Reso13 PC 13-09 2859 Initial Study Mitigated Negative Declaration Kensington

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Proposed Senior Assisted Living Facility PSI Project No. 575-308-2 August 3, 2011 Page 5 soil descriptions, stratification, penetration resistance, locations of the samples and laboratory test data. The stratification shown on the boring logs represents the conditions only at the actual boring locations at the time of our exploration. Variations may occur and should be expected between boring locations. The stratification that represents the approximate boundary between subsurface materials and the actual transition may be gradual. The samples that were not altered by laboratory testing will be retained for 60 days from the date of this report and will then be discarded. During the sampling procedure, Standard Penetration Tests (SPT) were performed and relatively undisturbed samples were obtained utilizing a 3-inch diameter California split-spoon sampler. The SPT for soil borings is performed by driving a 2-inch, O.D., split-spoon sampler into the undisturbed formation located at the bottom of the advanced borehole with repeated blows of a 140-pound hammer falling a vertical distance of 30 inches. The number of blows required to drive the sampler the last 12 inches of an 18 inch penetration depth is a measure of the soil consistency and is referred to as the N-value (see Appendix A). The blow counts obtained from the California sampler should be reduced by approximately 40% to obtain a rough correlation to SPT blow counts (N-value). Samples were identified in the field, placed in sealed containers and transported to the laboratory for further classification and testing. 3.4 Groundwater Groundwater was encountered in borings B-1 and B-6 at depths of between 17 and 22-'/2 feet bgs. Groundwater was not observed within the other borings during or upon completion of drilling. It is possible that transient, oversaturated ground conditions at shallower depths could develop at a later time due to periods of heavy precipitation, landscape watering, leaking water lines, or other unforeseen causes. Variations in groundwater levels should be expected seasonally, annually, and from location to location. Groundwater is not expected to significantly impact the proposed construction. 3.5 Laboratorv Evaluation Selected samples of the subsurface soils encountered were returned to our laboratory for further evaluation to aid in classification of the materials, and to help assess their strength, expansive nature and corrosivity. The laboratory evaluation consisted of visual and textural examinations, moisture and density tests, Atterberg limits testing, expansion index testing, sieve analyses, and unconfined compression testing. Additionally, pH, sulfate, chloride and resistivity testing were performed to evaluate the corrosive potential of the site soils. A brief discussion of the laboratory tests performed and a portion of the test results are presented in Appendix B. The remainder of the test results are shown on the boring logs (Appendix A) and in the body of the report.