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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 />A geotechnical investigation was conducted in the field and laboratory to <br />evaluate the materials that comprise the dam, foundation, and reservoir. The <br />results of this evaluation were input into stability and seepage analysis of <br />the embankment, and were uti 1 i zed to assess the properties of the local <br />materials in order to formulate alternatives for rehabilitation of the <br />observed deficiencies. <br /> <br />The field work consisted of surficial geologic mapping and subsurface <br />exploration by three rotary boreholes, 11 test pits, and 1600 linear feet of <br />sei smi c refracti on survey. Fi e1 d tests of permeabi 1i ty, penetrati on <br />resistance, and in-place density were performed in the boreholes and test <br />pits. Laboratory testing of samples obtained from the boreholes and test pits <br />consisted of visual classification, sieve analysis; plasticity <br />characteri zati on, shear strength, and permeabil ity. In additi on; tests for <br />dUrability were performed on samples of material with potential as concrete <br />aggregate. A trial mix of roller compacted concrete (RCC) was also prepared <br />and tested. <br /> <br />The results of the geotechnical investigation showed that the dam section is <br />homogeneous, composed of low density silty sand and gravel with a high mica <br />content, tieri ved from weathered bedrock, and contai ni ng blocks of weathered <br />rock to ei ght inches in di ameter. The dam is founded on sound to sl i ghtly <br />weathered gneiss and pegmatite. The borings showed the rock mass to be <br />moderately jointed. <br /> <br />Glacial deposits located in the upper half of the reservoir consist of clayey <br />to silty sand and gravel with boulders, and could be a source of shell <br />materi al or, after processi ng, fi 1 ter and drai n materi a1 or concrete <br />aggregate. A small all uvi a1 fan contai ni ng a 1 imited quanti ty of impervi ous <br />materi al was a1 so located in the upper reservoi r. The lower hal f of the <br />reservoi r is formed by weathered bedrock and is generally a heterogeneous <br />mixture of silty sand with irregular rock fragments and a high mica content, <br />making it a poor source for construction materials. <br /> <br />iv <br />