trolled by the Commissioners of the District of Columbia, called the Fort Reno reservoir, with a capacity of about 4,500,000 gallons, the reference of its water surface when the reservoir is full being about 420 feet. This reservoir, like the high-service reservoir in Georgetown, is supplied with water taken from the supply mains by the U street pump. The Dalecarlia and distributing reservoirs supply this station and that part of the District which lies below 100 feet above datum. The areas lying between the levels of 100 and 210 feet above datum are supplied by pumping from the U street station directly into the distributing mains, the Georgetown high-service reservoir being held as a reserve supply. The areas having a greater elevation than 210 feet above datum are supplied from the Fort Reno reservoir. It will be observed, therefore, that the total present storage capacity of all reservoirs is a little less than 307,000,000 gallons, or about seven days' normal supply. Until the average daily consumption of water becomes considerably greater than at present, the reference of the surface of the water at the lowest stage of the Potomac will be about 151 feet at the mouth of the feeder at Great Falls, about 146.75 feet at the Dalecarlia reservoir, and 146 feet at the distributing reservoir. From August 17 to November 16, 1896, Maj. Charles J. Allen, Corps of Engineers, was in temporary charge of the Washington Aqueduct and its accessory structures during my absence on duty in Alaska. The following statement shows the operations upon the aqueduct and its accessory works during the fiscal year and their condition at its close: GATEHOUSES, WATCHMEN'S QUARTERS, AND OTHER BUILDINGS. The watchman's house at the Dalecarlia Reservoir was furnished with a new roof and a complete set of new window shutters. The laborer's house at the same reservoir was extensively repaired throughout. The engine house on the Virginia shore at Great Falls was provided with a new felt roof. The four gatehouses at the Dalecarlia and distributing reservoirs, and the house over the entrance to the valve chamber at the latter, which had become much discolored and weather-stained, were covered with a wash of Portland cement, which greatly improved their appearance. All other buildings were repainted or whitewashed, and such minor repairs as were necessary for their proper preservation were made. THE RESERVOIRS. The improvement of the Dalecarlia Reservoir was completed under the supervision of Col. George H. Elliot, United States Corps of Engineers, retired, on November 15, 1895, with the exception of the acquirement by condemnation of a small piece of land, four hundred and eight one-thousandths of an acre, the property of John P. Hickey, proceedings for the acquirement of which were in progress at the close of the last fiscal year. These proceedings were completed early in the present fiscal year and the award was paid to Mr. Hickey on September 5, 1896. The works were designed to divert from the reservoir the drainage from a watershed of about 3,825 acres, which drainage had so polluted its waters as to cause the reservoir to be thrown out of service in the spring of 1888. This drainage formerly entered the reservoir by three streams, Little Falls Branch, Mill Creek, and East Creek, with drainage areas of about 2,700, 900, and 225 acres, respectively. The plan of improvement adopted consisted in constructing dams across these streams just above their mouths, and carrying the waters of East Creek by an open intercepting channel around the margin of the reservoir into Mill Creek above its dam, from which point by a similar and proportionally longer channel around the reservoir and a short tunnel through a hill the drainage of the two streams and the slopes adjacent to the open channels were carried into Little Falls Branch above its dam. The drainage of the entire watershed, thus collected, was carried into a shaft 51 feet deep, excavated in the bed of the latter stream. From the bottom of this shaft a tunnel 1,000 feet long and 7 feet in diameter carries the water under Dalecarlia Hill to its former course leading into the Potomac River. These works are in excellent condition, are very sightly in appearance, and effect perfectly the object for which they were designed. A large number of trees blown down in the storm of September 29, 1896, near the northwest shore of this reservoir were cut up and removed, and the underbrush, leaves, and straw around the borders of the reservoir have been burned or carted away. Some of the more irregular banks of this reservoir were graded and the excess of materials used in filling the few shallow, marshy portions of the reservoir. The unsightly spillway was extensively repaired and its appearance much improved thereby. A gauging weir for computing the overflow of the spillway was constructed in the channel beneath the wooden bridge. A boathouse in course of construction near the south connection of the reservoir will afford much needed protection for the boat used in operating the works at this