiating 
arms, with canvas wings projecting downward from them (Plate 
IV., Fig. 4). Upon calm days this form indicated very fairly 
the surface velocity ; but was too easily influenced by winds 
and waves to be used in windy weather, as it then invariably 
grounded on a lee shore. 

A "surface and sub-surface " can-float (Plate IV., Fig. 5) was 



Plate IV. 




nil tiiii 



wminMiiiiMiHiimimiwMwlumiM tiiiiiiudiiMiiiiiiniliM J "tlM ii|iiimiiiihiiii>I)hv jiiiiiii/jniiuuiiwMi iiiiaiiiiMiiHwinmiiiin 



31! 



Iiin7ni)l|iiiiliiiili<iiiiliiiliiiliiii>liii<liiii|iiiiiliiiiiii<iiuiiimiiiiiv ^^ yiiiiinwiiiiiwiMiii»i|iiii\iiii«iiniiiiiiiiiiiiiMiiiniiniiii|iiiiiMiliiill 



PRELIMINARY INYESTIGATIONS. 23 

used somewhat, and gave better results ; but an ordinary pole- 
float (Plate IV., Fig. 6), about 14 fefet long and 4 inches in 
diameter, was finally found to be the most satisfactory, indicat- 
ino; the mean current, which often differed both in direction and 
velocity from the surface current. This float supported a flag, 
or lantern, and, when there was danger of its grounding, a 
shorter one was substituted for it. 

In all, about 50 " free-float " experiments were made upon 
the currents in the vicinity of Moon, Castle, Thompson's, and 
Spectacle Islands. The trips varied in duration from 6 hours, 
or one ebb-tide, to 52 hours. Angles to determine the posi- 
tion of the float were taken each half-hour, and were re- 
corded together with the direction and force of the wind and 
other data. During observations a man was stationed at a tide- 
gauge, and all velocities were reduced to a mean rise and fal) 
of ten feet. The results obtained from the float experiments, 
stated briefly, were as follows : — 

Favorable ebb currents were found to pass both Moon and 
Castle Islands. That passing Spectacle Island was suflicient in 
strength, but unsuitable, owing to its direction and some other 
characteristics ; while that skirting Thompson's Island was alto- 
gether unfavorable. Floats leaving the vicinity of Moon Island 
with the early ebb would travel seawards with an average 
velocity of .74 miles an hour, passing between Rainsford and 
Long Islands, through Black Rock Channel, and at the turn of 
tide would reach a position between the Brewsters and George's 
Island about four miles from the point of starting. This course 
is, for its whole extent, outside of the inner harbor. Floats from 
Castle Island followed Main Ship Channel and Broad Sound, 
and travelled about as far as those from Moon Island. Return- 
ino; with the flood-tide the floats would travel about two miles 
towards the city, and with the succeeding ebb would once more 
move seaward, not again to enter the harbor. 

Sewage, being fresh water, remains for a while at least upon 
the top of the denser sea-water, and is more affected by surface 
currents than by deeper ones. An attempt, more interesting 
than practically instructive, was made to ascertain to what ex- 
tent sewage put into Boston Harbor would be diffused within 



24 MAIN DRAINAGE WOEKS. 

a few days. Fifty bottles were put into the water at Moon 
Island, each containing a postal card, which the finder was re- 
quested to mail, stating when and where it was found. Ten of 
these bottles were picked up within the next three weeks. One 
of them was found at Marshfield, about 25 miles south of its 
starting-point ; another at Salem, about the same distance 
north ; a third, 30 miles south-east of Cape Ann, and the re- 
maining seven outside of Cape Cod, near Provincetown, "Well- 
fleet, and Chatham, from 50 to 80 .miles distant. 

Castle Island would have been much more easily accessible 
from the city than Moon Island, but its selection involved sev- 
eral serious disadvantages. It belongs to the United States, 
and is the site of Fort Independence. Although this old fort 
is of little practical value, there were no reasonable grounds 
for hope that the government would permit a storage reservoir 
to be located on the island. It would have been necessary to 
place that structure on the main land in South Boston. The 
area available for the purpose would have been restricted on 
account of its great cost. Even if the works could have been 
so constructed as to be wholly inoffensive, the natural prejudice 
in the community against the proximity of sewage would have 
caused great opposition to the building of a reservoir so near 
to a densely populated district. Moon Island, on the contrary, 
afforded an excellent site for a reservoir. The neighboring 
country is sparsely settled, and there is no dwelling within a 
mile of the works. The outlet, therefore, was finally located 
at this point. 

The next problems considered were the selection of a route 
for the outfall sewer between the city and Moon Island and the 
location of the pumping-station. As any route would neces- 
sarily cross a portion of the harbor near the mouth of Neponset 
Eiver, it was thought best to explore the nature of the ground 
underlying the harbor in that vicinity. To this end a number 
of artesian borings were made from a scow fitted for the pur- 
pose. Five-inch or smaller gas-pipe was driven to the required 
depth, varying from 20 to 100 feet, and the earth excavated 
from within them. In all, 139 such borings were made. 
Those on the line selected by the commissioners, between Fox 



PRELIMINARY INVESTIGATIONS. 25 

Point and Squantum Beach, showed deep beds of mud under- 
laid by sand and gravel ; so that any method of crossing at that 
point would have been difficult and expensive. Moreover Fox 
Point was thought to be too near to the valuable residence 
property of Savin Hill to make it a suitable place for a pump- 
ing-station. Borings at the mouth of the river opposite Com- 
mercial Point also found deep beds of mud, but the crossing- 
being much shorter, it would have been comparatively easy to 
have constructed a stable siphon on that line. Commercial 
Point itself was a fairly good site for a pumping-station, but 
would have been somewhat difficult of access from the city. 
Ground suitable for tunnelling was discovered between Old 
Harbor Point and Squantum Neck. This was the most direct 
line from the city to Moon Island, and comparative estimates 
showed it to be also the cheapest line. Its chief merit, however, 
which caused it to be selected, was that it permitted the use of 
Old Harbor Point as a site for the pumping-station. This 
point comprises over 100 acres of marsh land, valued by 
the city assessors at only $200 an acre. It is itself destitute 
of habitations, and sufficiently remote from any to afford assur- 
ance that operations carried on there will not be a source of 
offence. 

Before adopting the tunnel line a plan was considered by 
which the sewage, instead of being raised at Old Harbor Point, 
was to flow thence by gravitation to a pumping-station at Moon 
Island, on a nearly direct line between the two points. The 
sewer was to be built above ground and sunk into a trench dug 
to an even o-rade in the bottom of the harbor. To determine 
the feasibility of this plan borings were made to test the 
nature of the ground on the proposed line. The character of 
the ground developed by these borings was not considered very 
favorable, and a decision of the Harbor Commissioners requir- 
ing the sewer to be placed lower than was considered practi- 
cable caused the proposed plan to be abandoned. 

Having decided to locate the pumping-station at Old Harbor 
Point the routes of the main and intercepting sewers were 
next selected. The peculiar geological formation of the region 
about Boston, causing frequent elevation of the bed-rock, not 



26 MAIN DRAINAGE WORKS. 

always shown by surface indications, and the sometimes un- 
suspected presence of deep beds of marsh mud, rendered it 
necessary to test carefully the nature of the ground through 
which it was proposed to build the sewers, since its character 
would form such an important element in their cost and sta- 
bility. The slowness and expense of artesian methods of 
boring precluded their use. Light auger-rods were therefore 
constructed, and it was found that b}^ them the character of the 
ground could be ascertained with approximate accuracy and 
with little expense or delay. These tools, and the manner of 
using them, are shown on Plate IV., Figs. 1 to 3. Including 
work done before and after the beginning of construction, more 
than 30,000 lineal feet of borings were thus made, at an average 
cost of about 25 cents per foot. 

There was no trustworthy information extant concerning the 
position and condition of the city sewers which were to be inter- 
cepted. Careful surveys were therefore made, of about 50 
miles in extent, of such sewers as were in the vicinity of the 
proposed intercepting sewers. Plans and profiles of these 
were made, with cross-sections and such details of construction 
as could be ascertained. 

Nearly all buildings in the Back-Bay and South-End districts 
of the city are supported on piles. By city ordinance the tops 
of the piles are not to be higher than Grade 5, or mid-tide 
level ; in fact many of them are a foot or two higher. Fears 
were expressed that the intercepting system (by doing away 
with the semi-daily damming up by the tide of the contents 
of the sewers) might lower considerably the soil-water in such 
regions, and, by reducing it below the tops of the piles cause 
them to decay and endanger the stability of the buildings sup- 
ported by them. 

To see if such danger Avas to be apprehended, it was decided 
to produce in one of the Back-Bay sewers the precise condition 
which would exist if the new system was constructed, and to 
notice the effect upon the soil-water. To this end a steam 
pump was put into the Berkeley-Street sewer near the outlet 
and by continual pumping (except at low tide) the sewage 
was kept but a few inches deep, as it would be if discharging 



PEELIMINAEY INVESTIGATIONS. 27 

into an intercepting sewer. Previously 20 pipes had been 
driven below the surface of soil- water ; some within a few feet 
of the sewers, others a few hundred feet away, and still others 
several blocks distant. The height of the soil-water standing 
in each pipe was measured twice each day during the continu- 
ance of the pumping. 

The method of making these measurements was ingenious, 
and perhaps novel. The elevation of the top of each pipe was 
known, and the distance from the top to the surface of water 
was taken with a steel tape. To the bottom of the tape was 
attached a lead weight, with a needle fixed in its top so adjusted 
that the point of the needle was just opposite to the end of the 
tape. A small bit of metallic potassium was put on the point 
of the needle. The instant this touched the water it ignited 
explosively, and the flash and sound could be easily distin- 
guished from above. A sketch of the apparatus is shown by 
Fig. 7, Plate lY. 

It was found that the surface of the soil-water was nearly 
level over the whole Back-Bay district, averaging 7.7 feet 
above mean low water, and its height, while slightly affected 
by local contours of the surface, was independent of the sewers 
in its vicinity. For instance, the water in the vicinity of the 
Dartmouth-Street sewer was at the same level as that near the 
Berkeley-Street sewer, although the latter sewer is two feet 
lower than the former. Also it was found that the soil-water 
rose and fell, responding quickly to any rain or melting of 
snow (the extreme rise due to four inches of surface-water being 
one foot) , and that the variation was nearly uniform over the 
entire district. 

Finally it appeared that the pumping, which continued 53 
days, affected but slightly, and that only within 100 feet of the 
sewer, the soil-water in the vicinity of Berkeley Street. At 
the close of the experiment, the sewer resuming its former 
conditions, the soil-water in its immediate vicinity rose from 
an inch to an inch and one-half, and thereafter fluctuated in 
unison with the water in other localities. 

The experiment was thought to show that no dangerous low- 



28 MAIN DEAINAGE WORKS. 

ering of the ground-water need be apprehended in consequence 
of the adoption of an intercepting system. 

The following was the general basis of calculations for 
amounts of sewage and sizes of sewers. It was necessary to 
assume some limit to the territory which should be tributary 
to the intercepting system. A natural limit in this case seemed 
to be afforded by the Charles and Neponset Rivers, which, with 
Mother Brook connecting them, include an area of about 58 square 
miles. Of this area about 46 square miles is high land, 40 or 
more feet above low water, and, as suggested by the com- 
missioners, drainage from districts above Grade 40 could, if 
necessary, be intercepted by a " high-level " intercepting sewer 
and could flow by gravitation to the reservoir at Moon Island. 
There remain 12 square miles below Grade 40 which must 
forever drain into the " low-level" system. As, however, it will 
be long; before the hioh-level sewer is built, and in the mean 
time sewers from areas above Grade 40 must connect with the 
low-level system, for purposes of calculation, it was assumed 
that 20 square miles would be tributary to the proposed sys- 
tem. 

The prospective population was estimated at an average of 
62| persons to each acre, or 800,000 in all. This estimate of 
62| persons to the acre was used in calculations affecting the 
main sewer ; but in proportioning branch intercepting sewers 
greater densities of population were assumed, to provide for 
possible movements of population. The amount of sewage per 
individual was estimated at 75 gallons, or 10 cubic feet, in each 
24 hours. The maximum flow of sewage per second was esti- 
mated at one and one-half times the average flow due to 10 
cubic feet per day. 

On this basis the maximum flow of sewage-proper to be 

provided for would be „ . ' ,.,, Cl ,.n X 1.5 = 138.88 cubic feet 
^ 24 X 60 X 60 

per second. 

This amount was nearly doubled by adding to it 100 cubic 
feet per second as a provision for rain-water. This would rep- 
resent a little less than one-fourth inch of rainfall in 24 hours, 
per acre of tributary area ; but it was intended, in practice, to 



PEELIMINARY INVESTIGATIONS. 29 

admit little, if any, rain from regions where the cellars were 
not subject to flooding, and reserve the full capacity of the 
sewers and pumps to relieve certain low districts where the 
cellars are generally much below high tide, and were often 
partly filled with water in time of rain. 

For purposes of calculation, therefore, the prospective maxi- 
mum flow per second in the main sewer was assumed to be 
138.88 + 100 = 238.88 cubic feet per second. The inclination 
of the sewer was 1 in 2,500, and it was designed (as were all 
of the sewers) to flow about half full with its calculated maxi- 
mum amount of sewage. Although this rule required that the 
sewers should be larger than they would be if designed to flow 
full, it was adopted because it gave about three feet less depth of 
excavation for the whole sewer system, saved three feet lift in 
pumping, provided storage-room for large additional amounts 
of sewage due to intermission of pumping or to rain, and 
aflbrded more head-room to workmen entering the sewers. 

In designing the smaller intercepting sewers the method em- 
ployed was somewhat as follows : the districts drained by the 
several city sewers were ascertained, and their respective areas 
in acres were calculated. The largest population which by any 
chance might live on these areas in the future was estimated, 
i.e., guessed. The future average amount of sewage proper 
due to such population was doubled for safety, and an addi- 
tional amount added for rain, usually equalling that from .25- 
inch rainfall in 24 hours. If an intercepting sewer large, enough 
to carry this total amount when flowing half full would have 
been too small to be entered conveniently, its size, or sometimes 
only its height, was increased sufiiciently to aflbrd convenient 
head-room. 

Velocities of flow were calculated by the formula V ^ C l/RI, 
with Mr. Kutters coeflScients, obtained by using .013 as the 
coeflEicient for roughness. 

During the early stages of the work, the City Engineer, Mr. 
Davis, made a trip to Europe to examine the foreign sewerage 
works of best repute. Information was thus gained which was 
used in designing the Boston works. 

In July, 1877, the City Engineer reported the results of his 



30 MAIN DRAINAGE WORKS. 

preliminary survey, and on August 9 of the same year orders 
of the City Council were approved, authorizing, and making an 
appropriation for, the construction of an improved system of 
sewerage, in general accordance with the proposed plan, under 
authority of the Act of Legislature. 

The City Council committed the charge of building the Main 
Drainage Works to a Joint Special Committee on Improved 
Sewerage, consisting of three Aldermen, and five members of 
the Common Council. This committee changed its member- 
ship every year except when one or more of its members were 
reelected and were again appointed on it. By city ordinance 
all engineering works are built by the City Engineer. The 
Main Drainage Works, therefore, were constructed under the 
direction of Mr. Joseph P. Davis, C.E., City Engineer, until 
his resignation in 1880, and since that date by his successor in 
office, Mr. Henry M. Wightman, C.E.^ 

> Since the above was written the city has sustained a great loss in the death of Mr. 
Wightman. Mr. WilUam Jackson has been elected City Engineer. 



MAIN SEWER. 31 



CHAPTER V. 



MAIN SEWER. 



The main sewer is about 31 miles long, and extends from the 
pumping-station at Old Harbor Point to the junction of Hunt- 
ino'ton Avenue and Camden Street. Its inclination throuo-hout 
its whole extent is 1 foot vertical in 2,500 horizontal. At 
the pumping-station the water-line of the invert, i.e., its bot- 
tom, is about 14 feet below the elevation of mean low tide. From 
this point, in its course towards the city, the sewer passes for 
about a mile across the Calf Pasture Marsh, so called. The 
surface of this marsh is about six inches above mean high water, 
and, the mean rise and fall of the tide being ten feet, the aver- 
age depth of excavation required for this section of work was 24 
feet. Up to the junction of the South Boston intercepting 
sewer the main sewer is ten feet six inches in diameter. It was 
founded sometimes upon clay and sometimes upon sand. 
Figs. 1 and 2, Plate VI., show the usual methods of construc- 
tion. Rubble side walls were built for the greater portion of the 
distance. Fig. 3 shows the bond used in the spandrels. 

On this section occurred the only case during the construction 
of the entire Main Drainage Works in which a sewer was 
broken so that a portion of it had to be taken down and rebuilt. 
At one point, for a distance of 150 feet, the marsh mud, which 
usually was from five to ten feet deep below the surface of the 
ground, came down below the spring-line of the sewer. Owing 
to carelessness, on the part of the contractor, in back-filling 
around the haunches, or in withdrawing the sheet planks, the 
sewer spread six inches, and sank correspondingly at the crown. 
Fig. 4 shows the shape assumed at the point of maximum dis- 
tortion. Although even this portion was probably stable, it was 
not considered wise to establish a precedent of accepting any im- 
perfect work. Accordingly the trench was reopened, the sewer 
uncovered, and its arch broken down with sledge hammers. 



32 MAIN DRAINAGE WORKS. 

It was found that the 12-inch Akron drahi-pipe built under 
the sewer, to facilitate drainage of the trench during construc- 
tion, was broken at this point, and the water from it, accumu- 
lated from 4,000 feet of trench, found an outlet and poured 
over the side walls into the invert. This water was controlled 
by pumps, but was found to have washed out a quantity of 
sand, causing a considerable cavity under the sewer platform. 
The limits of the cavity having been determined, five holes, 
ten feet apart on centres, were made through the bottom of the 
sewer and 3-inch wrought-iron gas-pipes were inserted into 
them. Two of these pipes were about 30 feet long and three 
others, for vents, were five feet long. Constant streams of 
grout, made from 47 casks of neat, quick-setting Portland ce- 
ment, were forced under a 25-foot head, through the long pipes 
into the cavity until it was filled, as proved by the cement ris- 
ing in the short pipes. The grout hardened and furnished a 
secure foundation. Special ribs were cut to fit the invert, which 
was again arched over and the trench refilled. 

Figs. 5 and 6, Plate. VI., show methods of connecting man- 
holes with the main sewer. These structures are about 400 
feet apart, and are placed alternately on one side of and over 
the centre of the sewer. At man-holes the arch is supported 
by cut-granite skewback stones. At the top of the man-holes 
are cast-iron frames supporting circular iron covers. The cov- 
ers are perforated for purposes of ventilation. The holes are 
quite large, so that they are not liable to become stopped up. 
They also taper considerably, being larger below than they are 
on top. To prevent road detritus and miscellaneous rubbish 
from falling into the sewers, catch-pails are suspended below 
the covers to receive whatever may fall through the holes. The 
pails are of galvanized iron, well coated with tar. They can be 
lifted out, emptied, and replaced, as occasion demands. 
Wrought-iron steps were built into the man-holes during 
construction. These details are shown on Plate VI., Figs. 
7 and 8. 

Above the point where the South Boston i atercepting sew- 
ers join the main sewer the latter is nine feet in diameter. For 
about half a mile the ground is high, but a location through 




SIDE ENTRANCE AND BOAT CHAMBER 



_Fi^J6_ 



MAIN SEWER. 33 

it could not be avoided without making a considerable detour. 
For 1,900 feet, in Mount Vernon Street, the sewer was built by 
tunnelling through conglomerate rock and coarse sand. The 
rock, where it surrounded the tunnel, presented no serious ob- 
stacle ; but the sand tended to run into the excavation, and re- 
quired close sheeting and heavy bracing to support it. Fig. 
9, Plate VI., shows the sewer in tunnel on this section. For 
several hundred feet the sewer grade was near the surface of 
the ledge and, the latter being very irregular and covered with 
boulders, tunnelling operations were attended with much diffi- 
culty, and several caves occurred. For a length of 160 feet 
the ground was opened from the top and the sewer was built in 
an open trench about 45 feet deep. 

The sewer in the tunnel was well built, but after completion, 
on removing the pumps so that the water table in the vicinity 
was permitted to rise above the sewer, the latter was found to 
leak a good deal. The leaks, however, could be successfully 
calked. The process consisted in raking out a joint, where a 
leak occurred, to the full depth of the brick and driving in 
sheet lead for half the depth, the remainder being filled with 
cement. 

Excepting a section in East Chester Park, from Clapp Street 
to Magazine Street, the main sewer was built by contract. The 
laying out as a street of East Chester Park, east of Albany 
Street, had been contemplated by the authorities for some time, 
and action to that end was taken in time to permit the sewer 
beinsr located there. The borins^s on this line showed that there 
were beds of marsh mud between Clapp and Magazine Streets 
which were from 20 to 86 feet deep below the marsh surface. 
As it would have been difficult to build a stable sewer in such 
ground, and impossible to prevent one, if built, being destroyed 
when the street should be filled over and around it, it was de- 
cided to fill the street to full lines and grades before attempting 
to build the sewer. 

A contract was accordingly concluded by which the street 
was filled with gravel brought by the N.Y. and N.E. Eailroad. 
So great was the settlement of this filling into the mud that 
over 106,000 cubic yards of gravel were required. The marsh 



34 MAIN DRAINAGE WORKS. 

level for 100, or more, feet on either side of the filled 
street was pushed up by the filling from 8 to 14 feet high. A 
surcharge, 20 feet wide on top and eight feet high, was put 
upon the street, west of the N.Y. cS: N.E. Kailroad, where the 
mud was deepest, to insure prompt settlement. 

Building a stable sewer in a street so recently filled being a 
difficult operation, requiring methods of treatment which can- 
not be determined upon beforehand, it was thought best to 
build this section by day's labor. 

As a masonry structure would have been broken when the 
trench was refilled, a wooden sewer was adopted (Fig. 10, 
Plate yi.) . This consisted of an external wooden shell, formed 
of 4-inch spruce plank, ten inches wide, every fourth plank 
being wedge-shaped ; the whole securely spiked and treenailed 
together and finally lined with four inches of brick or concrete 
masonry. 

The depth of excavation for this sewer was from 32 to 36 
feet, and the pressures were so great as to require very heavy 
bracing. As many as 60 braces of 8 inch X 8 inch, or heavier 
timber, were sometimes used for a length of 18 lineal feet of 
trench ; and these, when taken out, were all found to be either 
broken, or so crippled as to be unfit to use again. Frequently 
the earth on one side of the trench was found to be different 
from that on the other, which caused very unequal pressures, so 
that internal bracing was necessary to maintain the sewer in its 
proper shape until tlie trench had been baclv-filled. It was 
found necessary to build the shell with a vertical diameter 
four inches greater than was required for the masonry lining, 
to allow for settlement, change of shape, and compression of 
the timber. The vertical diameter inside of the lining was also 
increased, so that, if in places the sewer should settle as a whole, 
the bottom could be brought to the true grade, and still leave 
the established sectional area. 

The length of this section was 1,894 feet. Ground was first 
broken in August, 1879, and the work was completed in Octo- 
ber, 1880. For excavating and back-filling the trench, machin- 
ery designed by the Superintendent, Mr. H. A. Carson, was 
used. The average cost per lineal foot of the completed sewer 



MAIN SEWER. 35 

was $56. For several hundred feet, where the mud hud been 
deepest, a continual slight shrinkage and settlement of the 
gravel filling under the sewer occurred for a year or more. 
The sewer itself, also, settled in a long curve, whose greatest 
depth below the original grade line was about 18 inches. A 
masonry sewer would have been broken by such movement, 
but the wooden one having considerable flexibility w^as appar- 
ently uninjured. At present (1885) the street seems to have 
assumed a condition of permanent stability. 

In East Chester Park, from Magazine Street to Albany 
Street, clay w^as chiefly encountered, and the sewer generally 
consisted of a simple ring of brick-work without side walls, and 
its construction presented few features of special interest. As 
a precaution in passing within 35 feet of a large gas-holder, 
tongued and grooved 4-inch sheet planks were driven, and 
the trench was back-filled with concrete to the crown of the 
sewer arch (Fig. 11). In passing gicross the old Eoxbury 
Canal, which had been recently filled by the city, an influx of 
tide-water along the loose walls of the canal and through the 
filling occasioned some delay and expense. The water was 
finally kept out by double rows of tongued and grooved sheet- 
piling. A side entrance and boat-chamber (Fig. 12), were built 
on this section, at the corner of Swett Street. The latter 
structure resembled a very large man-hole, with a rectangular 
opening from the street, 11 X 4 feet in dimensions. This was 
built to allow the lowering of boats into the sewer. 

At Albany Street the east-side intercepting sewer joins the 
main, and above this point the latter is again reduced in size, to 
eight feet three inches wide by eight feet five inches high. The 
extra horizontal course w^as put in at the spring line because it 
was supposed to facilitate dropping and moving the centres. 
In East Chester Park, and Washington Street from Albany to 
Camden Street, the sewer was built chiefly in clay, and con- 
sisted of a ring of brick-work. For about 300 feet, however, 
near Albany Street, mud was found, and a foundation, consisting 
of a timber platform supported on piles, became necessary 
(Fig. 13, Plate VL). 

In Camden Street, from Washington Street to Tremont 



36 MAIN DRAINAGE WORKS. 

Street, a distance of 1,391 feet, the depth of trench required 
would have been 26 feet. Camden Street is rather narrow, and 
contams sewer, gas, and water pipes. As good clay was found 
at a depth five or more feet above the top of the sewer, it was 
thought that it would be as cheap to the city, and decidedly 
less annoying to residents on the street, to build the sewer by 
tunnelling beneath the surface (Fig. 14). Working shafts were 
sunk about 250 feet apart, and headings in each direction driven 
from them. At one or two points the miners permitted the 
roof of the tunnel to settle slightly, by which the common sewer 
above was cracked, and some trouble caused by the sewage 
leaking into the tunnel. The main sewer was back-filled above 
the arch with clay, packed in under the lagging as firmly as 
possible. On the whole the method of construction was suc- 
cessful, and a well-built sewer was obtained. Its cost was 
$22.52 per lineal foot. 

At Tremont Street the Stony-Brook intercepting sewer is 
taken in. At this point, as at all other places where intercept- 
ing sewers join the main sewer, the grade of the latter rises 
abruptly somewhat less than a foot, or enough to maintain the 
established inclination on the surface of the sewage at the time 
of maximum flow. From Tremont Street to the present end of 
the main sewer, at Huntington Avenue, the sewer was built in 
open cut (Fig. 15), and for a large part of the distance needed 
side walls and piling for its support. Just west of the B. cS; 
P. E.R. another boat-chamber and side entrance (Fig. 16) 
were built, and a third side entrance, reached by a stone stair- 
way leading from the sidewalk, was constructed at Huntington 
Avenue. 

The total cost of the 3.2 miles of main sewer was $606,031 
being an average of $36.09 per lineal foot. 



INTERCEPTING SEWERS. 37 



CHAPTER VI. 

INTERCEPTING SEWERS. 

As before stated, and as shown by the plan (Plate V.), the 
South Boston intercepting sewer is the first to join the main 
sewer in the latter's course from the pumping-station towards 
the city proper. This intercepting sewer, by its two branches, 
is intended finally to encircle the peninsula on which South 
Boston is situated, and intercept the sewage flowing in the com- 
mon sewers, which have heretofore discharged their contents at 
nineteen outlets, in the immediate vicinity of a dense popula- 
tion. 

At the point of junction the grade of the intercepting sewer 
is 1.5 feet higher than that of the main sewer, so that the sew- 
age in the former shall not be dammed back, and the established 
rate of inclination shall be maintained on the surface of the 
sewao'e in both sewers at the time of maximum discharge. In 
all cases where a main-drainage sewer joins another, the junc- 
tion is made at a " bell-mouth " connection chamber, in which 
the axes of the sewers meet by lines or curves tangent to each 
other, so that the two currents may unite with the least dis- 
turbance to either. Sections of the " bell-mouth " junction of 
the two branches of the South Boston sewer, at Hyde Street, 
are shown by Fig. 14, Plate VII. On each intercepting 
sewer, just before it reaches the main sewer, is built a penstock 
chamber, containing a cast-iron penstock gate, by which the 
flow can be cut off", so that the main sewer can be entirely 
emptied, should it ever be desirable to do so. At such times 
the city sew^age would be discharged at the old outlets, which 
are all retained and protected by tide-gates. A sketch of the 
penstock on the South Boston sewer is given by Fig. 6. 

Up to where it divides this sewer is circular, six feet in 
diameter. The average depth of excavation was 20 feet. Clay 
or sand was usually found, and the sewer consists of a simple 



38 MAIN DRAINAGE WOEKS. 

ring of brick- work, 12 inches thick, though for about 350 feet, 
where the sand was wet and inclined to run, abutment walls of 
rubble masonry were used. Figs. 12 and 13 show cross- 
sections of this sewer. The brick invert was laid with Port- 
land cement mortar, one part cement to two parts sand, and the 
arch was laid with American (Eosendale) cement mortar, one 
part cement to 1.5 parts sand. This was the common practice 
in building the main-drainage sewers, Portland cement being 
used in the mverts, on account of its greater resistance to abra- 
sion. When Rosendale cement was used for building inverts, 
the proportion required was equal parts of cement and sand. 

