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7.A. - Page 291 <br /> area has been stripped of vegetation, soft earth materials and debris, we recommend <br /> that the exposed subgrade be proof-rolled with heavy construction equipment (e.g. <br /> loader or smooth-drum roller) to disclose areas of soft and yielding material. Where <br /> soft and yielding material is observed, it should be overexcavated and replaced as <br /> engineered fill. Due to the potential for expansion, we do not recommend compacting <br /> fine-grained soils (clays) to 95 percent relative compaction in the accordance with <br /> standard Costco design requirements. Fine-grained soils should be compacted <br /> between 88 and 92 percent of the soils maximum dry unit weight (ASTM D1557), as <br /> recommended in Section 9.4.1 of our November 15, 2004 report. Moisture contents <br /> should be maintained between 2 and 5 percent above optimum during compaction. <br /> The subgrade for new asphalt concrete pavements should be compacted to at least <br /> 90 percent at these high moisture contents to help reduce soil expansion. The <br /> properly prepared subgrade should be covered with aggregate base within 24 hours <br /> to reduce drying of the subgrade soil. <br /> Elevated moisture contents should be expected in areas that are currently <br /> landscaped. The contractor should be aware that significant processing (moisture <br /> reduction) of these materials will likely be required prior to placement as engineered <br /> fill. Processing may require ripping the material, disking to break up clumps, and <br /> blending to attain uniform moisture contents necessary for compaction. The <br /> contractor should also anticipate that pumping subgrade conditions are likely to be <br /> encountered during site grading activities, and the subgrade may need to be <br /> stabilized with geotextiles and crushed rock. The contractor should consider these <br /> moisture conditions when selecting equipment for earthwork and compaction. <br /> Site Drainage <br /> Costco's standard design includes foundation drains tied into the storm drain. In <br /> addition, due to poor draining subgrade, Costco should consider installing radial <br /> finger drains at drainage inlets in the parking areas, and underdrains <br /> beneath/adjacent to planter islands, and around the canopy in accordance with its <br /> current standards. <br /> 2010 CBC Seismic Design Parameters <br /> According to the 2010 California Building Code (CBC), every structure, and portion <br /> thereof, including non-structural components that are permanently attached to <br /> structures and their supports and attachments, shall be designed and constructed to <br /> resist the effects of earthquake motions in accordance with ASCE 7-05, excluding <br /> Chapter 14 and Appendix 11 A. The seismic design category for a structure may be <br /> determined in accordance with Section 1613 of the 2010 CBC. Based on our prior <br /> field explorations, we classify the site as Site Class D, Stiff Soil. The 2010 CBC <br /> Seismic Design Parameters are summarized in the following table. <br /> 127119/IRV12L0328 Page 2 of 3 May 10, 2012 <br /> Copyright 2012 Kleinfelder <br /> KLEINFELDER 2 Ada,Suite 250, Irvine, CA 92618 p� 949.727.4466 f� 949.727.9242 <br />