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the ordinary disks or covers, which will be lifted by a rod and geared
wheels. The outlet gates from the ovas ohody
tower are to be ordinary slide gates on steel rollers, with a clear opening of 2 by 4 feet. They will be operated by means of a rod and geared wheels, like the inlet valves. These outlet gates will normally remain open, but may be closed or partly closed in case the inlet valves should fail to close or break. They will also serve to regulate the pressure in the tower in case it is difficult to operate the inlet valves. As the water will be used solely for irrigation, all the inlet valves were placed near the bottom of the tower. If desirable, however, others can be placed at different levels at any time. The outlet tunnel is to be driven through the shale rock and lined with concrete to prevent erosion.
The location of the spillway and dam is favorable for cheap and rapid handling of rock by means of two overhead cableways. The rock when blasted will doubtless shatter into sizes easily handled, probably small enough to be loaded into skips with a steam shovel.
The following is a summary of the estimated cost of the Foster dam and reservoir:
Fig. 17.-Profile of outlet tower and tunnel of proposed Foster reservoir.
Estimated cost of Foster dam and reservoir.
Loose rock fill in dam
51, 240 !4, 738
7, 173 10,918 9, 630 3, 640 3, 900
per cent Reservoir and dam site.
12, 182 5,000
The estimated cost of storage at this locality is $15.61 per acre-foot if the reservoir is filled once during the winter, or 7.80 per acre-foot if filled twice.
The proposed Currier reservoir is on Arroyo Seco, 11 miles south of Soledad in an air line and about 12 miles by the wagon road (Pl. II). The dam site lies in the NE. I of sec. 19 and the NW. 4 of sec. 20, T. 19 S., R. 6 E., M. D. M., and the reservoir site extends westward about 3 miles to the Foster dam site. A survey was made of this loca
tion by the writer in the summer of 1902. The topographic map of the reservoir is shown in fig. 18. The altitude of the stream at the dam site is 380 feet by aneroid observations. The survey was made for a dam which would raise the water 120 feet above the bed of the stream, or to the 500-foot contour. Such a dam will impound 24,657 acre-feet of water. The accompanying table shows the area and capacity of this reservoir at the various contours.
Area and capacity of proposed Currier reservoir, Arroyo Seco, California.
Fig. 19 shows the capacity curve of the reservoir, by means of which the amount of water stored can be ascertained for any depth. The drainage area tributary to this reservoir is 189 square miles. The table on page 54 shows the estimated monthly discharge of Arroyo Seco at the Pettitt ranch, 1 mile below. The discharge here will be practically the same as at the gaging station. The reservoir is a portion of the terraced valley of Arroyo Seco. Pl. IX, A, shows the character of this valley looking upstream from below the dam site. The canyon has a width of about 340 feet at the bottom and
FIG. 19. -Capacity curve of proposed Currier reservoir, showing capacity in thousands of acre
feet, with the water surface at various levels.
of about 550 feet at the level of the first terrace, 125 feet above the stream. The rock at the dam site is the Monterey shale. This formation has been described on page 62. At this point the shales are evenly stratified in thin beds, which are sharply folded and somewhat faulted just below the axis of the dam. Pl. IX, B, shows this fold on the south side of the canyon and Pl. X, A, shows the nearly horizontal beds of shale in the north side of the dam site. The shale east of the axis of the fold strikes N. 70° W., and dips southwestward at an angle of from 40° to 45°. Rock is exposed in the sides