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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 third test pit, which was not logged, Was excavated to collect aggregate for <br />RCC testi ng. The materi al encountered was simil ar to that in the upper 7.5 <br />feet of test pit BMP-3. <br /> <br />It appears from the test pit explorations that the finer-grained Zone II <br />impervi ous fi 11 may not have been carri ed to the dam crest as shown on the <br />"as-built" drawings. Instead the Zone II fill may have only been placed to <br />approximately four feet above the top of the original dam. Zone III <br />"pervi ous" fi 11 may then have been used to fl atten the upstream slope to 3H to <br />1 V and rai se the dam the fi na 1 ni ne to ten feet. Even though the Zone II I <br />fi 11 was c1 assifi ed as pervi ous on the "as-buil t" drawi ngs, the wi de range of <br />particle sizes in conjunction with approximately 15 to 25 percent fines <br />creates an impervi ous materi a1. Laboratory fall i ng-head permeabil i ty tests <br />conducted on a sample of this material indicated it is indeed impervious with <br />a permeability of approximately 10-5 cm/~ec. <br /> <br />The seismic refraction surveys clearly defined the contact between the <br />embankment dam and the foundation by a velocity change from 1,900 to 2,500 <br />feet per second (fps) for the dam, to 1,800 to 8,900 fps for the foundation. <br />The refraction indicated the presence of bedrock with velocities in excess of <br />16,000 fps at a depth of about 60 to 100 feet below the foundation contact on <br />the ri ght abutment. The results of th~ sei smi c refracti on survey corre1 ated <br />well with the borehole information. B~drock was not detected by any of the <br />boreholes. <br /> <br />2.1.3.2 Downstream Dam Foundation <br /> <br />Two exploratory holes were drilled and one test pit was excavated to <br />investigate the downstream foundation area. Bore hole BM-4 was drilled <br />approximately 40 feet downstream of the toe and 80 feet to the left of the <br />outlet basin. Bore hole BM-5 was drilled about 40 feet downstream of the toe <br />and 70 feet to the ri ght of the outl et basi n. Test pit BMP-4 was excavated <br />about 40 feet downstream of the toe and 40 feet to the ri ght of the outl et <br />basin. <br /> <br />1231 H <br /> <br />-50- <br />