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1 <br /> June 23,2014 <br /> Project No. T-6241 <br /> The following sections provide detailed recommendations regarding the above issues and other geotechnical <br /> design considerations. These recommendations should be incorporated into the final design drawings and <br /> construction specifications. <br /> 5.2 Site Preparation and Grading <br /> To prepare the site for construction, all vegetation, organic surface soils, and other deleterious materials should <br /> be stripped and removed from the site. Based on conditions observed in our test pits, we expect that surface <br /> stripping depths of about six inches will be required to remove organic surficial soils. These organic surficial <br /> soils will not be suitable for use as structural fill, but may be used for limited depths in nonstructural areas or for <br /> landscaping purposes. <br /> Where existing site gradients are 15 percent and less and required structural fill thickness is 7 feet or greater, in <br /> our opinion, it would not be necessary to strip the organic surface layer or remove the organic fill material. In <br /> this case, after grubbing of the brush and tree vegetation, grass areas can be mowed short. to the surface with <br /> clippings collected and removed followed by scarifying and compacting the exposed surface. The new structural <br /> fill can be then placed on the newly compacted surface. The exception to this occurs beneath new embankment <br /> slopes. Where fill embankment slopes are constructed such as along the western and northern site margins the <br /> organic surface layer should be removed a minimum lateral distance of 30 feet back from the new slope crest. <br /> Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired <br /> grades. Prior to placing fill, all exposed bearing surfaces should be observed by a representative of Terra <br /> Associates to verify soil conditions are as expected and suitable for support of new fill. Our representative may <br /> request a proofroll using heavy rubber-tired equipment to determine if any isolated soft and yielding areas are <br /> present. If excessively yielding areas are observed, and they cannot be stabilized in place by compaction, the <br /> affected soils should be excavated and removed to firm bearing and grade restored with new structural fill. <br /> Beneath embankment fills or roadway subgrade if the depth of excavation to remove unstable soils is excessive, <br /> the use of geotextile fabrics, such as Mirafi 500X, or an equivalent fabric, can be used in conjunction with clean <br /> granular structural fill. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular <br /> structural fill placed and compacted over the geotextile fabric should establish a stable bearing surface. <br /> The native soils encountered at the site contain a sufficient amount of soil fines that will make them difficult to <br /> compact as structural fill when too wet or too dry. The ability to use native soil from site excavations as <br /> structural fill will depend on its moisture content and the prevailing weather conditions at the time of <br /> construction. If wet soils are encountered, the contractor will need to dry the soils by aeration during dry weather <br /> conditions or use an additive such as cement or lime to stabilize the soil. If the soil is amended, additional BMPs <br /> addressing the potential for elevated pH levels will need to be included in the Storm Water Pollution Prevention <br /> Program (SWPPP) prepared with the TESL plan. <br /> 1 <br /> 1 <br /> Page No. 7 <br /> 1 <br />