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<br />I <br /> <br />I <br /> <br />4. No evidence has been observed suggesting that construction of the <br /> <br /> <br />original 10 foot high dam in 1961 (crest elev. 9,053) resulted in any <br /> <br />foundation stability problems. <br /> <br />I <br /> <br />I <br /> <br />5._ Disturbance of the left abuttnent will be kept to a minimum. The only <br /> <br /> <br />construction activity will be stripping of vegetation where embankment <br />~ <br /> <br />is to be placed, relocation of the Forest Service road across the dam <br /> <br /> <br />crest, and removal of surface cobbles and boulders to obtain riprap. <br /> <br /> <br />The spillway structure will be located on the right abutment and <br /> <br /> <br />removal of borrow material will be restricted to an area upstream from <br /> <br /> <br />the dam within the proposed reservoir. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />6. The left abutment of the proposed dam will be located as far as <br /> <br /> <br />feasible upstream from the existing crack (which is found about 80 <br /> <br /> <br />feet downstream from TP 3). This crack will be filled with clay soil <br /> <br /> <br />from the borrow area to prevent entrance of surface runoff into the <br /> <br /> <br />crack in an effort to minimize further slumping. <br /> <br />I <br /> <br />I <br /> <br />7. The site is not located in an area likely to receive high earthquake <br /> <br /> <br />shaking. The area is in Zone 1 on the ESSA/Coast and Geodetic Survey <br /> <br /> <br />seismic risk map of the western United States. Structures located in <br /> <br /> <br />Zone 1 can expect minor damage in the event of earthquake activity. <br /> <br />I <br /> <br />I <br /> <br />8. Due to planned Proj ect operation, rapid reservoir drawdown to the <br /> <br /> <br />extent that would result in shoreline instability will not occur. <br /> <br />I <br /> <br />I <br /> <br />9. The portion of the side mass where the left abutment will be located <br /> <br /> <br />contains a high content of basalt cobbles and boulders which should <br /> <br /> <br />increase the shear strength of the material. <br /> <br />I <br /> <br />5.5 Construction Materials: <br /> <br />I <br /> <br />Impervious Materials <br /> <br />I <br /> <br />Four test pits were excavated in the proposed reservoir area to locate a <br /> <br /> <br />source of fine-grained materials for use as dam embankment. The soils were <br /> <br />I <br /> <br />-15- <br /> <br />I <br /> <br />- <br />