HISTORY, E LE C TRIG A L IE ST A.LAT IONS
AND PC :HGO PROJECI 1
With ueption of the St. Lawrence, the busquehanna
River basin is the largest and most Important on the Atlantic
Coast, and embraces a total area of 27,1+00 sq» miles, which com-
prises h7% of the total area of the State of Pennsylvania, ]
of the total area of the State of Mew York, and 2.% of the total
area of the State of ..aryland.
The annual precipitation over this area, according to
records of the United states Weather bureau, varies from 5I.I4.
inches to I4.i1- J inches, with a mean of J9«U inches. The run off
which eventually finds its way to the sea through the Susquehanna
River, varies from 16. 6 Inches to 29. 1 inches and averages ^% of
the rainfall. ±he run off is at a minimum in August, September,
and October, during which months it ranges from ^ to $0% of the
rainfall and averages about l%c Like all other Pennsylvania
streams, the Susquehanna River has a natural run off extremely
variable, both from day to day or week to week and from season to
High waters frequently occurs in January from melted
snow. Floods accompanied by ice gorges occur usually in : arch
and result in a- high water level, although with lesser volume of
flow than at times of clear water floods caused by heavy rainfalls,
occurring over the whole or a port! on of the water shed as late as
June. In late summer or fall, periods of low water are frequently
not ed .
During the past century there have been several great
floods in this river, the most notable of which ".'as that of June
~), which was coincident with, although not caused by the
Johnstown Flood, and which probably exceeded any flood that ever
occurred in this stream. It is estimated that during this flood
the flow reached a maximum of 7^; , C cubic feet per second.
'icial hydrograph of the ..usruehanna River for
years 1691 to 19^5 shows that the minimum discharge at Larrisburg,
Pa. was ^,aOC cubic feet per second, this occurred in 1909*
The head waters of this river system are on the elevated
plateau 'which separates the waters which flow south and east, into
the Atlantic streams from those flowing north and west Into the
ississippi, St. Lawrence and Great Lakes.
The Susquehanna river has a fairly uniform grade of 2
feet per mile throughout its entire upper region. Below, or !
the lov.-er forty miles of its course the slope increases to an
average of ^ feet per mile to tidewater and the width of the river
becomes contracted, narrt into a gorge, which in places is re-
duced to a width of two-tenths to one-half mile.
In the last ^7 "ilea of its run the river drops from an
elevation of 225 fset with an average slope of 5.6 feet per mile,
causing a swift current, which has worn a low water channel of
great depth in many places.
long this lower section the river has cut its way thro -
a range of tableland and its bed is walled by steep rocky bluffs on
both sides, affording excellent foundation for water power develop-
For more than forty years the possibilities of power de-
velopment In this lower course of the Susquehanna River have en-
gaged the attention of engineers and capitalists. The first
evidence of contemplated power development In this river is found
In the act of Legislature of the state of Maryland which was
passed in Ibbij. authorizing the busquehanaa Water Power and Paper
Company of Harford County to acquire certain property, hy condem-
nation, necessary for the proper extension and development of its
existing dam or any dam it might locate or build near that site.
This water development consisted of a small wing dam in
the bed of the river an Intake channel, head gate, power plant and
tail race. Part of this work is still in existence and comprises
what might be termed the first water power development of the
Until, however, the growth of the steam generated elec-
tric systems In nearby cities had developed a market capable of
absorbing a large part of the energy in the flow of this river Its
power development was not economically feasible.
However, in 19 10 the Pennsylvania Water and Power Com-
pany completed a dam and power house at Holtwood, Pennsylvania,
which now has an lied horse power.
The . .lecvrlc j t %t 'c . its subsid-
iary, Philadelphia Electric Power Company and the latter's .''ary-
land subsidiary, The Susquehanna Power Company, obtained a Federal
License, which was approved February 20, 1926, to build a da^ and
power house at ConoYvingo, ,.d.
The dam and power house will be located in Maryland, but
the upper half of the reservoir and the greater portion of the
transmission lines will he in Pennsylvania. This required joint
action by the Public Service Commissions of the two states. i lso,
as the sr Department has ruled that the busquehanna is a navi-
gable river, a license from the Federal Power Commission was re-
The reason for the dam being in Maryland was to be able
to produce the required maximum head.
