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Project No. 9929.G Geotechnical Investigation/Vineyard Avenue, Pleasanton 8 August 2003 <br />Foundations <br />34. As mentioned previously, the proposed structures may be supported on either structural <br />mat slab or post-tensioned slab foundation systems. The following are the recommended <br />geotechnical design parameters for both systems. <br />Structural Mat Foundation: <br />35. Structural mat slabs should be a minimum of 8 inches in thickness and designed using the <br />method presented in the 1997 Uniform building Code, Chapter 18, Division III, Section 1815, <br />Design ofSlab-on-Grade Foundations to Resist the Effects of Expansive Soils. <br />36. It is recommended to design the foundation for an effective Plasticity Index of 20 which <br />is applicable for the soil profile at the subject site. The maximum allowable bearing pressure at <br />the base of the mat should not exceed 1,500 p.s.f. for dead plus sustained live loads. Those <br />recommendations are contingent upon adequate surface drainage being provided as designed by <br />the project Civil Engineer and maintained by the property owners at all times. <br />37. Design criteria for structural mat slabs on less expansive on-site soils, bedrock or select <br />import fill, if necessary, can be provided once the properties and thickness of the select import <br />layer are known. <br />Post-Tensioned Slab: <br />38. Post-tensioned slabs should be a minimum of 10 inches in thickness and designed using <br />the following criteria which is based on the design method of the 1997 Uniform Building Code, <br />Chapter 18, Division III, Section 1816 and 1817, Design ofPost-Tensioned Slabs on Ground: <br />TERRASEARCH, inG Page 21 of 53 <br />