Laserfiche WebLink
Proposed Senior Assisted Living Facility <br /> PSI Project No. 575-308-2 <br /> August 3, 2011 <br /> Page 1 <br /> 1.0 EXECUTIVE SUMMARY <br /> Professional Service Industries, Inc. (PSI) has conducted a geotechnical evaluation for the <br /> proposed Senior Assisted Living Facility at the subject site in Redwood City, California. Six (6) <br /> soil borings were advanced using a truck-mounted, hollow-stemmed auger drill rig and two (2) <br /> additional soil borings were advanced using a hand auger. Five of the borings were advanced <br /> within the footprint of the proposed structure to a depth of approximately 16 to 51 feet below the <br /> existing ground surface (bgs). The remaining three borings were drilled in proposed pavement <br /> parking areas to a depth of approximately 2-'/2 to 6 feet bgs using a hand auger and drill rig. <br /> At the time of the subsurface investigation the subject site was developed with two buildings, an <br /> active jewelry store and a vacant restaurant. The subsurface soils encountered consisted <br /> primarily of inedium to dark brown and olive-brown clay, silt and sand with varying amounts of <br /> gravel. The consistency of the materials was observed to range from firm to very stiff and <br /> medium dense to dense. Two layers of potentially liquefiable, saturated sands were <br /> encountered in boring B-1 from about 23 to 27 feet and 32 to 36 feet below grade. Bedrock was <br /> not encountered in our borings. Groundwater was encountered in two of the deeper borings at <br /> a depth of between 17 and 22-'/2 feet bgs at the time of drilling. <br /> A detailed liquefaction study was performed as part of this report and indicated that the sandy <br /> soils noted above are subject to soil liquefaction upon application of the design earthquake. The <br /> most significant effect of the soil liquefaction is expected to be surface settlement. Based on the <br /> analysis performed, we estimate potential total and differential liquefaction-induced settlements <br /> of about 2-'/2 and 1-'/4 inches, respectively. Based on these settlement estimates, ground <br /> modification to reduce the effects of potential liquefaction are not deemed warranted. <br /> The proposed building may be supported by conventional shallow spread foundations and floor <br /> slabs underlain by low-expansive Engineered Fill. The footings may be designed for an <br /> allowable soil bearing capacity is 2,500 pounds per square foot, which can be increased by one- <br /> third for wind and seismic loading. The site soils are noted to be potentially corrosive to buried <br /> metal materials. We recommend that a corrosion engineer be consulted to determine what, if <br /> any, corrosion protection is needed at this site. <br /> The owner/designer should not rely solely on this Executive Summary and must read and <br /> evaluate the entire contents of this report prior to utilizing our engineering recommendations in <br /> preparation of design/construction documents. <br /> ....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... <br /> Professional Service Industries�4703 Tidewater Ave., Ste. B�Oakland,CA 94601 �Phone 510.434.9200�Fax 510.434.7676 <br />