By agreement with the Pennsylvania Water and Power Com-
pany, a pool elevation for the Conowingo Dam of 10b. 5 feet above
mean sea level, has been adopted. At this, elevation the i^ater
will be backed up over a portion of the Holtwood riant ' s tail
race, which has not yet been excavated but which when excavated,
.will result in development of increased head and power at the
Holtwood Plant. It was mutually agreed that this addtional head
could be developed more economically at Conowingo, and it there-
fore has been arranged, subject to approval by commissions having
jurisdiction, that the Cpnowingo pool be maintained at elevation
IO8.5, the holtwood Company to share in Conowingo' s Plant's gain
accruing from the increased head.
ith the pool elevation decided upon, it was desirable,
in order to develop the maximum head, to locate the dam as close
to tidewater as possible. Here, the Columbia and Port Deposit
Branch of the Pennsylvania Railroad Company, located on the east
bank of the river., imposed a limitation, In that it was necessary
to provide a satisfactory grade from the present road "bed to the
north end of Port Deposit to the elevation of the relocated
tracks above the Coiowingo Dam. A grade of •J5/& was finally
accepted by the Railroad Company.
Five possible sites for the conowlngo Dam were examined
and an exhaustive study made of the head and power available and
the total cost of development at each. The site as finally
adopted is located approximately two miles belcw the village of
Conowingo, Maryland, and is far enough north of Port Deposit to
permit the use of the accepted maximum run off grade of the rail-
road. A reservoir having an area of approximately llj. square miles
will be formed.
The hills on either side of the river at this location
form natural abutments, that on the Cecil County or east side
rising to an elevation of 250 feet above sea level, and on the
Harford County or west side rising to an elevation of 155 feet.
The river bed and banks to a height well above the pond
level, are of granitic formation. During the Autumn of 192^ twen-
ty six core borings were made along the line of the up- stream face
of the dam, between the two abutments. These were drilled to
depths varying from 5 feet to JO feet below the rock ledge. All
these cores showed firm hard granite or gabbro. In additional to
these, four borings were made to a depth of 100 feet below the
rock ledge, and these also showed hard rock for their entire
Qn the east bank then Is ample space for the erection of
construction carp and plant and for storage of materials* Trans-
portation facilities are supplied by the Columbia and Port Deposit
The main channel of the river at this site is along the
west bank. The power house therefore is being built at this end
of the dam. Space for construction plant on 'this side of the river
is somewhat limited, but an old canal which formerly operated on
this bank has been partially filled in to provide space. To sup-
ply transportation facilities for the power house construction It
was necessary to construct approximately 10 miles of railroad to
connect with the Pennsylvania Railroad System at Havre de Grace.
The tow path of the old i'idewater Canal afforded an excellent road
bed, requiring very little grading, and within three months of
the start of construction work this railroad was in operation.
Early In March, 19^6 the construction of the Conowingo
Dam and Power House was started, with an initial wheel capacity of
•57&,000 h. p. (;?9lj.,000 h. p. nit I -ate capacity). As the Phila-
delphia Electric Company will use practically the entire output
of the Conowingo Project, It was necessary that it should control
the operation of the plant- It was also essential, In order to
make the securities of the project attractive to the investing
public, that the Philadelphia Electric Company should guarantee
the completion of the project and be responsible for the payment
upon which the securities of the project depend for support. As
the Philadelphia Electric Company is not allowed by its charter
to do business in Maryland, these requirements were met by ar-
ranging to have three subsidiary corporations as follows:
First, the Susquehanna Power Company, incorporated in Maryland,
will own all physical property of the project located in that
state, comprising the dam, power honse and tail race, and portions
of the reservoir and transmission lines.
becond, the Philadelphia Electric Power Company, incorporated in
Pennsylvania, will own all physical property located in Pennsyl-
vania, this being principally lands for the reservoir, and also
the greater portion of the transmission lines. This company also
owns all of the stock of the Susquehanna Power Company.
The voting stock of Philadelphia Electric Power Company
is all owned by the Philadelphia Electric Company, which also
leases the transmission lines owned by Philadelphia Electric
And third, the Susquehanna Electric Company which was formed for
the purpose of leasing for the term of license, the properties of
The Susquehanna Power Company in Maryland, under contract with
the Philadelphia Electric Company, will operate the plant and
will sell all energy generated to Ihe Philadelphia Electric Com-
pany. All stock of The Susquehanna Electric Company is owned by
The Philadelphia Electric Company.
