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4.2 Foundations <br />4.2.1 General <br />Preliminary recommendations for foundation design and foundation construction are presented <br />herein. When the structural loads for the proposed structures are known they should be <br />provided to our office to verify the recommendations presented herein. <br />The following foundation recommendations are provided for support of anticipated at grade <br />residential structures, and parking structure: conventional, post -tension, and Mat slab <br />foundations, for use as needed. For preliminary design purposes a high expansion potential <br />should be considered for design. The as -graded soil conditions should be verified as the <br />completion of grading. <br />The information and recommendations presented in this section are not meant to supersede <br />design by the project structural engineer or civil engineer specializing in the structural design <br />nor impede those recommendations by a corrosion consultant. Should conflict arise, <br />modifications to the foundation design provided herein can be provided. <br />4.2.2 Soil Bearing <br />Proposed minor site at -grade improvements may be supported on spread footings provided <br />that the earthwork recommendations outlined in this report are properly implemented. An <br />allowable soil bearing pressure of 1,500 psf may be used for the design of footings placed in <br />compacted fill having a minimum width of 12 inches and minimum embedment of 24 inches <br />below lowest adjacent ground surface. This value may be increased by 300 psf for each <br />additional foot of embedment and 100 psf for each additional foot of foundation width to a <br />maximum value of 3,000 psf. These allowable bearing pressures are applicable for level <br />(ground slope equal to or flatter than 5H:IV) conditions only. <br />Bearing values indicated above are for total dead loads and frequently applied live loads. The <br />above vertical bearing may be increased by one-third for short durations of loading which will <br />include the effect of wind or seismic forces. <br />4.2.3 Conventional Foundations <br />Footings for proposed structures should have minimum depths (below lowest adjacent finish <br />grade) of 24 inches for exterior footings and 18 inches for interior footings, for one, two, and <br />three/four story structures for the anticipated high expansion potential (91-130 Expansion <br />Index). <br />Shallow foundations may be designed for a maximum allowable bearing capacity of 2,500 <br />IMF (gross), for the design of footings placed in compacted fill having a minimum width of <br />12 inches and minimum embedment of 24 inches below lowest adjacent ground surface. <br />Shallow foundations for continuous footings should be a minimum of 12, 15, and 18 inches <br />wide for one, two, and three/four story structures, respectively, and spread footings 24 inches <br />wide founded into compacted fill or competent native soils. A factor of safety greater than 3 <br />was used in evaluating the above bearing capacity values. This value may be increased by <br />Project i y 66n,61 18 — 833 1 3 , 2021 <br />