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, ~~ ;.:..,'- -''"\ 6. Prepare a data analysis report summarizing our results. The geophysical survey was conducted on July 11 and 12, 1992 and the exploratory drilling program was conducted between October 6 and October 11, 1992. The results of the investigation, combined with a review of existing geologic data and the results of the drilling program were used to develop a geologic model of the dam and foundation to assist with evaluation of existing conditions. The geophysical survey consisted of self-potential (sp) techniques to investigate the subsurface in areas along the upstream dam face, the dam crest, and the downstream face of the dam. The purpose of the survey was to detect subsurface zones indicative of fluid seepage through or beneath the dam and along the dam abutments. The exploratory drilling program consisted of.drilling and sampling four test holes along the crest of the dam. Each of the test holes extended .into the foundation of the dam and was completed as a standpipe piezometer. --- """,--. 6.3 RESULTS The results of the field/investigation and data review work are summarized below. 1. Beaver Reservoir is underlain by sedimentary bedrock of the Mesaverde Formation under a relatively thin soil mantle. The bedrock has been tilted~and broken 'and has a strike of N50W, nearly perpendicular to the 'darri~centerline and Ii dip of 20 to 25 degrees to the northeast (towards the right abutment). 2.<I1ie bedrock consists primarily of layered sandstone and shale with some coal seams. Where observed, the primary joint sets have strikes of N50W and N50E with very steep to near vertical dips. 3. Bedrock quality, as measured by core recovery and rock quality designation (RQD) varies widely in both the horizontal and vertical planes. 23067/Rl.6 09-03*93(3:21pm)/RPT 6-2