By excavating the bottom to the depth contemplated, which is the lowest at which water can be drawn through the mains, it would be twenty feet below the flow line, and the capacity would be 243,550,000 gallons; which would be sufficient, at the present rate of consumption, for twenty days' supply, and would allow of ample time for making any repairs to the conduit above that might be necessary. In the Boston, New York, and Baltimore water-works annual examinations of the conduits from end to end have been found necessary, and annual repairs made to the masonry. On the Washington Aqueduct such examination and repair cannot be made until the completion of the distributing reservoir. The conduit leading from Great Falls to the distributing reservoir is apparently in good condition. Extensive repairs have been made to its embankments, especially at culverts Nos. 18, 19, 20, 25, and 26. The roadway over it has been kept in good order, but during wet weather the travel has necessarily been restricted to light loads. It has become the principal highway of Montgomery County, and should be macadamized. The connecting conduit at the receiving reservoir has been in uninterrupted use since it was finished in August, 1867, until last March. Dalecarlia tunnel, which is in connection with this conduit, was commenced in 1864; it is built through rock that is not self-sustaining. During its construction the roof and sides were supported with timbers. In March a slide occurred near the shaft, which completely obstructed the flow of water, and rendered it necessary to shut it off from the conduit and pass it through the receiving reservoir. An examination of this tunnel was made in April, to ascertain the cause of the slide; it was found that the timbers that supported the roof and sides were very much decayed, and where the slide occurred they were crushed into fragments. As many other places were in a dangerous condition, it was deemed true economy to expend a portion of the appropriation for superintendence and repairs in arching this tunnel. Accordingly arrangements were made for beginning the work; the slide was removed, new timbers were put in place of decayed ones, sand, cement, stones, and bricks were delivered in the vicinity of the work, and the arching was begun and continued until the middle of September, when it was suspended for the want of money. Over three hundred feet of the tunnel were securely arched, and a sufficient number of bricks purchased and delivered for arching the remainder. ers. During the progress of the work the roof and sides had to be shored with heavy timbers in order to protect the lives of the masons and laborIt is estimated that over sixty thousand feet, board measure, of timber were used for this purpose. Many places, in that part of the tunnel yet to be arched, are safe only while the timbers remain sound; and the remainder of the tunnel should be arched without delay. By referring to previous reports it will be seen that the estimated cost of arching 350 feet of this tunnel was $15,400. The amount expended has somewhat exceeded this sum; the increase is due to the fact that, since the estimate was made, nearly two years elapsed before the work was commenced; and in that time timbers decayed and masses of rock fell from the roof, greatly increasing the cost of the work. Every precaution was taken to protect the lives of the workmen, and only one man was injured. The slopes of the embankments of the connecting conduit should be faced with ripraps to protect them from the waves of the receiving res ervoir; and as this reservoir will always be used for storing water, a substantial fence should be built around it to keep out the large droves of cattle that are driven to the pastures on the government lands in its vicinity. POTOMAC DAM. This structure was completed to its present height from the Maryland shore to Conn's Island, in December, 1867. Since then it has been subjected to the heaviest freshets of the Potomac, and the fact that it has sustained no damage from the large masses of ice and flood-wood that accompany the spring freshets, proves that it is impregnable. During the months of August and September the water in the river above the dam was at a lower stage than at any time during the past ten years, and there was not sufficient in the Maryland channel to supply the conduit. As soon as this fact became apparent, a survey was made of the river from the dam to the head of Conn's Island. At this point the river divides into two channels, and during low water the greater part of it flows down the Virginia channel. It was found necessary to deepen the upper end of the Maryland channel, and to construct temporary dams from the head of Conn's Island to the small islands above. Since this was accomplished the supply has been abundant. The past season has been remarkable for the long-continued drought; very little rain has fallen since the middle of July, and