Plate XV I
MAIN DRAINAGE WORKS
CITY OF BOSTON
ELIOT C. CLAEKE
Principal Assistant Engineer, in charge"
ROCKWELL AND CHURCHILL, CITY PRINTERS
No. 39 Abch Street
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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.
Early history of sewerage at Boston 7
Character and defects of the old sewerage system . . . 12
Movements for reform — Commission of 1875 16
Preliminary investigations 22
Main sewer ............ 31
Intercepting sewers .......... 37
Outfall seweb . 62
Reservoir and outlet .......... 76
Details of engineering and construction ..... 83
Working of the new system 93
Eecord of tests of cement made foe Boston Main Drainage
List of officers connected with Boston Main Drainage Works, 140
MAIN DRAINAGE WORKS.
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.
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
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.
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
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
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
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
BOSTON CITY SEWERS.
iiiiT i f n f r [ ? ! r
ng.23 24 25 26 27
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.
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.
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 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
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.
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
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
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
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
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
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.
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
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
wminMiiiiMiHiimimiwMwlumiM tiiiiiiudiiMiiiiiiniliM J "tlM ii|iiimiiiihiiii>I)hv jiiiiiii/jniiuuiiwMi iiiiaiiiiMiiHwinmiiiin
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
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
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-
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
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
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
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
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
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
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
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
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-
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
VALE ST. SEWER
BOSTON MAIN DRAINAGE
Hj bd k d bil bd bd
SCALE OF FEtT
Fi$,.8 ,^ ^
BACK VIEW. FRONT VIEW
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
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
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
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
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
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
GENERAL PLAN OF
CONCORD ST. CONNECTION
BOSTON MAIN DRAINAGE,
O 15 20 FEET
O 5 10 15 20
M° ^3"^4H-ru--U-i-^1--H-r ^^
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 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
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-
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
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
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.
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
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
CITY OF BOSTON
MAIN DRAINAGE WORKS
ip 20 30 +0 50 60 70
CITY OF BOSTON.
SECTION^L VIEW OF
FILTH HOIST AND ENGINE HOUSE
S( noN THROUdH
FILTH HOIST AND CAGFS
SECTION THROUGH PIPE CHMllBER
'SHiXSSi a S ^S
SECTION THROUGH PUMP WELLS
SECTION THROU&H SIDE GALLERY.
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-
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-
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-
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
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-
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
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
nriTjii ummMTajuj wr
K 4-0 jl
CITY OF BOSTON,
PUMPS AND FILTH CAGEIS.
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
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-
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
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.
r : Vl
% ' :P!i'
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
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
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.
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
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
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,
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 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
CHAMBER CONNECTING DEPOSIT SEWERS
WITH WEST SHAFT OF TUNNEL
TRANSVERSE SECTION OF DEPOSIT SEWERS
AND END VIEW OF SCRAPER.
LONG, SECTION OF DEPOSIT SEWER
SHOWING SCRAPER .
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
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 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
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
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
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
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
HALF SECTION HALF PLAN
BULKHEADS ABOUT SHAFTS
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
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-
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
BOSTON MAIN DRAINAGE
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.
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
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
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
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
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-
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
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
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.
C/TY or BOSTON
D/SCHAf^GE S£IV£/?S BEYOND RESC/fVOm
P/ER AND COFFER DAM.
RETAINING WALL OF RESERVOIR
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-
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-
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
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
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
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
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
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
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
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
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
MT. VERNON ST. 1883.
CITY OF BOSTON
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
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
WORKING OF THE NEW SYSTEM.
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 : —
February . .
March . . .
April . . .
May. . . .
June . , .
July. . . .
August . . .
October . .
November . .
December . .
January . .
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
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,
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
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
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=
V = Velocity in feet per second
R = Hvdraulic mean radius
I r= Sine of inclination — —, — '^-—v-
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 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-
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.
20 to 25 per C(
sewage ; 75 to 80
cent, salt water.
20 to 25 per c
sewage ; 75 to 80
cent, salt water.
11-/^0 = A
ni JO 9"I«A
jgd laa^a: oiq
-no ni aran[o^
.lad pt39n JO 8901
u; PB8H JO aso^
•uadsg: jo aiuQ
xa JO wquiu^
« — ts t;
S = Hj~
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
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
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
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-
RECORD OF TESTS OF CEMENT mXdE FOR BOSTON
MAIN DRAINAGE WORKS.
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
TUBE AND BOX
FOB WEIGHING CEMENT.
PAT OF CEMENT
TES TED FOB CHECK CRA CKS.
PAN FOB KEEPING BRIQUETTES.
LIGHT & HEA VY WIRES.
Fi G. 5.
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
eo PER CENT
BARBEL OF CEMENT
9UPEB CENT FINE
SAND te^g^^M lOPEB CENT
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
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
. . 79
. . 82
. . 86
. . 90
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
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.
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
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
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
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,
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
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,
Cement, 1 ;
6 \ o
Cement, 1 ;
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.
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.
Cement, 1 ;
Cement, ] ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
One month .
Six months .
Two years .
ROSENDALE CEMENT MORTAR.
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
One month .
Six months .
Two years .
• • •
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.
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
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
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.
Cement, 1 ;
Cement, 1 ;
1-inch Section . . .
2|-inch Section . . .
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.
Kind of Bed.
Neat . 1
Marble . .
Plaster . .
Marble , .
