The Tabeaud Dam, in Amador County, Cal., built under the supervision of the author for the Standard Electric Co., is an example of the homogeneous earth dam. A somewhat fuller description and discussion will be given of this dam than of any other, not on account of its greater importance or interest, but because it exemplifies certain principles of construction upon which it is desired to put special emphasis. This dam was described in Engineering News of July 10, 1902, to which the reader is referred for more complete information than is given here.
FIG. 3.–PLAN OF TABEAUD RESERVOIR, WITH CONTOURS.
FIG. 4.–PLAN OF TABEAUD DAM, SHOWING BED ROCK DRAINAGE SYSTEM.
FIG. 5.–DETAILS OF BED ROCK DRAINS AT THE TABEAUD DAM.
[Fig. 3] is a contour map of the Tabeaud Reservoir, showing the relative locations of the dam, wasteway and outlet tunnel. [Fig. 4] shows the bed rock drainage system and the letters upon the drawing will assist in following the explanation given in the text. The whole up-stream half of the dam site was stripped to bed rock. As the work of excavation advanced pockets of loose alluvial soil were encountered, which were suggestive of a refill, possibly the result of placer mining operations during the early mining days of California. In addition to this were found thin strata of sand and gravel deposited in an unconformable manner. The slate bed rock near the up-stream toe of the dam was badly fissured and yielded considerable water. A quartz vein from 1 to 2 ft. in thickness crossed the dam site about 150 ft. above the axis of the dam. The slate rock above this vein or fault line was quite variable in hardness and dipped at an angle of 40 degrees toward the reservoir.
FIG. 6.–VIEW OF BED ROCK TRENCHES, TABEAUD DAM.