Evening star., 1897-01-11
WASHINGTON AQUEDUcT
Captain Gaillard's Report on the Raising Of
the Dam at Great Falls.
How the Work Was Accomplished at
Cost Less Than That
Estimated.

Capt. Gaillard. the engineer officer in
cnarge OF the Washington aqueduct. has
reported to the War Department the COM
pietfon OF the project for increasing the
water supply of the District by raising the
height of the dam at Great Falls. The
oam extends from the Virginia to the
Maryland shore of the Potomac, crossing
Conn's Island. The reference of the crest
OF the original dam was 14s feet 1t has
been raised to reference of 1908 feet The
project of improvement involved removing
the old coping stones. raising the height
OF the body of the dam two and one-half
feet end resetting and bolting in place the
coping stones: also Strengthening the con-
duit to Withstand the increased pressure
caused by raising the dam.
How the Work Was Done.
Part or the stone used in the work was
obtained from the government quarry at
Seneca, eight miles above Great Falls The
balance was furnished by Mr.. Asa B. Cook
OF Petersburg, Va, who had the contract
The stage of the river was so high that i;
vas impossible to commence laying the
stone until April 70 last, and even then IL
was done with considerable difficulty, as
the depth of water pouring over the crest
oL the Dam was over two feet. BY the use
OF horizontal movable shutters and sand
pags ana by caiking to prevent the smaller
leaks cheap and efficient cofferdam was
devised, by means of which the stone was
nnally laid against head of over five feet
on the dam. Riprap reyetment was laid
on the upstream side of tine dam as a pro-
tectlon against ice, and about 1873 cubic
yards OF this riprap were carried over the
dam during the flood of October last
Cost Of the Improvement,
Capt. Gaillard says that all the work on
the dam was completed December II, ana
the property collected and carefully stored
away. All the employees except the as
sistant engineer. were discharged on the
10Th ult. To strengthen the conduit against
the increased pressure which NAV be de-
veloped on account of raising the dam
the embankments in which the conduit
rests were widened. In this work $3.50
cubic yards of material were put i'm place
The work of raising the dam and strength
ening the conduit has been completed at
cost much below the original estimate.
Capt. Gaiflard says that when all the out
standing liabilities have been settled in
cluding the award to the Chesapeake and
ONO Canal Company, there will remain
surplus of about s23. 600. The amount ex-
pended TO the end of the last fiscal year
was $o2.266 leaving a balance available of
N2,134, Of which amount there has been
since expended s33,3i0 leaving balance
en- hand January l, 1897. s39,394, against
which there are outstanding liabilities OF
s1o4I5, leaving an unexpended balance OF
s2391S January l. out of the appropria-
ton Of S125,00O made by the act approved
March 2, 1885. Capt. Gaillard makes no
comment whatever as to the possible effect
or this Improvement upon the general
water supply.
Condition of the Water.
The condition of the water at the various
points of the system was unusually good
during the month of December. During
three days of the month the water was
slightly turbid at Great Falls, but at the
Dalecarlia receiving reservoir and at the
efHucnt gatehouse of the distributing reser-
voir 1t was entirely clear throughout the
month without single days exception.
The water level in the distributing reser-
vor varied during the month between
1870 and 146 above the datum plane
During January it is proposed to inser- a
12-inch blow-off in the 4S-inch main at
New Jersey avenue and L street, and to
complete the work OF inserting air valves
in he md Inph f,,-