reservoir. An iron hand rail was placed around the shaft at the Dalecarlia Reservoir as a measure of precaution against accidents. About 800 feet of the wooden fence around the distributing reservoir damaged by the storm of September 29, 1896, was repaired, and a number of ornamental plants and grasses were set out around the borders of the reservoir. During the past three months the fences around both reservoirs have been extensively repaired and all of them have been whitewashed. All cracks in the bottom and along the sides of the high-service reservoir in Georgetown were plastered up, and the interior surface was carefully covered with several washes of Portland cement to prevent exfiltration. The exterior was much improved in appearance by two washes of Portland cement over all masonry and two coats of paint on all ironwork of the reservoir and on the iron fence surrounding it. During the past year, not including the few occasions when the water was lowered by the supply being shut off for the purpose of repairs or of removing deposits from the conduit, the extreme fluctuations of the level of the water in the distributing reservoir had a range of but 1 foot as against 1.80 feet for the preceding year and 4.1 feet in 1894-95, the corresponding heights being as follows: It will be observed that the lowest stage of this reservoir during the fiscal year was 0.93 foot higher than the lowest stage during the preceding fiscal year and 3.63 feet higher than during the year before that. With the exception of the intensely cold period from January 27 to February 3, 1897, the water level in the reservoir at no time fell below 145.6 feet above datum. This marked improvement in the normal level of the reservoir arises from three causes: First, raising the dam at Great Falls; second, removing deposits from the conduit, and third, putting the Dalecarlia reservoir into service. From the spring of 1888 until July 27, 1895, this reservoir was out of service, and a sudden demand upon the comparatively small supply stored in the distributing reservoir affected its level much more than at present, when it is connected with the Dalecarlia Reservoir. In addition, when the latter reservoir was out of service the water was carried around it by means of a by-conduit, which for 625 feet of its length has a diameter of but 8 feet, and serves to throttle the flow materially. Since this reservoir has been put in service no throttling occurs and the flow is increased. THE CONDUIT AND THE BY-CONDUITS. With the amount appropriated by the act of March 2, 1895, the entire conduit and both by-conduits had been thoroughly cleaned during the preceding fiscal year for the first time since their construction, and 8,946 cubic yards of deposit had been removed therefrom. During the operations connected with the removal of these deposits a large number of longitudinal cracks were discovered and were carefully plastered up with cement mortar. A detailed description of all operations connected with the removal of deposits and a table showing the location of the cracks are given in Appendix B B B of the Report of the Chief of Engineers for 1896. During the months of May and June, 1897, all deposits were removed from the entire conduit between Great Falls and the distributing reservoir, and from the by-conduit around the distributing reservoir, and the interior of both the conduit and by-conduit was carefully scraped and swept. About 165 cubic yards of deposits were removed between Great Falls and the Dalecarlia Reservoir, and about 5 yards between the two reservoirs. An attempt was made to clean the by-conduit around the Dalecarlia Reservoir, but when it was entered for this purpose the north connection, which has been in particularly bad condition for several years, was judged to be too unsafe to warrant the risk of keeping men at work in the by-conduit. This by-conduit, which is 2,730.5 feet in length, and is a useful part of the aqueduct system, was constructed during the civil war, when the aqueduct was under charge of the Department of the Interior, but the rubble masonry used in its construction was of very inferior quality, and it has been in a leaky condition for many years. For a part of its length it is located too near the reservoir, the banks of which in this vicinity are very steep, and should it ever become necessary to draw off all of the water from this reservoir there is very grave danger that, relieved of the water pressure from the reservoir, portions of the bank between the by-conduit and the reservoir will slip into the latter, as has been the case on two occasions heretofore, and breaks in the by-conduit will result. To afford even a fairly efficient service the entire north connection and the portion of the by-conduit adjacent to it must be rebuilt, and an estimate for doing this work is submitted in the proper place. The deposits removed during the present fiscal year were confined almost exclusively to the seven unlined 11-foot tunnel sections and to the thirteen 9-foot 9-inches enlarged brick and masonry sections. A