The inclination of this sewer throughout the greater portion 
of its extent is 1 in 2,000, which affords a velocity of flow 
sufficient to prevent deposits of sludge, but not sufficient to 
keep in suspension sand and road detritus. A sharper inclina- 
tion would have been desirable had it been practicable to ob- 
tain one. Few of the main drainao;e sewers have a OTeater 
inclination than 1 in 2,000, and it was expected from the first 
that flushing would occasionally be required to prevent the 
accumulation of deposits. To provide for this, iron flushing- 
gates are built into the sewers at intervals of about half a mile. 
The first flushing-gate on the South Boston sewer is just below 
the fork at Hyde Street. A sketch of this gate is given by 
Fig. 15. Usually the gate stands above the sewer, in the 
man-hole. It is kept vertical by two small stop-bolts at its top. 
To flush the sewer the gate is lowered against its seat, built 
into the bottom of the sewer, and the sewage accumulates be- 
hind it as deep as the gate is high. The stops are then with- 
drawn and the gate raised until it clears its lower seat, when it 
tilts over into a horizontal position and opens a free passage 
for the dammed-up sewage. 

The greater part of South Boston is high land, and there are 
but few low cellars there which are subject during rain-storms 
to flooding at high tide. In order that the full capacity of the 
sewers and pumps might be available to relieve other parts of 
the city, less favored in this respect, it was necessary to ar- 
range that no more than a fixed quantity of sewage should 
ever be received by the main sewer from the South Boston 




Fi^.2 




LARGE REGULATOR 






PENSTOCK GATE 





CONNECTION WITH 

Fig.O 7 



VALE ST. SEWER 



PLAN 

BOSTON MAIN DRAINAGE 
INTERCEPTING SEWERS. 



SECTIONAL PLAN 



o z 

Hj bd k d bil bd bd 
SCALE OF FEtT 





Fi$,.8 ,^ ^ 

BACK VIEW. FRONT VIEW 

TIDE GATES. 





n^.i2 



Fig,. 13 





FLUSHING 

n^.i5 



GATE 



INTERCEPTING SEWERS. 39 

intercepting sewer. To accomplish this a " regulator " was 
built into the intercepting sewer just below its last connection 
with a common sewer, at Kemp Street. 

A sectional plan and elevation of this machine, and of the 
chamber containing it, is given by Fig. 9, Plate VII. 
As will be seen, the apparatus is very simple, and consists of 
stop-planks, closing the sewer from its top down to about 
the ordinary dry-weather ilow line, the sewer below the planks 
being lined with a cast-iron gate frame, or seat, curved to fit 
the invert, and also vertically to correspond with the curve of 
motion of a cast-iron valve, which plays up and down in front 
of it. The valve is held by two cast-iron levers, pivoted by a 
3-inch wrought-iron shaft in two bearings, the other encTs 
of the lever being connected by vertical arms to a 3-inch 
square bar. To the ends of this bar are fastened two boiler- 
plate floats, placed in wells on either side of the sewer. To 
avoid disturbance to the motion of the floats, hy waves caused 
by the rush of sewage under the valve, water is brought to the 
wells through a 5-inch pipe, as shown, from a point 50 feet 
below the regulator. 

The connection between the valves and the floats can be so 
adjusted that the former will begin to close when the surface of 
sewage in the sewer has reached any desired height. As the 
floats rise the valve descends until the opening below it is just 
sufiicient to let enough sewage pass to maintain the allowed 
depth of flow in the sewer. Should the amount of rain-water 
from low districts, reaching the main sewer through other 
intercepting sewers, exceed the capacity of the pumps to con- 
trol it, the main sewer fills, and its sewage backs up into the 
South Boston sewer, and still further raises the floats. The 
opening under the stop-planks is thus entirely closed, and all 
of the common sewers above discharge at their old outlets, and 
continue to do so until the amount of water reaching the pumps 
can be controlled by them. 

Above where this sewer divides, at Hyde Street, the branch 
which turns to the right, and skirts the southerly margin of 
South Boston, is egg-shaped, four feet six inches high by three 
feet wide (Fig. 11, Plate VII.). After passing under the 



40 MAIN DRAINAGE WORKS. 

Old Colony Railroad the shape is changed somewhat (Fig. 
3). At Vinton, Vale, and other streets, common sewers are 
intercepted. Fig. 7, Plate VII., shows the connection with the 
Vale-Street sewer, and may stand as a type of such connec- 
tions between common and intercepting sewers, wherever no 
reoulation of the amount to be received from the former is 
required. Nearly every individual case presented special con- 
ditions, which necessitated some modification of the method of 
construction ; but the general plan was the same in most cases, 
and its features are shown in this case. 

A sump hole, two feet deep, into which the sewage falls, is 
first built in the common sewer. Into the bottom of this sump 
is" built a short section of iron pipe (Fig. 5), from 12 to 24 
inches in diameter, protected by a cast-iron flap-valve. Ordi- 
narily this valve stands open, but can be closed if it is desired 
to break the connection between the two sewers. The bottom 
of the sump, around the pipe, is rounded ofi" with strong Port- 
land cement concrete, so that there shall be no corners in which 
deposits can lodge. The sewage passes to the intercepting 
seAver throuo-h a short branch connectino; with the lower end of 
the iron pipe. 

Beyond the sump the common sewer is provided with a 
chamber containing a double set of tide-gates. These gates 
give a clear opening of from two to four feet diameter. Each 
set of gates is hinged to a cast-iron ring, or gate seat (Fig. 
8), which is built into the brick-work. The two wooden gates 
close against each other. To make tight joints the bearing 
surfaces of the gates are covered with strips of rubber about 
three-eighths of an inch thick. The gates are inclined somewhat, 
so that they are self-closing. 

From the main sewer to the Old Colony Railroad this inter- 
cepting sewer was built by contract, at an average cost of $12.68 
per lineal foot. From the railroad to H Street it was built by 
day's labor, and cost $13.25 per lineal foot. On Ninth Street, 
between Old Harbor Street and G Street, for a distance of 
about 800 feet, the sewer location crossed a beach which was 
several feet below high-tide level. No cofier dam or other 
protection was used in this place, but construction was carried 



INTERCEPTING SEWERS. 41 

on only when the tide was down. When the sea rose it over- 
flowed and filled the trench. When it again fell the water in 
the trench was let off through the sewer already built, to pumps 
at the pumping-station, and work was resumed. From H 
Street to N Street, on Ninth Street, the sewer was built by 
contract. For about 1,000 feet, near K and L Streets, the 
average depth of the trench was about 27 feet. The sewer was 
nearly circular, three feet wide and three feet two inches high 
(Fig. 1, Plate VII.) . This section was among the earliest built, 
and its design is not in accord with later practice. It might have 
been made much more convenient for workmen to enter, at slight 
additional expense, by giving it a greater vertical diameter. Its 
fall is 1 in l,666f. 

From the point of division on Hyde Street the sewer which 
turns to the left, and follows the westerly shore of South Boston, 
is egg-shaped, five feet six inches by four feet nine inches, up to 
the Old Colony Railroad crossing, on Dorchester Avenue. A 
timber platform and rubble masonry side walls were required for 
the entire distance, and the usual cross-section of this sewer is 
shown by Fig. 10, Plate VII. This section was built by con- 
tract. Its length is 3,350 feet ; the average depth of excavation 
was about 24 feet, and the average cost per lineal foot was 
$16.85. 

After taking in the B-Street sewer the intercepting sewer 
changes its shape (Fig. 3), and continues in Dorchester 
Avenue, passing under the N.Y. & N.E. Railroad, and turns 
into Foundry Street, which it follows to its end, at the corner 
of Dorchester Avenue and First Street. Considerable difficulty 
was encountered in passing under the abutments of the bridge 
on Dorchester Avenue, over the N.Y. & N.E. Railroad. 
These were underlaid by running sand, and the northerly abut- 
ment over the sewer, which had been built without mortar, had 
to be taken down. Under the tracks of the same railroad, 
head-room being limited, the shape of the sewer was altered 
(Fig. 2), so that there should be no danger of its interfering 
with, or being injured by, repairs to the road-bed. This section 
of sewer is 2,820 feet long, and its average cost per foot was 
$19.25, 



42 MAIN DRAINAGE WORKS. 

The second large intercepting sewer which enters the main 
sewer, had its point of connection at the intersection of East 
Chester Park and Albany Street. It is called the East Side 
intercepting sewer, and is located in streets following the east- 
erly margin of the city proper for a distance of about 2\ miles. 
In Albany Street, from East Chester Park to Dover Street, a dis- 
tance of 4,524 feet, the sewer is nearly circular, with a vertical 
diameter of five feet eight inches, and a horizontal one of five 
feet six inches. The inclination is 1 in 2,000. The average 
depth of excavation for this section of work was 24 feet, and, as 
marsh mud and peat extended from near the surface of the 
ground to a depth always considerably below the bottom of the 
sewer, piles were required to furnish a secure foundation. A 
timber platform was fastened to the tops of the piles, and on 
the platform the sewer, with its rubble masonry abutment walls, 
was built. The bottom of the excavation was about 6.5 feet below 
the elevation of low tide, and considerable trouble was experi- 
enced from sea- water making its way into the trench, especially 
in places where old sea-walls and other such obstructions were 
encountered. The mud on the sides of the trench exerted much 
lateral pressure, and close sheet-piling and heavy bracing were 
necessary. Opening so deep a trench in such material drained 
the water out of the adjacent soil, rendering it spongy and some- 
what compressible, so that the whole street settled and had to 
be resurfaced and repaved. This section was built by contract. 
One firm of contractors gave up the job, and the work was re-let 
under provisions of the contract. The average cost per lineal 
foot of the completed sewer was $26.16. 

The first common sewer taken in by the intercepter is that 
on Concord Street. This sewer drains a district in which the 
cellars are not subject to flooding from rain-water during high 
tides. It was not necessary, therefore, to let this sewer dis- 
charge into the intercepter an amount of sewage in excess of 
its ordinary maximum dry-weather flow, and temporarily, during 
rain-storms, the whole dilute contents of the sewer could, with- 
out injury, be permitted to discharge into the bay at the old 
outlet. An arrangement to efiect this was desirable, because, 
during very heavy rain-storms, the whole capacity of the inter- 



INTERCEPTING SEWERS. 43 

cepting sewer might be needed to afford relief to sewers drain- 
ing low districts beyond Concord Street. 

Accordingly the connection between this sewer and the 
intercepting sewer was made through a chamber containing a 
small regulating apparatus, designed to control or cut oS the 
flow automatically. Figs. 1 and 2, Plate VIII., show sec- 
tions of this apparatus and its arrangement. Eight similar 
appliances, with slight modifications in the methods of arrange- 
ment, were used in connection with the same number of common 
sewers. 

The operation of the apparatus will be understood from an 
examination of the figures. Under ordinary circumstances the 
sewage falls into a sump, and thence passes to the regulating 
chamber, which it enters through a cast-iron nozzle. This nozzle 
is circular, 12 inches in diameter at its upper end, and rec- 
tang-ular 20 X 6 inches at its orifice. In front of the orifice 
plays a cast-iron valve, moved by afloat in a tank set in the floor 
of the chamber. The water in the tank stands at the same 
elevation as that in the intercepting sewer, a 4-inch iron pipe 
connecting one with the other. The apparatus can be adjusted 
so that the valve will begin to close and cut off the flow of 
sewage when the water in the intercepting sewer reaches any 
desired depth. When not cut off, the sewage flows around the 
tank and passes on through an opening at its further end. 

The second common sewer taken in is that in Dedham Street. 
This sewer drains a district which used to suffer greatly from 
flooclino; durino; rain-storms. In order to afford relief this sewer 
was connected directly with the intercepter by a branch two feet 
in diameter, the inlet to which is never closed. 

The third sewer taken in is that in Union Park Street. The 
district drained by it has suffered but slightly from wet cellars, 
and that only during severe storms and very high tides. The 
flow from this sewer was regulated in the same manner as that 
from the Concord-Street sewer, but the apparatus was so 
adjusted that it cuts off the flow later than in the case of most 
other sewers, and only when the intercepting sewer is nearly 
full. 

The fourth common sewer met with is that in Dover Street. 



44 MAIN DEAINAQE WORKS. 

This drains a low district, and a free connection, tv/o feet in 
diameter, was made with it. According to the usual practice 
in such cases this sewer would have been connected with the 
intercepter at or near the point in Albany Street where their 
two locations intersect. But it was found in examining the 
cit}^ sewers, with reference to connections with them, that the 
Dover-Street sewer was not in condition to be intercepted at 
any point east of Harrison Avenue. Between that street and 
its outlet it is a rectangular wooden structure, 5 x ^ feet in 
dimensions, placed close to an old stone retaining- wall and 
surrounded by loose stone ballast. It is considerably broken, 
so that the tide-water from the bay which ebbs and flows about 
the wall and in the ballast has free access to the sewer, and 
would have flowed into the intercepting sewer, and so 
reached the pumps. From Harrison Avenue westerly, the 
Dover-Street sewer was built of brick, and was tight so that sea- 
water could be excluded from it by tide-gates. Accordingly 
the connection was made west of Harrison Avenue, and a 2 X 3 
feet oval branch sewer (Fig. 3), 588 feet long, was built from 
that point to convey the sewage to the intercepting sewer at 
Albany Street. 

Above Dover Street are few districts which suffer from flood- 
ing. Accordingly a large regulating apparatus, to control the 
flow from above, was built into the intercepting sewer at this 
point. It resembled that on the South Boston sewer, before 
described, and shown on Plate VII, by Fig, 9. 

From Dover Street to its upper end on Atlantic Avenue the 
East Side sewer was built by day's labor, under a superintend- 
ent appointed by the city. This was done because above 
Dover Street the sewer location was confined to crowded 
thoroughfares, in which peculiar management was required to 
prevent serious obstruction to travel and to the business of 
abutters ; and also because, operations being principally car- 
ried on in filled land, beds of dock mud, old walls, wharves, 
and other obstructions were continually encountered, requiring 
frequent changes in methods of construction which could not be 
foreseen and provided for in the specifications of a contract. 

From Dover Street the sewer location extends in Albany 



Plate VIII. 




GENERAL PLAN OF 
CONCORD ST. CONNECTION 



Fig. 15 

BOSTON MAIN DRAINAGE, 

INTERCEPTING SEW^ERS. 



O 15 20 FEET 



O 5 10 15 20 

M° ^3"^4H-ru--U-i-^1--H-r ^^ 



SECTIONAL PLAN. 



FALMOUTH ST. SEWER. 



INTERCEPTING SEWERS. 45 

Street to Lehigh Street, at which point it enters private land, and 
crosses the freight and switch yards of the Boston and Albany, 
and Old Colony Railroads, to Federal Street near the bridge, 
a total distance of 2,331.5 feet. In Albany and Lehigh Streets 
are the tracks of a Freight Railway Company, and in the rail- 
road yards are about 40 lines of rails in constant use, which 
it was very important should not be disturbed. The whole 
section of work is in filled land, underlaid by beds of mud from 
5 to 20 feet deep, below the bottom of the sewer, which is 
itself several feet below the level of low tide. At different 
points obstruction in the shape of old walls and wharves were 
encountered, which admitted sea-water freely to the trench, so 
that, as a rule, work could only progress during low stages of 
the tide. 

The sewer is oval, five feet high (Fig. 4), and generally 
required piling for its support. It is built partly of wood, lined 
with two inches of concrete, and partly of brick-work resting on 
a solid cradle of wood, six inches thick. Travel upon the streets 
was not interrupted, and with considerable difficulty the freight- 
railway tracks were supported and maintained. As it would 
have been impossible to have had an open trench through the 
Albany and Old Colony Railroad yards without interfering with 
their traffic, operations at that point were carried on entirely 
below the surface. The tracks were supported by stringers, 
and the spaces between them floored over. By the use of 
special machinery all the earth excavated or refilled, as well as 
materials for constructions, was conveyed by tracks suspended 
below the floor. The trench was well braced, and its sides pro- 
tected by lag-sheeting, which, together with the piles -driven to 
support the sewer, were all put in place without encroaching 
upon the surface. It is believed that not a single train was 
delayed, nor any inconvenience caused, by these operations. 
The average cost of this section of sewer was about $31.26 per 
lineal foot. 

In Federal Street, and Atlantic Avenue to its end at Central 
Street, the intercepting sewer is oval, four feet six inches high by 
two feet eight inches wide. Fig. 5, Plate VIII., shows the usual 
mode of construction. Federal Street contained double horse- 



46 MAIN DEAINAGE WORKS. 

railroad and single freight-railway tracks, and beneath its sur- 
face were one sewer, two water pipes and two gas pipes. 
Beds of dock mud extended from 5 to 20 feet below the bottom 
of the new sewer, and old dock walls and timber structures 
were frequently encountered. A location on the east side of 
the street was found to be most practicable, and the sewer was 
built by methods which left the roadway open for travel. By 
flooring over the trench at intervals, passages were maintained 
through the excavating machine (shown on Plate XXV.) to the 
yards and wharves bordering Fort Point Channel. 

The freight-railway tracks were shifted towards the centre 
of the street, and were used during the day for the passage of 
horse-cars in one direction. Bricks, cement, and other mate- 
rial were piled on the outer edges of both sidewalks where 
they would cause least inconvenience, and always so as to leave 
a clear passage-way four feet wide. Endeavors were made to 
cause the least possible annoyance to corporations and individu- 
als ; and in general these eflx)rts seemed to be appreciated and 
reciprocated by the public, so that complaints were rare'. 
This section of work was 5,159 feet long. The average depth 
of excavation was about 21 feet, and the average cost of com- 
pleted sewer was $15.06 per lineal foot. The Stony-Brook in- 
tercepting sewer joins the main sewer at the intersection of 
Camden and Tremont Streets. This sewer intercepts the sew- 
age wdiich formerly emptied at seven outlets, into Stony Brook, 
and thence found its way into the Back Bay. In Tremont and 
Cabot Streets, from Camden to Ruggles Street (Plate V.), a 
distance of 2,135 feet, the sewer was built by contract. The 
rate of inclination is 1 in 700, and the average depth of excava- 
tion required was 21 feet. The sewer is nearly circular, four feet 
six inches wide l)y four feet eight inches high, and is chiefly 
founded on clay, so that side walls were only needed for about 
300 feet, and the average cost per lineal foot, including inspec- 
tion, was $11,97. The customary iron penstock gate was built 
into the sewer just above the bell-mouth connection chamber 
by which it joins the main. 

As the territory drained by the sewers which empty into 
Stony Broolc is high land, a large automatic regulating appara- 



INTERCEPTING SEWERS. 47 

tus, similar to the one shown on Plate VII., was built into the 
intercepting sewer at Ruggles Street, by means of which the 
flow is partly or wholly cut off during severe and continuous 
rain-storms. Above the regulator is a three-way bell-mouth 
chamber (Fig. 10, Plate VIII.), from which radiate three 
principal branch sewers. The centre or main branch, about 41- 
feet in diameter, is 1,700 feet long, and intercepts . the sewage 
formerly discharging into the brook by outlets at Elmwood and 
Hampshire Streets. This sewer passes twice under the brook, 
at so low an elevation that it preserves its regular grade and 
shape. The other two branches are built just large enough to 
enter, being 2X3 feet, egg-shaped, with the smaller end 
down. These also cross twice under the brook, at Tremont 
Street and at Euggles Street. Including the regulating cham- 
ber, and all sewers above it, this section of work was built by 
the day, under the City Superintendent, Mr. H. A. Carson. 
There were built in all 4,229 lineal feet of sewers, including 415 
feet of 15-inch pipe. The average cost per foot of the whole 
was $14.30. A considerable portion of the 2X3 feet sewers 
was built during the winter of 1880-81. The sewers were 
from 14 to 19 feet below the street surface, and the excavation 
was done by tunnelling from pits about 10 feet apart. The 
outlets of the city sewers being below the level of high tide, in 
order to prevent back-water reaching the intercepting sewer, it 
was necessary to build gate-chambers just beyond the points 
of interception, each chamber containing a double set of tide- 
gates. 

The last of the large intercepting sewers joins the main sewer 
at its present end at the intersection of Camden Street with 
Huntington Avenue (Plate V.). It is commonly called the 
West Side intercepting sewer, and is located in streets border- 
ing the westerly margin of the city proper, and intercepts the 
sewage which formerly discharged into Charles River. This 
sewer is about 3^ miles long, and its inclination from end to end 
is 1 in 2,000. 

From the main sewer to Beacon Street, and in that street to 
Charles Street, a distance of 9,325 feet, the West Side sewer 
was built by day's labor, at an average cost of $13.35 per lineal 



48 MAIN DRAINAGE WORKS. 

foot. This section of work includes, besides the customary 
man-holes, six common-sewer connections, five small regulators, 
one side entrance, one penstock, and three flushing-gates. The 
usual form of this sewer is shown by Fig. 8, Plate VIII. It is 
egg-shaped, five feet six inches high by four feet nine inches wide. 
It will be noticed that the usual position given to an egg-shaped 
sewer is reversed in this case, the larger end of the egg forming 
the invert. This position was adopted because, while afibrding 
convenient head-room, it kept the flow line as low down as was 
practicable. As the flow in this sewer is always a foot or 
more deep, the hydrg^ulic mean depth, and consequently the 
velocity of flow, is greater than it would have been had the 
smaller end of the sewer been below. 

A case of slight injury to this sewer may be worth noticing. 
When the sewer was built on the line of Falmouth Street that 
street had not yet been filled and graded, and the mud and peat, 
which underlay the marsh surface in that locality, sometimes ex- 
tended down below the top of the sewer. About a year after- 
wards the street was graded with gravel about seven feet high 
above the original surface of the marsh over the sewer. One 
side of the street was filled before the other, and the unequal 
pressure which resulted was transmitted to the sewer, and 
caused its arch to bulge, as shown by Fig. 12. Fortunately the 
amount of distortion was not sufficient to endanger the sewer's 
stability, and the crack was pointed with Portland cement. 

In Hereford Street, for a distance of 282 feet, the sewer lo- 
cation passed under a freight-yard of the Boston & Albany 
Railroad, in which were about 20 lines of track. Piles were 
driven and stringers placed to support these tracks, and nearly 
all of the sewer building operations were carried on beneath 
the surface of the ground, so that the traffic of the railroad was 
not interfered with. At this point, and beyond the railroad 
location for a total length of about 800 feet in Hereford Street, 
a common sewer was built in the same trench, directly above 
the intercepting sewer. This was done by an arrangement with 
the City Sewer Department, which designed and paid for the 
upper sewer. A cross-section of the two sewers, showing their 
arrangement, is shown by Fig. 9. 



INTERCEPTING SEWERS. 49 

In Beacon Street, for a distance of 590 feet in the vicinity of 
Exeter Street, 22 old stone walls, from five to twelve feet thick, 
were encountered and had to be cut through. These walls con- 
stituted the sluiceway of the old mill-dam, and their removal 
caused considerable delay. The cost of excavation per lineal 
foot of trench, 20 feet deep in this street, varied from $3.94 to 
$14.49. The section from Camden to Charles Street was 
built in 1878. During a portion of the season work was car- 
ried on day and night at two different points. The largest 
number of men and boys employed at any one time was 369. 
The rate of progress varied greatly ; where no special obstacles 
were met, 108 feet of completed sewer was built each 24 
hours. 

On Beacon Street the large common sewers in Hereford, 
Fairfield, Dartmouth, and Berkeley Streets are intercepted. 
The sewage from each of these sewers passes to the intercept- 
ino- sewer throuo-h a chamber in which is a small automatic 
regulating apparatus, similar to the one shown on Plate VIII. , 
so adjusted as to cut off the flow whenever the water in the 
intercepting sewer exceeds an established depth. The sewers 
just mentioned are too low to pass over the intercepting sewer, 
and a somewhat different method of construction was necessary 
in connecting them. The arrangement at 'Berkeley Street is 
shown by Fig. 13, Plate VIII. 

A secondary intercepting sewer was built in Brimmer Street, 
which collects all of the sewage flowing westward from Beacon 
Hill, and conveys it to the principal intercepting sewer in Bea- 
con Street. For the sake of economy and simplicity, the old 
outlets of the common sewers in Revere, Pinckney, Mt. Ver- 
non, Chestnut, and Beacon Streets were abandoned, and the 
total flow from these sewers, including rain, is taken by the new 
Brimmer-Street sewer, a single storm overflow being provided 
at Back Street. The construction of the Brimmer-Street sys- 
tem involved the building of 1,456.5 feet of oval brick sewers, 
varying from 2X3 feet to 3 X 4 feet 6 inches in diameter ; 
also the rebuilding of about 556 feet of common sewers, which 
were found to be too low or otherwise defective. The flow 
from the Brimmer-Street sewer into the intercepting sewer in 



50 MAIN DRAINAGE WORKS. 

Beacon Street is regulated in the same manner as that from the 
ordinary city sewers. 

A little beyond Brimmer Street a large common sewer, which 
comes from the south across the Public Garden, is intercepted. 
This drains what is called the Church-Street district, compris- 
ino- low territory, in which are many cellars which used often 
to be inundated. Sewage from tliis sewer, therefore, is taken 
directly into the intercepting sewer without the intervention 
of any regulating apparatus. 

On Charles Street, from Beacon to Cambridge Street, a dis- 
tance of l,y32 feet, the sewer was built by contract. It is egg- 
shaped, 4 X 4.5 feet in diameter (Figs. 6 and 7), and cost 
$10.10 per lineal foot. This was the only section of the West 
Side sewer which was built by contract. In excavating the 
trench many of the hollow-log water-pipes of the old Jamaica 
Pond Aqueduct Company were found in a perfect state of pres- 
ervation. A house-drain was found which the drain-layer had 
connected with one of these water-pipes, although the street 
sewer was but a few feet distant. The log had but three inches' 
bore, and, of course, led to no outlet. 

At the intersection of Cambridge and Charles Streets a large 
automatic regulating apparatus, similar to the one shown on 
Plate VII., was built into the sewer, to control the flow from 
above. The excavation in which the chamber for this appa- 
ratus was built was 30 feet square ; but, by flooring over the 
top of the excavation, and supporting the various hues of street- 
railway tracks at that place, travel was not impeded, all build- 
ing operations being carried on below the surface of the street. 

From Cambridge to Leverett Street, a distance of 2,150 feet, 
the intercepting sewer is oval, four feet six inches by three feet 
in diameter. It is of brick-work, eight inches thick, and usu- 
ally required a timber cradle support. The work on this section 
presented the usual difliculties met with in excavating through 
filled land, in the way of old obstructions and the free access of 
tide-water. By a rather curious coincidence, for a distance of 
about 500 feet, the remains of an old wharf or bulkhead were 
found, with longitudinal rows of piles within the trench in such 
positions that, by cutting tliem ofl'at the proper elevation, they 



INTERCEPTING SEWERS. 51 

served as a support for the sewer, in the place of new piles which 
would otherwise have been necessary. Seven hundred and one 
feet, in all of the Fruit-Street and Livingstone-Street sewers, 
which were too low to be intercepted, were replaced by 2X3 
feet oval brick sewers. The private sewer from the Massachusetts 
General Hospital was also too low to be intercepted. This was 
found to be a rectangular wooden scow, 2.5 X 2.5 feet in diam- 
eter, with its bottom at low-tide level. The Trustees of the 
hospital themselves replaced it with a 10-inch drain-pipe at a 
higher elevation. 

From Charles Street to its upper end at Prince Street, a dis- 
tance of 3,571 feet, the West Side sewer maintained, with rare 
exceptions, an even size, of three feet wide and four feet six 
inches high. The arch consisted of eight inches of brick, and 
the invert was generally made with four inches of brick resting 
on a timber cradle, also four inches thick. The common sewer 
in Lowell Street, which was a large, flat-bottomed wooden scow, 
was too low to be intercepted. It Avas accordingly abandoned, 
and all branch sewers and house-drains were connected directly 
with the intercepting sewer. To facilitate making these connec- 
tions the intercepting sewer was located exactly on the line of 
the old sewer. The top planks of the latter were removed, but 
its side planks were retained, and the new sewer, with its width 
reduced to two feet eight inches, was built between them. The 
flow of sewage was maintained during construction through 
channels above the floor of the old sewer and below the bottom 
of the new one, which was supported on timber saddles (Fig. 
14, Plate VIII.). 

Causeway Street is one of the most crowded thoroughfares of 
the city. It contains two lines of track for horse-cars and one 
for freight-cars. On its north-westerly side are the depots of 
three railroads, with no outlet for their passengers and freight 
except into this street. The tracks of another railroad cross 
the street. The territory traversed by the street is all made 
land, consisting of loose materials filled upon a mud bottom. 

