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GEOTECHNICAL STUDY SUMMARY PROPOSED VINEYARD PASS SUBDIVISION 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 entire 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 • The existing undocumented fill should be excavated and recompacted as shown in Figure 9, Typical Buttress and Subdrain. The fill limits shown on Figure 7 are approximate. Our representative should be present during grading to observe that all undocumented fill in the building pad areas has been excavated and recompacted. Compaction recommendations are discussed in Section 6.1.4 Fill Placement and Compaction. • We recommend that the subgrade soils for floor slabs, if used, and exterior flatwork be a r replaced with 12 inches of non-expansive compacted fill, Class 4 material or an approved equivalent placed on moisture-conditioned, compacted fill. The non-expansive fill should extend at least 2 feet beyond the and exterior area. 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 pier and grade beam foundation established in native soil and/or engineered fill. The recommended allowable skin friction capacity is 500 pounds per square foot (psf) for native soil/engineered fill. Lateral load recommendations are given in Section 6.3. The foundation should be designed according to the criteria presented in Table 3. y~,orbmacher Engineering, Inc.