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REPORT OF COLONEL GEORGE H. MENDELL, CORPS OF ENGINEERS.

UNITED STATES ENGINEER OFFICE,

San Francisco, Cal., June 14, 1887. SIR: I have to report in regard to works under my charge, that no piers, breakwater, or other structures built by the United States in aid of commerce or navigation are used, occupied, or injured by a corporation or by an individual, except that near the in-shore ends of both jetties of Oakland Harbor, California, a little injury has been done by fishermen in removing the top of the stone work so as to enable them to pass small fishing-boats, and save the distance required to pass around the outer ends of the jetties. Very respectfully, your obedient servant,

G. H. MENDELL,

Colonel, Corps of Engineers. The CHIEF OF ENGINEERS, U. S. A.

APPENDIX Y Y.

MAINTENANCE AND REPAIRS OF WASHINGTON AQUEDUCT_INCREASING WATER SUPPLY OF THE CITY OF WASHINGTON-ERECTION OF FISHWAYS AT THE GREAT FALLS OF THE POTOMAC.

REPORT OF MAJOR G. J. LYDECKER, CORPS OF ENGINEERS, OFFICER

IN CHARGE, FOR THE FISCAL YEAR ENDING JUNE 30, 1888, WITH OTHER DOCUMENTS RELATING TO THE WORKS.

IMPROVEMENTS.

1. Washington Aqueduct.
2. Increasing the water supply of the city

of Washington, District of Columbia.

3. Erection of fish-ways at the Great Falls

of the Potomac.

OFFICE OF THE WASHINGTON AQUEDUCT,

Washington, D. C., July 10, 1888. Sır: I have the honor to transmit herewith reports of operations on the Washington Aqueduct; increasing the water supply of Washington, D. C., and erection of fish-ways at Great Falls of the Potomac, for the fiscal year ending June 30, 1883. Very respectfully, your obedient servant,

G. J. LYDECKER,

Major of Engineers. The CHIEF OF ENGINEERS, U. S. A.

Y Y 1.

WASHINGTON AQUEDUCT.

Operations on this work are, in general, of a routine character, and have for their object the maintenance and repairs of the aqueduct and its accessory structures, the care and repairs of the Government mains by which the water supply is taken from the distributing reservoir to the system of distributing mains of Washington and Georgetown, and the care of the high service reservoir in Georgetown. To this end the gates by which the supply of water to and through the aqueduct is reg. ulated, at the several influent and effluent gate-houses, were regularly worked and oiled, and also the various stops on the Government main; surface drains and culverts along the line of the aqueduct road were

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kept clear and free from obstructions; the fencing about Government property at the Great Falls, the two reservoirs, and aqueduct office were repaired and white-washed; at the receiving reservoir some repairs were made to the keeper's dwelling, including the renewal of cornice, gutter, and down spouts. At the distributing reservoir the screens of the effluent gate-house, having been destroyed by ice, were renewed, and the domes of both gate-houses were repaired and painted. For the protection of the old dam across the Maryland Channel at the Great Falls about 850 cubic yards of riprap stone was placed as a backing.

The security of the aqueduct requires that considerable work be done annually to the overlying roadway in order to prevent heavily laden vehicles from cutting through and injuring the arch of the conduit ; to this end all ruts and holes are filled with broken stone as they develop, and a macadam roadway is being gradually completed throughout the entire extent of road which overlies the conduit—the length of road so treated during the past year was about 16,700 linear feet, principaliy on the Great Falls division; the amount of broken stone used for that purpose being 4,682 cubic yards. The flooring of bridge spanning the

. waste channel at the receiving reservoir was renewed with 3-inch Georgia pine.

During the year three leaks appeared on the line of the Government mains, and were duly repaired, two of them being small affairs only, but the third a serious matter, as follows: 1st, in August, 1887, in the roadway a short distance west of the Aqueduct Bridge over the Potomac, near Georgetown, which was found to result from an abandoned service-pipe that had been tapped into the 30-inch main; it was taken out and the main securely plugged. 20, in November, 1887, at the College Pond crossing, the calking having been blown out of a joint in the 30-inch main. 3d, about 3 o'clock on the morning of June 29, 1888, a serious break appeared at the pipe-line crossing of Foundry Branch, the repairs of which required uninterrupted work through thirty con secutive hours, during which the supply of water in the city was reduced to a dangerously low limit; one entire section of the 36-inch mair, 121 feet long, was destroyed by this break and had to be removed; another section in the immediate vicinity was found cracked, but this section was easily and quickly repaired by banding. The speedy re. pairs made on this occasion were rendered possible only by reason of measures that had been taken in advance, to have on hand spare joints, collars, bands, plates, etc., fitted to the size of the main, in readiness for instant application. The break appears to have been caused by the fact that this large main was at this point supported on timber sills which bad rotted out and left the main, with its load of water, without proper support.

