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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Geotechnical Engineering Investigation <br /> <br />II. Review of Existing Conditions <br /> <br />The following summary of existing conditions is based on our discussions with Mr. Barry <br />Nelson, Superintendent of Santa Maria Reservoir Company, review of previous investigations, <br />reports and letters by Hydro-Triad, the inspections and correspondence by the Colorado State <br />Dam Safety Division and our field reconnaissance and investigation. <br /> <br />A. Seepage History <br /> <br />Continental Dam has experienced seepage conditions during high reservoir levels <br />throughout much of its operational life (since 1942). Specific areas of seepage have been <br />identified. They are: <br /> <br />. Near the left abutment about 33 feet above the bottom of the original outlet, <br />width of this zone is about 30 feet. <br /> <br />. Seepage was noted above the outlet conduit to the "north" <br /> <br />. Seepage was observed near the left abutment about 2/3 of the way down from <br />the top of the dam. <br /> <br />. Seepage was found 82 feet from the spillway and 47 feet below the dam crest. <br /> <br />. A second seep was observed 47 feet below the dam crest and 162 feet from the <br />spillway. <br /> <br />· Seepage was found in 1993 near the left abutment at elevation 10,246 and <br />10,248 feet as well as lower at 10,224 and 10,226 feet. <br /> <br />These seeps emit 10 gpm to 35 to 40 gpm individually. All seeps appear to be inactive or <br /> <br />insignificant when reservoir level is at or below reservoir elevation 10,264.5 feet (gauge height <br /> <br />64.5 feet). The flows from these seepage areas have been reported as sediment free, by Santa <br /> <br />Maria Reservoir Company personnel. <br /> <br />Considering this background infonnation as well as the response characteristics during <br />attempts to limit seepage (1993) as described in the Hydro-Triad, L TD report, Harza is providing <br />the following evaluation and recommendations. <br /> <br />During the reservoir raise between May 31 and June 18, 1993 seepage increased <br />progressively from elevation 10,225 feet upward into two areas adjacent to the plan location of <br />the lateral toe drain and eastward about 50 feet. As seepage moved laterally from the initial zones <br />more seeps became evident at elevations 10,242.5 and 10,247.5 feet. <br /> <br />These zones developed as the reservoir reached a gauge height of 69 feet. During this <br />period piezometer observations indicated maximum rises of the phreatic surface in the abutment <br /> <br />Continenbll Dam <br /> <br />Page 3 <br />