On September 29, 1894, a contract was entered into with the Shailer & Schniglau Company, of Chicago, Ill., for the repair of Piers Nos. 2, 3, 5, 6, 7, and 8 by Portland cement concrete in bags put in place by a diver, and for the repair of Pier No. 4 by means of a cofferdam within which new masonry was to be laid in the eroded cavity, the bridge spans resting on Pier No. 4 to be supported on false work during the repairs to provide against any possible further failure of the pier when the water was pumped out of the cofferdam and the effective weight of the overhanging masonry of the upstream end thereby increased.

After the cofferdam had been pumped out and débris disposed of, the overhanging masonry of the ice breaker was removed in order that the reconstruction of this part of the pier might be safely prosecuted. This masonry, which was just above the eroded cavity, was found to be well laid in lime mortar and was removed with some difficulty. The removal of the débris below the eroded cavity was next undertaken, the excava tion being carried down to solid rock and as far downstream as the first line of cross braces of the original cofferdam of 1838, which timbers, 21 in number, had been left in place and built into the masonry of the pier. As this work went on, it was found that the old masonry had not been started from solid rock, and part of it was of poor quality.

The Acting Secretary of War and the Chief of Engineers made an inspection of the work on June 24, 1895, and in view of the poor quality of the masonry at the base of the pier it was decided that after the completion of the present contract (for the upstream end of the pier) it would be necessary in the near future to remove the defective masonry in the remainder of the pier and replace it by masonry of proper quality founded on the solid rock. The existing appropriation was insufficient for this purpose, and it was therefore necessary to ask a further appropriation from Congress. The cofferdam would be needed for the proposed work, and the contract was therefore modified June 27, 1895, so as to provide for the purchase of the cofferdam from the contractors for the sum of $3,000 in lieu of its removal by them, for which last they were to be paid $1,500 and were to have the timber.

The work of repairs under the appropriation of August 7, 1894, was completed in August, 1895. The total expenditure, including contract work, hired labor, purchase of materials and cofferdam, superintend ence, inspection, etc., was $46,379.70, leaving a balance of $4,690.30, which reverted to the United States Treasury.

Full reports of the work of repairs to the bridge piers will be found in Appendix A A A to the annual reports of the Chief of Engineers for 1895 and 1896.

A complete report and estimate of the cost of reconstruction of pier No. 4 will be found in the report dated November 30, 1895, of the officer then in charge, and published as Document No. 158, House of Representatives, Fifty-fourth Congress, first session. The estimated cost of reconstruction of the pier was $65,000, which sum was appropriated as follows, by the act of Congress of June 8, 1896:

Repairs to Aqueduct Bridge: For reconstruction of pier numbered four of the Aqueduct Bridge across the Potomac River at Georgetown, District of Columbia, to be available until expended, sixty-five thousand dollars.

A contract for the work of reconstruction of the pier was made May 17, 1897, with the Houston Construction Company, of Philadelphia, Pa. The contract was approved May 28, 1897. The work to be completed November 1, 1897. Amount of contract, $30,000.

The contractors commenced work on the 28th of May, and by the close of the fiscal year had most of their plant in position on the coffer

dam; had made some progress in quarrying stone at their quarry, which is on the east bank of the Potomac, and about 3 miles above Georgetown; and had done some work toward putting in repair the false work for supporting the spans adjoining pier 4, and also the cofferdam.

Other work during the fiscal year ended June 30, 1897, consisted in some slight necessary repairs by hired labor to the cofferdam.

Amount expended during fiscal year ended June 30, 1897, $1,446.43.

July 1, 1897, outstanding liabilities..

$136.00

July 1, 1897, amount covered by uncompleted contracts....

July 1, 1897, balance available

33, 117.57

Abstract of proposals for reconstruction of pier No. 4 of the Aqueduct Bridge, District of Columbia, opened by Lieut. Col. Chas. J. Allen, Corps of Engineers, March 22, 1897.

All the above proposals were rejected and the work was readvertised under date of April 10, 1897.

Abstract of proposals for reconstruction of Pier No. 4 of the Aqueduct Bridge, District of Columbia, opened by Lieut. Col. Chas. J. Allen, Corps of Engineers, April 30, 1897.

NOTE.-The bid of R. H. Hood was not made in accordance with printed form.

The contract was awarded to the Houston Construction Company, the lowest bidder. Date of contract, May 17; approved May 28, 1897. Date of commencement, on or before May 30; date of completion November 1, 1897.

APPENDIX A A A.

WASHINGTON AQUEDUCT AND INCREASING THE WATER SUPPLY OF WASHINGTON, DISTRICT OF COLUMBIA.