It was with some apprehension of trouble that work was 
begun on this section. The most difiicult feature of the work 
was so to conduct it that travel should not be seriously impeded. 



52 MAIN DRAINAGE WOEKS. 

Owing to the skill and care of the superintendent and his subor- 
dinates, and to the appliances used for handling the earth and 
other material, the sewer in this street was built within four 
months, without closing any portion of the street to travel, and 
with the minimum of inconvenience to the public. At street- 
crossings and entrances to railroad-yards, work was carried on 
below timber platforms, or bridges, without encroaching upon 
the street surface. In crossing the Boston and Maine Railroad 
tracks, the excavating apparatus, with its steam-engine, was so 
elevated as to leave head-room for the passage of trains. 
Plate IX. is from a photograph taken at this point. 

As a precaution, where the foundation seemed insecure, the 
vertical diameter of the sewer was increased by six inches, so 
that, should slight unequal settlements occur, the invert may be 
brought to its true grade without lessening the desired size of 
the sewer. For about 76 feet, to avoid interfering with the 
street surface, the intercepting sewer was built entirely within 
an abandoned common sewer (Fig. 15, Plate VIII. ). At the 
upper end of the intercepting sewer, at Prince street, the grade 
of the invert is about four feet above mean low water, which is 
the highest elevation of any portion of the Main Drainage Sys- 
tem. At this point a direct connection with the harbor has 
been made, which is closed under ordinary circumstances by a 
three feet square penstock gate. By opening this gate at the 
time of high tide the sewer can be thoroughly flushed. 



Plate IX. 




PUMPING-STATION. 53 



CHAPTER VII. 

PUMPING-STATION. 

As before stated, and as shown by the phm (Plate V.), the 
Main Drainage Pumping-Station is situated at Old Harbor 
Point, on the sea-coast in Dorchester, about a mile from any 
dwelling. In flowing by gravitation to this point the sewage 
has descended, so that it is from 11 to 14 feet below the eleva- 
tion of low tide. To reach its final destination it must flow 
about 21 miles further, to Moon Island, and be high enough, 
after arriving at the storage reservoir on the Island, to be let 
out into the harbor at the time of high water. That it may do 
this it must first be raised by an average lift of 35 feet. 

The essential parts of the pumping-station are : a filth- 
hoist (so called), where the sewage passes through screens to 
remove solid matters which might clog the pumps ; pump-wells, 
into one or more of which the sewage can be turned ; pumping- 
engines to raise the sewage ; an engine-house to protect the 
engines ; a boiler-house, containing boilers to furnish steam 
power; a coal-house to store a supply of coal, and a dock and 
wharf, where vessels bringing coal can be unloaded. The posi- 
tion and arrangement of these principal structures and apparatus 
are shown on Plate X. 

The filth-hoist is a solid masonry structure, extending from 
the surface of the ground down to below the main sewer. Its 
inside dimensions are 25 X 32 feet, and its exterior walls are from 
4 to 5 feet thick, founded upon two courses of 10-inch timber. 
In excavating for building the filth-hoist, the ground, which con- 
sisted of wet sand, was held hy round wooden curbs. The 
total depth of excavation was 35 feet, and the upper 12 feet 
were dug without bracing to natural slopes. Below this, three 
tiers of 4-inch sheet planks, each 10 feet long, were driven, and 
were braced by circular ribs. The three curbs were 71.61 
and 57 feet in diameter, respectively, and by this method of 



54 MAIX DRAINAGE WORKS. 

bracing an unobstructed space was secured for building the 
masonry. 

As will be seen by referring to Plates X. and XI., the main 
sewer passes through the westerly foundation wall of the filth- 
hoist. At this point the sewer has granite voussoirs cut to 
form a bell shaped opening. Facing the sewer opening are two 
gate-openings, protected by iron penstock gates, 7 X 6.5 feet 
each, through one or both of which the sewage flows. These 
gates are counterbalanced and are moved by hydraulic pressure 
derived from a city water-pipe. The pressure is sufiicient to 
move them freely ; but to start them when down, with a head of 
water against them, a hydraulic force pump is added, by means 
of which the initial pressure can be increased to any extent re- 
quired. Beyond the gates the structure is divided longitudinally 
by a brick partition wall into two parts, in each of which are 
chambers containing two independent cages, or screens, one 
before the other. The cages are rectangular in shape 7 feet 8 
inches high, 7 feet 31- inches wide, and 3 feet 4^ inches deep. 
They are shown in detail by Fig. 4 on Plate XIV. Their 
backs, sides, and tops are formed of |-inch round iron rods, 
with 1-inch spaces between them. The cages are counterbal- 
anced, and are raised and lowered by four small steam-engines. 
The steam for these engines, as well as for heating purposes, 
is brought underground from the boiler house. The super- 
structure of the filth-hoist is 30 X 37 feet outside dimensions, 
and is built of quarry-faced granite dimension-stones, lined 
inside with brick. A view of the outside of this building is 
shown at the left side of Plate XVII. Plate XII. is from a 
photograph taken inside of the filth-hoist when one pair of 
cages was raised. It gives a general idea of the arrangement 
of the hoisting machinery. 

After passing through the cages the sewage is conveyed by 
one or both of two sewers, nine feet in diameter each, to galleries 
on either side of the engine-house substructure, from which 
galleries it can be admitted through gate openings to one or 
more pump-wells, situated between the galleries. The bottom 
of the pump-wells is 10.5 feet below low-tide level and 36.5 



MAIN SEWER 







CITY OF BOSTON 

MAIN DRAINAGE WORKS 

PUMPING STATION. 

ip 20 30 +0 50 60 70 




CITY OF BOSTON. 
MAIN DRAINAGE. 

SECTION^L VIEW OF 

FILTH HOIST AND ENGINE HOUSE 




S( noN THROUdH 
FILTH HOIST AND CAGFS 



J] nf. 




SECTION THROUGH PIPE CHMllBER 



'SHiXSSi a S ^S 



SECTION THROUGH PUMP WELLS 



SECTION THROU&H SIDE GALLERY. 



PUMPING-STATION. 55 

feet below the surface of the ground. From the wells the sew- 
age is raised by the pumps to its required elevation. 

The complete design of the pimiping-station, as indicated on 
Plate X., consists of an engine-house, two boiler-houses and a 
coal-house, so arranged as to include a court-yard. The build- 
ings are to be of dimensions suitable for containing eight pump- 
ing-engines with their boilers and other appurtenances. Only 
the portions of these buildings shown on the plan by full lines 
are at present constructed or needed. 

The foundation walls of the engine-house aggregate about 
350 feet in length. They are 37.5 feet in height and nine feet 
thick at the bottom, where they rest on a timber platform, 24 
inches thick, which also extends under the whole building, and 
furnishes a foundation course for the piers which support the 
engines. To build the exterior walls trenches 16 feet wide 
were first excavated. A core of earth was left inside these 
trenches until the walls had been erected, when it was removed 
to make place for the pump-wells and engine foundations. The 
exterior retaining and foundation walls were built of granite, 
and, although called rubble masonry, yet, owing to the sizes 
and shapes of stones used and the care taken in selecting and 
laying them, the work more nearly resembles a fair quality of 
roughly coursed block-stone work. 

The pump-wells and engine foundations are built chiefly of 
brick, but contain in addition about 300 dressed granite stones. 
These stones are used for copings, as bearings for holding-down 
bolts, for lining gate and other openings, etc., etc. There are 
nine iron gates, with suitable attachments and shafting, operated 
by two small steam-engines. Eight of these gates, 4 feet 91- 
inches by 6 feet 3^ inches each, control the flow of sewage from 
the side galleries into the four pump-wells. Another gate, 4 X 
4 feet square, controls the admission of salt water from the salt- 
water conduit. 

This last-mentioned structure, as shown by the plan (Plate 
X.), is a solid masonry conduit, with its bottom six feet below 
the elevation of low tide, and connects tide-water at the dock 
with one of the engine-house galleries. Its ofiice is to conduct 
salt water to the engine-house for use in the condensers, and 



56 MAIN DRAINAGE WORKS. 

also to furnish an additional supply of water to the pumps for 
flushing or other purposes, whenever the amount of sewage re- 
ceived from the main sewer is insufficient for such purposes. 

As has been stated, the sewage is elevated to heights (de- 
pending at any time upon the depth of sewage in the reservoir) 
which average about 35 feet. 

As the city sewers receive rain-water, and as it is desired to 
take as much of this as possible, especially from certain districts, 
it follows that during short periods of time, when it rains, very 
much greater pumping capacity is needed than is usually suffi- 
cient. There must, therefore, be a pump, or pumps, to run 
continuously, and others to run only when it rains or thaws. 

The chief item of expense in pumping is the cost of fuel. 
For the sake of economy the pumping engines for continuous 
service must do their w^ork with as little consumption of fuel as 
possible, and to accomplish this an expensive machine can be 
aflbrded. For the engines which run only occasionally cheaper 
machines are more economical, the saving in interest on the first 
cost more than compensating for the extra fuel consumed by 
them. The pumping plant of the Boston Main Drainage Works 
includes two expensive high-duty engines and two cheaper lower- 
duty engines. 

The high-duty engines w^ere designed by Mr. E. D. Leavitt, 
Jr., on general specifications prepared by the City Engineer, 
Mr. Davis, They were built by the Quintard Iron Works, of 
New York, and cost about $115,000 each. Apian and elevation 
of one of them is given on Plate XIII. 

As Avill be seen, it is a compound beam and fly-wheel engine, 
working two single-acting plunger-pumps. The steam cylin- 
ders are vertical and inverted, their axes coinciding with those 
of the pumps below them, the pistons of the engines and 
plungers of the pumps being connected in the same line with 
the 6nds of the beam. 

In designing these engines particular attention was given to 
the following conditions : — 

First. The distribution of the weight of the engine so as 
not to produce concentrated pressure on any part of the foun- 
dations. 



Plate 




PUMPING-STATION. 57 

Second. Great strength in the details and combinations of 
the parts, to render the liability of breakage a minimum. 

Third. A proportion of the wearing surfaces such as will 
allow of an uninterrupted running for extended periods, with 
the least wear. 

Fourth. Easy accessibility of all the parts for examination, 
repairs, and renewals. 

Fifth. An adaptation of the pumps and their valves to the 
peculiar duty required of them, i.e., to allow the passage of 
rags, sticks, and such other small bodies as will not be detained 
by the filth-hoist ; and, in addition, a construction which will 
admit of the easy removal of an entire pump or any of its 
parts, without disturbing any important part of an engine. 

Sixth. A high degree of economy in the consumption of 
coal. 

The following are a few of the leading dimensions : — 

Diameter of high-pressure cylinder, 251- inches. 

Diameter of low-pressure cylinder, 52 inches. 

Diameter of plunger, 48 inches. 

Stroke, 9 feet. 

Distance between centres of cylinders, 15 feet 2 inches. 

Eadius of beam to end centres, 8 feet 3 inches. 

Radius of crank, 4 feet. 

Diameter of fly-wheel, 36 feet. 

Weight of fly-wheel, 36 tons. 

Nominal capacity, 25,000,000 gallons a day. 

Speed for capacity, 11 strokes per minute. 

Steam at a pressure of about 100 pounds is admitted from 
the supply-pipe, A (see Plate XIII.), through the side-pipe, B, 
to the steam-chests of the high-pressure cylinder, C. The dis- 
tribution of steam is efi'ected by gridiron slide-valves, having a 
short, horizontal movement imparted by revolving cams, D, 
fixed on a horizontal shaft, E, running along the bases of the 
cylinders, and driven by the crank-shaft through suitable gear- 
ing, F. The steam is cut off by the further revolution of the 
cam. The cut-ofi" is adjustable, and controlled by the gov- 
ernor, G. 

After expanding to the end of the stroke the steam passes 



58 MAIN DRAINAGE WORKS. 

through the exhaust steam-chests to reheaters, H. These are 
cast-iron boxes, each containing about 750 |-inch brass tubes, 
two feet nine inches long. These tubes are filled with high- 
pressure steam, and in circulating about them the working 
steam is thoroughly dried. 

From the reheaters the steam is admitted to the low-pressure 
cylinder, I, where further expansion takes place. Thence it 
passes to the condenser, J, where it is condensed by salt water 
from a rose jet. K is the air-pump, and L the outboard 
delivery-pipe. 

The pumps, M, are hung to heavy girders supporting the 
engines by cast-iron hangers, N. A part or the whole of the 
weight of the pumps can also be supported by the wheels, O, 
resting on very strong cast-iron beams, P, built into the ma- 
sonry on either side of the pump-wells. By disconnecting 
their hangers, the pumps, supported entirely by these wheels, 
can be run back on the beams (which then serve as tracks), 
and can be hoisted out of the pump-wells without interfering 
with the fixed parts of the engine. 

At Q are side galleries, through either of which the sewage 
reaches the gateways, R, leading into the pump-wells. In front 
of these gateways are iron gates, not shown on the plate, which 
admit or exclude the sewage. S S are the plungers. U U are 
man-holes. T is the force-main. The discharge from one 
pump passes through the delivery-chamber of the other. 

The interior construction of the pump is shown by Fig. 1 
on Plate XIV., which is a vertical section through the pump 
under the high-pressure cylinder. The plunger is represented 
as just completing its down stroke. The suction-valves (of 
which there are 36 to each pump) are closed, and the delivery- 
valves (27 in number) are wide open, to permit the discharge 
of the sewage displaced by the plunger. In the other pump, 
at the same moment, the plunger would be completing its up- 
ward stroke, and the action of the valves would be reversed. 

The valves are of somewhat novel construction, and are 
shown by a section of a portion of one of the valve-plates and 
the whole of one valve (Plate XIV., Fig. 2). As will be seen, 
they are simply rubber flaps, f-inch thick, with wrought-iron 



PLAlt XIII. 




nriTjii ummMTajuj wr 



K 4-0 jl 




LEAVITT PUMP 

Fig. I 



WORTHINGTON PUMP 

Fig. 3 



TOP BOTTOM 

FILTH CAGES 

Fig,. 4 



CITY OF BOSTON, 
MAIN DRAINAGE. 

PUMPS AND FILTH CAGEIS. 



PUMPING-STATION. 59 

backs and washer plates, the rubber faces bearing on cast-iron 
seats inclined at an angle of 45°. The valves form their own 
hinges, and open against guards or stops faced with leather. 
The clear opening is 4| x l^l inches. Pieces of board 10 
inches wide and 24 inches long have passed through these valves. 

The ordinary workmg duty of these engines is nearly or 
quite 100,000,000 foot-pounds to each 100 pounds of coal.^ 

The two pumping-engines for storm service were built at the 
Hydraulic Works, Brooklyn, L.I., by the firm of Henry R. 
Worthington, of New York, from their own designs, and cost 
$45,000 each. 

They are of the Worthington duplex, compound, condensing 
type. Each machine consists in reality of two distinct com- 
pound engines coupled together, each engine working a double- 
acting plunger-pump. The capacity of each double engine is 
25,000,000 gallons of sewage a day raised against a total head 
of 43 feet. This requires about twelve double strokes a minute 
and a piston speed of about 115 feet per minute. 

Steam at from 40 to 50 pounds is carried full pressure 
through the stroke of each high-pressure cylinder. Thence it 
passes through reheaters to the adjoining low-pressure or ex- 
pansion cylinders, and is expanded during the reverse stroke. It 
is then admitted to the condenser and condensed by a jet of salt 
water. The steam cylinders are 21 and 36 inches in diameter 
respectively. The}' are steam-jacketed all over and suitably 
coated and lagged. The stroke is four feet. 

The steam-valves are moved by a novel and ingenious con- 
trivance, called by the makers " the hydraulic link." Each 
engine has two small vertical cylinders, in which are plungers 
worked from the air-pump bell-crank. These plungers force 
water forward and backward through pipes leading to a 
cylinder in front of the high-pressure steam-chest. In this 

1 Two duty trials, of 24 hours' duration each, have been made recently of one of the 
Leavitt pumping-engines. These tests were very carefully conducted, and all fuel burned 
under the boiler was charged, no deductions being made for ashes and clinkers. In the 
first trial steam required for the feed-pump was supplied from a separate boiler. Making 
no deduction for this, the duty developed was a little over 125,000,000 foot-pounds for 
each 100 pounds of coal. In the second trial the same boiler supplied steam for the 
pumping-engine and the feed-pump, and the duty developed was about 122,000,000 foot- 
pounds. 



60 MAIN DRAINAGE WORKS. 

cylinder is a piston connected with the main valve-stem of the 
engine, and the pressure imparted by the water alternately to 
opposite sides of the piston, moves the valve-stem and effects 
the steam distribution . 

There are two pumps to each machine. Fig. 3, Plate XIV., 
is a section through the pumps of one engine. Each pump is 
double-acting, being divided transversely in the middle by a 
ring which packs the plunger. The plunger is hollow, 45 
inches in diameter, and has a 4-foot stroke. It displaces its 
bulk of sewage at each stroke in either direction. The positions 
of the valves, suction and delivery chambers are indicated by 
the section. The valves are similar to those of the Leavitt 
engines. 

The engines and pumps are compact, and very conven- 
iently arranged for inspection of all their parts. A fair idea of 
their appearance can be obtained from Plate XV., which is a 
photograph taken inside the engine-house. The guaranteed 
duty of these engines is 60,000,000 pounds of sewage raised 1 
foot high by the consumption of 100 pounds of coal. 

To supply steam for the four engines there are four boilers, 
of a nominal capacity of 250 horse-power each. They were 
built by Kendall & Roberts, of Cambridge, Mass., and cost 
about $9,500 each. 

The boilers are of the horizontal fire-box, tubular form, and 
are made of homogeneous steel , having a tensile strength of not 
less than 60,000 pounds per square inch, an elastic limit of 
37,000 pounds, and an elongation of 30 per cent. The shell is 
j"g-inch, and the tube-sheets are i-inch thick. The length over 
all is 39 feet 10 inches. There are 132 tubes, 3-inch internal 
diameter, 15 feet long. 

Each boiler has two fire-boxes, 31 feet wide, 5 feet high, and 
11 feet long. At the ends of the fire-boxes is a combustion 
chamber four feet long. 

The smoke-flues return into chambers containing flue-heaters, 
composed of 80 seamless brass tubes, 2|- inches in diameter and 
15 feet long;. The heaters are on a level with the boiler-house 
floor, and can be run out from their chambers for cleaning or re- 
pairs. From the heaters the smoke passes by brick flues under 
the floor to the chimney. 



Plate XV. 




Plate XVri 




m 

r; 



0) 
CO 



r : Vl 



% ' :P!i' 



PUMPING-STATlOlSr. 61 

The chimney has a circular flue, 66 inches internal diameter 
and 140 feet high. 

Among the minor engines and pumps appertaining to the 
pumping-station are four engines for raising and lowering the 
filth cages; two engines for moving the gates in the engine- 
house galleries ; two pair of double-acting steam-pumps for 
feeding the boilers ; two double-acting steam-pumps for supply- 
ing salt water to the condensers ; one large steam-pump for 
emptying the pump-Avells and galleries in the engine-house. 

The buildings are warmed by a system of steam-pipes and 
radiators, and are lighted by gas made on the premises from 
gasoline. 

The coal-house is 129 X 59.5 feet in internal dimensions; 
It contains six coal bins, or pockets, with a combined capacity of 
about 2,500 tons of coal. These bins are 23 feet high, and are 
built with solid walls formed of 2X6 inch spruce lumber, 
planed to an even thickness, and spiked flatwise on each other, 
— a method of construction similar to that used in building grain 
elevators. The coal-house floor is made of Portland cement 
concrete. Iron cars are used for bringing coal from the bins 
to the boilers, and suitable tracks, turn-tables, and scales are 
provided. 

To furnish access to the pumping-station for colliers and 
other vessels, a channel one-half of a mile long was dredged out 
to the ship-channel in Dorchester Bay; 380 feet of dock-wall 
and a Avharf 280 feet long were constructed. To facilitate the 
unloading of coal a coal-run, supported on a trestle 27 feet high, 
connects the wharf with the coal-house, and extends over the 
tops of the bins within the house. 

Above their foundations all buildings at the puniping-station 
were designed and built by the City Architect's Department. 
A front view of the main building is given bv Plate XVI 
(frontispiece) , and a side view by Plate XVII.. This building 
cost about $300,000. 



62 MAIN DRAINAGE WORKS. 



CHAPTER YIII. 



OUTFALL SEWER. 



The sewage is pumped through 48-iiich iron force mains 
(Plates X. and XL) into what is called the pipe-chamber. At 
this point the sewage reaches its greatest elevation, and is high 
enough to flow into the reservoir at Moon Island. The pipe- 
chamber is a granite "masonry structure, 51 feet long inside, 
resting on a foundation bed of concrete, 24 inches thick. 
The walls are 21 feet high, from 4 to 7.5 feet thick, and contain 
more than 100 dressed stones. The force mains from the four 
pumps already provided pass through the westerly wall of the 
pipe-chamber, and four more short sections of 48-inch pipes 
are also built into that wall, to connect finally with the four 
additional pumps, which it is expected may be needed in the 
future. 

From the pipe-chamber the sewage passes into what are 
called the deposit sewers, and through them flows nearly a 
quarter of a mile to the west shaft of the tunnel under Dor- 
chester Bay. These sewers are supported and protected by a,, 
gravel pier, or embankment, built from the original shore line 
at the engine-house out to, and including, the tunnel shaft. 
Plate XVIIl. gives a general view of this pier from its outer 
end. The picture is a reproduction of a photograph taken 
during the winter when the bay was frozen over. A cross- 
section of this pier is shown by Fig. 5, Plate XIX. It is 
built of gravel, which was mostly dredged from the harbor. 
On its northerly or most exposed side the pier is protected by 
a rip-rap embankment, ballasted with broken stones and oyster- 
shells. The southerly slope is ballasted and paved with stone, 
and the easterly end of the pier is protected by a retaining- 
wall (Fig. 4) of cut-stone masonry, laid in mortar and 
backed with concrete, the whole resting on a pile foundation. 
In all there Avere used in building this pier about 41,000 tons 



Plate XVIII. 



c 



M 



\ 



OUTFALL SEWER. 63 

of rip-rap, 16,000 yards of ballast, 120,000 yards of gravel, 
600 yards of dimension stone, and 650 piles. The pier was 
built by contract, and its total cost, excluding that of the sewer, 
was $142,064.97. 

The general character of the deposit sewers is shown by 
Fig. 7. As will be seen they consist of a monolithic struct- 
ure of concrete, forming two conduits, each 16 feet high and 8 
feet wide. This height is necessary to accommodate the daily 
variations in the elevations of the surface of the sewage due to fill- 
ing and emptying of the reservoir at Moon Island. The sewers 
are dammed at their lower ends to maintain a depth of from 8 
to 10 feet, in order that the velocity of flow through them maybe 
very sluggish, so that any suspended matters may be deposited 
here before reaching the tunnel. They are provided with gates 
and grooves for stop-planks, so that the sewage can be turned 
through either or both sewers, and either can be entirely emp- 
tied if necessary. 

The whole structure contains about 10 cubic yards of con- 
crete to the lineal foot, or over 12,000 yards in all. The 
bottom portion up to the straight walls is formed of Rosenclale 
cement, sand, and stone, in the proportion of each, respect- 
ively, of 1, 2 and 5. Al)ove this elevation, for the outer side 
walls, the same proportion is maintained ; but the cement used 
was a mixture of 1 part Portland and 2 parts Rosendale. 
For the concrete forming the centre wall and top arches only 
Portland cement was used. The best Rosendale and very fine 
ground Portland cement were procured for the work. The 
sand was screened on the spot from the gravel forming the pier, 
and a portion of the stone was obtained in a like manner. A 
still larger proportion of the stone came from the tunnel exca- 
vation, being brought in lighters from the middle shaft and 
passed through a stone-crusher. Machine concrete mixers 
were used, into which the cement, sand, and stones, in proper 
proportions, were continuously shovelled. 

The concrete was rammed thoroughly in 6-inch courses. 
Long sticks of timber were embedded in each layer of concrete 
while it was being rammed mto place, and were removed after 
it had set, and before the next layer was added. The spaces 



64 MAIN DRAINAGE WORKS. 

occupied by the sticks formed grooves, into which the succeeding 
layers bonded. In cutting through one side of this structure six 
months after its completion the whole mass was found to be 
perfectly homogeneous, and lines of demarcation between the 
different layers could not be detected. 

The bottoms of the sewers are lined with one layer of hard- 
burned bricks to resist erosion when the sewers are cleaned. 
The sides are plastered with a i-incli coat of Portland cement 
mortar. The arches are of long radius and but 13 inches thick. 
As they were to be loaded at once, they were tied, as shown, by 
1^-inch wrought-iron rods, spaced five feet apart. Brick man- 
holes were built at intervals of 300 feet. 

Comparatively heavy matters, such as gravel and sand, settle 
almost at once at the west end of the deposit sewers. Lighter 
mattei s travel a little further ; but only a very light semi-fluid 
precipitate is ever found at the easterly end of the sewers, near 
the shaft. 

The best way to clean out this deposit was long considered, 
and the following plan was finally adopted. A large wooden 
tank was built near the end of the pier, just outside of its 
southerly slope, about 120 feet distant from the sewers (Figs. 
3, 5, and 6, Plate XIX.). It is supported on piles, its floor 
being three feet above high water and one foot lower than the bot- 
toms of the sewers. One end of this tank is connected with the 
deposit sewers by two 6-inch iron pipes, the other end is con- 
nected with the chamber about the tunnel-shaft by a 12-inch 
pipe. By means of stop-planks the surface of water is made to 
stand about three feet higher in the deposit sewers than it does 
in the shaft-chamber. Circulation is thus established from the 
deposit sew^ers through the 6-inch pipes into the tank, and 
thence through the 12-inch pipe to the shaft, and a part of the 
sewage goes to the tunnel through this by-pass. 

The 6-inch pipes' leave the deposit sewers near their bot- 
toms, and the sewage which enters the pipes draws sludge along 
with it and again deposits it in the still water of the tank. The 
tank is 10 feet wide, 15 feet high, and 50 feet long, and will 
hold about 150 yards of sludge. It has on its seaward side 
three gate-openings, terminating in cast-iron nozzles, 12 inches 



SECTIONAL PLAN ON LINES E.F.GH K.L. 




CITY or BOSTON 
MAIN DRAINAGE 
OUTFALL SEWER 



CHAMBER CONNECTING DEPOSIT SEWERS 
WITH WEST SHAFT OF TUNNEL 





TRANSVERSE SECTION OF DEPOSIT SEWERS 

AND END VIEW OF SCRAPER. 

riG.7 



LONG, SECTION OF DEPOSIT SEWER 

SHOWING SCRAPER . 

FIG. 8 



OUTFALL SEWER. 65 

in diameter. When the tank is full of sludge a scow is laid 
alongside it, and the nozzles are connected with the interior of 
the scow by means of canvas tubes. The gates are then opened, 
and the shidge flows from the tank into the scow. 

In order to draw down to the 6-inch pipes the sludge which 
has been deposited at the upper ends of the deposit sewers 
scrapers are used. These consist of floating rafts (Figs. 7 and 
8, Plate XIX.), made of 12-inch hollow iron tubes, to the bot- 
toms of which are hung wooden aprons, a little less wide than 
the sewers. The aprons are weighted so that their lower edges, 
which are provided with broad iron teeth, sink somewhat into 
the sludare. The current in the sewers carries the whole 
apparatus down stream, and the sludge is scraped and flushed 
before it. 

The deposit sewers connect with the tunnel shaft at a masonry 
chamber built about the latter (Figs. 1 and 2, Plate XIX.). 
At the ends of the sewers are placed gates 7X8 feet in size. 
These gates maintain a depth of eight or more feet in the sewers. 
They are so arranged that on tripping a latch they can swing 
open and empty suddenly the liquid contents of the sewers into 
the tunnel, producing temporarily a strong flushing velocity. 
Immediately about the shaft is a wrought-iron cage , to prevent 
any bulky object which may fall into the sewers from reaching 
the tunnel. 

The shaft chamber is encircled by two 6|-feet " waste sewers," 
into which the deposit sewers can overflow above waste weirs, 
or with which they can directly connect instead of discharging 
into the tunnel. The waste sewers unite just east of the shaft- 
chamber and pass to an outlet built through the sea-wall at the 
end of the pier. Should the tunnel ever be emptied for inspec- 
tion sewage can temporarily be pumped into Dorchester Bay 
through this outlet. Above the shaft chamber is a brick gate- 
house of ornamental design, built by the City Architect. 

The second section of outfall sewer comprises the tunnel 
under Dorchester Bay. Exploratory borings made on the 
tunnel line during the preliminary survey showed that the sur- 
face of bed rock was but little below the bottom of the harbor, 
from Squantum to about the middle of the bay. From that 



6Q MAIN DRAINAGE WORKS. 

point westwardly towards Old Harbor Point the rock dipped 
rapidly, so that under the pumping-station its surface is 214 
feet below the surface of the ground. The surface of the rock 
is somewhat shaken, and immediately above it is a water-bearing 
stratum of sand, gravel, and boulders. Above this, clay extends 
nearly to the harbor bottom, which is composed of a bed of mud 
of. varying thickness. 