the water in the river has been at its lowest stage. It has become evident that, in order to have sufficient water in the Maryland channel at all times, it will be necessary either to extend the dam entirely across the river, or to build a dam from the head of Conn's Island up the river to a point that will give sufficient head. The rocks, trees, and bushes between the dam and the head of the island should be removed, as they materially obstruct the flow of water during its low stages and affect its purity. GATE-HOUSE AT GREAT FALLS. The roof of the gate-house has been slated, the decayed wooden floor removed, and an iron floor, supported by cast-iron girders, has been substituted. The large timbers that supported the gates, being also decayed, were removed, and Phoenix wrought-iron "H" beams were put in their place. The lifting-screws, twenty in number, together with their gearing, were thoroughly cleaned and repaired, and have since been kept in good order. TUNNEL NO. 1. In tunnel No. 1, about six hundred feet below the gate-house, several cubic yards of rocks have fallen from the roof. As they do not materially obstruct the water, they have not been removed, but only rolled to the sides of the tunnel. It would be safer to remove them, and arch that part of the tunnel. STONE BRIDGES. Bridges Nos. 1, 2, 3, and 4 for many years have remained unfinished. Nos. 1 and 2 require coping; Nos. 3 and 4 require parapets and coping. No work has been done toward completing either of them since 1863. Estimates of the cost have been annually submitted, and will be found in the present report. IRON BRIDGES. Bridge No. 5, over College Pond, has been painted and is in good order. Bridge No. 6, over Rock Creek, has been painted and the floor repaired. The plank are very much worn, but probably can be made to last till next spring. The present floor was put down in 1865; it is not decayed, but it is worn out by the large amount of travel constantly passing over it. The floor-beams have been in use over ten years, and are very much decayed; they must soon be renewed. PIPE LINE. The pipe line is generally in good condition. All the vaults were cleaned and whitewashed, and the stop-cocks repaired. In Foundery Branch pipe vault a brick floor was laid. The stop-cocks on the thirtyinch, twenty-inch, and twelve-inch mains were cleaned and repaired, and new street boxes were set in place of decayed ones. The twenty-inch main in North B street was completed to First street east, and a twelve-inch main laid in First street east from North B street to North A street; making complete the connection between the thirtyinch main in New Jersey avenue and the twelve-inch main on Capitol Hill. WATER-PRESSURE ENGINE. The water-pressure engine that supplies Georgetown Heights is in thorough repair. During the year new pistons were placed in the motive cylinders and new rings in the pumping cylinders. On the 21st of February one of the piston rods was broken, and a new one was put in its place. Owing to the increased consumption of water in the two cities, the pressure on the motive pistons has become reduced, and the engine does not supply as much water to Georgetown Heights as formerly. In order to afford a full supply permission has been granted to the authorities of Georgetown to furnish and erect a steam pump in the engine-room, and to connect it with the mains of the high and low service. HIGH-SERVICE RESERVOIR. On Sunday, the 4th of April, the watchman reported a leak in the gallery of the high-service reservoir. The engine that supplies it was immediately stopped, all the dividing valves between the high and low service were opened, also several fire plugs, and the reservoir was rapidly emptied-not any too soon, however, as the leak, which when first discovered was a very small stream, before the reservoir was empty had increased in size equivalent to a stream three inches in diameter, and washed from the foundation about thirty-five cubic yards of clay. This was replaced with concrete made of broken bricks, sand, and cement, and as soon as the repairs were finished the water was again let in. It now contains half a million of gallons, which is kept as a reserve in the event of fires. This reservoir has been left for many years in an incomplete state, and its unfinished dome presents a very unsightly appearance. It should be cut down to the level of the gravel walk surrounding it, and inclosed by a substantial iron railing. CONSUMPTION OF WATER. Experiments were made during the summer on the flow of water in the conduit leading from the receiving to the distributing reservoir. The result showed that the two cities were consuming an average daily supply of about twelve million gallons. Assuming that the population of the two cities is one hundred and thirty thousand, it makes the average daily consumption of water per head over ninety-two gallons. A large proportion of this is consumed at the government