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GEOTECHNICAL STUDY SUN. ~iY PROPOSED VINEYARD PASS SUBDIb'ISION 865 CLARA LANE PLEASANTON, CALIFORNIA The following report was prepared for Vineyard Pass, LLC for the proposed Vineyard Pass Subdivision to be located on 865 Clara Lane in Pleasanton, California. Based on our geotechnical study, it is our opinion that the site may be developed for the proposed project. The contents of this report have been brief/y summarized be%w for your convenience; however, the use of the summarized information without first reviewing the entice contents of the fo/%wing report is not recommended. Based on our geotechnical study, we present the following summarized discussions and/or recommendations: SUBSURFACE CONDITIONS • Undocumented fill was encountered to a depth of 5 feet below existing grade in the borings at the time of drilling. There may be varying depths of fill in areas beyond or between our exploratory borings. In general, the native soils consisted of stiff to very stiff silty clay and gravelly clay and medium dense to very dense clayey sand and silty sand . Laboratory testing indicates that the near-surface soils have a moderate expansion potential. Groundwater was not encountered in borings at the time of drilling. We expect groundwater levels to fluctuate due to variations in rainfall, groundwater recharge, and site conditions. SITE PREPARATION • To help reduce the potential for differential settlement, we recommend the foundation subgrade soils for Lot 1 and the Lot 2 cut areas be over-excavated a minimum of 2 feet below the proposed footing elevation for the foundation areas, moisture-conditioned, and recompacted in the foundation area and at least 5 feet beyond the structure and exterior flatwork/sidewalk areas in plan view, if practicable. Deeper sub-excavation may be required depending on soil conditions encountered during grading. Figure 8, Foundation Materials Under Building, presents the details for over-excavating and replacing the soil with compacted, engineered fill within the building limits. Compaction recommendations are discussed in Section 6.1.4 Fill Placement and Compaction. On-site soil generated by site grading may be used as structural fill provided the soil is free of deleterious and organic materials and is approved for use as fill by our representative. The on-site soils should be moisture-conditioned, and compacted to a minimum of 90 percent relative compaction at a minimum of 2 percent over the optimum moisture content according to the latest ASTM test methods and procedures. All import fill to be placed must be compacted to a minimum relative compaction of 90 percent of the maximum dry density and moisture-conditioned to a minimum of 2 percent over the optimum moisture content according to ASTM test methods. The upper 12 inches of pavement subgrade soils should be scarified, moisture-conditioned as necessary, and recompacted to a minimum of 95 percent relative compaction. FOUNDATIONS • If the earthwork recommendations included in this report are complied with, the proposed residences may be supported by a conventional foundation established on compacted, engineered fill. The recommended footing widths for continuous and isolated footings is 12 inches and 24 inches, respectively. The recommended minimum embedment depth is 18 inches. The recommended allowable bearing capacity is 2,500 pounds per square foot (psf) for engineered fill. Lateral load recommendations are given in Section 6.3. The foundation should be designed according to the criteria presented in Table 3. lirrti Korbmacher Engineering, Inc.