Evening star., 1896-02-22

Three-ring arch, with inyert- Dry stone backing.
carlia reservoir. which crosses the bound
airy Of the District of Columbia. y continue
alton of this conduit. nearly two miles long
conveys the water from the Dalecarlia TO
the distributing reservoir. which is about
1.iJ miles from Rock creek. Water is dis
tributed from this reservoir by four pipes
twelve, thirty. th:rty-s.x and forty-eiSht
inches in diameter.
The storage capacity OF these two reser-
voirs IS about %4o.0'tl.00O gallons, and the
daily consumption and use of water. as
measured recently. was 41.1S2GS1 gallons
Or lao gallons per head.
Great Falls Dam.
Tho present height of the dam at Great
Falls is three feet below the crown of the
mouth of the conduit. At lowest stages OF
the river the water is six inches higher than
the dam. The dam is now being raised .
feet and inches. so that when raised the
mouth of the conduit will just be filled at
the lowest stages OF the river
The work of increasing the water supply
of this city was commenced pursuant 20 ar
act of Congress approved July IL, 1852 and
included ID raising the dam in the Maryland
channel at the Great Falls to az elevation Of
lis feet above mean high tide at the Wash
1ngton navy yard. and its extension at that
height across Co1n's Island and the Vir-
giniI channel of ,he river: t2) tunnel con-
duit: 60 a reservoir, and CS connecting this
reseryCir with the existing system of water
Ifdl1S " q new Hne OF large mains. Inc
dam was finished in August, 1SSi and the
new mains laid up to the site of the reser-
vo!r in 1SSJ.
The "LyiecI>er" Tunnel.
The tunnel conduit extends 2o696 feet in
straight line from the east end of the dis
tributing reservoir to new reservoir OF
about ayo.oOOoo1 gallons capacity situated
east of Howard University. and at the south
west corner Of the grounds of the Soldiers
Home. The cross section varies with the
class of lining used. the minimum area of
this section being 1si3I square feet. and its
hydraulic radius :. ID; feet. The denth of the
bottom of this conduit below the proposad
hydraulic grade line varies from II to 1T5
feet.
The original plans for the tunnel did not
contemplate the recessity OF lining the
walls. as IL was estimated that the rocl.
through which the conduit was pierced
would he sufficiently solid 70 retain the
water without lining, but after the excava-
tions had been made Il was fo,ind that the
Iock deteriorated under atmospheric in
nuences, and became so soft as 10 cause
the water to per2olate through the many
fSsures. This necessitatcd ;he lining of
the tunnel. and the plans were amended so
as to provide for the construction of
brick conduit inside OF the rock excavation
Owing TO the irregularities of the surface
caused by the Blasting of the rock the
linen wall of brick had to be backed ly
rubble masonry or filling. so as to present
solid wall TO resist the pressure of the
water, instead of q hollow shell. The con-
tractors found that the darkness of the
tunnel enabled them to do the work in n
sltpshod manner, and in long spaces he
lining wGs left without backing Whenever
an inspector approached a warning was
given and a buikhead or false wall was
thrown up by the men, thus giving the an
pearance OF solid backing and covering
many rods OF dishonest workmanship.
Fraudulent Work Discovered.
In the summer OF 1883 rumors reached .his
city that frauds of this character were be-
ing precticed in the work on the new Gro
ton aqueduct tunnel in New York, which
was IN the hands Of the same contractors
as the local enterprise, and suspicion was
raised against the integrity OF the work