The clay is of uniform character, and contains occasional 
veins and pockets of sand. Using reasonable precautions a 
tunnel could be safely and expeditiously built in it. The per- 
vious stratum over the rock and the demoralized upper portion 
of the rock itself were not at all favorable for tunnelling opera- 
tions, and could only have been penetrated with extreme pre- 
caution and a considerable chance of failure. The rock itself 
was well adapted for tunnelling. It consists of a succession of 
clay-slates and conglomerates, and belongs to the series known 
as the Roxbury "pudding-stone" beds. 

When the trough in which these beds lie was formed they 
were subjected to great pressures, which crumpled and tilted 
them, and produced many faults, fissures, and joint planes. 
The fissures were filled solidly from below, and few shrinkage 
seams were found sufficiently open for the passage of water 
from above. The existence of the joint planes, especially in 
the clay-slates, greatly facilitated the breaking and removal of 
the rock. 

As at first designed, the tunnel was to start from a shaft 100 
feet deep at Old Harbor Point and be built in the clay for about 
2,100 feet, when it would enter the rock and continue in it to 
its end, at Squantum. Further consideration of the difficulty 
and possible danger of passing gradually from soft ground into 
rock, and of tunnelling for several hundred feet wholly or 
partly through very wet and loose material, led to locating the 
west shaft at such a distance from the shore that rock could be 
reached at a practicable depth and the tunnel could be safely 
built wholly within it. 

The average elevation of the tunnel is 142 feet below low 
water (Plate XX., Fig. 1). The total length through which 
the sewage flows is 7,160 feet. Of this distance 149 feet is in 



OUTFALL SEWER. 67 

the west shaft, 6,088 feet is nearly horizontal between the west 
and east shafts, and 923 feet is in the inclined portion leading 
from the bottom of the east shaft to the end of the tunnel, on 
Squantmn Neck. 

To fticilitate construction there were three working shafts 
about 3,000 feet apart. 

The tunnel was built under a contract which was drawn with 
sreat care. The contractor was first to build, in accordance with 
plans furnished, three timber bulkheads, or piers, to protect 
the shafts. Inside of these bulkheads he was to sink iron 
cylinders, constituting the upper portions of the shafts. These 
cylinders were paid for by the lineal foot, and the contractor 
was permitted and required to build as much of the shafts as 
possible in this way, loading and forcing the iron to the greatest 
attainable depth. Below the cylinders the shafts could be ex- 
cavated of any desired size and shape. The tunnel, also, could 
be excavated of any size, provided that both it and the shafts 
were finally lined with a 7^- feet diameter circular shell of brick 
work, 12 inches thick, backed with brick or concrete masonry 
to the sides of the excavation. Bricks and cement were to be 
purchased from the city at stipulated prices. The completed 
tunnel was to be paid for at the proposed price per lineal 
foot. 

Great stress was laid upon the precautions to be adopted to 
prevent delay and damage arising from an influx of water into 
the shafts. Appliances to "control any such influx were to be 
kept in readiness, and, should these prove insuflicient, the ple- 
num process, or use of compressed air within the shafts, was to 
be resorted to. 

The work was let Oct. 29, 1879, and the contractor at once 
proceeded with the building of the bulkheads. These were alike, 
and consisted (Fig. 2, Plate XX.) of wooden boxes 20 feet 
square inside, formed of large oak piles, driven two feet on 
centres, capped and braced with hard-pine sticks, and tied 
diagonally at the corners with 2-inch iron bolts.. The boxes 
were lined inside with 4-inch tongued and grooved sheet-piling, 
and the spaces between the sheet planks and cylinders were 
filled with puddled clay. The tops of the bulkheads were eight 



68 MAIN DEAINAGE WORKS. 

feet above mean high water, and the contract price for them 
was $2,500 apiece. 

Having completed the bulkheads the cylinders were smik 
inside of them. Each cylinder (Plate XX., Fig. 3) consisted 
of a circular shell of cast iron, 9.5 feet inside diameter, with 1| 
inches thickness of metal. They were cast in sections, five 
feet long, and united by l^-inch bolts passing through inside 
flano-es. The abuttins; ends of the sections were faced, and the 
bolt-holes, of which there were 30 in each flange, were drilled 
to a templet, so that the sections were interchangeable. The 
bottom section of each cylinder had its lower 10 inches cham- 
fered off to a cutting edge. The contract price for furnishing 
the cylinders, which weighed a ton to the foot, was $88 per 
lineal foot. 

At the east and middle shafts the cylinders were easily 
forced down to the rock, at depths below the surface of the 
ground of 21 and 38 feet respectively. It was known that it 
would be impossible to drive the cylinder at the west shaft down 
to the rock. By weighting it with about 180 tons of iron dross 
it was finally forced into the clay to a depth of about 60 feet 
below the harbor bottom. Below this point a square shaft, 10 
feet across, was excavated with great ease in plastic clay, pene- 
trated with occasional veins of fine sand, but yielding little 
water (Plate XXL, Fig. 1). 

The timbering of this shaft was hastily and, as it seemed to 
the engineers, carelessly clone, the timbers being insecurely 
braced, and cavities being continually left outside of them. 
The engineer in charge consulted the City Engineer as to the 
possibility of requiring greater caution in doing this work. It 
was decided, however, that the spirit of the contract would not 
permit interference with the contractor's method of building this 
portion of the shaft. 

No difficulty was encountered until the rock was neared, when 
water, to the amount of 10,000 gallons an hour, broke in from 
below, and, no provision having been made for its removal, filled 
the shaft. Pumps were obtained and the shaft emptied, when 
it was found that the water, following the cavities behind the 
lining, had softened the clay and loosened the timbering, so that 



CITY OF BOSTON - MAIN DRAINAGE. 
OUTFALL SEWER. DORCHESTER BAY TUNNEL. 








LONGITUDINAL SECTION OF TUNNEL 




SIDE ELEVATION 



HALF SECTION HALF PLAN 



BULKHEADS ABOUT SHAFTS 
FIG e. 




IRON CYLINDERS 
FIG. 3. 



OUTFALL SEWER. 69 

it was in very bad shape. About 40 feet in length of the shaft 
had to be retimbered, the old sticks being cut out with chisels. 

This work was not accomplished without great difficulty. 
Although the quantity of water to be dealt with was not great, 
the cramped dimensions of the shaft aiforded little room for 
the pumps, or opportunity for supporting them. When these 
gave out, as they occasionally did, the shaft filled with water, 
causing considerable delay and damage. To counteract a 
downward pressure exerted by the clay upon the timber lining, 
a portion of it was suspended by heavy wire cables from the 
cylinder above. During all these operations the whole shaft, 
including timbered portion and cylinder, also the surrounding 
clay and the bulkhead above, were in motion, settling slowly. 
By the time the shaft had been firmly founded on the rock the 
pile bulkhead had settled nearly five feet. 

After the shafts had been sunk and secured the excavation 
for the tunnel proper encountered no serious obstacles. The 
work was carried on at six different headings. From the mid- 
dle and east shafts work progressed in both directions, and 
from the west shaft and the upper end of the incline at Squan- 
tum single headings were driven. 

The incline descends one foot vertical in six feet horizontal. 
At this pomt a heading was driven downwards for about 400 
feet and then stopped, owing to the difiiculty and expense of 
removing the water which accumulated at its face. At the 
middle shaft power drills, driven by compressed air, were used, 
and at other points hand drilling was employed. 

There was not much difference as to either ex[)ense or rapid- 
ity in the two methods. By either an advance of four feet was 
considered a fair day's work. The chief merit of the air drills 
seemed to be that they were not demoralized by pay-days, and 
never struck for higher wages. 

Various forms of nitro-glycerine were employed as explo- 
sives, and no casuality occurred through its use. The average 
diameter of the excavation (Plate XXL, Fig. 2) was about 10.2 
feet, approximating very well to the 9.5 feet required to receive 
the final brick lining. The excavated material, amounting to 
about 25,000 yards in all, was deposited ai'ound the shafts, 



70 MAIN DEAINAGE WORKS. 

forminor small islands. The maximum amount of water leakino^ 
into the tunnel at any time was 64,000 gallons an hour. 

The headings between the east and middle shafts met Jan. 
24, 1882, and those between the middle and west shafts met 
June 22, 1882. Lining the excavation with brick-work began 
March 10, of the same year. Projecting portions of rock were 
first trimmed off, so that room for a solid brick lining, 12 inches 
thick, laid in courses, could always be obtained. Eosendale 
cement mortar was used, composed of equal parts of cement and 
sand. All spaces between the coursed lining and the sides of 
the rock excavation were solidly filled with masonry, principally 
brick-work. The amount of backing thus required to make solid 
work averaged about three-fourths of a yard per lineal foot. Fig. 
5, Plate XXI. is a section of the tunnel at the point of maximum 
size where the largest amount of backing was needed. In all, 
7,416,000 bricks and 23,377 barrels of cement were used in 
building the tunnel. About 12 lineal feet of tunnel could be 
completely lined in 24 hours, at any one point. 

In putting in the lining, iron pipes were built into the brick- 
work (Plate XXI., Fig. 3) wherever necessary to furnish out- 
lets for the water, which would otherwise have washed out the 
mortar. Some of these pipes were afterwards plugged, but 
most of them were left open. The pressure of the water when 
kept from entering the tunnel was about 64 pounds per square 
inch, and it was not practicable to build brick masonry which 
should be water-tight under such a pressure. When the tunnel 
is in use the pressure of the sewage within it is somewhat 
o-reater than that of the water outside the lining, so that leak- 
age would be outwards, except that the particles in the sewage 
will quickly clog any fine holes in the masonry. 

Some experiments were made to determine to what extent 
the porosity of the brick lining could be destroyed by silting 
from without. An iron pipe extending up the east shaft was 
connected at its lower end with the pipes built through the 
brick-work, and water containing clay, cement, and fine sawdust 
was forced outside the lining. 

The finer portions of these materials came through holes and 
cracks in the joints of the masonry. Fine holes were thus filled 



PLATE XXI. 




BOSTON MAIN DRAINAGE. 
DORCHESTER BAY TUNNEL 





AVERAGE SECTION OF TUNNEL 



OUTFALL SEWER. 71 

and leakage through them prevented. Holes of apparent size 
were calked with lead. By these means the leakage into the 
inclined portion of the tunnel was reduced from 2,200 to 500 
gallons an hour. It was not, however, considered practicable, 
except at considerable expense, thus materially to reduce the 
leakage ; and, in view of its slight importance in respect to the 
use of the tunnel, the attempt was given up. 

The west shaft was lined with brick-work. The middle shaft 
was abandoned, its only purpose having been to facilitate con- 
struction. The arch of the tunnel where it passes under this 
shaft was made three feet thick, and a counter arch, two feet 
thick, was built over it to resist upward pressure, in case the 
tunnel should ever be filled suddenly after having been pumped 
out for any purpose. The shaft itself was not filled up, but 
near its top an arch was built to prevent any heavy substance 
ever falling down it (Plate XXL, Fig. 4). 

The east shaft was lined throughout. A large Cornish min- 
ing pump has been purchased, and is to be set up at this shaft 
as soon as certain legal complications affecting the city's right 
to the location shall have been settled. This pump will have 
sufficient capacity to empty the tunnel, including the leakage 
into it, within 48 hours. It is to be set up as a precaution, as 
it did not seem wise to leave any portion of the work entirely 
inaccessible. Should the tunnel ever be pumped out at this 
point it would first be filled with salt water, so that no possible 
nuisance could be created by the operation. 

A sump, or well-hole, seven feet deep, from which to pump, was 
built under the east shaft (Plate XXL, Figs. 6 and 7). Pairs 
of cast-iron beams were built into the lining from the bottom of 
the shaft to its top. To these are bolted two sets of upright 
iron guides. One set of these will hold in place the rising col- 
umn of the pump, and the other set will serve for an elevator, 
to be used in visiting the pump and tunnel. 

It was thought that should deposits occur in the tunnel, they 
might be removed by passing a ball, somewhat smaller in diame- 
ter than the tunnel, through it. To guide this ball past the east 
shaft, four wooden guides, suitably shaped, were built in place 



72 MAIN DRAINAGE WORKS. 

at that point. Appliances for handling such a ball were pro- 
vided at the two ends .of the tunnel. 

The tunnel was practically finished July 25, 1883. Its com- 
pletion required the removal of all elevators, pumps, pipes, etc., 
used in constructing it and the closing up with masonry of all 
pump-wells, except the one before referred to, at the east shaft. 
This work was attended with considerable anxiety, as the pump- 
ing capacity of the three shafts was but little more than was 
necessary to control the leakage of water. 

The finishing and remoJrals were successfully accomplished 
by systematic and careful management. The last shaft to be 
cleared was the east shaft, and it was necessary to isolate it from 
the rest of the tunnel by a timber bulkhead, behind which the 
water entering the tunnel accumulated while the pumps and 
their appurtenances were being removed. By the time the shaft 
was clear the tunnel was two-thirds full of water. The bulk- 
head was so made and fastened in place that on tripping a catch 
it fell apart into three pieces, which were hauled out by ropes 
attached to them. 

The contract price for the shafts, exclusive of iron, was $86, 
and for the tunnel $48, per lineal foot. The contractor lost 
money, and after about two years abandoned his contract, 
alleging his inability to complete it for the prices therein stipu- 
lated. He otfered to complete the tunnel for prices about one- 
half greater than those before agreed upon. Considering that 
he had the requisite plant on hand, and had acquired valuable 
experience concerning the character of the work and the best 
methods of conducting it ; and also considering that the bad 
reputation which the tunnel would have, if abandoned, would 
probably deter other bidders from making reasonable offers, — 
it was thought for the best interests of the city to make a second 
agreement with the same contractor, which was accordingly 
done. The final total cost of this section of work, including 
inspection and all incidental expenses, was $658,489.97, amount- 
ing to about $92 per lineal foot of tunnel. 

The methods of alignment employed by the engineers in 
immediate charge of the tunnel, while not entirely novel, may 
be of sufficient interest to be mentioned. The west shaft was 



OUTFALL SEWER. 73 

out of plumb, so that by dropping plumb-lines a base only 5.7 
feet long could be obtained. This by itself would have made accu- 
rate alignments tedious. Moreover, each shaft contained about 
six lines of steam, water, and exhaust pipes, besides guides for 
its cage. As the shafts were 160 feet deep, were dripping with 
water, and had currents of air produced by hot pipes and leak- 
ages of steam, it would have been necessary to protect plumb- 
lines by tubes for the whole depth of the shafts. At the west 
shaft it would have been impracticable to use such tubes, as 
they would have been directly in the way of the cage. 

On account of the difficulty attending the use of plumb-bobs, 
the line was transferred below by means of a large transit 
instrument set up at the top of the shaft. The telescope, 
havino-been set on line, was directed down the shaft, and a fine 
string, extendino; about 100 feet into the tunnel, was rano-ed in 
line. The string was illuminated by light reflected from a 
mirror placed beneath it. Communication between the engi- 
neers at the top and at the bottom of the shaft was maintained 
by the use of hand telephones. 

At first the line within the tunnel was produced by means of 
instruments ; but, as the headings advanced, the ventilation be- 
came so bad that at times a light distant only 75 feet could not 
be seen. The line was then produced by stretching a stout 
linen thread, about 600 feet long, and taking offsets to it. The 
success attending these methods of alignment was very gratify- 
ing, as the headings met without appreciable error. 

Should a "high-level" intercepting sewer ever be built to 
conduct a part of the city's sewage, by gravitation, to Moon 
Island, it is expected that it will join the present system, on 
Squantum Neck, at the further end of the tunnel. To provide 
for such a contingency the present outfall sewer is much 
increased in size beyond this point, being 11 X 12 feet in dimen- 
sions. 

The connection between the tunnel and the outfall sewer 
beyond is made in an underground chamber (Fig. 1, Plate 
XXII.). From this chamber, also, branches a short section of 
sewer with which to connect the future "high-level" system, 
should it ever be built. The chamber is covered by a substan- 



74 MAIN DRAINAGE WORKS. 

tial brick building, and a flight of stone steps leads to a land- 
ing in the sewer below. The floor of the building is supported 
on iron beams, and can be taken up so that boats can be low- 
ered into the sewer, and a flushing-ball can be taken out. To 
facilitate these operations the roof was made exceptionally 
strong, and from it was hung an iron track supporting a traveller 
and blocks capable of lifting five tons. 

As far as the easterly shore of Squantum Neck the outfall 
sewer (Figs. 4, 6 and 7, Plate XXII.) was built partly in rock 
excavation and partly in embankment. In the latter case the 
sewer is tied through its arch by l|-inch iron rods, 8 feet apart. 
These are designed to prevent the possibility of distortion, due 
to movements of the bank below the sewer, or on the side of 
it. The ties will, doubtless, rust out in time, but not before 
the need of them is over. 

From Squantum to Moon Island an embankment (Plate 
XXII., Fig. 5) was built. It is a mile long, from 20 to 30 
feet high, 20 feet wide on top, and about 120 feet at its base. 
Up to the established sewer grade the embankment was chiefly 
built of dredged gravel, and, above that height, of material ob- 
tained in excavating for the reservoir on Moon Island. Up to 
six feet above high water the slopes are protected by ballast 
and rip-rap. In all, about 141,000 yards of dredged gravel, 
260,000 yards of other earth, 20,000 yards of ballast, and 
54,000 tons of rip-rap were used in building the embankment. 

About 4,100 feet in length of the site of the embankment 
consisted of beds of mud, from 10 to 40 feet deep. It was 
hoped that the filling would displace this mud and reach hard 
bottom. It did so at a few points, but not as a rule. As an 
experiment an attempt was made to assist this action by explod- 
ing dynamite cartridges under the embankment. No results of 
importance were thus obtained ; but the experiment demon- 
strated the resistance of the mud to displacement and the prob- 
able future stability of the embankment. 

Broad plates, with vertical iron rods fastened to them, were 
placed near the bottom of the bank on its centre line, and the 
amount of settlement as filling progressed was noted. After 
the bank was completed slight settlements still continued. It 



Plate XXH. 



CONNECTION CrfAMBER. 




BOSTON MAIN DRAINAGE 
OUTFALL SEWER 



Fig.7 



OUTFALL SEWER. 75 

was, therefore, thought more prudent to postpone building a 
masonry structure for some years, or until there was assurance 
that the bank had assumed a condition of permanent stability. 

For temporary use therefore, a wooden flume (Fig. 2, Plate 
XXII.) was substituted for the masonry sewer at this point. 
The flume is located outside of the embankment, and 200 feet 
south of it. It is supported on piles, in bents ten feet apart, 
generally with three piles to the bent. In all, about 1,300 piles 
were driven, some of them to a depth of 40 feet. 

The flume proper consists of a square wooden box, six feet in 
diameter. Its sides, top, and bottom are formed of Canadian 
white pine, three inches thick, planed all over. The planks, 
except a single filling in course on each side, are all of even 
width, so as to allow breaking joint. They are grooved on 
each edge, and also on their ends (Fig. 3), for 1^ X |-inch 
tongues. The box is surrounded, at intervals of three feet four 
inches, by square frames of spruce timber, mortised together and 
tightened with bolts and wedo-es. 

The pine and spruce were fitted at the mills, so as to go to- 
gether with the least possible fui^ther fitting. As much as 250 
feet in length was assembled and spiked in a single day. After 
completion the whole was given two coats of cheap paint. The 
total cost of the flume was a little under $10 per lineal foot. 

From the further end of the flume the outfall sewer (Fig. 
6) extends up to and in front of the storage reservoir. 



76 MAIN DRAINAGE WORKS. 



CHAPTER IX. 



RESERVOIR AND OUTLET. 



Moon Island is distant about a mile from the main land. It 
comprises about 36 acres of upland, surrounded by about 145 
acres of beaches and flats. The easterly end of the island rises 
to an elevation about 100 feet above tide-water. On the west- 
ern or landward side is another smaller area of rising ground, 
about 45 feet high. Between these two portions of high land 
was a valley, crossing the island from north to south, whose 
central portion was but a few feet above the level of high water. 
In this comparatively low land the reservoir is situated. 

Plates XXIII. and XXIV. give views of the reservoir and 
its surroundings, reproduced from photographs. The former 
was taken from the high part of the island just east of the res- 
ervoir. It shows the embankment between Moon Island and 
Squantum, and also the flume, parallel to and south of the 
embankment. Near the centre of the plate the pumping-station 
can be dimly discerned, although partly hidden by a clump of 
trees on Thompson's Island. Plate XXIV. gives a nearer 
view of the reservoir, looking eastward. It shows one basin 
partly filled with sewage. 

The reservoir, as at present built, covers an area of about 
five acres. It is expected that in the future, when the amount of 
sewage to be stored shall have increased, it will be necessary to 
extend and enlarge the reservoir to about double its present 
capacity. The portion already built i^ so located and arranged 
that the contemplated extension can readily be made on the 
south side of the present structure. 

The site for the reservoir was prepared wholly by excavating. 
On the centre line of the valley this excavation was about ten 
feet deep, while on the east and west sides the cutting in places 
was forty feet deep. A drive-way surrounds the reservoir, and 
the banks are sloped back from it. The excavated material 



Plate XXIII. 




Plate XXIV. 






> 

0) 

Oi 
CC 

iu 




EESERVOIR AND OUTLET. 77 

was chiefly hard clay ; but a bed of gravel and sand was found 
near the centre of the valley, which, in places, went 20 feet 
below the reservoir bottom. Part of the reservoir, therefore, 
is founded on clay, and another, smaller part on sand and gravel. 

The earth was dug by steam excavators, and was carried 
away in cars by locomotives. It was used for building the up- 
per portion of the embankment between the island and main 
land. As more earth was needed for this purpose than could 
be supplied from the reservoir excavation a further quantity 
was borrowed from the island in such places and to such lines 
and grades as partly to prepare the site for the proposed future 
extension of the reservoir. In all, about 283,000 cubic yards 
of material were taken from the island, and the contractor's 
price for digging and disposing of it averaged about 59 cents 
per yard. 

The retaining- walls of the reservoir (Fig. 2, PL XXVI.) are 
17.5 feet his^h, and from 6 feet 10 inches to 7 feet 10 inches 
thick at the base. They are classed as rubble-stone masonry 
laid in mortar, and are l)uilt of split and quarry stone mostly 
brought from granite quarries in Maine. On top of the walls 
are large coping-stones with pointed surfaces. The rubble 
stones were laid in somewhat uneven courses. The reservoir is 
divided into four basins, of nearly equal area by three division 
walls (Fig. 3) , built of the same class of masonry as that 
formino- the retainino-vvalls. Eosendale cement mortar, made 
with one part of cement to two of sand, was used in building 
rubble-stone masonry. The contractor's price for this class of 
masonry was $7.47 per cubic yard. 

The floor of the reservoir consists of a bed of concrete, nine 
inches thick (Fig. 6, Plate XXV.). The lower five inches was 
made with Rosendale cement, sand, and pebbles, in the propor- 
tion of one, two, and five parts of each respectively. In the 
upper four inches of concrete, Portland cement was substituted 
for Rosendale. The floor of each basin was shaped into alter- 
nate ridges and gutters. The gutters are paved with bricks set 
on edge. 

Considering the distance of Moon Island from habitations, 
it did not seem that any just cause for complaint would be 



78 MAIN DRAINAGE WORKS. 

occasioned if the reservoir were left uncovered, and, therefore, 
no roof was built over it. But, to provide for any future contin- 
gency which might require it to be covered, foundation blocks 
were built into the floor, on which piers to support a roof can 
hereafter be built, if needed. These foundation blocks are 
.spaced 20 feet apart in one direction, and 30 feet in the other, 
and consist of granite stones 3 feet square and 18 inches thick. 
They are rough-pointed on top and are bedded in concrete. 
They cost, laid, $7.25 each. 

The reservoir was divided into four distinct basins, in order 
that one or more of them might be kept empty for cleaning, or 
some similar purpose, while the others were in use. Under 
such conditions, however, there might be danger that water 
from a full basin would find its wav down throuo;h the thin 
sheet of concrete under it, and, passing below the division wall, 
would blow up the floor of an adjacent empty basin. This 
would be especially apt to occur where the basins and walls are 
underlaid by the pervious bed of gravel before referred to. 

To diminish the liability to such a catastrophe, beneath all 
walls, not founded on clay, was driven a solid wall of tongued 
and grooved 4-inch sheet-piling. This protection penetrated 
the gravel stratum and entered the clay below it. As an addi- 
tional precaution at such places a line of 10-inch drain-pipe 
was laid just below the floor on each side of the division wall. 
These drains were connected with others surrounding the 
reservoir outside of the retaining-walls. The drains within 
the reservoir also have 10-inch safety-valves opening into the 
basins. The drain-pipes were laid with open joints, and were 
surrounded, below the concrete, with dry-laid ballast and peb- 
bles. Water accumulating beneath the floor of any basin has 
free access to the drain under that basin. Should any water 
find its way under a division wall it is immediately intercepted 
by the line of pipe just beyond the wall. Should a drain under 
an empty Ijasin become gorged for any reason, the water is 
discharged into the basin, through the safety-valve, before suffi- 
cient head has accumulated to endanger the concrete. 

The northerly 100 feet of each division wall, being the end 
nearest to the discharge sewers, is made hollow, and 1.75 feet 



Plate XXV. 



BOSTON MAIN DRAINAGE 1 1 m> 1 ^ I ^ t i ^ ^ I ^ ^ ^ I L ^ I I 

SEWERS ABOUT RESERVOIR. 




SCALE OF FEET FOR' FfG. 6. 



RESERVOIR AND OUTLET. 79 

lower than the rest of the reservoir walls (Plate XXV., Fig. 
4). Long chambers are thus formed, open on top, but other- 
wise enclosed within the walls. These chambers connect di- 
rectly with the discharge sewers, and through them with the 
harbor. These portions of the division walls serve as waste 
weirs, by which the sewage in the basins can overflow, if, owing 
to negligence on the part of the employees, the gates which 
empty any basin should not be opened before the basin be- 
comes too full. 

The arrangements by whi'ch the sewage is turned from the 
outfall sewer into the reservoir and is again permitted to empty, 
throngh the discharge sewers, into the harbor, will be under- 
stood from an examination of Fig. 1, Plate XXV., which is a 
transverse section of said sewers. The upper sewer in the fig- 
ure is a continuation of the outfall sewer, and extends along the 
whole front of the reservoir. Immediately below it are the 
discharge sewers, which also extend alono; the front of the 
reservoir, and, also, about 600 feet beyond it out into the sea. 

In the side of the outfjill sewer are 20 3 X 4 feet, cut-stone 
gate openings. Only eight of these are at present provided with 
gates, the others being bricked up until an increased amount of 
sewage and an extension of the reservoir shall require their use. 
In the side of the discharge sewer nearest the reservoir are also 
20 gate openings, of which 12 are provided with gates. The 
two discharge sewers are connected directly by 11 large trans- 
verse passages. The amount of masonry contained in and 
surrounding the sewers equals that contained in all of the res- 
ervoir walls. 

Between the sewers and the reservoirs is what is called the 
six-foot gallery. This serves as a protection for the gates 
against frost and as a foundation for a gate-house above. The 
hollow division walls between the basins extend across the gal- 
lery and divide it into four sections, corresponding with the 
four basins of the reservoir. Brick brace-walls, about 10.5 
feet apart, are thrown across from the sewers to the reservoir 
wall. 

The 20 gates, with their frames and seats, are made of cast- 
iron. The frames were cast in one piece and closely fitted to 



80 MAIN DRAINAGE WORKS. 

the openings prepared in the masonry. They are secured to the 
stone by |-inch anchor-bolts, let in 4| inches and fastened with 
brimstone. The seat of each gate is a separate piece of cast- 
iron, planed |^-inch thick, fastened to its frame with screw 
rivets, and scraped true and straight. Fastened to each side of 
the frame is a guide, which holds the valve in its proper posi- 
tion while moving. The lace of the valve is planed and scraped 
to fit the facing of the frames, so that there shall be no leak- 
age. The valve is pressed tight to its seat by means of adjust- 
able gibs, which bear against inclined planes, cast on the 
guides. 

The gates are moved by lifting-rods and screws, connected 
with suitable brackets, gearing, and clutches, above the floor 
of the gate-house (Plate XXV. Fig. 2). A main line of shaft- 
ing, from 2^ to 3'^ inches in diameter, extends the whole length 
of the gate-house, or about 575 feet. The clutches for each 
gate are thrown in and out by a hand lever, and also by the 
gate itself when it reaches either end of its course. The 20 
gates, with all their appurtenances and the gearing and shafting 
for operating them, cost, in place, about $12,000. 

To furnish power both a steam-engine and a turbine wheel 
are provided. The latter, which is most commonly used, is 
21 inches in diameter, and is placed in a well near the north- 
easterly corner of the reservoir. It takes water either from 
the reservoir or from the outfall sewer, and drains into the dis- 
charge sewers. Under ordinary circumstances it furnishes 
without expense ample power for moving the gates, running 
pumps, and other necessary operations, and requires no atten- 
tion beyond opening and shutting the gates leading to it. 

