Laserfiche WebLink
<br />e <br /> <br />Drill holes were completed on each old river terrace to better define <br />the abutment and foundation materials and to evaluate the location of <br />the underlying bedrock. Four drill holes were completed in the river <br />valley between the abutments, each encountering bedrock (see Drawing <br />No.6 in Appendix A). Three borings (B-1, B-2, and B-3) are located <br />on the south side of the river valley. Each boring encountered and <br />penetrated bedrock (Wasatch Formation) at depths ranqing from 43.5 to <br />66.0 ft. The overburden material consisted of fluvial sand and <br />gravel interbedded with silt overbank deposits. Basalt boulders were <br />present throughout the overburden material. Very few oil-shale frag- <br />ments are present in the river deposit at this point. <br /> <br />Dri 11 hole B-4, located on the north bank of the river, encountered <br />bedrock (Wasatch Formation) at a depth of 16.0 ft and continuously <br />cored it to a depth of 50.5 ft. The overburden consisted mainly of <br />s and and qrave 1. <br /> <br />e <br /> <br />Drill holes B-8 and B-I0 were completed on the south and north river <br />terraces, respectively. Each encountered a calcite cemented <br />conglomerate at an elevation of approximately 5,250 ft, when the <br />drilling could not continue because of the hard nature of this <br />material. The conqlomerate is a prevolcanic (no basalt) river <br />deposit that has been cemented by groundwater flowing along the top <br />of the impermeable Wasatch Formation. The material overlying the <br />conglomerate consisted of sand and gravel stream flow deposits and <br />large basalt boulders. This material is above the proposed pool <br />elevation, and is therefore not critical to the dam performance. <br /> <br />Drill holes B-5, B-6, B-7, and B-9 were not completed because they <br />encountered large basalt boulders that could not be penetrated. <br /> <br />e <br /> <br />During the advancement of the holes, constant-head permeability tests <br />were performed in the bore holes. A zone of rock or soil was sealed <br />off, and water was pumped into the formation under pressure. <br />Measuring the rate of flow and geometry of the hole allowed the <br />permeability of the formation to be calculated. These field test <br /> <br />3686-a/8 <br /> <br />IV-3 <br />