REPORT OF CAPT. D. D. GAILLARD, CORPS OF ENGINEERS, OFFICER IN CHARGE, FOR THE FISCAL YEAR ENDING JUNE 30, 1897.

1. Washington Aqueduct.

2. Increasing the water supply of Washington, D. C.

OFFICE OF THE WASHINGTON AQUEDUCT,

Washington, D. C., July 17, 1897.

GENERAL: I have the honor to forward herewith the annual reports for Washington Aqueduct and increasing the water supply of Washington, D. C., for the fiscal year ending June 30, 1897,

Very respectfully, your obedient servant,

Brig. Gen. JOHN M. WILSON,

D. D. GAILLARD, Captain, Corps of Engineers.

Chief of Engineers, U. S. A.

A A A I,

WASHINGTON AQUEDUCT.

Appropriations for the Washington Aqueduct are applied to the improvement, maintenance, and repair of all of those parts of the water supply that have been placed under the supervision of the Chief of Engineers, except the new reservoir near Howard University and the tunnel connecting it with the distributing reservoir. These are the masonry dam across the Potomac at Great Falls, the works there for regulating the supply to the conduit, the conduit from Great Falls to the distributing reservoir, the three reservoirs for supplying the city, the mains for delivering water from the reservoirs into the city's distributing system, and the two bridges for carrying the mains across Rock Creek.

The water supply is taken from the Potomac River at Great Falls, about 14 miles above the city.

At this point a masonry dam extends across the river from the Maryland to the Virginia shore. Its total length is 2,877 feet, and the width

of its crest in the Virginia channel and across Conns Island is 8 feet 3 inches and in the Maryland channel 7 feet 9 inches. In 1895-96 the crest of the dam was raised from a reference of 148 feet above mean tide at the Washington Navy-Yard to 150.5 feet above the same datum plane.

The top of the mouth of the feeder of the conduit at Great Falls is at a reference of 149 feet and the bottom at a reference of 139.5 feet. The water passes from the feeder through the gatehouse and into the conduit, which at this point has a reference of 152 feet at the interior surface of the crown of the arch.

The slope of the conduit is uniform between the gatehouse at Great Falls and the distributing reservoir and is 9 inches in 5,000 feet.

The conduit is circular in cross section, and for the greater part of its entire length is 9 feet in diameter and composed either of rubble masonry plastered or of 3 rings of brick, but where the soil in which it was built was considered particularly good the inner ring of brick was omitted and the diameter is 9 feet 9 inches. Where the conduit passes as an unlined tunnel through rock the excavation was sufficient to contain an inscribed circle 11 feet in diameter.

The lengths of the conduit and its connections are as follows:
Length of feeder at Great Falls, 256 feet.

Area of cross section at mouth, 157.45 square feet.

Length of conduit between gatehouse at Great Falls and north connection of Dalecarlia Reservoir, 47,896.5 feet; least diameter, 9 feet. Length of by-conduit around Dalecarlia Reservoir, 2,730.5 feet; diameter for 625 feet, 8 feet; for rest of distance, 9 feet.

Length of conduit between south connection of the Dalecarlia Reservoir and north connection of the distributing reservoir, 10,149.87 feet; diameter of conduit, 9 feet.

Length of by-conduit around the distributing reservoir, 2,274.35 feet; diameter, 7 feet.

At the distributing reservoir the water passes into 4 cast-iron mains 48 inches, 36 inches, 30 inches, and 12 inches in diameter, respectively. The Dalecarlia Reservoir has a storage capacity of about 150,000,000 gallons, is practically without paved slope wall, is perfectly protected against pollution from the drainage of the surrounding country, and is provided with a spillway, the reference of the bottom of which is 146.5 feet. The reference of the interior surface of the crown of the arch of the conduit at the north connection of this reservoir is 143.77 feet and at the south connection 143.39 feet. The distance between these points, measured along the line of flow of the water across the reservoir, is about 3,550 feet.

The distributing reservoir has a storage capacity of about 150,850,000 gallons and is divided by a puddled and paved wall, through which is a passageway which can be closed with stop planks, into two sections, containing 97,600,000 and 53,250,000 gallons, respectively.

The interior surface of the crown of the arch of the conduit at the north connection of this reservoir has a reference of 141.87 feet.

The Georgetown high-service reservoir is circular in plan and has an available capacity of about 1,500,000 gallons. The reference of its water surface when the reservoir is full is 220.5 feet. Although this reservoir is under the charge of this office, the duty of keeping it filled by pumping devolves upon the water department of the District of Columbia.

In addition to the three reservoirs already mentioned, which form a part of the aqueduct system, there is another reservoir, built and con