The outflow of water from the distributing reservoir, as measured during the twenty-four hours ending at 6 a. m. June 23, 1888, was 29,115,774 gallons, being 2,237,350 gallons more than the outflow as measured about the same time in the year preceding. (See Table 1.)

The water supply, as it passed the effluent gate-house of the distributing reservoir, was clear on 240 days, slightly turbid 16, turbid 52, and very turbid 58. (See Tables 2 and 3.)

The water level at the inlet to the aqueduct at the Great Falls has varied from a maximum of 2.5 feet (on February 26, 1888) to a minimum of 0.6 feet (on August 10, 1887) above the crest of the dam. (See Table 2.)

The average water pressure for the year in the supply-mains at the crossing of Rock Creek, as reported daily at 9 a. m., was 29.93 pounds

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per square inch; the maximum 9 a. m. pressure was 34} pounds, and the minimum was (disregarding the exceptional and temporary reduc. tion caused by the breaking of the 36-inch main) 28 pounds. The average pressure during 1887 was 31.03 pounds. (See Tables 2 and 4.)

The following tables, from which the items above noted were deduced, will furnish more detailed information in relation to the same points:

TABLE 1.-Showing hourly flow from distributing rescrvoir for the twenty-four hours end

ing June 23, 1888.

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Fert.
.09
.08
08
08
.08

Juno 22

From 6 a. m. to 7 a. m....
From 7 a. m. to 8 a. m....
from 8 a. m. to 9 a. m.
From 9 a. m. to 10 a. m...
From 10 a, m. to 11 a. m..
From 11 a. m. to 12 m
From 12 m. to 1 p. m.
From 1 r. m. to 2 p. nu
From 2 p. m. to 3 p. m
From 3 p. m. to 4 p. m
From 4 p. m. to 5 p. m
From 5 p.m. to 6 p. m
From 6 p. m. to 7 p. m
From 7 p. m. to 8 p. m

Gallons.
1, 256, 705
1, 116, 250
1, 115, 475
1, 114, 699
1, 113, 923

Feet.
.07

09
. 10
09
09
10
09
09
10
09
09
09
10

June 22-Continued

From 8 p. m. to 9 p. m
From 9 p. m. to 10 p. m
From 10 p. m. to 11 p. m
From 11 p. in. to 12 m....

From 12 m. to 1 am
June 23-

From 1 a.m. to 2 a. m
From 2 a. m. to 3 a. m
From 3 a, m. to 4 a. m
From 4 a. m. to 5 a, in
From 5 a, m. to 6 a. m

Gallons.

988, 384 1, 269, 906 1, 409, 856 1, 267, 834 1, 266, 652 1, 406, 462 1, 264, 780 1, 263, 798 1, 403, 069 1, 261, 726 1, 260, 744 1, 239, 763 1, 398, 585 1, 257, 690

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. 09

The outflow during twenty-four hours, as measured in the latter part of June, for the past fifteen years is as follows:

Year.

Gallons.

Year.

Gallons.

Year.

Gallons.

1874. 1875. 1876. 1877. 1878.

15, 554, 848
21,000,000
24, 177, 797
23, 252, 932
24,885, 945

1879.
1880.
1881.
1982.
1883.

25, 947, 642
25, 740, 138
26, 525, 991
29, 727, 861
24, 314,715

1881.
1885.
1880.
1837.
1888.

24, 827, 013
25, 219, 191
25, 512, 476
26, 878, 424
29, 115, 774

TABLE II.-Showing-for each day in the year—(a) condition of water at Great Falls, receio

ing reservoir, and distributing reservoir ; (b) heights of water over dam at Great Falls (c) 9 a. m. pressures at Rock Creek.

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