As set up, therefore, the Conowingo Hydro Electric
Development is being made by and for The Philadelphia Electric
Company and when completed, will be operated as a part of that
Company's system. Th construction of the development is in
charge of the Engineering Department of The Philadelphia Electric
Contract for the design and construction of the dam and
and power house has been awarded to Stone & Webster, inc., who
have subcontracted the construction of the greater portion of the
dan to The Arundel Corporation of Baltimore. The Arundel Corpora-
tion has been awarded also the contract for relocation of the
tracks of the Columbia&Port Deposit Branch of the Pennsylvania
Railroad. Contract for the design and construction of the trans-
mission lines, and for t itching station located on roof of
the power house has been awarded to Day & Zimmermann, Inc.
The west abutment of the dam is in a projecting hill or
rock, into which a retaining wall section, extending IJ4.5 feet from
the power house to the abutment, will be built to for'- an adequate
seal for the impounded waters. The head works for the power house
providing for eleven main units and two station service units,
then extend 900 feet to the beginning of the spillway section which
is ^56^ feet long. Prom the east end of the spillway the retain-
ing wall section continues 1^00 feet to the east abutment, which
also serves as the abutment for the highway bridge over the re-
located tracks of the Columbia and Port Deposit Railroad.
The dam. is solid nasonry construction of gravity type,
founded on rock at an average elevation fifteen feet above sea
level. The spillway section is designed to take care of floods
up to 860,000 cubic feet per second. It has fifty movable crest
gates for the purpose of regulating the level of the storage
. ■ .
reservoir. They are &>\ feet high by I4O feet long and weigh
about I4.2 tons eac. .
The , , is located adjacent to
the west shore. The head works provide intakes for the eleven
main units and two service units. By locating the top of the i -
e openings l f feet below the pool level, protection from float-
ing ice has been secured without expense of constructing the usual
rock fill nnd skimmer arch to protect the forebay.
The superstructure of the power house will be concrete,
with a structural steel frame* The high-tension switching station
will be located on the roof.
Seven main water wheel units will be Installed at this
time, fair will come from the Allis-Chal tiers Manufacturing Company
three from the . Crao ons Ship ngine Building. Company .
Each unit will have a capacity of $l[ t 000 h. p., and will be the
vertical shaft, single runner, cis reactic e.
The two station service water wheel units, supplied by
the S. organ S lith Company, will be 1900 h. p. each and of the
same type as the main water ''heel units.
Seven main generators and two station service generators
i.l be Installed; four main generators to be provided b; Gen-
eral Electric Company and three main generators and the station
service generators by the westinghouse Electric and Manufacturing
pa ny *
Each main generator will have a capacity of 1+0, CT(" ' va.,
generating at I3.&OO volts, J phase, 60 cycle, will be direct con-
nected to a main water wheel unit and I LI be provided with direct
connected 71> kva. auxiliary a.c. generator.
Each station service generator will have a capacity of
lbOO kva., generating at I4.6O volts, 5 phase, 60 cycles, will be
direct connected to one of the station service water wheel units,
and will be provided with a direct connected d.c. exciter.
Stationary power transformers will consist of four
of three transformers each having the following rating: 26,667 kva.,
rated capacity, 29,553 kva., overload rating, single phase, water
cooled, 15,b00 low tension voltage and 127,000-222,000 volts Y at
the high voltage terminals. The guaranteed efficiency at rated
capacity is in c-
The li - plant will be transmitted
to 3elphla at 220,' 0< volts to be utilized in The Philadel-
phia Electri c Coi
expected that the seven units
of the initial Installation will generate 1,580,000,000 kilowatt
sn the Pennsylvania Railroad is electrified between
Philadelphia and .'ashington, they will receive all of their
from the Plant at Gonowingo.
Current News, Philadelphia Electric Go.
Records, 0.3. Wenther Bureau
Public Ledger Philadelphia
nlex«nder Villi son 3rd. Const rut ion Engineer of the Philadelphia
V. H. Jones Philadelphia Electric Co.
Present Progress on the
Power Project as
Viewed From the Air
LOOKING ACROSS THE GREAT DAM FROM THE WEST BANK OF THE SUSQUE
In the foreground is the construction city, which has sprung up like a mushroom since the start of the work
ago. The huge power plant will rise in the triangle at the western end of the dam. The cleared track ex'
picture is the route of the sixty-five-mile transmission line to Philadelphia. The winding white road is the I
run over the completed dam, shortening the auto route to Washington by four and a half miles. The white 1
marks the. relocation of the Columbia and Port Deposit Railway, which is being moved back for a di
WILL BE FORMED
Paper Mill Island,
just above the darn,
will be entirely sub-
merged. Across the
narrows is the Cono-
wingo Bridge, which
will be abandoned
when the Baltimore
Pike is carried over
the t we n t y - foot
roadway atop the
dam. The work will
be inspected next
Friday by the Gov-
ernors of Pennsyl-
vania and Maryland
and a distinguished
Photos (c) Victor Damn
THE KING OF
mechanism of his
plane to King Albert
at the Evere aero-
<c> p. 4 A.
