Evening star. [volume] (Washington, D.C.) 1854-1972, 1908-09-19
DAM ISN'T STRONG
Engineers Improving the Dale
CarIia Reservoir.
MIGHT BREAK SOME DAY
Such Accident Would Cut Off City's
Water.
REMOVING MUD DEPOSITS
Shallowness at Upper End Causes
Choking Up and Prevents
Proper Flow.
MIGHT BREAK SOME DAY
DEPOSITS

Extensive improvements are being made
to the Dalecarlia. or receiving. reservoir.
an important adjunct to the water sup
ply system of the District.
This reservoir is located on the Conduit
road a short distance above Georgetown.
and has a storage capacity of 1j0,OOD.OOO
gallons. 1t is part of the original aque-
duct system constructed about fifty years
ago. 1t has rendered good service during
most of that period. Several years ago
however. it's efficiency became seriously
impaired because of heavy deposits of silt
and otter material. The quantity of mud
deposited in the reservoir since that time
has averaged about o.4OO cubic yards A
year. These deposits occurred mainly
near the inlet, where the reservoir has
the least natural depth. Observations
showed also, that the waves washing
on the shallow mud banks produced a
considera BILE turbidity in the water flow
ing through the reservoir. On one oc-
casion the rise in turbidity was from
100 to 17J.
The shoaling in the north end near the
inlet required constant attention To pre-
vent its seriously restricting the capacity
of the entire water supply system. For
could not flow over the bar in the north
end. and it was necessary to bypass the
reservoir in order to maintain the rate
of supply.
Earthen Dam Holds Water.
The reservoir is formed by an earthen
dam across a valley and in this dam is
the by-conduit. The army engineers say
that if this dam should break the by
conduit would be destroyed and the sup
ply of the District completely cut off. In
order to remedy the defects in the resar-
voir appropriations were secured from
Congress to strengthen the by-conduit, to
riprap the sloping sides for width of
about twenty feet all around the reservoir,
and to use a small hydraulic dredge and
pontoon line to take out the large amount
of sediment already deposited in the reser-
voir above the level of the outlet, and to
keep the north end open.
When the present opera tons began in
1906 it was estimated that there were
about 1874. POO cubic yards of sediment or
other soft material distributed over The
bottom of the reservoir above the outlet.
In asking for the appropriation ii was
stated that the removal of this sediment
would increase by 27.1OO.OOO Gallons the
average storage capacity of the reservoir
In his latest report of operations Maj.
Spencer Crosby, the engineer officer in
charge Oh the water supply SNS-
TEN. says that excellent progress has been
made in the work, except for slight delays
last month, when number of small
stones were encountered. > according to his
report several banks for retaining the
dredged material have been constructed
and about $1,000 cubic yards of sediment
has been removed.
A Quarry Opened.
A quarry has been opened and plant
installed for duarrying and transporting
the stone used in riprapping the sides of
the reservoir. The grading is already %
per cent completed and the riprapping is
62 per cent completed. The dredge used
in the work is small one, having a
capacity of about 400 cubic yards a day.
AT the present rate of progress it is ex-
pected that the entire work of rlprapping
and dredging will be completed late in
the coming spring, depending on weather
conditions