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 9 5.0 CONCLUSIONS AND RECOMMENDATIONS Based on the results obtained from our exploration and analysis, it is our opinion that the site can be adopted for the proposed development. The results of our liquefaction analysis indicated two layers of potentially liquefiable soils, which could result in building total and differential settlements of 2-'/2 inches and 1'/4 inch, respectively. Based on these magnitudes of estimated settlement, ground modification to reduce the effects of the soil liquefaction are not deemed wa rra nted. The proposed construction at the site should be performed in accordance with the following recommendations. Our recommendations have been developed on the basis of the previously described project characteristics and subsurface conditions encountered. If there are any changes in these project criteria, including project location on the site, a review should be made by PSI to determine if modifications to the recommendations are warranted. Once final design plans and specifications are available, a general review by PSI is recommended as a means to check that the evaluations made in preparation of this report are correct and that earthwork and foundation recommendations are properly interpreted and implemented. 5.1 Site Preparation Prior to construction, the location of any existing underground utility lines within the construction area should be established. Utility lines to be abandoned should be properly capped off at the property line and removed. Utilities to be preserved should be re-routed around the construction zone, as necessary. All soils disturbed by site clearing should be removed and stockpiled for future use, if suitable. Site preparation should also include demolition of the existing buildings and pavements, which should also include removal of all foundations, floor slabs and any below-grade construction. All debris generated by the demolition operations should be legally disposed off-site. The new building and pavement areas should be cleared of surface vegetation and soils with significant deleterious materials.. As a minimum, it is recommended the clearing operations extend at least five feet beyond the development perimeters, where possible. If any trees or shrubs in the proposed construction area are planned for removal, the root system of these trees and/or shrubs should be thoroughly grubbed. The cavity created by the removal of the tree or shrub and of all loose material should be excavated in a dish shape to provide access for compaction equipment. The dished area should be scarified a minimum of 6 inches, moisture-conditioned, and recompacted to the subgrade surface with engineered fill in accordance with the recommendations of"Section 5.2 — Engineered Fill." Based on our subsurface exploration and laboratory testing it is our opinion that the near-surface native soils at the site can be adopted for the support of the proposed building. Within the building pad area, we recommend that the soils should be removed to a depth of at least 18 inches below the bottom of the proposed footings and floor slab and to a depth of at least 18 inches below existing grade, whichever is deeper. The lateral extent of this recommendation should extend at least 5 feet beyond the building exterior. The soils exposed at the base of this over-excavation should be examined by a representative of PSI to document that they are suitable for building support. The soils exposed at the base of the over-excavation