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F) COMPARISON OF WATER DEMAND AND AVAILABILITY Based on the Lytle Water Solutions report, the Company irrigation demands are regularly greater than the availability but with a supplemental supply from Cucharas Reservoir, the target demand was met in 11 of 24 years. G) WATER QUALITY ISSUES Storage and periodic releases from Cucharas Reservoir improves the water and stream qualiry in the Cucharas River Canyon below the dam. If a zero storage restriction were imposed by the SEO and the two operational 30-inch diameter gates were left fully open, allowing all tributary inflow to pass through them, Iarge quantities of silt would be eroded by stream flow through the reservoir basin and be deposited in the pristine river canyon below. The qualiry of Aquatic habitat, wildlife and esthetic values would be significantly impacted. H) FIELD INVESTIGATIONS Existing data from previous field investigations was reviewed and determined suitable for this level of study. Further field investigations may be required based upon more detailed engineering analyses. Previous geotechnical investigations include those performed for the original construction of the dam and those completed in 1986 by GEI Consultants. Following is a summary of the findings contained in those reports. Prior to construction of the dam in 1909, five test holes were drilled in the canyon floor. Four holes in the 200-foot wide river channel section and one hole 35 feet above the river channel on the right abutment. These borings indicated that the foundation consists of 20 to 40 feet of sandy soils and boulders over shale bedrock in the channel section and approximately 30 feet of clayey soils and boulders over bedrock on the right abutment. A geotechnical field exploration was also performed in 1986 by GEI during a safety evaluation of Cucharas Dam. The investigation consisted of drilling five test borings into the dam and at the downstream toe of the dam, including five observation wells. Three bore holes located along the downstream toe were advanced to an approximate depth of 25 feet and two bore holes located on the crest of the dam were advanced to an approximated depth of 140 feet. The foundation soils at the toe of the dam and under the dam consisted of 10 - 17 feet of silty sand, silty gravelly sand and silty sand and gravel overlaying 0- 4 feet of clayey gravels. The silty sand layer was composed of mostly fine to medium sand, with approximately 10 to 501ow plasticity fines and 0 to 20 percent gravels up to 1-inch maximum size. The clay gravel was composed of 1/z - 1-inch gravels with a 30 percent widely graded sand with about 30% medium plasticity fines. Standard penetration tests (SPT) ranged from 7 blows/ft to 50 blows/3 inches and averaged 23 blows/ft. Bedrock was encountered at depths of 17 to ZO feet along the toe of the dam and consisted of hard to very hard claystone and shale with interbedded sandstone layers. Borings were advanced approximately 5 feet into bedrock. The materials in the embankment can be divided into two types: 1) Mixed earth fill/rock fill in the upper section of the dam and 2) Sound rock fill in the lower section of the dam. The mixed Cucharas Feasibility Study ~ Project Background and 1Veed