C153705 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I Beaver Reservoir Company Attention: Mr. Neil Thompson February 4, 1993 Page 4 inches by driving with a 140-pound hammer falling 30 inches. The penetration resistance (N) in blows per 12 inches of penetration, was recorded for samples taken with the sampler. Bedrock was sampled using NX wire-line coring techniques. Recovered samples are approximately 2 inches in diameter. Piezometers were installed to the bottom of each of the four test holes completed. Each piezometer, I-inch diameter, had 20 feet of machine slotted screen at the bottom and were completed with 22 feet of sand around the slotted portion, 2 feet of bentonite, and sand in the remainder of the well. Flush-mount well covers were grouted into place at the top of the well. All the test holes were dry at the time of drilling and the wells were dry several days after installation. Subsurface conditions encountered, in the test holes generally indicated embankment fill overlying bedrock. The embankmentTill-vaxted in thickness from approximately 11 feet to 79 feet and generally consisted of clayey_sand. -Bedrock extended to the maximum depth of our borings, 69 to 104 feet below existing ground elevations. The bedrock encountered generally consisted of interbedded sandstone and shale. Detailed analysis of the bedrock is presented in the geology. section of this report. Test hole logs are shown on Figure 3 and in Appendix B. Samples obtained during the field iI!vestigation were returned to our laboratory for testing. Tests perfonnedincluded grain-size analysis, Atterberg Limits, and pin-hole dispersion tests. Laboratory test,results are summarized in Table 1 and are included in Appendix A. GEOPHYSICAL-INVESTIGATION Geophysical surveying consisting of self-potential (SP) was used to investigate the subsurface ,in areas along the upstream dam face, the dam crest, and the downstream face of the dam. The pUIpOse of the survey was to detect subsurface zones indicative of fluid seepage below the toe of the dam and along the dam abutments. A description of the self- potential technique is included in Appendix C. The geophysical survey was conducted on July 10 and 11, 1992. By the time WCC personnel had arrived to the site, the reservoir had been drawn down significantly, and previously observed large seep zones near the outlet pipe had subsided to nearly no flow. Five transect lines were conducted and oriented parallel to the dam crest. One transect was conducted on the upstream dam face, one on the dam crest, and three transects were conducted along the downstream face of the dam. Each transect line was separated by a ~, 23067/LEIO 02..()4-93(4:24pm)/RPT