The engine, which is seldom used, is of 30 horse-power. To 
furnish steam for it and also for heating in winter, there are two 
upright tubular boilers. The machinery and gates are pro- 
tected by suitaljle brick buildings, designed and built by the 
engineers. The principal one of these, called the Long Gate- 
House, extends for 575 feet along the front of the reservoir. 
Connecting with it, at the north-easterly corner of the reservoir, 
is another larger Iniilding, containing engine, boiler, and coal 
rooms. A chimney, 40 feet high, is also built. 



Plate XXVI. 



C/TY or BOSTON 

D/SCHAf^GE S£IV£/?S BEYOND RESC/fVOm 

SHOW/NG 

P/ER AND COFFER DAM. 



MA/N dra/nage:. 




RETAINING WALL OF RESERVOIR 
GENERAL SECTION. 



DIVISION WALL 
ON PER VIOUS MA TERIAL . 



HOLLOW DIVISION WALL 
SECTION M. N. PL . XX V. 



RESERVOIR AND OUTLET. 81 

The sewage flows through the gates in the outfall sewer 
into the six-feet gallery, whence it passes through openings in 
the reservoir wall into the reservoir. There it accumulates 
during the latter part of ebb-tide and the whole of the flood- 
tide. Shortly after the turn of the tide the lower gates are 
opened, and the sewage flows from the reservoir, through the 
gallery, into the discharge sewers, which conduct it to the out- 
let. 

That portion of the discharge sewers beyond the reservoir 
was called the Outlet-Sewer Section, and was built under a 
separate contract. There are two sewers of brick and concrete 
masonry (Fig. 1, Plate XXVI.), each 10 feet 10 inches high, 
by 12 feet wide inside. They extend from the reservoir about 
600 feet out into the sea, where there is five feet depth of water 
at low tide. The bottoms of the sewers are 1.5 feet above the 
elevation of low water. The arches, 12 inches thick, were laid 
with Rosendale cement mortar, and the inverts and sides with 
Portland cement mortar. In the top of each sewer are built 
three large vent-holes, to relieve the arch from any pressure of 
air due to a succession of waves entering the sewers. 

The immediate outlet consists of a cut granite pier-head laid 
in mortar. In this are chambers containing grooves for gates 
and stop-planks. The stones forming the pier-head are quite 
large, in order to withstand waves and ice. Several of them 
weighed about eight tons each. Most of the horizontal joints 
are dowelled, and the vertical joints of the coping-stones are 
secured by gun-metal cramps. 

The sewers are covered by an earth embankment, with its side 
slopes protected by ballast and rip-rap. This eml>ankment 
constitutes a pier extending into the harbor, and its top is 
ballasted and surfaced for a roadway. Near the end of the pier 
is a strong wharf, about 40 feet square, supported by oak piles. 
This is used for landing coal and other supplies. 

To facilitate construction on this section the site of the work 
was enclosed by building about 1,100 feet of cofter-dam around 
it. The dam consisted of tw^o rows of spruce piles, ten feet apart, 
the piles in each row being spaced six feet on centres. Inside 
the piles were rows of 4-inch tongued and grooved sheet-piling. 



82 MAIN DEAINAGE WORKS. 

The dam was tied across with iron bolts and was filled with 
earth. When pumped out it proved to be very tight, and 
enabled the work inside it to proceed without interruption. After 
the sewers were built and covered, the dam was cut down below 
the surface of the embankment slopes. The total cost of this 
outlet section was $96,250. 

The top of the reservoir floor is about one foot below the eleva- 
tion of high water. The paved gutters are a little lower, and in- 
cline nearly a foot from the back of the reservoirto its front. This 
insures there beino- a good current in them when the reservoirs 
are nearly emptied, so that the light deposit of sludge which has 
been precipitated upon the bottom of the reservoir is mostly 
washed into the discharge-sewers. 

To assist in cleansing the basins, a system of pipes and 
hydrants furnishing salt water under pressure is provided. The 
water is drawn from tlie sea to a pump in the engine-house, 
which forces it about the reservoir. A 4-inch pipe, with 
double hydrants, about 75 feet apart, is laid through the middle 
of each basin. A line of hose can be connected with any 
hydrant, and a fire-stream directed against any part of the floor 
or side walls. The pump can also be used to pump sewage with 
which to irrigate the banks and grounds surrounding the reser- 
voir. 

To obtain fresh water for domestic purposes and for the 
boilers, the high portion of the island has been encircled with 
ditches, which collect rain-water and conduct it to a cistern hold- 
ing 75,000 gallons. 

Within the gate-house is provided an automatic recording 
gauge, moved by clock-work and connected with floats in the 
sewers. The records traced by this machine furnish a per- 
fect check on the vigilance of the employees. Each day's record 
shows, by inspection, the hours at which the gates were opened 
and closed and the height of tide. 

The total expenditure l)y the city on account of Main Drain- 
age Works, from the beginning of the preliminary survey, 1876, 
to the present time, is about $5,213,000. 



DETAILS OF ENGINEERING AND CONSTRUCTION. 36 

CHAPTER X. 

DETAILS OF ENGINEERING AND CONSTRUCTION. 

About one-half of the work required to complete the Main 
Drainage System was done by contract, and the rest by day's 
labor, under superintendents appointed by the city. The general 
rule by which it was decided whether any given section of work 
should be built by contract, or not, was this : if the work was of 
such a nature that its extent and character could be determined 
in advance, so that full and explicit specifications for it could be 
drawn, it was let out by contract to the lowest responsible 
bidder. If, on the other hand, all of the conditions liable to 
aifect the work could not be ascertained, so that it was antici- 
pated that modifications in the proposed methods of construction 
might prove necessary or desirable, the work was done by day's 
labor. 

Thus, wherever in suburban or thinly populated districts the 
character of the earth to be excavated was supposed to be of 
uniform quality, most of the sewers there located were built by 
contract. Those located in crowded thoroughfares, where it 
was necessary to interfere as little as possible with the use of 
the street, and those in places where there was liability of en- 
countering deep beds of mud, old walls, wharves, and other ob- 
stacles, were built by day's labor. 

There was little diflference in the quality of the work obtained 
by these diflferent methods of construction. The contract work 
was built under more favorable conditions, and as a whole is 
somewhat superior to the other. It also, as a rule, cost much 
less. Several reasons can be given for this fact. The physical 
conditions were generally more favorable. Low prices were 
obtained through competitive bids. Most of the contractors 
made no profit; some even lost money. The contract work 
was largely done during the first few years of construction, 
when all prices were lower ; while the bulk of the work 
done by day's labor was built later, when prices for labor and 



84 MAIN DRAINAGE WORKS. 

materials had risen. The wages paid city laborers were fixed 
by the City Council, and were always higher than the market 
rates. At times the city superintendents were not untrammelled 
in respect to hiring and discharging their employees. 

Sixteen sections of sewer were let by contract. In two 
cases the contractors failed, and the sections were relet. In 
four other cases the contractors abandoned their work, which 
was completed by the city, by day's labor. In connection with 
the Main Drainage System about 50 more contracts were made 
for materials and machinery, and for construction and work 
other than sewer building. These contracts were drawn by the 
engineers. 

In preparing a contract for building a sewer the object kept 
in view was to describe only the general character of the work, 
and to leave for further decisions, as construction progressed, 
the exact shape, methods of construction, and amounts and 
kinds of materials to be used. That this might be done with- 
out unfairness to the contractor the precise character (but not 
the amount) of every kind of work and material, which miglit 
be called for, was specified, and a price was agreed on for each. 
Should anything not specified be called for, the contractor 
agreed to furnish it at its actual cost to him, plus 15 per cent, 
of said cost. 

This is a convenient form of contract, because it permits the 
engineer to modify his methods of construction whenever ex- 
perience shows that a change is desirable. One kind of mate- 
rial can be substituted for another ; cradles, side walls, and 
piling can be added or discarded. Kather more opportunities 
for contention are afforded by this form of contract than by a 
simpler one ; but, on the whole, it was considered the best for 
our purposes. 

Contract work was carefully watched, an inspector being 
continually on the ground. Great care was taken to select 
suitable men for such positions. They were all experienced 
masons, and were paid $4.00 or more a day. 

A daily force account was always kept, both of work done 
by the city and that built by contract. This recorded the number 
of hours' labor of every class and the amount of material which 



DETAILS OF ENGINEERING AND CONSTRUCTION. 85 

entered into each part of the work, so that its cost could be 
ascertained. On contract work this record proved very useful, 
because it furnished conclusive evidence in any case of disa- 
greement as to quantities or cost. 

All materials were carefully inspected for quality. Especial 
care was exercised in inspecting bricks and cement. About 
50,000,000 of the former and 180,000 casks of the latter 
material were used in building the works. It was required 
that the bricks should be uniform in size, regular in shape, 
tough, and burned very hard entirely through. Bricks with 
black ends Avere not excluded if otherwise suitable. No machine- 
made bricks were accepted, as they were usually found to have 
a laminated structure. A moderate proportion of bats was 
allowed, but only in the outer ring of the covering arch. From 
the accepted bricks the most regular were culled out for inside 
work. Bricks from different localities varied considerably in 
size, and this fact, so often disregarded, was taken into account 
in making purchases for the city. For instance, 1,175 Bangor 
bricks were required to build as much masonry as could be 
built with 1,000 Somerville bricks. 

A requirement that no bricks should be used which would 
absorb more than 16 per cent., in volume, of water, although 
not always enforced, was occasionally found useful, because it 
permitted the rejection of bricks made of liglit, sandy stock, 
which were, however, perfectly hard and shapely. The fol- 
lowing was the method employed in testing for porosity. The 
brick to be tested was first dried thoroughly by artificial heat, 
and then weighed. Next it was put in a pan containing one- 
half inch of water and allowed to soak for 24 hours, the pan 
being gradually filled, by adding water from time to time until 
the brick was covered. When thoroughly soaked it was again 
weig-hed, both in water and in air. The difierence between 
the weights dry and soaked, in air, was the weight of water 
absorbed, and the difference between the weights of the soaked 
brick, in air and in water, was the loss of weight in M^ater, 
i.e., the weight of a bulk of water equal to that of the 

1 • 1 ,1 The weisrlit of water absorbed ,1 j.' • l 

brick ; then The loss of weight m water was the proportion, in volume, 
of water absorbed by the brick. 



86 MAIN DRAINAGE WORKS. 

Natural " Rosendale " cement was chiefly used on the work, 
but about 26,000 barrels of Portland cement and a little Roman 
cement were also used. Portland cement mortar was often 
used in building the inverts of sewers and, in general, where 
there was liability to abrasion or where especial strength was 
needed. It was often mixed with Rosendale cement in order to 
make a somewhat stronger mortar. Very quick-setting Roman 
cement was used for stopping leaks, and was also mixed with 
other cements for wet work, because it would set at once and 
keep the mortar from being washed down before the stronger 
cements had hardened. 

In Appendix A is given a full account of the methods em- 
ployed for testing cement, and also the results derived from 
the tests made for experimental purposes. One advantage 
resulting from the careful and systematic testing was that manu- 
facturers and dealers were themselves careful to offer or send 
no cement but that which they felt confident would be accepted. 
During the first year or two much of the cement offered was 
rejected, but later very little of it proved unacceptable. In 
making contracts for cement a standard of strength and fine- 
ness was seldom given. It was simply stipulated that the 
cement should be, in every respect, satisfactory to the engineer, 
and, if not satisfactory, should be rejected. 

In one contract, however, for 5,000 barrels of Portland ce- 
ment, a certain fineness and strength were required. As some 
of the specifications of this contract are believed to be novel 
and practically useful, they are here cited : — 

Fineness. The cement to be very fine ground, so that not over fifteen 
(15) per cent, of it will be retained by a certain sieve dei^osited in the office 
of the City Engineer of Boston, said sieve having 14,400 meshes to the 
square inch. 

Strength. The cement, when gauged with thi-ee parts by measure of 
sand, to one part of cement ; formed into briquettes having a breaking area 
■ of 2^ square inches ; kept 28 days in water and broken from the water, to 
have a tensile strength of 150 lbs. per square inch. 

Price. We agree to receive as full payment for the satisfactory delivery 
of said cement, subject to its fulfilment of the foregoing requirements, as 
determined by the City Engineer of Boston, the sum of three dollars ($3.00) 
]jer cask delivered and accepted. 

We further agree, that, shall the cement, or any portion thereof, fail to 



DETAILS OF ENGINEERING AND CONSTRUCTION. 8< 

fulfil the above-mentioned requirement as to fineness, but shall nevertheless 
be accepted by the city, we will receive as full payment for said cement, or 
said portion thereof, a sum to be determined by the City Engineer, by 
deducting from the full price, of three dollars ($3.00) per cask, the sum 
of two cents ($0.02) per cask for each per cent, greater than 15 j)er cent, 
that is retained by the sieve before mentioned. 

Contractors were required to use only clean, sharp, coarse 
sand for making mortar. On city work, if clean sand was not 
conveniently accessible, a moderately dusty or dirty sand was 
considered almost as good, and quite good enough. So, also, 
in making concrete, contractors were obliged to use screened 
sand and stone ; but a city superintendent might mix his cement 
directly with the gravel dug from the bank, if it was more con- 
venient and cheaper to do so. Comparative tests of concrete 
made by these different methods failed to distinguish any supe- 
riority in one over the other. 

The city sewers were so low that the intercepting sewers, 
which had to be lower still, required unusually deep trenches. 
The average depth of cut for the whole system was more than 
21 feet. The bottom of these trenches was generally several 
feet below the elevation of low tide. As the new sewers fol- 
lowed the margins of the city near the sea, tide-water frequently 
found access to the trenches, so that construction could only 
proceed during a few hours at about the time of low tide, when 
the leakage of water could be controlled. Sometimes the trench 
could not be kept entirely free from watpr. Many of the streets 
traversed by the sewers were underlaid by beds of mud. Gen- 
erally the mud was not so deep but that an unyielding founda- 
tion could be secured by driving piles through the mud down 
into the hard ground beneath. Sometimes, however, the mud 
was so deep that hard bottom could not be reached by piling. 

It was under such conditions that the use of wood to form 
the whole, or the lower part, of the sewer was resorted to. 
Wood was no cheaper in itself than masonry ; but a wooden 
sewer could be built very much more rapidly than a brick one, 
and could be built by unskilled laborers. Also, a wooden 
invert could be fastened in place, if necessary, under a foot or 
two of water. Moreover, a wooden sewer, fastened by spikes 



88 MAIN DRAINAGE WORKS. 

and oak treenails, possessed considerable elasticity, and could 
settle slightly in places, or assume an undulating form, without 
breaking. 

Therefore, under conditions such as those just mentioned, 
the use of wood to form the shell of a sewer was often resorted 
to. There were disadvantages attending this mode of con- 
struction. The elasticity which permitted the sewer to bend 
longitudinally without breaking, also made it tend to yield trans- 
versely, sinking at the crown and bulging at the sides, when- 
ever the earth outside was at all compressible. It was not easy 
to prevent the wooden shell from leaking badly, especially at 
the end joints. All wooden sewers had to be lined with brick- 
work, or concrete, to make them smooth and tight ; but putting 
such lining inside of a leaky sewer is a somewhat tedious and 
difficult operation. 

The tops of most of the intercepting sewers are several feet 
below the level at which ground water stands in the earth about 
them. Great pains were taken to insure every joint being 
thoroughly filled with mortar, and the arches were always plas- 
tered outside with a half-inch coating of cement mortar. By 
such means the greater part of the system was made perfectly 
tight and dry. In places, however, especially where there were 
slight settlements and cracks, a considerable amount of leakage 
occurred. All leaky joints were calked as well as possible. 
Various materials were used for this purpose. Among them 
were neat cement ; cement mixed with grease or with clay ; 
oakum ; dry pine wedges, and sheet lead. By one or several of 
these methods the leakage could either be entirely stopped or 
reduced to an insignificant amount. 

A considerable item in the total cost of building the inter- 
cepting system was the expense incurred in repairs to street 
surfaces and paving, over the sewers. The trenches were so 
large and deep that the backfilling, often of a peaty consist- 
ency, could not be sufficiently compacted by ramming or pud- 
dling, but continued to settle for a year or more after the 
sewer was built. As it was necessary to keep the surface in a 
safe and reasonal>ly smooth condition the portion over the 
trench was sometimes repaved three, or even more, times before 



DETAILS OF ENGINEERING AND CONSTRUCTION, 89 

it would remain permanently in place. Where the earth mi- 
derlying the street was of a peaty nature, it would be rendered 
spongy and compressible by its water draining out into the open 
trench during construction. Then the whole street surface, 
including sidewalks and sometimes even adjacent yards, would 
settle out of shape and need repairing. 

Another source of expense and trouble was the breaking of 
house-drains where they passed across the sewer trench, due to 
the settlement of the backfilling. The intercepting sewers 
were frequently, indeed generally, built in streets which 
already contained a common sewer. The house-drains from 
one side of the street crossed the trench of the intercepting 
sewer. These drains were maintained, or replaced, as securely 
as possible, but many of them were afterwards broken. 
These were generally found to be sheared off on the line of the 
sides of the excavation, and the portion within the trench sunk 
bodily, half a foot or so, below the rest. 

As a rule the streets in which sewers were built were kept 
open for traffic. When the trench was in the middle of the 
street, passage-ways for vehicles were maintained on both sides 
of it, even when the width between sidewalk curbs was only 26 
feet. This was accomplished by the use of an apparatus for ex- 
cavating and backfilling, invented by the superintendent, Mr. H. 
A. Carson, and afterwards patented by him. Various merits 
are claimed for it, but the chief advantage in its use at Boston 
was, that by it sewers could be built with very little encroach- 
ment on the surface of the street. Views of the apparatus are 
given on Plate XXVII. Although a patented article, a brief 
description of it seems proper, since it was used in building 
more than one-half of the intercepting sewers. 

In its general features the apparatus consisted of a light 
frame structure, extending longitudinally over the server trench 
from a point in advance of where excavation had begun, to 
another behind where the trench was completely backfilled. 
All operations, therefore, were carried on beneath the machine. 
Excavation proceeded under the forward portion of the 
frame, the sewer was built under the central portion, and 
backfilling progressed near the rear. A double-drum hoisting 



90 MAIN DRAINAGE WORKS. 

engine was carried on a platform at the front end of the frame. 
From the top of the frame were suspended iron tracks, on which 
were travellers, moved backwards and forwards by wire ropes 
leading to the engine. A number of tubs, loaded by the dig- 
gers in front, were hoisted simultaneously by the engine, and 
run back to be dumped over the completed sewer. They were 
then returned and lowered to the points whence they had been 
taken, by which time a second set of tubs had been filled ready 
for hoisting. 

Any surplus earth was dumped through a hopper into carts 
which were backed under the machine. When it was neces- 
sary to furnish a passage across the work the trench was 
bridged, and the frame trussed. When one section of excava- 
tion was completed, the whole apparatus, which rested on 
wheels, was pulled forward 30 or more feet by its own engine. 
The average total length of one apparatus was 200 feet, and its 
total weight about 10 tons. 

Sewer building, done by the city, was frequently carried on 
through the winter months. Contractors, on the other hand, 
were not allowed to lay masonry between November 15 and 
April 15. The temperature at the bottom of a deep trench was 
always considerably higher than that at the surface of the ground ; 
so that it was only when the mercury was at ten or more de- 
grees (F.) below the freezing-point that work was suspended. 
Much extra precautionary work was needed. Bricks were 
steamed in a close box before using ; sand and water were 
warmed, and completed work was protected by coverings of 
straw or sea-weed. Winter work was not economical, and was 
resorted to chiefly for the purpose of employing laborers, who 
otherwise might have been idle. 

Experience is probably a better guide to designing stable 
sewers than are theories concerning lines of pressures and geo- 
static arches. The physical conditions which determine the 
direction and amount of the earth pressures are seldom the same 
in the case of any two sewers. They differ at different points 
about the same sewer, and often are not alike on both sides of 
one sewer. The best that can be done is to judge as well as 
possible of the character of the ground to be penetrated, and 



Plate XXVII 



TRENCH MACHINE 




MT. VERNON ST. 1883. 




ng. I 

CITY OF BOSTON 

MAIN DRAINAGE 



DIAGRAM MACHINE 



STOP PLANKS 

Fig. 3 




Fig. 2 



Fig. 4- 



DETAILS OF ENGINEERING AND CONSTRUCTION. 91 

beo;in to build such a sewer as has proved stal)le under similar 
conditions. The sewer should then be examined carefully, 
during and after loading, for signs of weakness. 

In the case of the main drainage sewers such examinations 
were made graphically, by taking diagrams of their inside 
shape. These diagrams were taken by the aid of a machine 
s^iown on Plate XXVII. It consisted of a light frame, which 
could be so fixed against the masonry that its centre should 
be in the axis of the sewer. A movable iarm was then rotated 
radially from the centre, with its outer end bearing lightly 
against the inside perimeter of the sewer. At the centre of the 
machine was a disk, on which was placed a sheet of paper. A 
pencil point, attached to the rotating arm, traced upon the 
paper a diagram, showing the shape of the sewer and its varia- 
tion, if any, from the established form. 

The shape and amount of any distortion suggested the cause 
which produced it, and the remedy to be applied. The most 
common causes were too early removal of centres ; too rapid 
or unequal loading ; the use of improper material for backfilling 
about the sewer ; insufficient ramming of backfilling against the 
haunches ; withdrawing sheet planks after backfilling ; inherent 
weakness in the design of the sewer. Such errors could be 
corrected and the design of the structure could l^e modified 
until the diagrams taken from the sewer were found to corre- 
spond with its proper shape. 

The Main Drainage System is so arranged that any principal 
portion of it can be isolated and emptied for inspection and re- 
pair. Any intercepting sewer can be thus isolated by closing 
the penstock gate at its lower end, and also the inlet valves 
connecting it with the common sewers, the latter then discharg- 
ing at their old outlets. By closing the gates at the ends of all 
intercepting sewers the main sewer can be emptied. Wher- 
ever an opportunity for isolating a small portion of the works 
might prove desirable, but the use of iron gates for such pur- 
pose would have entailed unwarranted expense, as a cheaper 
substitute, grooves of iron or stone were built into the masonry 
for stop-planks. Such grooves for stop-planks were always 
built above any iron gates, to afford a means of access in case 



92 MAIN DRAINAGE WORKS. 

of needed repairs. Where slight leakage could be afforded, a 
sino'le pair of grooves were considered sufficient. Where a 
tio'ht dam was desirable, a double set of grooves was provided, 
so that a double set of stop-planks, with an inside packing of 
clay, could be used. Some hundreds of stop-planks, of differ- 
ent lenoths, are kept in readiness. Their form is shown on 
Plate XXVII. They are made of hard-pine planks, from three 
to five inches thick, planed and oiled. 

The connections between the common sewers and the inter- 
ceptino- sewers were usually made during the construction of 
the latter. The valves of the inlet-pipes, built into the common 
sewers, were closed and made tight by a little cement around 
their edges. By raising these valves the connection between 
the old and new system could at any time be established. 



WOEKING OF THE NEW SYSTEM. 93 



CHAPTER XI. 

WORKING OF THE NEW SYSTEM. 

January 1, 1884, the connections between the common and 
intercepting sewers were first opened. Pumping began at the 
same time, and the sewage was sent to the reservoir at Moon 
Island, and thence discharged into the Outer Harbor. Connec- 
tion with about one-half of the conmion sewers was made on 
that day, and most of the others were connected within a month 
thereafter ; so that by February, 1884, nearly all of the city 
sewage was diverted from the old outlets. The upper portion of 
the West Side intercepting sewer, in Lowell and Causeway 
Streets, was built in 1884. The common sewers, tributary to 
it, were intercepted as construction progressed. A common 
sewer draining a portion of Dorchester, intercepted by the main 
sewer at East Chester Park just east of the N.Y. & N.E. 
Railroad, was not connected until early in 1885. 

Although the whole intercepting sj'stem, therefore, was not 
entirely completed until the present year, yet the greater part 
of it has been in operation for fifteen months, — a long enough 
period to aflibrd a fair indication of its practical working, and of 
the results which will be derived from it. 

As elsewhere stated, the Main Drainage Works were designed 
and built to correct two principal evils inherent in the old sys- 
tem of sewerage. These were : — 

First. The damming up of the common sewers by the tide, 
by which, for much of the time, they were converted into stag- 
nant cesspools, and the air in them was compressed, and to find 
outlets was driven into house-drains and other openings. 

Second. The discharge of the sewage on the shores of the city 
in the immediate vicinity of population, thereby causing nui- 
sances at many points. 

The first of these evils has been entirely corrected by the new 
system. The old sewers now have a continual flow in them, 



94 MAIN DRAINAGE WORKS. 

independent of the stage of the tide, as has been ascertained by 
frequent observations, and also from the testimony of drain-lay- 
ers, who formerly were only able to enter house-pipes into the 
the sewers when the latter were empty at low tide, but now can 
make such connections at any time. 

The new system has also substantially remedied the second 
evil. From the moment that any of the city sewers was con- 
nected with an intercepting sewer, the sewage which had before 
discharged on the shore of the city was diverted, and has since 
been conveyed to Moon Island and emptied into the Outer Har- 
bor at that point. 

It is true that about twenty-four times during the past year, 
or an average of twice a month, during rain-storms and freshets, 
the amount of water flowing in the sewers has exceeded the 
capacity of the pumps. At such times the excess has been dis- 
charged at the old sewer outlets. But this occasional and tem- 
porary discharge of very dilute sewage does not seem to have 
occasioned any nuisance. Examinations and inquiries concern- 
ing- the condition of the shores and docks at the sewer outlets 
have shown that water, once continually foul, has become pure, 
bad odors have ceased, and fish have returned to places where 
none had been seen for years. The stenches, referred to by the 
City Board of Health (p. 13), which formerly, at times, were 
prevalent over the city, were not noticed during the past year. 

The attempt to relieve certain low districts, subject to flooding 
of cellars during rain-storms at high tide, by discriminating in 
favor of such districts in respect to the interception of storm- 
water, has met with marked success. No case of flooding in such 
districts has been reported since the sewers draining them have 
been connected with the intercepters ; and many cellars, which 
used often to be filled several feet deep with water, are known 
to have been perfectly dry during the past year. 

Building the intercepting sewers has also dried cellars in other 
parts of the city in a way which was not at first anticipated. 
When land on the shores of the city was reclaimed for building 
purposes, most of the old walls and wharves were covered up 
by the new filling. Tide- water followed along any such struct- 
ures through the ground, and entered cellars lower than high-tide 



WORKING OF THE NEW SYSTEM. 95 

level. The new sewers were generally built along the present 
marghis of the city, and in digging deep trenches for them the 
old structures found were cut off and removed. The backfilled 
earth in the trenches forms an impervious dam surrounding the 
city, beyond which tide-water cannot pass. 

The sewers have been examined frequently since they went into 
operation. The average depth of dry-weather flow in the inter- 
cepting sewers is from ten to twenty inches, so that they can be 
entered on foot. So, also, can the main sewer above Tremont 
Street, and, sometimes, above Albany Street. Below that point 
the dry-weather flow is from two to three feet deep, necessitating 
the use of a boat. 

The velocity of flow in the sewers varies from about two feet a 
second upwards. An attempt was made to measure the velocity 
at several points with a current meter. While integrating, the 
meter rarely could be kept under water longer than ten seconds 
at a time without danger of its being clogged by paper, hair, 
and similar substances. By the use of a stop-watch the instru- 
ment could be removed for cleaning and again immersed without 
interfering with the experiment. The inclination of the surface 
of the sewage, though approximately the same as that of the 
sewer, was seldom precisely the same, and the observations 
were not sufficiently exact, in any case, to determine just what 
inclination then existed. The mean velocity at the points of 
measurement were, however, accurately ascertained, and the 
results may be of sufficient interest to cite. 

In the case of a 4 X 4.5 feet sewer (Fig. 7, Plate VIII.), with 
an inclination of 1 in 2,000, flowing 1.23 feet deep, the mean 
velocity was 1.9 feet per second. This sewer had some gravel 
on its bottom. In the case of a 4.75 X 5.5 feet sewer (Fig. 8, 
Plate VIII.), with an inclination of 1 in 2,000, the depth was 
1.45 feet, and the mean velocity was 2.45 feet per second. In 
a 4.5 feet circular sewer, with an inclination of 1 in 700, and 
a depth of 1.15 feet, the mean velocity of flow was 2.56 feet per 
second. In the case of an 8.25 feet circular sewer (Fig. 14, 
Plate VI.), the inclination being 1 in 2,500 and the depth 1.76 
feet, the mean velocity was 2.59 feet per second, sufficient to 
keep in suspension and carry along all sewage sludge. Most of 



96 MAIN DRAINAGE WORKS. 

the city sewers, when first intercepted, were found to contain 
deposits of sludge varying from a few inches to several feet in 
depth. All these deposits were carried into the intercepting 
sewers, and the sludge reached the pumping-station and was 
pumped up into the deposit-sewers. Gravel, stones, and brick- 
bats also were swept along and taken out at the filth-hoist. 
Fine sand, however, did not move so freely, but settled in 
ridges here and there, and had to be removed by hand. 