careful inspection of the conduit, made while the work of remov ing deposits was in progress, shows that none of the cracks plastered up during the preceding fiscal year have opened, and that no new ones have developed. A new board walk was constructed in the tunnel leading to Wasteweir No. 2. THE CONDUIT ROAD AND ITS FENCES. For use in repairing the Conduit road 1,714 cubic yards of flint stone were purchased during the fiscal year. The following quantities of stone were crushed and spread upon the Conduit road at the localities mentioned below: Forty-five cubic yards of flint stone near the distributing reservoir; 356 cubic yards of blue stone near the Dalecarlia Reservoir, and 999 cubic yards of flint stone between Cabin John Bridge and Bridge No. 3. The breaking of the crusher and the low state of the annual appropria tion prevented the crushing of the remainder of the flintstone purchased. Extensive repairs were made to the dirt road between the Club House and Great Falls, a distance of about 2 miles. General repairs were made to all other portions of the road, ditches were cleaned, bushes cut down, slopes trimmed, and deposits removed from culverts. A new painted board fence was erected on each side of the road at the northwest approach of Cabin John Bridge. All of the guard fences on the embankments along the Conduit road have been extensively repaired and whitewashed. Year by year the travel on the Conduit road, which is the most beautiful driveway in the vicinity of Washington, increases, and with it increases the amount of road metal necessary to keep the road in repair, until at the present time the cost of repairing this road entails a most serious drain upon the very limited annual appropriation for the maintenance of the Washington Aqueduct and its accessory structures, amounting during the past two years for the surface repairs of the road alone to more than 12 per cent of the total annual appropriation for the Washington Aqueduct during that period. Although the Conduit road is the property of the Washington Aqueduct, it is so extensively used as a public driveway that it does not seem fair to charge the annually increasing cost of maintaining it entirely against the appropriation for supplying the District of Columbia with water, thereby reducing the amount available for use on other parts of the system. Although much appreciated in its present condition by the thousands of persons who use it, the condition of the road would be greatly improved if a fixed amount were appropriated annually, exclusively for supplying and spreading road metal upon the road, the repairs to culverts, ditches, bridges, etc., being essential to the safety of the Washington Aqueduct, to be paid as at present from the regular appropriation for the maintenance and repair of the Washington Aqueduct. An estimate of the annual cost of supplying and spreading road metal upon the Conduit road between Georgetown and the Club House is accordingly submitted in the proper place. THE MAINS. The trunk mains, aggregating 21 miles in length, which lead from the distributing reservoir and supply the distributing system of street mains, were laid by the United States and are under the control of this office, but the distributing mains were laid by the District of Columbia and are under the care of the Commissioners of the District. By act approved June 11, 1896, $5,000 was appropriated for inserting air valves and blow-off valves in the 36-inch and 30-inch mains. The project for this work was approved on June 26, 1896, and operations were commenced in October, 1896, and completed in February, 1897. With this appropriation air valves and blow-off valves with the necessary casings, covers, masonry work, etc., were inserted in the 36inch and 30-inch mains at the following places: 12-inch blow-offs in the 36-inch main. One at New Jersey avenue and L street NW. 3-inch air valves in the 36-inch main. One in vault at distributing reservoir. 12-inch blow-offs in the 30-inch main. One at Twenty-first and K streets NW. One at Sixteenth and K streets NW. One at Massachusetts avenue between Fourth and Fifth streets NW. 3-inch air valves in the 30-inch main. One in vault at distributing reservoir. One at Thirty-fourth and M streets NW. One at Thirty-second and M streets NW. One at Pennsylvania avenue between Twenty-third and Twenty-fourth streets NW. One at Nineteenth and K streets NW. One at Thirteenth and K streets NW. One at Third street and Massachusetts avenue NW. One at New Jersey avenue and I street, NW. One at New Jersey avenue and B street NW. From the annual appropriation for maintenance and repair of the Washington Aqueduct, a 12-inch blow-off was placed in the 48-inch main at New Jersey avenue and L street NW. The air valves and blow-offs were all inserted by the use of the A. P. Smith tapping machine without the necessity at any time of shutting off the water from the mains. In doing this work the pieces cut out of the mains indicated their condition as regards "tuberculation," which was as shown in the following table: |