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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 />Presently, the majority of seepage from the reservoir is <br />occurri ng through the foundati on; however, foundati on grouti ng in <br />the location proposed may result in local increases of seepage <br />through the homogenous clay embankment. Since it is unl ikely that <br />the embankment foundation was prepared to present construction <br />standards prior to placement of the embankment fill, a major <br />consideration is the possibil ity of inducing internal erosion of <br />the embankment at its contact with bedrock. Therefore, the position <br />of the grout curtain has ,been selected so as to provide an <br />embankment thickness to hydraulic head ratio greater than one above <br />the downstream side of the curtain, which will ensure a hydraulic <br />gradi ent 1 ess than one through the core at its shortest seepage <br />path. This will, however, require that the grout curtain be <br />advanced through about 20 to 25 ft of the embankment materi a 1 of <br />the upstream slope. An access road will be constructed to a width <br />of about 20 ft over the riprap on the upstream slope parallel to <br />the dam axis, at about elevation B,250 ft. The location of the <br />grouti ng pl atform and the proposed dri 11 i ng pattern are shown on <br />Fi gure 13. <br /> <br />To minimize the risk of hydraulically fracturing the <br />embankment during construction of the grout curtain, borings <br />through the embankment will be drilled dry and cased. The casing <br />will be seated into the top of rock prior to grouting and <br />relatively low pressures will be used when injecting grout at the <br />contact between the embankment and foundation rock. The additional <br />wei ght of the embankment wi 11 permi t the grout to be injected at <br />higher pressures deeper in the foundation. <br /> <br />A three line grout curtain is proposed with primary holes <br />spaced 40 ft on centers, secondary hol es 20 ft on centers, and <br />tertiary holes 10 ft on centers. The depth of the curtain, in view <br />of available funds and based on the available foundation <br />permeabil ity data, wi 11 be 1 imited to the upper 50 ft of the <br />foundation. Drilling will be done by skid mounted rotary drill <br />rigs. To maximize the number of joints intersected by the grout <br /> <br />-26- <br />