The bottoms of the sewers are, as a rule, perfectly clean. No 
slime accumulates there, or, if it ever begins to grow, it is at 
once scoured off by the attrition of moving particles. The sides 
of the invert below the surface of the water have a thin coating 
of slime, making them very slippery. The arch and the portion 
of the invert above the w^ater exposed to the air are clean, and 
often quite dry. In some portions of the sewers earthy accre- 
tions form on the arch. Where the sewer is surrounded by 
marsh mud these are turned black by sulphuretted hydrogen, 
sometimes they are colored yellow by iron, often they appear 
as white stalactites. In clayey soil the arch seems to be about 
as clean as when laid. 

The atmosphere in the sewers is not offensive, although a 
faint sewage smell can be detected on first entering them. For 
the first eight months after the sew^ers went into operation they 
were not ventilated at the man-holes. This was because it was 
know^n that much sludge would be turned into them from the 
common sewers, and it was feared the smell from it might be 
noticed. Finally the ventilating covers, shown on Plate VI., 
were put in place. No smell has ever been noticed from them, 
and they considerably improved the condition of the atmosphere 
in the sewers, which is now quite fresh and hardly at all dis- 
agreeable ; not so much so, for instance, as is that in most railway 
carriages after an hour's use. The temperature of the sewage 
varies from 50° to 65° F., and that of the air in the sewers from 
40° to 60° F., depending upon the outside temperature. 

A small force of men has been constantly employed during 
the past year, in caring for the main and intercepting sewers. 
This force has consisted of a foreman, one carpenter, and four 
laborers. They have also done minor items of work and repairs 



WORKING OF THE NEW SYSTEM. 97 

which might properly be charged to construction. After every 
rain, whenever there was any likelihood that water might have 
overflowed at the old outlets, all of the tide-gates have been 
visited. As a rule they are found to be quite tight. Occa- 
sionally one pair of a set (but never both pairs) are found to be 
leaking somewhat at high tide. This is caused by rags, corks, 
pieces of wood, or other such matters, catching near the hinges. 
At such visits the gates are washed clean, the hinges greased, 
and the iron-work examined for traces of incipient rust. 

Some of the tide-gates were made of white pine and some of 
spruce. A few of the latter, which have been in place for three 
years, already show signs of decay. These are inside gates 
situated above the elevation of mean tide, so that they are com- 
paratively seldom wet. To replace them creosoted lumber 
will probably be used. The rubber gaskets, fastened to the 
gates, are in perfectly good condition after about three 
years' use. They were made of what was called by the manu- 
facturer " pure rubber ; " but as they cost 75 cents a pound, 
when crude rubber was selling at more than $1.00 a pound, 
thej^ probably merely contained a larger percentage of that 
material than is usual in rubber goods. They were made with 
special reference to resisting the effects of sewage and grease. 

The penstocks, flushing-gates, and regulators are also in- 
spected periodicall3^ Moving parts are cleaned, slushed, and 
moved, so as to insure their being in good working condition. 
The iron, when carefully painted, does not appear to suffer 
from rust. About once in eight months it receives a coat of 
asphaltum paint. Duplicates are provided of all pins and other 
small parts, so that these can be taken to the yard to be warmed 
and recoated. The chains attached to the inlet valves, by which 
they are lifted, are most subject to rust. These are frequently 
changed and taken to the yard, where, after being cleaned and 
scraped, they are warmed in a furnace and coated with hot pitch. 

The catch-pails under the ventilating man-hole covers are 
emptied as occasion demands. In some localities, and at some 
seasons, pails will be filled in less than a month. Others will 
not require attention for three months. Men drive along the 
sewer line with a cart, remove a man-hole cover, lift out the 



98 MAIN DRAINAGE WORKS. 

pail, empty its contents into the cart, and again replace the pail 
and cover. A few extra pails are carried in the cart, so that 
if any of those in use shows signs of rust it can be replaced by 
another, and be taken to the yard for cleaning and recoating. 

The filth-hoist at the pumping-station seems satisfactorily to 
answer the purpose for which it was designed. In dry weather 
the cages are raised three times a day, and the average daily 
yield from them is about 16 cubic feet. The matters inter- 
cepted are, rags, paper, corks, half lemons, lumps of fat, dead 
animals, pieces of wood, bottles, children's toys, pocket-books, 
and such-like miscellaneous articles, which by accident or design 
are thrown into house-pipes . Comparatively little solid fecal mat- 
ter is caught, as most of it dissolves before reaching this point. 

When it rains, and deposits are scoured out of the old sewers, 
very much more tilth is caught in the cages. The amount some- 
times equals three or four cubic yards in 24 hours. At such 
times it is necessary to raise and clean the cages every half-hour, 
during the night as well as in the day, in order to prevent their 
becoming clogged and backing up the sewage in front of them. 

At first what was removed from the cages was buried in pits 
near the pumping-station. This not being considered a satis- 
factory method of disposal an attempt was made to burn the 
filth in the furnaces under the boilers. It was found that the 
filth, as taken from the cages, contained so much water that the 
fires were injured. Accordingly a simple press, like a cider 
press, was procured, by which most of the water was pressed 
out. The comparatively dry cakes remaining after pressing 
are now burned without injuriously affecting the furnace fires. 

The two high-duty " Leavitt " pumping-engines and the two 
storm-duty " Worthington" pumping-engines have all been run 
more or less during the past year. Any one of them is able to 
pump the ordinary dry-weather flow of sewage. As a rule one 
of the Leavitt engines is kept running ; should it rain, and addi- 
tional pumping capacity be needed, the second Leavitt engine 
is, by preference, started ; if still more capacity is needed, the 
Worthington engines are started. When the amount of water 
arriving by the sewer decreases, the Worthington engines are 
first stopped. 



WORKING OF THE NEW SYSTEM. 



99 



The average daily quantity of sewage pumped in dry weather 
is about 24,000,000 gallons, and the average number of tons of 
coal consumed in doing the work is about d\. This, with 
some steam used for other purposes, gives a working duty in 
the case of the Leavitt engine, of about 95,000,000 pounds 
raised 1 foot high by the consumption of 100 pounds of coal. 
The Worthington engines, under similar conditions, show a 
working duty of somewhat more than 50,000,000 foot-pounds. 

The following table gives the results of the first year's pump- 
ing, beginning with February, 1884, when the works had got 
fairly into operation : — 





Daily 
Average 
Gallons 
Pumped. 


Daily 
Average 

Pounds 
OF Coal. 


Per 

Cent. 

OF 

Ashes. 


Gallons 

Pumped 

PER Pound 

OF Coal. 


Rainfall. 


Month. 

1884. 


Inches. 


Number 
of Days 
it Rained. 


February . . 


25,777,360 


14,028 


15.8 


1,836 


5.74 


20 


March . . . 


32,437,379 


18,880 


14.8 


1,709 


4.86 


19 


April . . . 


29,949,356 


15,671 


16.2 


1,913 


4.76 


17 


May. . . . 


25,121,056 


13,127 


15.6 


1,915 


3.31 


11 


June . , . 


26,712,298 


13,265 


16.5 


2,015 


4.01 


7 


July. . . . 


25,900,400 


13,529 


19.2 


1.912 


4.25 


17 


August . . . 


31,674,621 


14,704 


16.0 


2,174 


5.01 


14 


September 


28,412,431 


11,099 


12.1 


2,568 


.31 


8 


October . . 


27,601,557 


10,206 


13.3 


2,698 


3.17 


13 


November . . 


27,501,283 


8,985 


8.0 


3,073 


3.03 


9 


December . . 


30,883,501 


10,181 


7.2 


2,885 


4.46 


15 


1885. 














January . . 


38,498,668 


11,448 


7.2 


3,265 


5.33 


9 



It will be seen that the daily average, as given, is larger than 
the dry-weather flow, because it includes the extra quantities 
pumped during rains. The largest day's work thus far has 
been 81,280,883 gallons, but for a few hours this rate has 
been much exceeded. Until August, 1884, the pumping was 
not done economically. At that time a change was made in 



100 MAIN DRAINAGE WORKS. 

the management of the station, with a considerable increase in 
economy. A further gain was made in November, 1884, by 
substituting bituminous coal for anthracite, which had pre- 
viously been used. The former coal makes more steam, and 
costs about $1 less a ton. The comparatively low duty shown 
by the table for December was due to the fact that the Worth- 
in^ton engines were largely used during that month, while a 
temporary building over the Leavitt engines was being taken 
down. 

There are no means for determining accurately the actual 
amount of the city water supply in the district whose sewers 
are tributary to the Main Drainage System. But it is evident 
that even in dry weather the amount of sewage reaching the 
pumping-station by the main sewer is greater than the water- 
supply of the districts drained by it. The excess is not con- 
stant ; sometimes it is estimated to be 10 per cent, of the 
whole, and at other times it is probably 25 per cent., or 
even more. This excess comes from several sources. Many 
dwellings and factories in sewered districts have private water 
supplies. Breweries, and other similar large establishments, con- 
tribute largely in this way. A single sugar refinery was found 
to pump and use, daily, about 1,000,000 gallons of salt water, 
all of wdiich properly might have gone back into the harbor, 
but was, instead, turned into the sewers. In the spring, when 
the ground is full of water, much of it leaks into the common 
sewers, and is by them carried to the intercepters. Sea-water 
also, at high tide, finds its way along some of the old box-sew- 
ers, and leaks into them back of the tide-gates. It will prob- 
ably prove to be true economy to rebuild many of the old 
sewers, in whole or in part. 

The permanent working force employed at the pumping- 
station at present is as follows : — 

1 Chief Engineer, 

3 Assistant Engineers, 
^ 9 Oilers, 

3 Firemen, 

3 Coal-passers, 

1 Clerk. 



WOEKING OF THE NEW SYSTEM. 101 

The men employed in the filth-hoist, included in the above, 
rank as oilers. The administration at this point is, of course, 
not as economical as it would be if there were a uniform, 
constant amount of work to be done. 

The deposit-sewers have perfectly answered their purposes 
in arresting all heavy matters contained in the sewage. The 
cross-sectional area of these sewers is so large, and the result- 
ing velocity of flow is so sluggish, even when four pumps are run- 
ning::, that all suspended matters subside before reaching the 
tunnel. Sand and gravel are deposited at once, as soon as they 
enter the sewers ; lighter substances are carried a little farther ; 
but only floating matters or those having about the same spe- 
cific gravity as water, remain in suspension long enough to reach 
the further end of the sewers. 

As elsewhere stated, the sludge, contained by the common 
sewers at the time connection was made between them and 
the intercepting sewer, passed to the pumping-station and was 
pumped into the deposit- sewers. The amount of this was 
12,000 cubic yards, or more. The best way of removing it was 
long considered, and it was only in the autumn of 1884 that 
the appliances described in Chapter YIII. were adopted and 
constructed. When the six-inch pipe connecting one deposit- 
sewer with the sludge-tank was first opened, the deposits near 
where the pipe entered the sewer were drawn into the tank, 
which in the space of two days was filled with about 100 yards 
of sludge. 

The floating scrapers (Plate XIX.) were not completed un- 
til the winter. They work very well, with a combined scrap- 
ing and flushing action, and by their use the sand and gravel 
deposits can be moved from one end of the sewer to the other. 
The sludge-tank was filled a second time, principally with clear 
sand, when operations were stopped by the harbor's freezing 
over. The bay remained closed by ice until early in March, 
when the removal of the deposits was again resumed. It seems 
probable that this method of removal will prove as satisfactory 
as any which could be adopted. 

As the tunnel is 142 feet below the harbor, and has been con- 
stantly full of sewage since pumping began, there has been no 



102 MAIN DRAINAGE WORKS. 

opportunity for inspecting it. For the first few months of 1884, 
before all of the city sewers had been intercepted, a compara- 
tively small amount of sewage was pumped, especially at night. 
At such times the velocity of flow through the tunnel was very 
slight, often less than one-half of a foot a second. Occasionally 
pumping would be stopped for a few hours at night, to allow 
the sewage to accumulate. At present the ordinary flow in the 
tunnel is seldom faster than 1 foot a second. As the sewao-e takes 
from two to four hours to pass through the tunnel , at these slow 
velocities, it was to be expected that deposits would occur there. 

To ascertain the extent of such deposits, and whether they 
were likely to become permanent, some experiments were made. 
These were based upon the following laws : 

That the flow through the tunnel is produced by the difier- 
ence in elevation of the water at its two ends ; 

That the amount of this difference is a measure of the fric- 
tional resistance which the tunnel opposes to the flow of the 
sewage ; 

That, in proportion as the water-way of the tunnel is ob- 
structed by deposits, the resistance, and therefore the difierence 
in elevation of the water at its two ends, will be greater than 
they would be if the tunnel was clean. 

The method of making the experiments was as follows : — 

The quantity of water passing through the tunnel was ascer- 
tained by pump measurement, with allowance for slip. The 
difference in elevation at the two ends of the tunnel was deter- 
mined by means of sliding gauges, with knife edges where they 
came in contact with the surface of the water. 

The coefficient was then calculated for the formula 

V = C 1/RI or C = rX= 

in which 

V = Velocity in feet per second 

area 



R = Hvdraulic mean radius 



wet perimeter 

I r= Sine of inclination — —, — '^-—v- 

length 

C = A coefficient ascertained by experiment. 



WORKING OF THE NEW SYSTEM. 103 

As the tunnel is circular, 7.5 feet in internal diameter, the 
value of R, corresponding to the full cross-sectional area, is 1.875 
feet. Experiments on the flow of water in the Sudbury-River 
Conduit,^ which was a brick structure like the tunnel, gave a 
coefficient corresponding to R =: 1.875, of about 137. It was 
not anticipated that the coefficient found for the tunnel, even 
when it was clean, would be quite so large as that of the con- 
duit ; since the surface of the former is somewhat rougher, and 
some loss of head would be occasioned by changes in direction 
at bends and by obstructions at the east shaft. 

It was also expected that the coefficient would vary somewhat 
with the velocity and with the dilution of the sewage. Under 
the most favorable circumstances, with the tunnel free from 
deposits, the coefficient would approximate 137, being that 
found by the experiments above mentioned. 

The full area of the tunnel was used in determining the values 
of V and R. This assumed that the tunnel was clean. Should 
the coefficient be found to be much lower than that anticipated, 
it would show that the foregoing assumption was incorrect, and 
that the area of the tunnel was partly obstructed. 

Whatever was the true value of the coefficient, its increase or 
decrease, as determined by successive experiments under the 
same conditions, would show whether the amount of deposit in 
the tunnel was becoming less or greater. 

Arrangements are provided for flushing the tunnel by running 
four pumps simultaneously, salt water being admitted to the 
pump-wells to supply any deficiency of sewage. The volume 
pumped is generally at the rate of about 114,000,000 gallons per 
day, which gives a velocity of about four feet per second through 
the tunnel. 

The first flushing with four pumps was done June 12, 1884. 
Just previous to this time, by two measurements on diflferent 
days, the loss of head through the tunnel was ascertained to be 
about .54 of a foot, and the values of C were found to be 80 and 
82. On June 13, the day after flushing, an experiment, with 

^ Transactions of the American Society of Civil Engineers, Vol. XII., No. CCLIIL 



104 MAIN DRAINAGE WORKS» 

the same conditions as those previously made, gave a loss of 
head of .30 of a foot, and a value of C = 110. 

This value was still too low to indicate an entirely clean tun- 
nel, but showed that the water-way had been increased by a 
removal of a portion of the deposit by the flushing. This was 
known to be a fact, since the sludge scoured out by the flushing 
had been observed in the reservoir. Inspection showed that 
the deposit carried into the reservoir was of a very light nature, 
containino; soft mud, horse-manure, water-looftyed match ends, 
bits of lemon-peel, paper, and similar substances. 

Beginning in June, 1884, flushing with four pumps has been 
done regularly about once a fortnight. At four different times 
measurements to determine the value of C have been made 
during the flushing. At such times the velocity of flow is high, 
and from 75 to 80 per cent, of the volume pumped is clean salt 
water, affording conditions favorable for obtaining a high co- 
efficient. The values of C, derived from these several experi- 
ments, were as follows : — • 

June 12, 1884. C = 129. 

Oct. 20, 1884. C = 120.7. 

Jan. 15, 1885. C — 146.3. 

Feb. 16, 1885. C = 146.6. 

The last two experiments were made on days following periods 
Avhen the quantity of sewage pumped had been unusually large, 
on account of rain and melting snow, which may account for the 
largeness of the coefficients. There may, also, have been some 
unusual slip in the valves. There can l)e little doubt, however, 
that at this time the water-way of the tunnel was not appreci- 
ably obstructed. 

Since these were experiments on the flow through a large pipe 
they may have some general interest for engineers, and their 
details are given in the following table i — 



WORKING OF THE NEW SYSTEM. 



105 



























02 


0) 

bo 

m 


= 


20 to 25 per C( 
sewage ; 75 to 80 
cent, salt water. 


6 

a; 

m 


20 to 25 per c 
sewage ; 75 to 80 
cent, salt water. 


- 


- 








^o 




IC 


CO 


t^ 


_ 


'tl 




. 


11-/^0 = A 


Ci 


o 


q 


CO 


CO 


CO 


CO 




© 


Binrajo^ 


1^ 


o 

CI 


d 


d 
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d 


d 
-* 


d 






ni JO 9"I«A 




00 










"-^ 








05 


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00 


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05 


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CO 


d 


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CO 


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CO 


CO 


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^■^. 



106 MAIN DRAINAGE WORKS. 

The wooden flume between Squantum and Moon Island has 
been watched carefully during the past year. It was at first 
tight, but the efifect of the summer's sun lying on one side of it 
tended to make the planks shrink and warp somewhat, so that 
leakage occurred in some places. These were stopped by 
tightening the bolts and wedges, and by fastening the corner 
bottom planks to the sides with lag screws. To guard against 
the sun the flume was given a second coat of paint. Putting a 
cheap roof over it would, doubtless, prolong the duration of its 
efiective service. 

When the sewage in the reservoir is low, the flume runs 
about half-full. As the basins fill, the depth of flow increases 
until finally it runs entirely full, acting as a pipe. The ordi- 
nary velocity of flow is about three feet a second, or less as the 
depth increases. Twice a day, when the reservoir is flushed, as 
described later on, the current through the lower end of the 
flume attains the remarkable velocity of about seven feet a second. 
This velocity is sufiiofent to move stones and brickbats. 

Nevertheless the flume is not clean. From its bottom up to 
the ordinary flow line the sides are covered with a slimy deposit 
from one-eighth to one-quarter of an inch in thickness. Above 
the middle and on the top there is also some slime, but not so 
much as below. The condition of this sewer is commended to 
the attention of those sanitarians who are accustomed to repre- 
sent flushing as a certain remedy for the accumulation of slime 
in pipes. 

Some experiments were made to determine the value of C in 
the formula V — C \/RI as applied to the flume. In one trial* 
the flume flowing about half-full with sewage, the value of E. 
was 1.45 feet, the velocity was 2.94 feet a second, and the value 
of C was found to be 116.9. In a second trial, under similar 
conditions, the following values were obtained : R = 1.41 ; V = 
2.87; C=116.6. In a third trial, when four pumps were running 
and the flume was flowing full, 75 to 80 per cent, of the water 
pumped being clean salt water, the values of R, V, and C respect- 
ively, were 1.5, 4.80, and 134.8. It will be noticed that the 
value of R was about the same in the last trial as in the first two, 
but that the value of C was very much greater. It is thought that 



WORKING OF THE NEW SYSTEM. 107 

this may be due to the fact that the first trials were made with 
clear sewage, whereas, in the case of the last trial, the water was 
comparatively clean. It seems reasonable to suppose that some 
head would be expended in maintaining in suspension the solid 
particles contained by the sewage. The subject is worthy of fur- 
ther investigation, because it concerns the applicability to the 
flow of sewage of hydraulic formulae derived from experiments 
on the flow of clean water. 

The reservoir has a capacity of 25,000,000 gallons. As sew- 
age is stored in it for about ten hours at a time, between the 
end of one period of discharge and the beginning of another, the 
basins, as a rule, have been filled only about half-full during 
the past year. The process of discharging is begun about one 
hour after the beginning of ebb tide. By this time the surface 
of the sea is as low as the bottom of the reservoir, and a good 
harbor current is setting outwards past the outlet. Water is 
admitted to the turbine, and by the power transmitted from it 
the upper gates in the outfall sewer are first closed. The sew- 
age then arriving is thus stored in the sewer, and its surfiice 
rises several feet. Meantime the lower gates in the discharge 
sewer are opened, and the sewage in the reservoir flows through 
them to the outlet. Under ordinary circumstances the basins 
are emptied in about 30 minutes. 

There is left in the basins a thin deposit of semi-fluid mud, 
generally about one-quarter of an inch thick, but in greater quan- 
tity after storms. To remove this, flushing is first resorted to. 
During the past year four brick partition-walls were built across 
the gallery between the sewers and the reservoir. One of these 
was built op})osite the middle of each basin. As soon as a basin 
is empty an upper gate is opened on one side of the divid- 
ing wall just mentioned, and the lower gates on the other side 
of it. The sewage, which has by this time accumulated to 
a considerable depth in the outfall sewer, passes through the 
openings into one side of the basin, and flows with moderate 
force up the gutters to the back retaining-wall. As the gutters 
fill the sewaofe overflows across the rido^es and dovvn the o-utters 
on the other side of the basin. Much of the sludge is in this 
way washed off" into the gutters and carried into the discharge 



108 MAIN DRAINAGE WORKS. 

sewers. The flushing is done alternately from one and the 
other side of the basin. 

If a basin cannot thus be entirel}'' cleaned, men descend into 
it with broad wooden scrapers, convex on one side, to fit the 
gutters, and flat on the other. With these the mud is scraped 
into the gutters and pushed down into the gallery, whence it 
is washed out into the sea at the next time of discharge. Such 
cleansing operations occupy about one-half hour for each basin, 
and are not especially disagreeable for the men.^ 

When the sides of a basin need cleaning the pump in the 
engine-house is started, and one or more lines of hose are 
coupled to the hydrants on the 4-inch pipe fastened to the floor 
in the middle of each basin. The pump will give two strong 
fire streams with sufficient force to wash off" any crust which has 
hardened on the walls. The streams can also be used in con- 
nection with scraping and washing the floors of the basins. 

The first sewage which discharges at the outlet contains a 
considerable amount of sludge which has settled in the 
gallery and discharge sewers, and gives to the efifluent a dark, 
muddy appearance. After a few minutes the color is somewhat 
lost, and the efiluent looks like moderately dirty water. 

Its efiect in discolorino' the salt water, and its course as it 
joins the current out of the harbor, can be plainly noticed. 
Being fresh water it rises to the surface, and when a half-mile 
from the outlet seems to lie on top of the salt water in a 
stratum but a few inches thick. The greasy nature of the sew- 
age tends to quiet the ripples commonly seen on the surface of 
the harbor, so that the area affected by the discharge is plainly 
determined. From experiments with floats it is known that 
the sewage travels nearly five miles, following the Western Way 
and Black-Rock Channel out to the vicinity of the Brewster 
Islands. By the time it has travelled a mile from the outlet 
most of the color is lost, and by the time it has gone two miles 
(before passing Rainsford Island) not the slightest trace of it 
can be distinguished. 

^ Since this was written slight changes have been made in the method of flushing the 
floors and gutters, whicli render the operation so eifcctivo that it is no longer necessary 
to send men into the basins to clean them, 



WORKING OF THE NEW SYSTEM. 109 

When the works went into operation, and for the first nine 
months thereafter, there were no gates near the outlet at the 
end of the discharge sewers. As a consequence the last por- 
tion of sewage from the reservoir, filling the discharge sewers, 
flowed out into the harbor slowly as the tide fell. This was 
the dirtiest part of the sewage, because it contained scourings 
from the basins. By referring to the plan (Plate V.) it will be 
seen that a cove was formed between the island and the pier 
containing the discharge sewers. In this cove a foot or more 
of sludge accumulated. A thin layer of sludge also formed on 
the beach between the outlet and the extreme point of the 
island. This last-named deposit was only found between the 
levels of mid-tide and low water. 

In winter no smell comes from these deposits, and in sum- 
mer none is noticed except during low tide. On three occa- 
sions last summer, when the wind was from the east, the 
smell w^as so strong as to be noticed at Squantum, a mile 
away. 

In hopes of preventing, or at least lessening, the formation 
of such deposits, a set of gates have been placed in the cham- 
ber at the outlet. By these the sewage filling the discharge 
sewers is held back until the beginning of the succeeding dis- 
charge, when it is forced out into a o^oocl current. These gates 
have not been in place long enough to show how^ much they 
will accomplish ; but, should objectionable deposits still continue 
to form on the island, it is thought that an effectual remedy 
can be provided. This will consist in building a solid bulk- 
head wall near the line of low water, from the outlet to the ex- 
treme easterly point of the island. Such a structure could be 
built for $30,000. 

No trace of the sludge has been found on the shores in any 
other part of the harbor. Very little smell emanates from the 
reservoir in cool weather ; not enough to be perceptible at a 
contractor's boarding-house, about 200 feet distant. In sum- 
mer the smell is more noticeable ; but not nearly so much so as 
is that arising from the deposits of sludge on the beach. 

As a whole, the Main Drainage System works well, and no 
radical defect has been detected in any portion of it. It is not 



110 MAIN DRAINAGE WORKS. 

claimed that, by itself, it furnishes a perfect system of sewer- 
age for the city. Many defective house-drains and common 
sewers still exist, and must in time be replaced ; but the new 
system provides an outlet for the rest, without which other re- 
forms would be comparatively useless. 

By building the Main Drainage Works, Boston has taken 
the first, most essential step in the direction of efficient sewer- 
age. 



APPENDIX. 



APPENDIX A. 



RECORD OF TESTS OF CEMENT mXdE FOR BOSTON 
MAIN DRAINAGE WORKS. 

1878 -ISSd."^ 

The Main Drainage Works chiefly consist of brick, stone, and con- 
crete masonry. About 180,000 barrels of cement were required to 
build this masonry ; and to insure its stability and durability it was 
necessary that the cement should be of good quality. From the start, 
therefore, means for determining the qualities of all cements used or 
offered for use were provided. A room was set apart for these oper- 
ations and an inspector appointed to conduct them. 

The tests were devised, principally, in order to determine three 
points, namely : — 

1. The relative strength and value of any cement as compared 
with the average strength and value of the best quality of similar 
kinds of cements. 

2. The absolute and comparative strength and value of mortars of 
different kinds made from the same cement. 

3. The effect produced upon the strength of any cement mortar by 
different conditions and methods of treatment. 

This knowledge was chiefly sought by observations of the tensile 
strength of the cements and mortars tested. Reasons for adopting 
the tensile test were, that it required comparatively light strains to 
produce rupture ; that, as it was universally used, it afforded results 
which could be compared with those of other observers ; and, finally, 
because the tensile stress is precisely that by which the mortar of 
masonry, in most cases of failure, actually is broken. 

All the particles of any cement are of appreciable size, and its 
strength as a mortar depends on the extent to which the particles ad- 
here, at their points of contact, to each other or to some inert substance. 
This adherence may be overcome and the mortar broken, either by 
pulling the particles apart by tension, or by pushing them past each 

1 A paper presentBcl to the American Society of Civil Engineers. 



114 MAIN DRAINAGE WORKS. 

Other by compression. The effect upon the adhering quality of the 
particles is not very different in the two operations ; but in the latter 
the friction of the particles against each other must also be overcome, 
which requires the application of very much more force. Transverse 
tests are only tensile tests differently applied, and shearing produces 
a stress intermediate to tension and compression. When masonry is 
strained, one part of it is in tension, another in compression, and, as 
mortar yields more readily to tensile stress, failure generally occurs 
by rupture of the joints in tension. 

Briquettes for testing, with a breaking section of one square inch, 
were tirst used ; but it was thought that these, from their small size, 
were liable to be strained and injured by handling in taking them 
from the moulds and transferring them to the water. A larger pat- 
tern, with a breaking section one and one-half inches square, or two 
and one-quarter square inches, was finally adopted. Comparative 
tests with briquettes of one inch and two and one-quarter inches sec- 
tion respectively indicated that there was little, if any, diffei'ence in 
their strength per square inch. 

The shape of the briquette adopted is shown by Fig. 2, Plate XXVIII. 
Fig. 1 of the same plate shows the brass moulds in which the mortar 
was packed to form the briquettes. These moulds proved very sat- 
isfactory. They were strong, and easily clamped and opened. The 
clamp consisted of a piece of brass wire riveted loose in the project- 
ino- lug of one branch of the mould, and binding by friction when 
turned against the wedge-shaped lug on the other branch. If a fast- 
ening worked loose a single tap of the hammer would tighten it. All 
breaking loads were reduced to pounds per square inch of breaking 
section by multiplying by four and dividing by nine. 

