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1 AuLust 28, 1991 BALBI&CHANG ASSOCIATES <br /> File No. 1525-69 <br /> Backfills for trenches or other excavations within pavement areas and beneath slabs should <br /> be compacted mechanically in 6- to 8-inch lifts in order to provide adequate subgrade support. <br /> Jetting or flooding should not be permitted. We recommend a minimum relative compaction <br /> of 90 percent of maximum dry density as determined by ASTM test designation D1557-78 <br /> for all backfills except the landscaping areas. The uppermost 12 inches within the pavement <br /> area should be compacted to a minimum of 95 percent. The moisture content of compacted <br /> backfill soils should be at or slightly over the optimum moisture content. Poor compaction <br /> in utility trench backfill may cause excessive settlements resulting in damage to the pavement <br /> structural section. <br /> D. Foundation System <br /> After the proper site preparations, the proposed Mini-Market building may be supported by <br /> a conventional spread footing founded into a lime-treated soil subgrade while the proposed <br /> canopy and facility sign should be supported on either deepen footings or drilled piers. In <br /> developing the following foundation recommendations, we assume typical loading conditions <br /> for the type of proposed structures. If .the final design requires unusual foundation <br /> configurations or imposes loads greater than those anticipated for the proposed structures, our <br /> firm should be contacted for possible modification to these recommendations. <br /> 1. Mini-Market Building <br /> The proposed Mini-Market building may be supported on conventional spread footing <br /> foundation. All footings should be founded in properly compacted lime-treated <br /> engineered fill. The minimum footing width should be 12 inches and the minimum <br /> footing embedment depth should be 12 inches. Footing embedment depth is measured <br /> from the lowest adjacent soil subgrade to the bottom of footing. <br /> Footings constructed in accordance with the minimum size requirements stated above <br /> may be designed for an allowable soil bearing pressure not exceeding 2,500 pounds <br /> per square foot for dead plus live loads. The allowable soil bearing pressure may be <br /> increased by one-third for transient loads, including seismic or wind effects. The <br /> weight of foundation concrete extending below grade may be disregarded in footing j <br /> sizing computation. All footings should be properly reinforced as recommended by <br /> the structural engineer. <br /> Soils exposed in footing excavations should not be allowed to dry prior to the <br /> construction of footings. If shrinkage cracks should appear in footing excavations, the <br /> Pate 10 of 17 <br />