By acts approved June 30, 1898, and March 3, 1899, the sum of $8,000 was appropriated for "investigating the feasibility and propriety of filtering the water supply of Washington." This investigation was conducted and a report thereon submitted to Congress on March 28,

1900.

In this report it was recommended that for the filtration of the Potomac water, as delivered for the Washington water supply, the American or rapid sand filtration be adopted. This method involves the application of a coagulant-sulphate of alumina--to the raw water. By act approved June 6, 1900, an appropriation of $200,000 was made for establishing those portions of a filtration plant which are essential to the operation of either system of filtration adopted, including necessary land, grading, masonry, and appurtenances.

A project for the expenditure of this appropriation was submitted and was approved August 15, 1900. The project consisted of the pur

chase of land sufficient for the erection of the plant and a clear-water basin, in case the American system were adopted, the estimate for land alone for the slow sand system being more than $550,000.

During the second session of the Fifty-sixth Congress the subject of filtration was before the Senate Committee on the District of Columbia, and an examination of experts on the subject of filtration was held in New York City. The subject was also taken up by the subcommittee on the District of Columbia of the House Committee on Appropriations. At the examination of experts by the Senate committee and the hearing before the House subcommittee a strong opposition to the use of any chemical as a coagulant in any process of filtration of the Washington water supply was manifested by the resolutions of the Washington Board of Trade, the Washington Business Men's Association, and the Medical Society of the District of Columbia. This manifest opposition by the future consumers of proposed filtered water had the desired effect, and Congress, complying with the expressed desire of the citizens of the District, as manifested by the above organizations, by act approved March 1, 1901, appropriated $500,000 toward establishing a slow sand filtration plant, and for each and every purpose connected therewith, including the preparation of plans, and for the purchase of such scientific books and periodicals as may be approved by the Secretary of War, to be available immediately and until expended." The evident and manifest intention of Congress has thus been declared to be in favor of the establishing of a slow sand filtration plant for the Washington water supply, in contradistinction to any system of filtration which may require the use of any chemical as a coagulant.

The site for the filtration plant as recommended by the report from this office was on ground situated on either side of First street NW., in the immediate vicinity of the Washington City reservoir, and adjacent to the grounds of the Soldiers' Home. Some controversy or difference of opinion as to the location of a site for the plant arose, but it was finally decided to locate the plant as at first recommended, and to purchase enough land to provide for the filtration of the total daily capacity of the Washington Aqueduct, or 75,000,000 gallons per diem.

On September 29, 1900, from the appropriation of $200,000, act of June 6, 1900, the block bounded by First street, Detroit street, Emporia street, and the lands of the United States, containing 169,772 square feet, was purchased from Stellwagen and Edmonston, trustees, at a cost of 45 cents per square foot, or a total of $76,397.40. It was proposed to expend the remainder of the appropriation, or as much as was necessary, in the construction of a gatehouse and clear-water basin, with the necessary gates, valves, and connections, and an intake for pumping the water to the filter beds.

When, by act of March 1, 1901, Congress decided that the slow sand system should be adopted by appropriating $500,000 more toward filtration, all plans were adapted to this system, and an additional purchase of land was made, being enough to serve for a slow sand filtration plant with a capacity of 75,000,000 gallons per diem.

The land purchased consisted of lots 2 to 13, inclusive, in block 26 and all of blocks 29 and 30 in Stellwagen and Edmonston's addition to Le Droit Park, and squares 13, 14, 15, 16, and 39 in Dobbins's addition to the city of Washington, D. C., being in all 1,207,847 square feet, at 45 cents, thus requiring $543,531.15. This left available, less outstanding liabilities, a sum of about $30,000, which it was deemed would

be required to complete the gatehouse and its connections and the intake for the pumps. It was deemed wisest to expend this balance for this purpose, in order that the Washington City reservoir should be utilized in connection with the tunnel for increasing the water supply of Washington as soon as finished, without waiting for the completion of the filtration plant.

The work accomplished during the fiscal year 1901 consisted in making drawings of various details of the filtration plant, building the necessary buildings, erecting a derrick, excavating and making forms for the clear-water reservoir, building the substructure of a gatehouse, laying pipe lines between the gatehouse and the clear-water reservoir, and excavating for the intake for the pumps to supply water to the filter beds. A topographical survey of the site for the filtration plant was also begun. Four 48-inch pipe lines were laid from the east shaft gatehouse of the Washington City reservoir to the filtration gatehouse.

OPERATIONS DURING THE YEAR.

Clear-water reservoir. This work consisted of excavating for the foundation and building 274 linear feet of the east wall. The wall was built of concrete in sections of 24 feet each, with the exception of two sections which were 29 feet each. The sections were connected by a concrete tongue and groove in the vertical abutting faces. The materials used in the concrete were Atlas Portland cement, sand, and a mixture of broken stone and gravel in proportions (an average for the whole work) of 1 of cement, 23 of sand, and 5 of the mixture of broken stone and gravel. It was mixed very wet, and although no mortar faces were made the appearance was satisfactory, with the exception of a few places where leaks occurred in the forms. The amount excavated for foundations of the walls was about 5,500 cubic yards, and the amount of concrete in the walls about 800 cubic yards. Gatehouse.-Drawings have been made for a superstructure for the gatehouse, the wells and passageways cleaned, the ironwork painted, the brick cross wall in the central chamber built, and screens and stop logs made.

Pipe lines between gatehouse and clear-water reservoir. -This work consisted in laying four lines of 48-inch cast-iron pipe between the gatehouse and the clear-water reservoir. Thirty-eight 12-foot lengths of pipe and four bends were used in these lines. They were carried under the sewer, which was supported on timbers until the pipe lines were completed, when concrete piers were carried up between the pipe lines and the excavation refilled.

Intake. The excavation for the foundation of the intake and part of the trench for the four lines of 48-inch pipe connecting it with the pumping station has been made. The concrete substructure of the intake has been completed and the four 48-inch sluice gates set. The concrete used in this work was similar to that in the east wall of the clear-water reservoir. The four pipe lines were laid for a distance of 48 feet from the intake. They extended under the sewer, which was supported in the same manner as that portion between the gatehouse and the clear-water reservoir. The amount of concrete used in the intake was 360 cubic yards.

Survey. An accurate topographical land purchased for the filtration plant.

survey has been made of the Levels were taken at intervals