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<br />0.J2235 <br /> <br />Durango Pumoing Plant - Stage I <br /> <br />C. Nine drill holes, DH-lOl through DH-109, were bored from November 1988 to January <br />1989 by Reclamation. The holes were located to evaluate fOllildation conditions at the <br />proposed pumping plant, inlet channel, and switchyard sites. Drill holes DH-I 05 and <br />DH-109 were drilled to obtain information on fault F-l. All holes were cored into <br />bedrock using an HQ wireline system (3.78-inch hole diameter). Surficial deposits were <br />either cored or sampled using standard penetration sampling methods, These drill holes <br />were completed to measure groundwater levels using I-inch PYC slotted pipe <br />piezometers, Piezometer installations for drill holes DH-lOl through DH-109 were <br />pressure grouted and abandoned in May 1989 at the request of the UMTRA site <br />contractor. Geologic surface mapping was completed at a scale of one-inch equals 100 <br />feet during the investigation in 1989. <br /> <br />D, Eight drill holes, DH-I10 through DH-117, were bored in January, February, and March <br />1990 using a PQ wireline system (4.9-inch hole diameter) to investigate groundwater and <br />foundation conditions at the proposed pumping plant site. Drill hole DH-11 0 was drilled <br />to determine conditions in a fault zone (F-l). Drill holes DH-lll through DH-l13 were <br />bored within the anticipated excavation. Drill holes DH-114 and DH-115 were drilled <br />up-gradient from the raffinate site to monitor background groundwater conditions. Drill <br />holes DH-116 and DH-117 were drilled to monitor groundwater conditions down- <br />gradient from the raffinate site. Drill hole DH-118 was drilled with an HQ wireline <br />system (3.78-inch hole diameter) in May 1990 to monitor up-gradient background <br />conditions within the fault zone (F-l). <br /> <br />E. <br /> <br />These drill holes were completed with 2-inch slotted PYC pipe piezometers. Steel casing <br />was grouted into bedrock with lean cement to prevent potential mixing of aquifers during <br />drilling. Groundwater levels in these holes were measured weekly from March through <br />July 1990 and are currently monitored quarterly. Permeability and slug tests were <br />conducted in 1990 to determine transmissivity and obtain information for dewatering. <br />Sampling to evaluate groundwater chemistry is performed on a quarterly basis. Results <br />of the investigations are found in the Reclamation report Durango Pumping Plant _ <br />Hydrogeochemical Site Characterization dated November 1990 and addendums. Based <br />on results of these investigations, the proposed pumping plant location was adjusted to <br />avoid the fault. <br /> <br />( <br /> <br />F. Four drill holes, DH-119 through DH-122 were drilled during August 1991 to investigate <br />foundation conditions at preliminary pumping plant, switchyard, and air chamber sites. <br />The drill holes were cored using an HQ wireline system (3.78-inch hole diameter). The <br />holes were percolation tested at 10-foot intervaIs using an inflatable packer system. The <br />holes were abandoned and cemented to the ground surface with lean cement grout <br />following completion of drilling. <br /> <br />G. Nine test pits, TPDPP-IOl through TPDPP-I09, were excavated with a Case 780 backhoe <br />to obtain in-situ information of surficial deposits in the pumping plant area and to <br />determine excavation and foundation characteristics along the Ridges Basin Inlet Conduit <br />alignment <br /> <br />H. Drill hole DH-126 was drilled in 1992 on the east side of the pumping plant excavation <br />for foundation investigation purposes. <br /> <br />Geology <br />00320 - 3 <br />