Before testing a cement its color was first observed. The absolute 
color of a natural cement indicates little, since it varies so much in 
this particular. But, for any given kind, variations in shade may indi- 
cate differences in the character of the rock or in the degree of burn- 
ino-. With Rosendale cements a light color generally indicated an 
inferior or underbui-ned rock. An undue proportion of underburned 
material was indicated in the case of Portland cement by a yellowish 
shade, and a marked difference between the color of the hard-burned, 
unground particles retained by a fine sieve and the finer cement which 
passed through the sieve. 

The weight per cubic foot was also sometimes ascertained. As this 
would vary with the density of packing, a standard for comparison 
was adopted, which was the density with which the cement would 
pack itself by an average free fall of three feet. The apparatus used 



Plate XXVIII. 




TUBE AND BOX 
FOB WEIGHING CEMENT. 




Fig-. 3. 



FiG.7. 



BBIQUETTE. 



PAT OF CEMENT 
TES TED FOB CHECK CRA CKS. 




Fig. 2. 





Fig. 4. 



PAN FOB KEEPING BRIQUETTES. 




LIGHT & HEA VY WIRES. 
Fi G. 5. 



Fig. €. 




SCOOP 

T 'lKl ll ir iil i ll l iin lVriiigM"iii ii lT "i 



S^> Fig. 8. 



POP TAKING SAMPLES PBOM BARBELS . 



BARBEL OF CEMENT 
60 FEB CENT FINE 



40PEP CENT 



eo PER CENT 



BARBEL OF CEMENT 
9UPEB CENT FINE 



SAND te^g^^M lOPEB CENT 



90PER CENT 



\i^^:^ \ 



Fig. 9. 



APPENDIX A. 115 

is shown by Fig. 3, Plate XXVIII. Tlie cement was placed in a 
coarse sieve on the top of a galvanized iron tube, and, the sieve being 
shaken, the cement sifted through the tube into the box below. This 
box held exactly one-tenth of a cubic foot when struck level with its 
top. 

The weights per cubic foot as determined by this method varied 
considerably with different kinds and brands of cement, and some- 
what with different samples of the same brand. The avei'ages were 
as follows ; — 

Table No. 1. 

Rosendale 49 to 56 pounds. 

LimeofTeil 50 " 

Roman 54 '* 

A fine-ground French Portland 60 " 

English and German Portlands 77.5 to 87 " 

An American Portland 95 " 

The following table shows the effect of fine grinding upon the 
weight of cement. It gives the weight per cubic foot of the same 
German Portland cement, containing different percentages of coarse 
particles, as determined by sifting through the No. 120 sieve : — 

Table No. 2. 

per cent, retained by No. 120 sieve — W't per cubic foot 
10 " " " " " 

9Q <(. U ii tl << li 

30 " " " " " " 

40 " " " " " 

It was soon discovered that there was no direct ratio between 
weight and strength. As a general rule, subject to exceptions, 
heavy cement, if thoroughly burned and fine-ground, was preferred 
to light cement. Fine-ground cements were hghter than coarse- 
ground and underburned rock lighter than well-burned. While color 
and weight by themselves indicated little, yet, considered together 
and also in connection with fineness, they enabled the inspector to 
guess at the character of a cement, and suggested reasons for high 
or low breaking. A cement which was light in color and weighty, 
and also coarse-ground, would be viewed with suspicion. 

The test of fineness, which followed, was considered of great 
importance, as showing the quantity of actual cement contained in a 
barrel, and its consequent value. Small scales were used, made 



. . 75 


pounds 


. . 79 


(f 


. . 82 


(1 


. . 86 


li 


. . 90 


t( 



116 MAIN DRAINAGE WORKS. 

for this purpose by Fairbanks & Co. One-quarter of a pound of 
the sample was weighed out and passed through the sieve. The 
coarse particles retained by the sieve were returned to the scales, 
whose balance-beam carried a movable weight, and was graduated 
in percentages of one-quarter pound. The percentage of coarse 
particles retained by the sieve could thus be read directly from the 
beam. 

Standard sieves, varying from No. 50 to No. 120, were used. The 
number of meshes to the lineal inch in any sieve is commonly sup- 
posed to correspond with its trade number. As sold, however, they 
vary somewhat, and the number of wires is generally less, by about 
ten per cent., than the number of the sieve. A No. 50 sieve com- 
monly has about 45 meshes to the inch, and a No. 120 about 100, or 
a few more. In important contracts, where a certain degree of fine- 
ness was called for, it was customary carefully to compare two sieves 
and retain one, which was specified as the standard, while the other 
was delivered to the manufacturer for his guidance. 

In accordance with common practice the No. 50 sieve was first 
used. It was soon discovered, however, that so coarse a sieve did 
not always give a correct indication of the fiueness of the cement. 
This was especially true of Portland cements. Some brands, chiefly 
German, were evidently bolted by the manufacturers with special 
reference to tests by this sieve, in which they would leave no re- 
siduum. Yet the bulk of such cements, while containing no very 
coarse particles, might prove quite coarse when tested by the No. 
120 sieve. 

It is obvious that pieces of burned cement slag one-fourth of an 
inch in diameter would have no cementing quality, and the same is 
true of particles one one-hundredth of an inch in diameter. At 
precisely what smaller size the particles begin to act as cement it was 
impossible to determine. Those retained by a No. 120 sieve, in 
which the open meshes are approximately one two-hundredth of an 
inch square, were found to have some slight coherence, even after 
washing to remove the finer floury cement which was sticking to them. 
It was also found that the No. 120 sieve was about as fine a one as it 
was practicable to use, on account of the time required to sift the 
cement through it. It was, therefore, adopted as a standard. 

Assuming (what was only approximately verified by experiments 
on tensile strength) that only what passed through this sieve had real 
value as cement, and that the rest was not very different from good, 
sharp sand, the difference in the quantity of actual cement obtained 
in purchasing barrels 60 and 00 per cent, fine, respectively, is shown 



APPENDIX A. 117 

by Figs. 9 and 10, Plate XXVIII. This bas an important bearing 
on the proportion of sand to be added in practical use ; for when 
mortar is mixed for use in the proportion of one barrel of cement 
to two of sand, if there be nine parts of cement and one of sand in 
the barrel of cement itself, the actual proportion in the mortar will 
be .9 to 2.1 or 1 to 2.33. If there be only six parts of cement and 
four of sand in the barrel of cement the resulting proportion in the 
mixture will be ,G to 2.4 or 1 to 4. 

Fine cement can be produced by the manufacturers in three ways : 
by supplying the mill-stoues with comparatively soft, underburnt 
rock, which is easily reduced to powder ; by running the stones more 
slowly, so that the rock remains longer between them ; or by bolting 
through a sieve and returning the unground particles to the stones. 
The first process produces an inferior quality of cement, while the 
second and third add to the cost of manufacturing. 

The extra cost, as estimated by a firm of English manufacturers, of 
reducing a Portland cement from an average of 70 per cent, fine, 
tested by No. 120 sieve, to 90 per cent, fine, was 18 cents per barrel. 
The price at which 5,000 barrels of theii- ordinary make, 70 per cent, 
fine, were offered, delivered on our work, was $2.82 per barrel. The 
same cement, ground 88 per cent, fine, was delivered for $3 a bavrel. 
On the foregoing assumption of the value of fine and coarse particles, 
the city, by accepting the first offer, would have obtained in bulk 
3,500 barrels of actual cement and 1,500 barrels of sand for $14,100. 
By accepting the second offer it obtained in bulk 4,400 barrels of 
cement and 600 of sand for $15,000; that is, the 900 additional 
barrels of cement cost $1 a barrel. Experiments illustrating the value 
of fine grinding, and fnrther comments, will be given later. 

Tests were made both of neat cement and of cement mixed with 
sand in different proportions. The latter were preferred, because they 
showed the strength and value of the mortars used in actual work. It 
was found also that the strength of briquettes made of neat cements 
did not always indicate the capacity of these cements to bind sand, 
or the strength of the mortars made with them. This is illustrated 
by experiment No. 10, on page 127. 

The greater the proportion of sand in the mortar tested the more 
accurately was the actual cementing quality of the cement indicated. 
As, however, very weak mixtures took a long time to harden, and were 
liable to injury from handling, one part cement to three parts sand 
was adopted as the usual mixture for testing Portland cements, and 
one to one and one-half or two for American cements. Occasionally 
when testing large quantities of some well-kaown bi'and, the object 



118 MAIN DEATNAGE WORKS. 

being to see that a uuiform strength was maintained, it was found 
sufficient, and simpler, to omit the sand and make the briquettes 
of cement onl}'. 

In making mortars for testing, rather coarse, clean, sea-beach sand 
was used. 

The subsequent strength of the briquettes depended largely upon 
the amount of water with which they were gauged. The highest re- 
sults were obtained by using just enough water thoroughly to dampen 
the cement, giving the mass the consistency of fresh loam, which be- 
came past}^ by working with a trowel. For ordinary testing, sufficient 
water was added to make a plastic mortar, somewhat stiffer tlian 
is commonly used by masons. Different cements varied in the 
amounts of water needed to produce this result. As a rule American 
cements needed more water than Portland, fine ground more than 
coarse, and quick-setting more than more slow-setting cements. 
Experiment No. 9, page 127, shows the comparative strength of mor- 
tars gauged with different percentages (in weight of the cement) of 
water. The standai'd adopted was 25 per cent, for Portland cement 
and 33 per cent, for Rosendale ; but these amounts were increased or 
diminished by the operator to suit the circumstances, his aim being to 
obtain mortars of unvarying consistency. 

The way in which the test briquettes were made was as follows : 
the moulds, having been slightly greased inside to prevent the mor- 
tar sticking to them, were placed on a polished marble slab. This 
support for them was used because it was easily cleaned and the mor- 
tar did not stick to it. Experiment No. 6, page 124, shows that the 
use of porous or of non-porous beds to support the moulds does not 
materially affect the strength of the mortars. The requisite amounts of 
cement and sand for one briquette were weighed out and incorporated 
dry in a mixing-pan. The proper amount of water was also weighed 
out and added, and the mass worked briskly with a small trowel until 
of uniform consistency. A brass mould was half filled with the mor- 
tar, which was rammed into place by the operator with a small wooden 
rammer, in order to displace any bubbles of air whiclr might be con- 
fined in it. The mould was then filled to its top with the remaining 
mortar, which was in turn rammed down. Finally the mortar was 
struck even with the top of the mould and given a smooth surface 
by the trowel. 

The amount of mortar packed in the mould, and the consequent 
density of the briquette, would vary with any variation in the degree 
of force exerted by the operator in ramming. This variation was re- 
duced to a mininium by always mixing a fixed amount of mortar, 



APPENDIX A. 119 

which was barely more than sufficient to fill one mould. Irregularities 
in ramming would thus be detected by variations in the amount of 
surplus mortar, and could be checked. An attempt was made to do 
away wholly with this element of uncertainty by pressing the mortar 
into the moulds with certain fixed pressures. Apparatus was devised 
and used for this purpose, but was finally abandoned on account of 
the length of time required for its use. 

The initial energy of the cement — that is, the length of time after 
mixing before it " set" — was determined by noting the length of 
time before it would bear "the light wire" of y^ i^ch in diameter 
loaded with i-ponnd weight, and also " the heavy wire " ^L- inch in 
diameter loaded with 1 -pound weight. At the former time the cement 
was said to have begun to set, and at the latter it was entirely set. 
Different kinds and brands of cement varied greatly in the time after 
mixing when they would bear the wires. Some brands of English 
Roman cement would set in two minutes, and some of Portland re- 
quired over 12 hours. Cold retarded the setting, and fresh-ground 
cements set quicker than older ones. No direct relation was estab- 
lished between initial energy and subsequent strength. By judicious 
mixing of quick and slow setting cements a mixture could be ob- 
tained which would set within any desired period. 

As soon as the briquettes were hard enough to handle without injury, 
which with dilferent cements and mixtures varied from five minutes to 
twelve or more hours, they were removed from the moulds and placed 
in numbered pans filled with water. Before removal each briquette 
had marked upon it, with steel stamps, the name of the cement, date 
of mixing, and a number by which it could be further identified. The 
inscription might read thus : — 

"Alsenl-3. May 17, 1880. 47." 

Records were also kept in books and on blanks provided for the 
purpose. The briquettes were kept in the pans, covered with water, 
until they were broken. Their age when broken varied from 2<4 hours 
to five years. 

In testing a well-known American cement, of generally uniform 
quality, if it were an object to save time, the comparative excellence 
of the samples could be suflflciently determined by a 24 hours' test of 
briquettes made of neat cement. Under similar conditions neat Port- 
land cement could be tested in seven days. ,To test mortar of either 
kind of cement took a week, or, better, a month ; especially if there 
was a liberal pi-oportion of sand. 

The probable value of an untried brand of cement could hardly 



120 MAIN DRAINAGE WORKS. 

be ascertained with certainty in less than a month, and not always 
then. To illnstrate the occasional need of long-time tests a case may 
be cited. 

A new brand of cement, made b}' some patent process, was offered 
for nse on the work. When tested it set up well, and at the end 
of a week the neat cement had a tensile strength of 184 pounds per 
square inch. In a month this had iucreasec] to 267 pounds, indicating 
a strength equal to that of a low-grade Portland cement. At this 
time there was nothing in the appearance of the briquettes to indicate 
any weakness. Yet after about six months they fell to pieces, and had 
entirely lost their cohesive quality. 

The briquettes were broken by a machine made for the Department 
by Fairbanks & Co. It worked with levers, acting on a spring bal- 
ance, which was tested from time to time, and found to maintain its 
accuracy. 

During the progress of the work the following brands of cement 
were submitted for approval, and were tested with more or less thor- 
oughness : — 

Old Newark, Newark and Rosendale, Norton, Hoffman, Old Rosen- 
dale, New York and Rosendale, Lawrenceville, Rosendale, Arrow, 
Keator, Howe's Cave, Rock Lock, Buffalo, Cu;mberland, Round Top, 
Selenitic, Vorwholer, Star, Dyckerhoff, Alsen, Hemmor, Bonnar, 
Onward, Burham, J. B. "White, Knight, Bevan & Sturge, Brooks, 
Shoobridge & Co., Leavitt, Grand Float, Diamond, Spanish, Red 
Cross, La Farge, Lime of Teil, Saylor, Coolidge, Walkill, Cobb, 
Abbott. 

The following is a record of the more instructive tests, made for 
experimental purposes. Nearly all of them were made with special 
reference to the work then in hand, to elucidate some practical ques- 
tions affecting the purchase, testing, or use of the cements needed for 
building purposes. The names of the brands of cement tested in the 
several experiiuents are generally omitted. This is in order to avoid 
any unwarranted use of the results as recorded. 

The figures given in the tables always represent average breaking 
loads in pounds per square inch of breaking section. 

Experiment No. 1. 

Of natural American cements the Rosendale brands (so called) are 
the only ones which find a sale in the Boston market, and they were 
chiefly used on the work. Imported Portland cements were also 
largely used. It was important, therefore, to ascertain the actuai and 



APPENDIX A. 



121 



comparative strengths of these cements. The following table gives 
results compiled from about 25,000 breakings, of 20 different brands, 
and fairly represents the average strength of ordinar}^ good cements 
of the two kinds. Some caution, however, is necessary in using the 
table as a standard with which to compare other cements. Quick- 
setting cements might be stronger in a day or week, and show less 
increase in strength with time. Fine-ground cements would probably 
give lower results tested neat, and higher ones with liberal propor- 
tions of sand. 

Table No. 3, 

EOSENDALE CEMENT. 



Neat Cement. 


Cement, 1; 


Cement, 1 ; 


Cement, 1; 


Cement, 1; 


Cement, 1; 




Sand, 1, 


Sand, 1.5. 


Sand, 2. 


Sand, 3. 


Sand, 5. 




^ 
^ 


6 \ o 


o 


^ 
^ 


6 


o 


o 


^ 
^ 


d 


o 






d 


o 


o 




d 
1^ 


o 

a 


o 

k5 


^ 
^ 


d 




IB 
O 


^ 


"' 


i-H to 


r-f 


'-' 


"" 


CO 


'-' 


r-l 


'-' 


CD 


'-' 


t— I 


iH 


CO 


^ 


'-' 


rH 


CD 


'-' 


T-H 


tH 


CO 




71 


92 


145 '282 


290 


56 


116 


190 


256 


41 


95 


155 


230 


24 


60 


125 


180 


14 


35 


80 


121 


5 


16 


46 


80 



PORTLAND CEMENT. 



Keat Cement. 


Cement, 1; 


.@ement, 1; 


Cement, 1 ; 


Cement, 1; 


Cement, 1; 


Sand, 1. 


Sand, 1.5. 


Sand, 2. 


Sand, 3. 


Sand, 5. 






d 


o 


o 




d 


o 
1^ 


o 




d 


O 


O 




d 


6 


o 




d 


o 


o 


-M 
^ 


d 

a 




6 


*"* 










•"* 


'^ 




^ 


'^ 


T-i 


CD 


" 


'^ 


■^ 


CD 




r-i 


'"' 


CO 




'"' 


rH 


CO 


1-1 


lO"^ 


303 


412 


468 


494 


160 


225 


347 


387 










126 


183 


279 


323 


95 


140 


198 


257 


55 


88 


136 


"155 















The table is instructive in several ways. It shows that Portland 
cement acquires its strength more quickly than Rosendale ; that both 
cements (but especially Rosendale) harden more and more slowly as 
the proportion of sand mixed with them is increased ; that, whereas 
neat cements and rich mortars attain nearly their ultimate strength in 
six months or less, weak mortars continue to harden for a year or more. 
The table shows the advantage of waiting as long as possible before 
loading masonry structures, and the possibility of saving cost by using 
less cement when it can have ample time to harden. It also shows 
that Portland cement is especially useful when heavy strains must be 
withstood within a week. 



122 



MAIN DRAINAGE WORKS. 



Experiment No. 2. "™ 

These series of tests are like the preceding ones, except that a 
single brand of cement was used in making each. The average 
breaking loads per square inch were obtained from a less number of 
briquettes (about 500 in all), mortars with larger proportions of sand 
were included in the series, and the tests were extended for two years. 

Table No. 4. 

PORTLAND CEMENT MORTAR. 



Age -when 


Neat 


Cement, 1 ; 


Cement, ] ; 


Cement,! ; 


Cement, 1 ; 


Cement, 1 ; 


Cement, 1 ; 


Broken. 


Cement. 


Sand, 2. 


Sand, 4. 


Sand, 6. 
50 


Sand, 8. 


Sand, 10. 


Sand, 12. 


One week 


295 


166 


89 


33 


23 


17 


One month . 


341 


243 


132 


88 


67 


50 


41 


Six months . 


374 


843 


213 


149 


98 


76 


51 


Two years . 


472 


389 


226 


159 


98 


49 


31 



ROSENDALE CEMENT MORTAR. 



Age when 


Neat 


Cement, 1 ; 


Cement, 1 ; 


Cement, 1 ; 


Cement, 1 ; 


Cement, 1 ; 


Cement, 1 ; 


Broken. 


Cement. 


Sand, 2. 


Sand, 4. 


Sand, 6. 


Sand, 8. 


Sand, 10. 


Sand, 12. 


One week 
One month . 




24 


7 


5 










83 


33 


17 


8 


5 


. 


Six months . 




172 


93 


62 


60 


33 


21 


Two years . 


• • • 


211 


90 


56 


33 


22 


20 



The tables show that considerable strength is acquired in time, even 
when a very large proportion of sand is used ; also, that most mortars 
increase very little, if any, in tensile strength after six months or a 
year. They become harder with time, but also become more brittle 
and probably less tough. Specimens of mortar two years old, or more, 
break very irregularly. 

Experiment No. 3. 

The rate at which Rosendale and Portland cements, respectively, 
increase in strength during the first two months after mixing is very 
different, and has some bearing on their use, and more on the inter- 
pretation of tests of them made within that period. The curves (Fig. 



Plate XX LX. 



500 



40O 



SCO 



200 



90O 




4O0 



500 



200 



100 



APPENDIX A. 123 

1, Plate XXIX), which mdicate this rate of increase, were compiled 
from tests with neat cement. It is probable that tests with mortar 
would give somewhat similar results. By comparing the two curves it 
appears that after 24 hours Rosendale cement has about three-fourths 
of the strength of Portland. While the latter increases greatly in 
hardness during the next few days, the energy of the former becomes 
dormant, so that at the end of a week the Portland cement is more 
than three times as strong as the Rosendale. During the second 
week the Portland cement increases more slowl}-, and the Rosen- 
dale continues nearly quiescent. At about this period, and for the 
next six weeks, the Rosendale cement gains strength, not only rela- 
tively, but actually faster than the Portland, so that when two months 
old the former has one-half the strength of the latter. After two 
months the relative rate of increase and the comparative strength 
of the two cements remain nearly unchanged. A series of tests with 
a Buffalo cement, and one with a Cumberland cement, gave results 
similar to those with Rosendale cement. 

Experiment No. 4. 

For making tests it is not always convenient to obtain sand of uni- 
form size, and still less so to obtain such sand in sufficient quantities 
for use in work. The curves. Fig. 2, Plate XXIX, record some tests 
made to determine the effect of fineness and of uniformity of size 
in sand upon the strength of mortars made with it. 

'I'he curves show that for comparative tests it is advisable to have 
sifted sand of nearly uniform size ; that mortars made with coarse 
sand are the strongest, and that the finer the sand the less the 
sti'ength. It also appears that mixed sand, i.e., unsifted sand con- 
taining a mixture of particles from coarse to fine, makes nearly as 
strong a mortar as coarse or medium coarse sand. For use in work, 
therefore, it is well to avoid fine sands ; but it is not necessary to 
have sand of uniform size, or to sift out a moderate; proportion of 
fine particles. 

Experiment No. 5. 

As some experimenters on cement use a test briquette with a break- 
ing section of 1 square inch, and others one with a section of 2|- 
square inches, the following experiment was made to determine the 
difference, if any, in the strength acquired by the same mortars 
moulded into briquettes of these different sizes. Two series of tests 
were made, in the same way, with the same mortars. In one series 
the briquettes had a breaking section of 1 square inch, and in the 



124 



MAIN DEAINAGE WORKS. 



other the section was 2^ square inches. The results are given in the 
following table, in which the figures represent breaking loads in 
pounds per square inch, and are averages from five breakings ; — 



Table No. 5. 





RosBNDALE Cement. 


Portland 


Cement. 






Cement, 1 ; 


Neat 


Cement, 1 ; 




Neat Cement. 












Baud, 1.5. 


Cement. 


Baud, 1.5. 






^ 


-a 


i 


.14 


^* 


■3 


M 


.g 


,g 


M 


.g 


a 




cS 
ft 




o 


a 
o 


^ 



O 


a 

O 


0) 


a 

o 


o 


^ 


a 

O 


o 




'-' 


iH 


r-< 


to 


"^ 


'"' 


«5 


rH 


IH 


o 


^ 


1-1 


to 


1-inch Section . . . 


49 


73 


156 


286 


27 


53 


286 


309 


460 


657 


60 


96 


175 


2|-inch Section . . . 


49 


78 


173 


258 


27 


62 


311 


347 


391 


578 


67 


108 


230 



As is usual, the breaking loads are somewhat irregular, the inch 
section excelliug at some points, and the larger section at others. 
The experiment, however, seems to indicate that neither size will, as 
a rule, give higher results than the other. 

Experiment No. 6. 

Some experimenters have thought it important to place the moulds 
in which the mortar is packed for testing upon a porous bed, such as 
blotting-paper or plaster. Others use a non-porous bed of glass, slate, 
or marble. The following series of tests were made to discover the 
effect of these different modes of treatment.. The figures in the 
tables represent breaking loads, in pounds per square inch, and are 
averages of about ten breakings. 

Table No. 6. 

KOSENCALE CEMENT. 



Mixture. 


Kind of Bed. 


One Week. 


One Month. 


Bix Months. 


One Year. 


Neat . 1 


Marble . . 
Plaster . . 


95 
106 


151 

178 


288 
303 


325 
316 


Cement, 1, 
Sand, 1.5. 


Marble , . 
Piaster , . 


44 
62 


107 
120 


210 
219 


251 
2C5 



APPENDIX A. 



125 



A CUMBERLAND CEMENT. 



Mixture. 


Kind of Bed. 


One 
Day. 


One 
Week. 


One 

Month. 


Sis 

Months. 


One 
Tear. 


Neat . . j 


Marble . . . 
Plaster . . . 


128 
147 


133 
165 


142 
176 


231 
244 


241 

257 


Cement, 1 . . 
Sand 1 5 






107 
128 


161 
166 


275 
299 


889 


Plaster ... 




845 










Cement, 1 
Sand 2 . . . 


Marble . . . 




85 
111 


134 

148 


201 
241 


292 
294 












Marble . 




40 
46 


94 
91 


162 
164 


163 


Sand, 4 . . . 






170 











GERMAN PORTLAND CEMENT. 



Mixture. 


Kind of Bed. 


One Week. 


One Month. 


Six Months. 


One Tear. 


Cement, 1, 
Sand, 1 . 


Marble . . 
Plaster . . 


259 
213 


367 
376 


890 

411 


. . . . 


Cement, 1, 
Sand, 2 . 


Marble . . 
Plaster . . 


176 
196 


256 
258 


846 
326 


345 
. 357 


Cement, 1, 
Sand, 3 . 


Marble . . 
Plaster . . 


141 
147 


225 
220 


250 
258 


313 
312 


Cement, 1, 
Sand, 4 . 


Marble . . 
Plaster . . 


103 
120 


157 
150 


240 
233 


274 
264 


Cement, 1, 
Sand, 5 . 


Marble . . 
Plaster . . 


82 
103 


108 
140 


182 
193 


213 
197 



Making allowance for a few irregularities, it appears, from the fore- 
-going tables, that the use of a porous bed gives slightly higher 
results for the first one or two months, but that the difference disap- 
pears or becomes insignificant with age. 



126 



MAIN DRAINAGE WORKS. 



Experiment No. 7. 

It is a well-recognized fact that in experimenting with cements, even 
when great care is exercised, individual specimens break very irregu- 
larly, and that results even approximately conforming to theory can 
only be obtained from averages from a large number of breakings. 
The personal equation of the operator, and the degree of force with 
which he presses the mortar into the moulds, is one factor in pro- 
ducing irregular results. To do away with this a machine for packing 
the moulds was devised and used for a time. By this the mortar was 
pressed into the moulds by a metallic plunger, acting with definite 
pressures, varying from 50 to 400 pounds. 

The machine-made briquettes broke with somewhat greater uni- 
formity than hand-made ones. So much more time was required to 
make briquettes with this machine that it was found to be impracti- 
cable to employ it for general use. 

Experiment No. 8. 

By the sea it is frequently convenient to mix mortar with salt water. 
Brine is also used in winter as a precaution against frost. This 
experiment was made to obtain the comparative effect of mixing 
with, and immersing in, fresh and sea water respectively. The tests 
were made upon a Rosendale mortar, mixed one part cement to one 
part sand, and an English Portland mortar, one part cement to two 
parts sand. The figures are averages of about ten breakings, and 
give the tensile strength in pound per square inch with the different 
methods of treatment and at different ages. 

Except for some irregularity in the breakings for one year (which 
may have been due to the manipulation) the table indicates that 
salt, either in the water used for mixing or that of immersion, has no 
important effect upon the strength of cement. Salt water retards the 
first set of cement somewhat. 

Table No. 7. 



Rosendale CfiMENT Mortar. 

1 TO 1. 




Portland Cement Mortar, 

1 TO 2. 


Fresh Water. 


Fresh. 


Salt. 


Salt. 


Mixed with 


Fresh. 


Fresh. 


Salt. 


Salt. 


Fresh Water. 


Bait. 


Fresh. 


Salt. 


Immersed in 


Fresh. 


Salt. 


Fresh. 


Bait. 


40 
126 
247 
310 


48 
135 
250 
263 


50 
114 
243 
224 


61 

126 
224 
217 


One week. . 
One month. 
Six months. 
One year. . 


151 
213 
314 
342 


122 
191 
245 
231 


152 

203 
277 
346 


149 
200 
264 
295 



Plate XXX. 




15 .20 25 30 35 40 45 50 

PER CENT or WATER OrMfXTURE /N WE/GHT OF CEMENT. 



APPENDIX A. 



127 



Experiment No. 9. 

This was an experiment to determine the relation existing between 
the stiffness of cement mortar when first mixed and its subsequent 
strength. The stiffness depends on the proportion of water used in 
mixing, and varies somewhat with different cements. Natnral Ameri- 
can cements take up more water than Portland cements and fine- 
ground more than coarse cements. Many series of tests bearing on 
this point were made. The results obtained from two of the more 
complete series are shown bj^ the curves on Plate XXX. The cements 
used in these tests were a rather coarse English Portland and a fair 
Rosendale. Each of the points in the curves represents an average 
from about ten briquettes. The cements were tested neat, and the 
amounts of water used were different percentages, by weight, of the 
amounts of cement. The resulting stiff'ness of mortar is indicated on 
the curves. This varied from the consistency of fresh loam to a fluid 
grout. The time of setting is greatly retarded by the addition of water. 