A striking bust of
+Urt Trf\n+-"hfnl air
A VIEW DOWN THE RIVER TOWARD CHESAPEAKE
The dam is 4633 feet long, or 300 feet longer than the famous Wilsor^
ShoaLs. In the dis- ' '
THE UPPER END
The 9000-acre lake
formed by the com-
pletion of the dam
late this summer
will extend almost
up to the Holtwood
dam and power plant
(shown in center of
picture), which sup-
ply Baltimore with
power. The capacity
of the basin will be
9— East Plant, general
view showing progress a}
construction «« tiarn.
Fig. 10 — /;as/ Plant, showing constmction-bridge, deck, gantry
crane and concrete mixing plant.
Montrose -'"") v — N
'} MntiHllS, POUGHK£lPS,L c
w .■ i NEWBUH6"
^AZLETON atrouasburg \
- &&**»"% ,j MTERSCN
* *VJ A EWTON 4 ^ 8 ^BKVcW
SU.BNTOWrf' "sO.BETHljillEM J^ ^ J _ J^ •
tQNKERS 1 -
....jaw ° ,
y £. WtwtW'
^^TOwifcMifeo o N0BRBT0WN w"
,NWSTER / yf*6Mti
> / VtetGhKlW -?TjiMDE«
CHESTER 0. !
Harpers Ferry — y
fj£. J. MfljJ SbowiiiR Susquehanna River Basin.
A — West Plant — Looking upstream from towpath showing west abutment, west of first service unit, and retaining wail. B —
West Plant — Looking north-northeast from west ahntment at night, showing work in power home cofferdam. C—East Plant —
Looking south-southwest along downstream side of construction trestle during flood. Cofferdam under about 9 feet of water. D —
West Plant — Looking north-northeast from west ahntment showing progress in power house cofferdam and concrete at xvest
abutment. E — East Plant — Looking south from Petwa. Railroad showing progress on dam. Contraction joint of abutment sec-
tion is at station 34 50*
F — East Plant — Looking northeast from end of upstream cofferdam showing progress on spilhi'ay section, G — -East Plant —
Looking w? at -north west from construction trestle showing water tunning through }%-foot opening in spillway section during flood.
I! — East Plant — Looking north- northwest from construction trestle showing water running over cofferdam and through ? 9 -foot
opening in spillway section. I — East Plant — Looking southwest from construction trestle shotting abutment section of dam raised
to 1 12 J I feet. Four piers raised to final height y 108 J feet* One 4$" highway girder in place. Contraction joint is shown at
station 54 FO*
Fig. t, l-'iiitnl Stairs Gtohn'Ciil Survey Ms(i, \bowltif tbi territory in which the Ctujtowittgo Project is Inratt,!, iiiit iht
rrlitttt'f position!, nf Holtwooil ana Cr»um-hig,o Diim.
The frame of one of the Westinghouse waterwheel generators for the Conowingo development as It lay on the floor of the Weslinfthouse Works at East Pittsburgh,
This frame Is 38 feet in diameter and it is not exceeded in size by any other machine except the large steam
engine driven generators built by Westlnghouse two decades ago.
One of the seven
ft elf -cooled trans-
formers built by
WeKtin&house for the
Station of the Phlla-
d e I p h J a Electric
( ]o in pu ny ne:t r P h il-
-i d *• I \* h i -i IT. S. A.
These t ransf or m ers.
tire the largest tilnftle-
in the world. They
are rated at ££ T 333
-I I I !?■■> '**■
'■ : 'r, ; ^
l : i%. 4— Showing general plan ami sections of dam.
Cors + rvc-fsos? Ca mfe on
\fces f ^honk.
C rune. \t$o,d ~t* ra/fc
/^we/ /-/a use- &r><sf
Vie yV O / Dam 'from