Work on foundations limited to a low water season of only three months. Flood discharges up to 120,000 cf.s. Concrete with uncoursed rubble faces. Concrete composed of 25 parts hydraulic lime, 30 parts of sand and 100 parts of broken stone. Native labor. Lime was obtained from a quarry 16 miles from dam. Has 920 ft. of spillway, 403 ft. being formed by a masonry wall, rest excavated from rock. Outlet channel involves rock excavation 21 ft. wide on bottom 5500ft. long and running up to 50 ft. depth; also a rock tunnel 6650 ft. long with 80 sq. ft. section. Native labor, under difficult and expensive conditions. Estimated cost of entire work $3,220,000.
See also Water Supply fir Irrigation Paper No. 87.
Fig. 63. Section of Periyar dam, India; built 1888 to 1897; concrete masonry; length 1231 ft; height 173 ft.; contains 185,000 cu. yd.
Of the total length, 1800 ft. is solid masonry and the remainder contains 180 sluices provided with gates for passing the high water flow. Of the sluices 140 are 6.56 ft. wide X 22.96 ft. high, and forty are the same width by one-half the height. The original work includes 6540 ft. of canal 49 ft. wide, four locks each 263 ft. X 31 ft.; also the Assiout dam 350 miles downstream from the Assouan, built for the purpose of diverting the water into the irrigating canals.
Fig. 64. Section of Assouan dam, Egypt; built 1898 to 1903; granite rubble; length 6400 ft.; height 96 ft.; contains 704,000 cu. yd.; 1907 to 1910 raised 16.4 ft., involving additional thickness of 16.4 ft. normal to face; no addition to length, additional masonry about 475,000 cu. yd.
The Assiout dam is of masonry 2769 ft. long, with a maximum height of 48 ft., and retains about 33.5 ft. of water. It contains in arched openings each 16 ft. 4 in. span, closed by steel sluice gates 16 ft. high. The original contract price was œ1,500,000 for the Assouan and œ500,000 for the Assiout; but the foundation for the Assouan was considerably deeper than anticipated, and required expensive treatment, so that the actual cost of the Assouan dam was œ2,450,000.
In May, 1907, a contract was let at $5,110,000 for raising the dam 16.4 ft., including construction of an additional lock, etc. Iron and steel, incidental and additional work increased the cost to $7,410,000. The masonry added to the downstream face was not at once bonded with the old work, but built with a narrow intervening space which was grouted later when the new masonry had settled and acquired the temperature of the old. The capacity of the original reservoir was about 900,000 acre ft., this was increased by raising the dam, by about 1,070,000 acre ft.
The rubble was composed of 74 per cent, stone and 26 per cent, mortar; 0.78 barrels of cement was required per cu. yd. The cement was hauled 30 miles by wagon at a cost of 1 cent per 100 lb. per mile. Total cost of cement at dam was about $4 per barrel. Watershed 1800 square miles, maximum flood 1945 c.f.s. Reservoir capacity 3 1/2 billion cu. ft. The quarry from which the stone was obtained was about 2000 ft. from the dam.
The outlets from the reservoir consisted of three tunnels, aggregating 1300 lin. ft. The excavation at the dam-site amounted to 2600 cu. yd., mostly rock. It was only necessary to go down about 10 ft. below the river to reach a satisfactory foundation, and the handling of the stream seems not to have been an expensive matter. The total cost is stated to have been about $1,000,000. La Boquilla Dam.
On Rio Conchos, Chihuahua, Mexico; started 1010; length 840 ft.; max. height 261 ft.; bottom thickness 200 ft.; curved to radius 866 ft; will contain about 300,000 cu. yd.
The excavation amounts to 96,000 cu. yd. of earth and 360,000 cu. yd. of rock. Of the rock excavation 260,000 cu. yd. is from the spillway. Portland cement used. First masonry laid March, 1911, work suspended in 1913 on account of the Mexican revolution. Reservoir capacity will be 2,800,000,000 cubic meters and requires an auxiliary dam 2610 ft. long X 108 ft. maximum height.
Fig. 65. Section of Lake Cheesman dam, Colorado; built 1900 to 1004; granite rubble masonry; length 710 ft.; max. height 227 ft; curved to radius 400 ft.; contains 103,000 cu. yd.
Durango, Mexico: built 1001 to 1905; rubble masonry with cut stone facing; length 535ft.;max. height 132.8 ft; contains 28,000 cu. yd.
Crest length does not include 98 ft. of spillway 6 ft. below crest. Includes diversion tunnel 6 ft. X 6 ft. 5 in. in section and 77.6 ft. long.
Of the mass of masonry 37 per cent, equals mortar. Ten per cent, of the masonry was laid in Portland cement (using 1800 parcels) and 90 per cent, in hydraulic lime mortar manufactured nearby.
Mexican labor - very largely hand work. Total cost $200,000 Mexican.
Mexico; built 1002; limestone rubble masonry; length 1800 ft; max. height 87 ft; contains 92,000 cu. yd.
Used native hydraulic lime mortar, cost $500,000. Gold.