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<br />SE CTION III <br /> <br />ANAL YSIS OF THE DAM AND RE COMME NDA TIONS FOR REPAIR <br /> <br />Historical data on the dam is minimal with few records available <br />on its construction. The existing drawings do not match the as-built con- <br />dition of the dam but do indicate the intent for construction. The construction <br />took about three years being completed in 1907 according to the Council Minutes <br />Book. The dam was to be 513 feet long and to store 6,550,350 cubic feet of <br />water. The storage volume drawing for water rights purposes was filed in <br />the State Engineer's Office, State of Colorado, on the 10th day of October <br />A. D. 1906. The height of the dam was to be 33 ff2et. <br /> <br />Subsequent drawings found in the archives at Idaho Springs indicate <br />typicaI cross sections of earth core and rockfill. There is no indication of <br />seepage control measures along the downstream earthcore. The upstream <br />slope was shown as 3: 1 and a downstream slope of 2: 1 and with 2: 1 and <br />1-1/2: I respectively on the impermeable material slopes. The dam was <br />reported to contain 36,700 cubic yards of material placed on hard semi- <br />cemented graveI foundation. The archivf2 drawings were redrawn and are <br />included as part of this report. <br /> <br />The historical data was obtained during our investigations and to <br />a large degree supports fieId surveys and soils information obtained at <br />the dam site. <br /> <br />VISUAL OBSERVATION <br /> <br />On June 1, 1976, our firm was asked to inspect the dam and make a <br />report on this site investigation to council in terms of a proposaI of needed <br />corrective actions. The site inspection indicated three factors visibly oc- <br />curring within the dam and are shown on photos. <br /> <br />* <br /> <br />A vertical crack of 3 to 4 inches wide existed along the axis of the <br />da m for about 250 feet and cou Id be probed to a depth of 1 to 2 feet. <br /> <br />*. <br /> <br />A high seepage rate was occurring at two locations with some tOf2 <br />seepage at the high fill portion of the dam. <br /> <br />,..~ * * <br /> <br />A movemf2nt of the central portion of the dam had occurred, f2ithf2T <br />horizontal movement downstrf2am or subsidence of the rock mass. <br /> <br />The above factors indicated a need to study thf2 dam to determinp its <br />stability. A program of study was developed and outlined herein as: <br /> <br />III - ] <br />