Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-11-15
Maj. Davis First Report Of the
Operations for Increasing It.
GOOD RECORD FOR CLEARNESS SHOWN
Work Going On for Increasing the
Height Of the Dam.
CLEANING THE CONDUIT


ton. By act of Congress of March q 1895,
$4,000 were appropriated for engineering,
maintenance and general repairs Of the
Washington aqueduct. Major Davis briefly
reviews the work accomplished up to Octo-
Der l, and then tells what has been done by
the office since he took charge on the
date named. During the entire month the
height of the water on the gauge at
the mouth of the conduit at Great Falls has
been practically 1855 above the datum plane.
On October % the reading on the gauge was
14S.4S, but one-hundreth Of a foot above the
lowest reading ever recorded since the COM
pletion of the dam. The condition of the
water as regards clearness Is reported as ex-
cellent. According to the scale for recording
the condition, the numbers OF, inclusive,
correspond to very turbid water; STA, tur-
bid; 1921, Slightly turbid, and 1885, clear
The recorded condition of the water, both
at Great Falls and at the entrance to the
mains, was 80 for the entire month. Two of
the iron gates at the gate house at Great
Falls, which have been broken for several
years and unfit for use, have been removed
and new ones are being made.
The repairs to the roadway Of the Penn
sylvania avenue bridge across Rock creek
and to the wooden bridge crossing the spill
way at the Dalecarlia reservoir were COM
pleted. The telephone line from Georgetown
to Great Falls has been put in good repair
and four telephones were added to the
equipment. An inspection of the inside of
the conduit between the dam and waste
weir No. having disclosed the presence in
the conduit OF numerous Sunlsen logs five to
eight inches in diameter and several feet in
length, new screen at the intake near the
dam was deemed necessary. 1t is proposed
to construct this screen and put it in place
this month. The new gates will probably be
put in place this month.
Raising the Great Falls Dam.
Interesting details are given of the work
of raising the height of the dam at Great
Falls, for which Congress appropriated
S125,OOO at its last session. This dam ex-
tends from the Virginia to the Maryland
shore, crossing COINS Island. The pres
emit height of its crest is 14S feet, and it is
to be raised 20 height of 1915 feet. The
stone for the work is procured from the
government quarry at Seneca, on the Ches-
apeake and Ohio canal, eight miles above
Great Falls. 1t is brought down to the
dam on bargeo The work of getting the
stone and raising the dam at Conn's Island
was carried on during the last month under
the original approved project Maj. Davis
says the quarrying is attended with much
difficulty, owing to the great depth of over
lying material. which has to be stripped
Weather and water conditions have been
favorable for the work on the dam itself,
and good progress has been made. The
total amount of cut stone laid to date is
yet to be laid. So far 1873 cubic yards of
coping have been reset on the dam, leaving
915 cubic yards yet to be reset. There have
been placed II cubic yards of concrete and
yards of concrete and 1,64O cubic yards of
rip-rap yet to be placed. The work of the
contractor on the galloway between Conns
Island and the Virginia shore has pro-
crossed somewhat slowly, Maj. Davis says,
and 1T is not probable that it will be COM
pleted before the middle or the latter part
of November-too late to be used for this
seasons work. The work of raising the
dam will be continued until it is prevented
by freezing weather. The stripping of the
quarry at Seneca will also be continued as
long as possible.
The prir cipal part of the report is de-
voted to tie operations for the removal of
deposits in the conduit of the Washington
aqueduct. The approved project contem-
plates emptying the corduit as often as is
considered advisable, locsenirg up the de-
posits and sluicing them out through the
waste gates.
Removing Deposits in the Conduit.
By act approved March 2. 1895. $4,000
were appropriated for removing the ac-
emulation of deposits in. the conduit.
From the nature of the material 1t was
found impossible to clean the conduit prop
erly by sluicing, as provided in the project,
and the work Is now done by loading this
material into tubs and wheeling it to the
surface.
During the present fiscal year and up to
the beginning Of the month the conduit
had been cleaned from the Dalecarla res
ervoir to manhole 81, the length cleaned
being 1900 feet and the estimated quantity
of material removed $40 cubic yards.
In regard to recent operations, Maj. Davis
says:
the water was shut off from the conduit at
am. October 10 and turned on at 0 am.
October II. 1t was again shut off at
a m. October "a and turned on at am
October 26. The head above datum plane
at the distributing reservoir when the wa
ter was shut off on October 10 was 1882,
and when 1t was turned on on October II
the water level in this reservoir had fallen
to 141.6S, a total fall of 3.14. From this
level the water in the reservoir rose slowly
until October "a, when it had reached
height of 144.65, and was again shut off for
a like period and fell to 141.50, 315 during
clear ing operations.
After the water Is shut off it takes about
seven hours before the conduit is suf1i-
GENTLY emptied for men to work in it, so
until the river rises 1t appears that there
will never be more than about eighty-two
hours per month during which men can
work in the conduit.
Character of the Obstruction.
An inspection OF the inside Of the conduit
between its mouth and waste weir No. l.
and between manholes A and 4J, showed
that in the first reach the conduit was OBJ
structed principally by a sedimentary de-
posit of exceeding fine and tenacious clay,
and to some extent by sunken logs and
boulders several cubic feet in volume, the
latter occurring principally in the tunnel
portions of the conduit. Between mannoles
A and 40 the obstruction consisted entirely
of the fine, tough, clayey sediment Ac-
curate measurements of the area Of the
cross section Of the sediment between man
holes AZ and 45 showed that the greatest
cross section was 7.S9 square feet, and what
was judged to be about an average cross
section measured SIS square feet. The sedi-
ment is so tenacious that sluicing appears
to have but little effect on it, and 1t is now
loaded in tubs, which are wheeled to the
nnanhnla hnis ,I-itb