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Geotechniwl Data Report Bruce Park Dam <br /> Bowie Resources. Limited <br /> Apri1200~ <br />Executive Summa <br />Bowie Resources, Ltd. retained GEI Consultants, Inc. to evaluate potential impacts to the <br />Bruce Pazk Dam related to proposed underground mining activities near the dam. The scope <br />of work included geotechnical field investigations for evaluation of the existing dam and for <br />preparation of conceptual-level designs for raising the embankment 3 to 6 feet. <br />Bruce Pazk Dam, located in Delta County, Colorado, consists of a main dam and a saddle <br />(auxiliary) dam. In 1990, Bruce Park Dam was re-classified as a Class I (high hazard) dam. <br />The original dam was constructed in the 1940s. The dam was raised to a reported structural <br />height of 58 feet between 1950 and 1952. The reservoir has a reported storage capacity of <br />598 acre-feet with a water surface area of 33 acres. The outlet works consists of a 14-inch- <br />diameter, welded steel pipe with a reinforced concrete encasement. The intake to the outlet <br />works is a hand operated hoist slide gate. <br />Bruce Pazk Dam is located on the eastern edge of the Colorado Plateau physiographic <br />province within the Piceance Basin. The site topography is influenced by glaciation. The <br />bedrock below the site consists of interbedded sandstone, siltstone, and claystone, of the <br />Cretaceous Mesa Verde Group. A landslide mass is present along the northwest (right) side <br />of the reservoir. Movement was first noticed in the 1950s, with significant movement <br />occurring in 1983 and 1984. It is believed the slide mass is 5 to 20 deep and moving along <br />the contact with the Mesa Verde Formation. <br />Subsurface conditions identified in the Main Dam embankment and foundation consist of <br />four material types identified as new embankment, old embankment, foundation soils and <br />bedrock. The new embankment materials aze generally low to high plasticity clays with <br />varying amounts of sand. The old embankment materials are generally low to medium <br />plasticity clays with varying amounts of sand. Foundation soils aze apparently associated <br />with an older glacial till deposit, the Lands End Formation. The foundation soils aze <br />generally sandy low to high plasticity clays. The foundation bedrock below the main <br />embankment consists of siltstone, sandstone, and interbedded siltstone, silty claystone, and <br />silty sandstone of the Mesa Verde Group. Groundwater was encountered below the main <br />embankment at an elevation of 8,098 to 8,099 feet, which is approximately 88 feet below the <br />dam crest. The reservoir was empty at the time groundwater measurements were recorded. <br />• Subsurface conditions identified in the Saddle Dam embankment and foundation consist of <br />two material types identified as new embankment and bedrock. The ne~v embankment <br />materials are generally low to high plasticity clays with varying amounts of sand. The <br />foundation bedrock generally consists of clayey siltstone, silty claystone and claystone of the <br />GEI Consultants, InC. iii 992o~;~pe-i6 Geo~ecnmcai tau Reoaa <br />