The curves show that from 20 to 25 per cent, of water gives the 
best results with Portland cement, and from 30 to 35 per cent, with 
Rosendale ; that the differences in strength due to the amount of water 
are considerable at first, but diminish greatly with age ; that the soft 
mortars, even when semi-fluid, like grout, attain considerable strength 
in time. 

Experiment No. 10. 
From the first it was observed that fine-ground cements were less 
strong when tested neat, and stronger when mixed with sand, than were 
coarse cements. A few examples of this are given below. In the first 
table a coarse English Portland cement is compared with a fine-ground 
French Portland. The per cent, of each retained by the fine No. 120 
sieve is given, and the tensile strength, in pounds, per square inch at 
the end of seven days. 

Table No. 8. 



Kind of Cement. 


Per Cent, 
retained by- 
No. 120 Sieve. 


Parts of Sand to 
Cement 


1 part of 







2 


3 


4 


5 


English Portland .... 


37 


319 


125 


89 


59 
114 


43 


French Portland .... 


13 


318 


205 


130 


86 



128 



MAIN DRAINAGE WORKS. 



Such examples could be multiplied. German Portland cements 
were commonly finer ground than English, and, as a rule, were no 
stronger, or less strong, tested neat, but were much stronger with lib- 
eral proportions of sand. In the following table two lots of the same 
brand of English Portland cement are compared. The coarse cement 
was the ordinary make of the manufacturers ; the fine cement differed 
in no particular from the other except that it was ground more slowly 
and finer to meet the requirements of a special agreement. The age of 
the samples when broken was 28 days. 

Table No. 9. 



Kind of Cement. 


Per Cent, 
retained by 
• No. 120 Sieve. 


Parts of Sand to 1 part of 
Cement. 


- 





3 


5 


Ordinary Cement .... 


35 


403 


105 


68 


Fine-ground Cement . . . 


12 


304 


180 


96 



Different brands of Rosendale cement varied considerably in their 
fineness. Those of the best reputation would leave from 4 to 10 per 
cent, residuum in the No. 50 sieve ; other brands would leave in the 
same sieve from 10 to 23 per cent. In the following table is com- 
pared the average tensile strength obtained from experiments with 
three of the finer-ground brands, and also with three other brands of 
good reputation, but more coarsely ground. The age of the speci- 
mens was one week. 

Table No. 10. 



Kind of Cement. 


Per Cent, 
retained by- 
No. 50 Sieve. 


Parts of Sand to 1 part of 
Cement. 







1.5 


2 


Fine Rosendale 


6 


92 


41 


25 


Coarse Rosendale .... 


17 


98 


29 


16 



The foregoing experiments show that it is impossible, by tests on. 
the tensile strength of neat cements alone, to judge of their value 



APPENDIX A. 



129 



in making mortars, for practical use ; also, that fine-ground cements 
make stronger mortars than do coarser ones. 

A number of series of tests were made of cements which had been 
sifted through sieves of different degrees of fineness, and had thereby 
had different percentages of coarse particles removed from them. 
The results from these experiments were quite uniform, and showed 
that, in proportion as its coarse particles were removed, a cement 
became more efficient for making mortars with sand. The following 
table gives the results obtained from one such series of tests made 
with an English Portland cement. In the experiment comparison is 
made between the strength of mortars made with the ordinary cement, 
unsifted as it came from the barrel, and those made with the same 
cement after having been sifted through Nos. 50, 70, 100, and 120 
sieves, which, respectively, eliminated more and more of the coarse 
particles. The per cent, of particles which would still be retained by 
the fine No. 100 sieve, after sifting through the coarser sieves, is 
given in the second column of the table. There. is included in the 
table an extra coarse cement, which was made so by adding to unsifted 
cement a certain amount of the coarse particles taken from the sifted 
cements. The tensile strength is given in pounds per square inch. 

Table No. 11. 







One Week. 


One Month. 


Six Months. 


One Tear. 




o <] S 

ids 

p^ 










Kind of Cement 

used in makino 

Mortars. 


Parts of Sand to 1 part of Cement. 




2 


3 


4 


5 


2 


3 


4 


5 


2 


3 


4 


5 


2 


3 


4 


5 


Cement with coarse 
particles added . . 


55 


72 


39 


32 


19 


117 


80 


67 


40 


210 


135 


122 


84 


200 


128 


112 


92 


Ordinary Cement, un- 
sifted ..... 


33 


129 


92 


58 


43 


197 


143 


109 


88 


311 


236 


183 


136 


288 


247 


168 


165 


Cement whicli passed 
No. 50 Sieve . . . 


28 


159 


97 


67 


47 


210 


158 


125 


102 


324 


246 


190 


146 


328 


249 


214 


170 


Cement which passed 
No. 70 Sieve . . . 


18 


163 


117 


82 


65 


239 


168 


151 


112 


338 


256 


225 


173 


342 


295 


230 


193 


Cement which passed 
No. 100 Sieve . . . 


8 


177 


123 


84 


73 


255 


185 


156 


122 


257 


288 


239 


182 


382 


307 


257 


215 


Cement which passed 
No. 120 Sieve . . . 





198 


154 


95 


86 


271 


200 


161 


132 


379 


320 


238 


196 


386 


316 


262 


218 



130 



MAIN DRAINAGE WORKS. 



In a similar series of tests witli Eosendale cement mortars, the 
increase in strength obtained b}- substituting fine for coarse particles 
in the cement was much less mai'ked. The coarse particles were 
softer than those from Portland cement, and had, in themselves, some 
power of cohesion. As previous tests had shown that fine-ground 
Eosendale cements were stronger, with sand, than coarse-ground, it 
was assumed that the superiority was due, not so much to the absence 
of palpably coarse particles, as to the fact that the bulk of the cement 
was more floury, and thus better adapted to coating and binding the 
particles of sand. Probably natural American cement is as much 
improved as is Portland cement by fine grinding, but in the case of 
the former there would not be the same relative advantage in bolting 
out the coarse particles after grinding. 

The following series of tests may be of interest, on account of the 
age of the specimens. The mortars were made with an English 
Portland cement, both unsifted as taken from the cask, and also 
after it had been sifted through the No. 120 sieve, by which process 
about 35 per cent, of coarse particles was eliminated. 

Table No. 12. 





Neat Cement. 


Cement, 1 


; Sand, 2. 


Cement, ] 


; Sand, 5. 




2 Years. 


4 Years. 


2 Years. 


4 Years. 


2 Years. 


4 Years. 


Ordinary Cement, un- 
sifted 

Cement which passed 
No. 120 Sieve . . 


603 
374 


387 
211 


339 

478 


493 

580 


182 
250 


202 

284 



This table, also, shows that fine cements do not give as high re- 
sults tested neat as do cements containing coarse particles, even coarse 
particles of sand. It also shows (what is often noticed) that neat 
cements become brittle with age, and are apt to fly into pieces under 
comparatively light loads. 

The series of tests which follows was made for the purpose of as- 
certaining what value, if any, for cementing purposes, was possessed 
by the hard, coarse particles of Portland cement. Mortars were 
made with an ordinary English Portland cement, and compared with 
similar mortars made with the same cement, after sifting through the 
No. 120 sieve, which retained 33 per cent, of coarse particles. 



APPENDIX A. 

Table No. 13. 



131 





One Week. 


One Month. 


Six Months. 


One Year. 


Kind of Cement. 


Parts of Sand to one part of Cement. 





353 
311 


2 
139 

187 


3 

86 
132 



279 
243 


2 
201 
275 


3 
142 

201 



438 
268 


2 
328 
367 


3 

253 
310 



444 
306 


2 
343 
434 


3 


Ordinary Cement, unsifted . 

Cement which passed No. 120 
Sieve 


271 
333 



As usual, the coarse cement was stronger neat, and weaker with 
sand. Assuming that the 33 per cent, of coarse particles retained 
by the sieve had no value as cement, acting merely as so much sand, 
and assuming also that all which passed through the sieve was good 
cement, it follows that the ordinary unsifted cement with two parts of 
sand, made a mortar in which the proportion of real cement to sand 
was .67 to 2.33, or about 1 to 3.5. Hence, the mortar made with 
fine cement and three parts of sand should be as strong, or a little 
stronger, than that made with the coarse cement and two parts of 
sand. It will be seen that the results in the table sustain the assump- 
tion very well. 

If, then,, the coarse particles are assumed to act merely as so 
much sand, it will not lessen the efficiency of the cement to remove 
its coarse particles, and to substitute actual sand in their place. This 
was done in making the following series of tests. One set of bri- 
quettes was made with ordinary cement, and another set with the 
same cement, from which 33 per cent, of coarse particles had been 
removed and replaced with fine sand. 



Table No. 14. 



Kind of Cement. 



Ordinary Cement, unsifted, 

Cement with 33 per cent, 
coarse particles removed 
and fine sand substituted. 



One Week. One Month. Six Months. One Year, 



Parts of Sand to one part of Cement. 



139 



101 



3 


2 


3 


2 


3 


2 


86 


201 


142 


324 


253 


343 


67 


160 


100 


253 


206 


305 



271 



240 



132 



MAIN DEAINAGE WORKS. 



These briquettes refused to break in accordance with the theory, 
and the assumed hypothesis was not verified. It is evident that, for 
making mortar, the coarse particles of Portland cement are superior 
to ordinary sand, but much inferior to fine cement. In the mortars 
made with the cement, in which the coarse particles had been replaced 
with fine sand, the real proportions of cement to sand were 1 to 3.5 
and 1 to 5. It will be noticed that the tensile strength was not re- 
duced in like proportion. 

Experiment No. 11. 

While building masonry laid in American cement mortar it is some- 
times desirable to increase the strength of the mortar temporarily or 
in places. Rich Portland cement mortars are expensive, and those 
with large proportions of sand are too porous for many purposes. 
The desired strength can be gained by using, instead of the simple 
American cement, the same cement mixed with a percentage of strong 
Portland cement. 

The following series of tests was designed to ascertain the compara- 
tive strength of mortars made with a Rosendale cement, an English 
Portland cement, and also a mixture composed of equal parts of 
each : — 

Table No. 15. 



Kind of Mortar. 


1 Week. 


1 Month. 


6 Months. 


1 Tear. 


Rosendale Cement, 1; Sand 2 . . 

Rosendale Cement, 0.5, \ a„j,/i o 
Portland Cement, 0.5, / ' 

Portland Cement, 1 ; Sand, 2 . . . 


26 

79 

126 


60 
138 
163 


125 

268 
279 


180 
273 
323 



In the foregoing tests the mortar made with mixed cement had an 
unexpected strength, approximating to that of mortar made with pure 
Portland cement. In the following series of tests of mortars made 
with lime of Teil, a fine-ground French Portland cement, and the 
lime and cement mixed, the strength of the mortar made with the 
mixture is almost exactly a mean between those of the other two mor- 
tars, as also the cost of the mixed cement is a mean between the costs 
of the other two. 



APPENDIX A. 



133 



Table No. 16. 



Kind of Mortar. 


1 Week. 


1 Month. 


6 Months. 


1 Year. 


Lime of Teil, 1 ; Sand, 2 . . . . 

Lime of Teil, O-'^iXc,,,,! 9 
Portland Cement, 0.5, / ^*^""' " ' ' 

Portland Cement, 1 ; Sand, 2 . . . 


40 
100 
170 


65 
135 
265 


150 
255 
350 


195 
290 
365 



The best Portland cements sometimes do not set within an hour, 
which precludes their use for wet work. In such cases quick-setting 
cement should be added to them. Roman cements can be procured 
which will set in from one to five minutes. Mixtures of Roman and 
Portland cements were often used on the Main Drainage Works. Such 
mortars would set about as quickly as if made with Roman cement 
alone, and would acquire great subsequent strength, due to. the Port- 
land cement contained in them. This was proved by many experi- 
mental tests. 

It is probable that mixtures of any good cements can be used with- 
out risk ; but before adopting any novel combination it would be wise 
to test it experimentally. 

Experiment No. 12. 

Engineers are accustomed to require that only clean sand and water 
shall be used in making mortar. Occasionally these requirements 
cause delay and extra expense. This experiment was designed to as- 
certain how much injury would be caused by the use of sand contain- 
ing moderate proportions of loam. In mixing the mortar for these 
briquettes, sand containing 10 per cent, of loam was used in the place 
of clean sand. Each figure in the table is an average (in pounds per 
square inch) of ten breakings. 



Table No. 17. 

EOSENDALE CEMENT, 1; SAND, 1.5; LOAM, .15. 



One Week. 


One Month. 


Six Months. 


One Year. 


21 


46 


200 


221 



The tests do not give very decisive results. For one week and one 



134 



MAIN DRAINAGE WORKS. 



mouth the breaking loads are not much more than one-half what 
would have been expected with clean sand. For six mouths and a 
year they are full}^ equal to ordinary mortar. 



Experiment No. 13. 

This experimeut was similar to the foregoing one, except that clay, 
instead of loam, was added to the mortar. Clay, when dissolved or 
pulverized, consists of an almost impalpable powder, with particles 
fine enough to fill the interstitial spaces among the coarser particles 
of cement. By adding cla^' to cement mortar a much more dense, 
plastic, and water-tight paste is produced, which was occasionally 
found convenient for plastering surfaces or stopping leaky joints. 
Each figure in the Portland cement series of tests is an average from 
about fifteen briquettes ; those in the Rosendale cemeut series are 
averages from ten briquettes. 

Table No. 18. 

EOSENDALE CEMENT. 





Cement, 2 ; 
Clay, 1. 


Cement, 1 ; 
Clay, 1. 


Cement, 1 ; 
Sand, 1.5. 


Cement, 1 ; 
Sand, 1.5; 
Clay, 0.15. 


Cement, 1; 
Sand, 1.5; 
Clay, 0.3; 


Cement, 1 ; 
Sand, 1.5; 
Clay, 0.45. 


1 week . . . 


32 


23 


50 


52 


34 


33 


1 month . . . 


108 


52 


123 


116 


101 


100 


6 months . . 


303 


206 


217 


248 


247 


236 


1 year . . . 


208 


209 


262 


290 


265 


261 



PORTLAND CEMENT. 





Cement, 2; 
Clay, 1. 


Cement, 1 ; 
Clay, 1. 


Cement, 1; 
Sand, 2. 


Cement, 1; 
Sand, 2; 
Clay, 0.2. 


Cement, 1 ; 
Sand, 2; 
Clay, 0.4. 


Cement, 1 ; 
Sand, 2; 
Clay, 0.6. 


] week . . . 


185 


192 


150 


197 


185 


145 


1 month . . . 


263 


271 


186 


253 


245 


203 


6 months . . 


348 


322 


320 


361 


368 


317 


1 year . . . 


303 


301 


340 


367 


401 


384 



The tests seem to show that the presence of clay in moderate 
amounts does not weaken cement mortars. 



APPENDIX A. 135 

It was feared that the presence of clay in mortars exposed to the 
weather might tend to make them absorb moisture and become disin- 
tegrated. To ascertain whether this would be so, sets of briquettes 
were made, one set of Portland cement and sand only, the other con- 
taining also different amounts of claj- . They were allowed to harden 
in water for a week, and were then exposed on the roof of the oflSce 
building for two and one-half years, when they were broken. All of 
the briquettes appeared to be in perfectly good condition, with sharp, 
hard edges. Their average tensile strengths in p5unds per square 
inch are shown in the following table : — 

Table No. 19. 

Portland Cement 1 ; Sand 2 402 

" Clay 0.5 ........ 262 

" " " "1.0 256 

" " " " 1.5 ....... . 182 

" " " " 2.0 ....... . 178 

The mortars with clay show a very fair degree of strength, and 
the tests confirm the belief that the presence of clay works little, if 
any, harm. Tests of mortars made with lime and clay also gave 
favorable results. Such mortars would stand up in water. The sub- 
ject is worthy of further investigation. 

Experiment No. 14. 

Occasionally, for stopping leaks through joints in the sewers, it 
was found convenient to use cement mixed with melted tallow. The 
tallow congealed at once and held the water while the joint was being 
calked. Briquettes made of melted tallow mixed with Portland 
cement and sand, equal parts, acquired in 1 week, a tensile 
strength of about 40 pounds to the inch. After a month, six months, 
and a year, they were little, if any, stronger. It was thought that 
possibh' the ammonia in the sewage might gradually saponify and dis- 
solve out the grease, leaving the mortar to harden by itself. Bri- 
quettes of cement and tallow were kept in water, to which a little 
ammonia was added from time to time. After a year or two the bri- 
quettes had swelled to about double their former size, but the cement 
had acquired no strength. 

Experiment No. 15. 

Having occasion to build with concrete a large monolithic structure, 
in which a flat wall would be subjected to transverse stress, it was 
considered necessary to make experiments, to find the comparative 



136 



MAIN DRAINAGE WORKS. 



resistance to such stress of concrete made with different cements 
and with different proportions of sand and stone. 

The cements used in the tests were an English Portland and a 
Rosendale, both good of their respective kinds. Medium coarse pit 
sand was used, and screened pebbles about an inch or less in diameter. 
The beams were ten inches square and six feet or less long. They were 
made in plank moulds resting on the bottom of a gravel-pit about four 
feet deep. After the concrete had hardened sufficiently, the moulds 
were removed, and the undisturbed beams buried in the pit and left 
for six mouths exposed to the weather. They were then dug out, and 
broken with the results given in the table. The total breaking loads 
are given, including one-half of the weights of the beams, which aver- 
aged about 150 pounds per cubic foot. The constant, c, is obtained for 
the formula : — 

f w zzz centre breaking load in pounds. 
d zzz depth of beam in inches. 
X c, in wliich \ b z:z breadth of beam in inches. 

I I zzz distance between supports in feet. 

|_ c zz: a constant. 



d- X h 
I 



Since c has an average value, and there were generally more beams 
of one length than the other, the value of c as given does not exactly 
correspond with either load in the table. 

Table No. 20. 



Pbopobtion of 


Materials. 


AVEEAGB CbNTBE BREAKING 

Weight in Pounds. 


Average 
Modulus of 


Average 
Value of c 


















Dist. between 


Dist. between 


Rupture in 


in Pounds. 


Cement. 


Sand. 


Stone. 


Supports, 
2' 4i". 


Supports, 
5'. 


Pounds. 




Rosendale, 1 . 


2 


5 


1,782 


690 


67 


3.7 


l-H 


3 


7 


Beams broke 


in handling. 






Portland, 1 . . 


3 


7 


3,026 


1,995 


176 


9.8 


1 . . 


4 


9 


3,648 




146 


8.1 


1 . . 


6 


11 


2,822 


1,190 


112 


6.2 



The table shows that concrete has a rather low modulus, especially 
when made of Rosendale cement. When transverse stress is to be 
opposed it is very important to give ample time for the concrete to 
harden. 



Plate XXXI. 




4i 4 3t 5 2i- 2 li 

PARTS or SAND TO ONE PART OF CEMENT. 



APPENDIX A. 137 



Experiment No. 16. 



Many of the main drainage sewers were either built or lined with 
concrete, which was always smoothly plastered with a coat of mortar. 
It was important that this surface coat should be especially adapted to 
resist abrasion. This experiment was made to ascertain the best 
mixture for the purpose. Different mortars were formed into blocks 
1-^ inches square, and, after hardening under water for 8 months, 
were ground down upon a grindstone. The blocks were pressed upon 
the stone with a fixed pressure of about 20 pounds. A counter was 
attached to the machine, and the number of revolutions required to 
grind off 0.1 inch of each block was noted. The cements used in the 
test blocks were a rather coarse English Portland and a fair Rosendale. 

The curves (Plate XXXI.) show the results obtained. In making 
these curves the resistance to abrasion opposed by the Portland cement 
mortar in the proportion of one part cement and two parts sand is 
assumed to be 100, and the resistance of other mortars is compared 
with it. The effect of the grinding upon the test blocks is noted on 
the curves, and explains the somewhat striking results. 

It appears that cements oppose the greatest resistance to abrasion 
when combined with the largest amount of sand which they can just 
bind so firmly that it will grind off and not be pulled out. A little 
less or a little more of sand may greatly lessen the resistance. For 
any given cement the proper amount of sand would, probably, have 
to be ascertained by experiment. 

Experiment No. 17. 

It is a prevalent belief among masons that cement, even when it 
contains no free lime, and does not check, expands considerably after 
setting. It is stated that brick fronts laid with cement mortar (espe- 
ciall}^ of Portland cement) have been known to bulge, and even rise, 
owing to expansion in the mortar. Experiments were made to ascer- 
tain what truth there was in this belief. Several dozens of glass lamp- 
chimney's were filled with mortars made of various brands of American 
and Portland cements, both neat and with different admixtures of 
sand. The chimneys were immersed in water, and, without exception, 
began to crack within three days. New cracks appeared during the 
following ten days, after which time hardly a square inch of glass 
remained which did not show signs of fracture. This showed that 
the cement certainl}^ expanded, though very slowly, and that the ex- 
pansion continued for about two weeks. None of the cracks opened 



138 MAIN DRAINAGE WORKS. 

appreciably, however, so that the amount of expansion, which was 
evidently slight, could not thus be even approximately determined. 

A number of 10-inch cubes were then made of similar mortars, with 
small copper tacks inserted in the centres of all the sides. Some of 
these cubes were kept in the air, and others immersed in water, and 
the sizes of all of them were measured frequently by callipers during 
six months. The increase in size did not in any case exceed .01 inch, 
and may have been less. This indicated that, while cement mortars 
do expand, the increase in bulk in any dimension does not exceed .001 
part of that dimension, and is too slight to be of consequence. In 
the case of the walls before referred to, supposing them to have been 
80 feet high, with five ^-inch joints to each foot, the total height of 
mortar would have been 100 inches, and the extreme expansion of the 
whole could only have been .1 inch. It is probable that the appar- 
ent rise was merely a difference in elevation caused by settlements of 
partition or side walls laid with weaker and compressible mortar. 

Experiment No. 18. 

It having been reported that cement mortars in contact with wood 
had sometimes been found to be disintegrated, as if they might have 
been affected by the wood acids, this experiment was made to see if 
any such effect could be detected. About a dozen boxes were made, 
each formed of five different kinds of wood, viz., oak, hard-pine, white- 
pine, spruce, and ash. The boxes were filled with different cement 
mortars, and were some of them submerged in fresh and others in salt 
water. Briquettes were also made of cements mixed with different 
kinds of sawdust. At the end of a year no effect upon the cements 
could anywhere be detected. 

Experiment No. 19. 

Engineers are accustomed to insist on cement mortars being used 
before they have begun to set, and on their being undisturbed after 
that process has begun. With cements that set quickly workmen are 
tempted to retemper the mortar after it has begun to stiffen. Some 
experiments were made on mortars which were undisturbed after 
first setting, and others which were retempered from time to time. 
Unfortunately all of the conditions of these tests were not accurately 
recorded, and the results are not considered trustworthy. The follow- 
ing series of tests, which represents an extreme case not met with in 
actual practice, may be of interest. 



APPENDIX A. 



139 



A mortar made of one part of Portland cement and two parts of 
sand was allowed to harden for a week. It was then pulverized, re- 
tempered, and made into briquettes. These subsequently acquired the 
following tensile strength in pounds per square inch : — 

1' week 7 

1 month 13 

6 months 49 

2 years 93 

Under the circumstances it is somewhat surprising that the mortar 
developed as much strength as it did. Good tests to elucidate this 
subject are much needed. 

Experiment No. 20. 

A brand of " Selenitic" cement was offered for use on the work, and 
was said to possess great merits. It was made by treating an ordi- 
nary American cement by a patented process. It was tested by com- 
paring it with an untreated sample of the same cement of which it was 
made. The following are the results of the tests : — 



Table No. 2. 



Mixture, 


Kind of 

Cement. 


1 Daj'. 


1 Week. 


1 Month. 


6 Months. 


1 Year. 


Neat . . . 
Cement . . 


Untreated . 
Selenitic . 


124 

149 


185 

168 


140 
171 


164 

282 


186 
273 


Cement, 1 . 
Sand, 1.5 . 


Untreated . 
Selenitic 








121 
120 


176 

158 


296 
276 


316 
356 


Cement, 1 . 
Sand, 2 . . 


Untreated . 
Selenitic . 








92 
103 


154 
133 


259 
226 


305 
276 


Cement, 1 . 
Sand, 4 . . 


Untreated . 
Selenitic . 








38 
49 


87 
97 


158 
167 


168 
164 



The breakings are somewhat irregular, but seem to show that this 
cement was made somewhat stronger by the selenitic process of 
treatment when tested neat, but was little, if at all, improved for use 
as a mortar ; not enough, certainly, to compensate for the higher cost. 



APPENDIX B. 



LIST OF OFFICEES CONNECTED WITH BOSTON 
MAIN DEAINAGE WORKS. 



Commission of 1875. 

E. S. CHESBROUGH, C.E. 
MOSES LANE, C.E. 
C. F. FOLSOM, M.D. 

Engineers. 

City Engineers. 

.Joseph P. Davis 1876-1880. 

Henry M. Wightman 1880-1885. 

Principal Assistants to City Engineer. 

Henry M. Wightman 1876-1880. 

Alphonse Fteley 1880-1884. 

Principal Assistant in Charge of Main Drainage Worhs. 

Eliot C. Clarke ............ 1876-1883. 

Assistant Engineers. 

William Jackson 1876-1885. 

Frederic P. Stearns 1880-1885. 

Clemens Herschel 1878-1880. 

George S. Rice 1877-1880. 

George H. Crafts 1877-1881. 

Seth Perkins 1877-1885. 

Charles S. Gowen . * 1880-1881. 

E. R. Howe 1877-1880. 

F. A. May 1876-1880. 

F. W. Ring 1876-1877. 

R. Tappan 1876-1877. 



APPENDIX B. 



141 



Principal Superintendents of Construction. 
Sewer Construction. 
H. A. Carson. 

Pumping- Statio n . 
S. H. Tarbell. 



Joint Special Committee on Improved Sewerage 

1876, 

Aldermen. 

Alvah a. Burrage, Chairman. 
Solomon B. Stebbins. 
Thomas J. Whidden. 



1877. 



Aldermen. 

Choate Burnham, Chairman. 
Charles W. Wilder. 
Lucius Slade. 



1878. 

Aldermen. 

Thomas J. AVhidden, Chairman. 
Solomon B. Stebbins. 
Lucius Slade. 



Councilmen. 

Eugene H. Sampson. 
J. Homer Pierce. 
Warren K. Blodgett. 
Marcellus Day. 
Albert H. Taylor. 



Councilmen. 

Eugene H. Sampson. 
J. Homer Pierce. 
Warren K. Blodgett, 
Martin L. Ham. 
George L. Thorndike. 

Councilmen. 

Eugene H. Sampson. 
George L. Thorndike. 
J. Homer Pierce. 
Frederick B. Day. 
James B. Richardson. 



1879. 



Aldermen. 

Lucius Slade, Chairman. 
Solomon B. Stebbins. 
Daniel D. Kelly. 



Councilmen, 

Isaac Rosnosky. 
Thomas J. Denney. 
John P. Brawley. 
Daniel J. Sweeney. 
Oscar B. Mowry. 



142 



MAIN DEAINAGE WORKS. 



1880. 



Aldermen . 

Lucius Slade, Chairman. 
Asa H. Caton. 
Geokge L. Thorndike. 



Councilmen. 

Daniel J. Sweeney. 
Charles H. Plimpton. 
Howard Clapp. 
Malcolm S. Greenough. 
Benjamin Brintnall. 



1881. 



Aldermen. 

Lucius Slade, Chairman. 
William Woolley. 
Charles H. Hersey. 



Councilmen. 

Howard Clapp. 
Thomas J. Denney. 
Malcolm S. Greenough. 
Frank E. Farwell. 
John E. Bowker. 



1882. 



Aldervnen. 

Lucius Slade, Chairman. 
William Woolley. 
Charles H. Hersey. 



CoKncilmen. 

Malcolm S. Greenough. 
Thomas J. Denney. 
Frank E. Farwell. 
Prentiss Cummings. 
Nathan G. Smith. 



1883. 



Aldermen. 

Lucius Slade, Chairman. 
William Woolley. 
Thomas H. Devlin. 



Councilmen. 

Malcolm S. Greenough. 
Thomas J. Denney. 
Frank E. Farwell. 
John B. Fitzpatrick. 
Patrick J. Donovan. 



1884. 



Aldermen. 

Lucius Slade, Chairman. 
Charles H. Hersey. 
Malcolm S. Greenough. 



Councilmen. 

Thomas J. Denney. 
Patrick J. Donovan. 
Isaac Rosnosky. 
J. Edward Lappen. 
James B. Graham. 



APPENDIX B. 143 



1885. 
Aldermen. Councilmen. 

Patrick J. Dokotan, Chairman. Edward P. Fisk. 

George Curtis. J. Edward Lappen. 

William J. Welch. John Gallagher. 

William H. Murphy. 
Benjamin B. Jenks. 



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