departments, especially at the Navy Yard, where the aqueduct pressure is used to prove boilers, and at the Treasury, where two large fountains are constantly playing. The water that is wasted from them might be conveyed in a pipe to the vacant space at the intersection of Pennsylvania avenue with Louisiana avenue and Seventh street, and be used again for a similar purpose. On Capitol Hill and other high points the supply is not equal to the demand, because on the low points, where it is abundant, it is recklessly and willfully wasted. Periodically procla mations are issued by the city authorities forbidding the waste of Potomac water, to which not the slightest attention is paid. Some additional legislation is necessary in reference to the proper control of the distribution of the water in both cities. In my opinion it should be entirely under the control of this office. On the Cochituate, Croton, and Fairmount water-works the meter system is being gradually introduced in order to prevent unnecessary waste. It should be adopted in Georgetown and Washington, especially at hotels, livery stables, factories, and other establishments where large quantities of water are constantly used. If, however, it is deemed desirable that the two cities shall have a supply sufficiently abundant for all purposes, it can be had only by completing the distributing reservoir, and laying an additional main of thirty or thirty-six inches in diameter from the effluent pipe vault to Capitol Hill. No estimate of the cost of laying a new main is submitted as by act of Congress, whenever it becomes necessary to lay additional mains, the expense thereof shall be borne by the corporations of Georgetown and Washington. FIRE PLUGS. On Pennsylvania avenue, between the Capitol and the Treasury Department, there are fifteen fire plugs. Two of them are in good order and connected with the twelve-inch main. The others are old and out of repair, and are connected with a pipe designated as the four-inch or spring pipe. This pipe is in a leaky condition, and nearly worn out. It is located parallel with the twelve-inch main, with which it is connected only at Third street west and Thirteen-and-a-half street west. Owing to its small diameter, and the distance between its connections, only two plugs can be supplied by it at a time. It is respectfully suggested that the plugs which are worn out should be replaced by new ones, and that a new six-inch pipe should be laid in place of the four-inch. It could connected with the twelve-inch main at Third, Sixth, Twelfth, Thirteen-and-a-half, and Fourteenth streets west. plished, Pennsylvania avenue would have a bountiful supply of water With this accomin the event of fires. As it is now, there is a deficiency, and steamers have to obtain their supply from other streets. LANDS. The lands occupied by the Washington Aqueduct, and to which the United States have no title, are described as follows: At Great Falls, 5.44 acres, belonging to the estate of the late Hall Neilson. In Montgomery County, the road across the farms of Jackson, Collins, Brooke, and Anderson. In Georgetown, at the high-service reservoir, a lot of land fronting on High street, and partly covered by the reservoir embankment, owned by Mrs. E. M. Mosher. At bridge No. 6, a lot fronting on Montgomery street, the property of Mrs. Maria C. French. Each of the above-described parcels of land will be required always for the use of the Washington Aqueduct, and an appropriation should be made for their purchase. FINANCIAL STATEMENT At the date of the last annual report the balance in the $32,077 88 25,000 00 Total... 57,077 88 The expenditures to date are as follows: For amount of retained percentage due contractors for the construction of the Potomac dam... $5,247 64 For construction of gate-house at Great Falls... 1,302 94 For arching with bricks laid in cement a portion of Dalecarlia tunnel.. 17, 792 34 For purchase of 500,000 bricks from the United States arsenal for Delecarlia tunnel.... 2,102 50 1,745 07 1,061 15 609 39 895 68 375 00 153 39 18, 063 38 For raising and widening embankments over conduit. For repairs to water-pressure engine at bridge No. 6.. For office rent For office expenses, including gas, fuel, and stationery Total... 7,729 40 57,077 88 From the above statement it appears that the amount remaining to the credit of the Washington Aqueduct is only $7,729 40. This sum will not be sufficient for ordinary expenses during the remainder of the fis cal year. By referring to the last annual report it will be seen that the estimated amount for engineering, superintendence, and repairs for the year ending June 30, 1870, was $33,000; Congress appropriated only $25,000; leaving a deficiency of $8,000. Estimate of the cost of completing the Washington Aqueduct : 00 For rent and purchase of 5,44 acres of land at Great Falls. $1,320 00 For purchase of road-way from Great Falls to conduit road, 23 miles, 18 acres 1,012 00 |