IMPROVEMENTS AT SPOKANE, WASH.

IMPROVEMENTS AT SPOKANE, WASH.

The costly improvements to the waterworks system of Spokane, Wash., have been satisfactorily completed. The pressure had been defective, as the two 24-in. water mains from the pumping station to the city were inadequate, and the loss by friction was excessive. The daily consumption per capita in 1904—from 262 to 396 gals.—was also excessive—nearly equal to the total pumping capacity. To increase the supply from the Spokane river, it was determined to install four new pumps, with turbines to drive them, in a pumphouse adjacent to the old one, and that these new pumps have an aggregate capacity of 10,000,000 gals, of water each twenty-four hours. To reduce the friction-loss of head pressure of water it was proposed that a new 30-in. main, or its equivalent, should be laid right from the pumping station through the heart of the city to the new storage reservoir in the city, and other large feeder water mains to distribute the water through the central parts of the city. The water system in use until lately was direct pressure, and to equalise and maintain this pressure, as well as to store an adequate amount of water near the heart of the city at times when the demand was greatest, for firefighting purposes, and to allow the pumps to work at a nearly uniform rate, so as to keep the reservoir nearly always full, a new reservoir was proposed near the intersection of Ninth avenue and Pine street. New 10,000,000 gal. pumps were also to be added. The new pumphouse will nearly adjoin the old one on the west. It has a front age of 54.5 ft. and a depth of 38.25 ft. with a wing on the rear to contain the turbines of 19 ft depth and 50 ft. length. Its foundation is of monolithic concrete; the superstructure of brick. It affords accommodation for 2,500,000 gals. each. Three of these sets of pumps are already in place, and a fourth is soon to be moved to the station and set up. There are two turbine wheels, with beveled gears and jack-shafts, and each turbine is to drive two pumps. The turbines are supplied with water to create power from the canal, and the water flows to the turbines through a 12 ft. 4-in. steel penstock. The pipes from the pumps connecting with the force-mains to the city are now fully connected. The new 30-in. forcemain from this new pumping station is also connected with the pumps in the old station and the force mains leading from the old station to the city are also connected with the new pumphouse in the new pumping station. By means of these pipe-connections in both stations, water can be sent from either pump in either station through any one of the three force-mains to the city and the new extension works are thereby brought into use. The detail plans called for 50,373 ft. in the aggregate of 30-in., 24-in. and 20-in. pipes for the purpose of the general distribution of water through the principal streets and to the smaller mains leading into the remaining streets. The board of public works advised that 11,122 ft. of 30 in. main, in addition to that proposed in the original plan, be added. This additional pipe was in part substituted for 24-in. and 20-in. pipes, and this change, as approved by the city council, made an aggregate of 53,241 ft. of these large pipes. This addition of the large sized pipes and substitution for smaller pipes increased the cost of these several pipes $18,824. The new forcemain extends to the Cannon hill standpipe. Eighteen-inch, 16-in. and 10-in. pipe has been laid as Originally proposed, some thousands of feet of 12in. being wooden. The new 30-in. pipe extends from the pumping station to the reservoir; part of it forms the outflow pipe from the reservoir to the distribution in the business centre. Water has been flowing from the reservoir through the 30-in. effluent pipe into the water mains, covering a large part of the city, since July 16, 1906. During all that time the water pressures throughout the city distribution pipes have been maintained and equalised. Previous to July 16, while the water pressure at the old pumping station was at 100 to 115 lbs. per sq. in. in the early morning, the pressure in the business district of the city dropped at midforenoon and midafternoon to 40 and 50 lbs. Since July 16 the recording pressure gauge in the office of the chief engineer of the fire department, which is on the second story of the building, has shown an almost uniform water pressure at 78 to 79 lbs. per sq. in.-—giving an excellent fire pressure at the street level, equivalent to 200 ft. head of water. This uniform reservoir pressure has also maintained a good supply of water in the upper part of the low-service water district, where there are many residences. Previous to July 16 last the standard revolutions of the six 2,500,000-gal. pumps in the old pumping station were thirty revolutions per minute. Since July J6, twenty-four revolutions have sufficed to maintain the same amount of pressure, with the new 30 in. force-main in full use, the labor of the pumps has again been materially reduced, and the waterpower for pumping proportionately economised. The new reservoir, which is located on the slope of the hill in the southerly part of the city and near the intersection of Ninth avenue and Pine street, is divided into two basins, each 266.5 ft. square at the inside top of the inclosing slope linings, except that the southwest corner of the westerly basin has been cut off to admit of a new street passing along the southerly and westerly sides of this basin. The elevation of the water surface in the reservoir by the city datum is plus 2,114. The parapet wall is 3 ft. higher. The depth of the water at the outlet chamber is 20 1/2 ft. The present capacity of the water storage in the reservoir is 18,000,000 gals. The water surface is 314 ft. higher than Peaceful valley, 202 ft. higher than the crest of the dam at the pumping station, 222 ft. higher than the average altitude of the business district, 100 ft. higher than the street at the corner of Washington street and Seventh avenue. The lining of the reservoir consists of a monolithic concrete wall, which is 2 ft. 6 in. thick at the level of the water surface and increases in thickness on the water side by a 3-in.per-ft. batter. This wall on the outlet side of the reservoir is from 8 ft. 3 in. to 9 ft. in thickness at the base. The parapet wall above the water level is 19 in. thick. The partition between the twin basins is also of concrete. Its thickness is 4 ft. at the level of the top of the parapet, which is 3 ft. above, water surface and has a 3-in. batter on each side from the top to the bottom of the wall. A considerable part of this reservoir rests on a basaltic rock substructure, with many seams through it, and not watertight without a surface puddling. It was excavated, wherever necessary, to form a proper grade for the bottom of the reservoir. Between the higher parts of this rock and the socalled haycock boulders that rest upon it at frequent intervals there was found at some places a clayey loam and at other places a sandy loam. As under the north wall of the easterly basin and at one or two other points there were dips in the rock, the concrete wall was not carried down to rock. Instead, the rock was puddled over the entire floor of the reservoir to a depth of 5 ft. This puddle extended from within the line of the reservoir wall outwards under a portion of the earth embankment, which surrounds the concrete wall entirely round the reservoir. This wall is composed of Portland cement, sand, crushed rock in proportions, 1, 3, 5. The leakage is not considered worth mentioning. To facilitate cleaning, the floors, which slope towards the outlet drain-pipes on the north side of the basin, are covered with 4-in. of concrete over the puddling. A waterproof compound may be used to form a proper surface coating of portions of the basin floor as are below the puddling covering. These as the basaltic rock and the earth are pervious. The cost will be $5,000. The original estimated total cost of the improvements was $409,395.80. as follows: Powerhouses, turbines and pumps, $85.355.58; reservoir, $90,714.99; pipe-lines, $233,325.23 -total. $409,395.80. To complete the works it is estimated that $16,500 will be required.

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