Piaster , .
A CUMBERLAND CEMENT.
Kind of Bed.
Neat . . j
Marble . . .
Plaster . . .
Cement, 1 . .
Sand 1 5
Sand 2 . . .
Marble . . .
Sand, 4 . . .
GERMAN PORTLAND CEMENT.
Kind of Bed.
Sand, 1 .
Marble . .
Plaster . .
. . . .
Sand, 2 .
Marble . .
Plaster . .
Sand, 3 .
Marble . .
Plaster . .
Sand, 4 .
Marble . .
Plaster . .
Sand, 5 .
Marble . .
Plaster . .
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.
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.
One week. .
One year. .
15 .20 25 30 35 40 45 50
PER CENT or WATER OrMfXTURE /N WE/GHT OF CEMENT.
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
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.
No. 120 Sieve.
Parts of Sand to
1 part of
English Portland ....
French Portland ....
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.
• No. 120 Sieve.
Parts of Sand to 1 part of
Ordinary Cement ....
Fine-ground Cement . . .
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.
No. 50 Sieve.
Parts of Sand to 1 part of
Coarse Rosendale ....
The foregoing experiments show that it is impossible, by tests on.
the tensile strength of neat cements alone, to judge of their value
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.
o <] S
Kind of Cement
used in makino
Parts of Sand to 1 part of Cement.
Cement with coarse
particles added . .
Ordinary Cement, un-
Cement whicli passed
No. 50 Sieve . . .
Cement which passed
No. 70 Sieve . . .
Cement which passed
No. 100 Sieve . . .
Cement which passed
No. 120 Sieve . . .
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.
; Sand, 2.
; Sand, 5.
Ordinary Cement, un-
Cement which passed
No. 120 Sieve . .
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.
Table No. 13.
Kind of Cement.
Parts of Sand to one part of Cement.
Ordinary Cement, unsifted .
Cement which passed No. 120
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.
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
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.
Rosendale Cement, 1; Sand 2 . .
Rosendale Cement, 0.5, \ a„j,/i o
Portland Cement, 0.5, / '
Portland Cement, 1 ; Sand, 2 . . .
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.
Table No. 16.
Kind of Mortar.
Lime of Teil, 1 ; Sand, 2 . . . .
Lime of Teil, O-'^iXc,,,,! 9
Portland Cement, 0.5, / ^*^""' " ' '
Portland Cement, 1 ; Sand, 2 . . .
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-
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.
The tests do not give very decisive results. For one week and one
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.
Cement, 2 ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
1 week . . .
1 month . . .
6 months . .
1 year . . .
Cement, 1 ;
Cement, 1 ;
Cement, 1 ;
] week . . .
1 month . . .
6 months . .
1 year . . .
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
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
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.
AVEEAGB CbNTBE BREAKING
Weight in Pounds.
Value of c
Rosendale, 1 .
Portland, 1 . .
1 . .
1 . .
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
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.
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.
Neat . . .
Cement . .
Cement, 1 .
Sand, 1.5 .
Cement, 1 .
Sand, 2 . .
Cement, 1 .
Sand, 4 . .
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.
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.
.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.
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.
Principal Superintendents of Construction.
H. A. Carson.
Pumping- Statio n .
S. H. Tarbell.
Joint Special Committee on Improved Sewerage
Alvah a. Burrage, Chairman.
Solomon B. Stebbins.
Thomas J. Whidden.
Choate Burnham, Chairman.
Charles W. Wilder.
Thomas J. AVhidden, Chairman.
Solomon B. Stebbins.
Eugene H. Sampson.
J. Homer Pierce.
Warren K. Blodgett.
Albert H. Taylor.
Eugene H. Sampson.
J. Homer Pierce.
Warren K. Blodgett,
Martin L. Ham.
George L. Thorndike.
Eugene H. Sampson.
George L. Thorndike.
J. Homer Pierce.
Frederick B. Day.
James B. Richardson.
Lucius Slade, Chairman.
Solomon B. Stebbins.
Daniel D. Kelly.
Thomas J. Denney.
John P. Brawley.
Daniel J. Sweeney.
Oscar B. Mowry.
MAIN DEAINAGE WORKS.
Lucius Slade, Chairman.
Asa H. Caton.
Geokge L. Thorndike.
Daniel J. Sweeney.
Charles H. Plimpton.
Malcolm S. Greenough.
Lucius Slade, Chairman.
Charles H. Hersey.
Thomas J. Denney.
Malcolm S. Greenough.
Frank E. Farwell.
John E. Bowker.
Lucius Slade, Chairman.
Charles H. Hersey.
Malcolm S. Greenough.
Thomas J. Denney.
Frank E. Farwell.
Nathan G. Smith.
Lucius Slade, Chairman.
Thomas H. Devlin.
Malcolm S. Greenough.
Thomas J. Denney.
Frank E. Farwell.
John B. Fitzpatrick.
Patrick J. Donovan.
Lucius Slade, Chairman.
Charles H. Hersey.
Malcolm S. Greenough.
Thomas J. Denney.
Patrick J. Donovan.
J. Edward Lappen.
James B. Graham.
APPENDIX B. 143
Patrick J. Dokotan, Chairman. Edward P. Fisk.
George Curtis. J. Edward Lappen.
William J. Welch. John Gallagher.
William H. Murphy.
Benjamin B. Jenks.
BOSTON PUBLIC LIBRARY ^^
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