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August 28, 1991 BALBI&CHANG ASSOCIATES <br /> File No. 1525-69 <br /> j. Compaction specification recommended above is not the only criteria for proper fill <br /> placement. Other than the degree of relative compaction and the percentage of water <br /> content, the stability of the fill material is also an important factor to the performance <br /> of the fill. A fill can be unstable even if the fill material meets required compaction <br /> specifications. Therefore, a fill should not be considered compacted, regardless of the <br /> degree of relative compaction, if the material is unstable (such as "pumping") or if <br /> future instability is suspected. <br /> k. Finish grading for building pad should consist of rolling the surface to a dense <br /> condition for uniform slab support. The surface should be sloped away from the pad <br /> so that drainage will be directed away from foundations. <br /> 1. All site preparation and fill placement should be observed by a representative of the <br /> geotechnical engineer. It is important that during the stripping and scarification <br /> process a representative of the geotechnical engineer be present to observe whether <br /> any undesirable material is encountered in the construction area. <br /> 1' <br /> B. Wet Season Site Grading <br /> ,. ,. Reducing or maintaining soil moisture to within specified range for proper compaction is the J <br /> most critical task of site grading during wet season condition. When the soil moisture content <br /> prior to grading operation is higher than the recommended range, the grading contractor may <br /> employ one of the following four options to achieve the required moisture content. <br /> E <br /> • Scarify and aerate on-site soil. to reduce moisture <br /> • Over-excavate on-site soil and replace with imported material <br /> • Over-excavate on-site soil, install geotextile, and replace with imported material <br /> • Mix chemical additives with on-site soil to reduce moisture j <br /> Scarifying and aeration is generally the most economical method to reduce soil moisture. <br /> Since it is time-consuming to reduce the moisture content of a high plastic clayey soil, this <br /> method is considered impractical for this site. <br /> When scarifying and aeration is not a feasible solution, the wet on-site soils may be excavated <br /> and replaced with less moisture sensitive material such as sandy gravel. Over-excavation <br /> depth should be determined in the field based on the degree and depth of saturation. For <br /> typical ARCO AM/PM Market type of structure, the over-excavation depth may be on the <br /> order of 3 feet. Where exposed subgrade from over-excavation is not capable of supporting <br /> Page 8 of I7 <br /> E <br /> i <br />