319 76TH PL SW 2016-01-01 MF Import

SERS Public Safeh' 9-1-1 Communication Tower SI Report No. 704-05224-1 December 26, 2000 Page 6 All required structural fill materials should be moisture conditiu ied to within 3 percent of .aptimum moisture content and compacted by mechanical means to a minimum of 95 percent of the material's maximum dry density as determined in accordance with ASTM D 1557 (Modified Proctor), if density testable. Fill materials should be placed in layers that, when compacted, do not exceed about 12 inches, depending upon the type of compaction equipment used. Selected samples of the materials to be used for structural fill should be submitted to our laboratory at least one week prior to placing fill in order to evaluate the maximum density, optimum moisture content, and suitability of the soil for use as fill. 5.1.1 Site Preparation During Wet Weather Construction The on-site, silty sand is considered to be somewhat moisture sensitive and thus is no' recommended for use as structural fill during wet weather construction. Additional fill material, if needed, during wet weather construction should consist of an all-weather, clean, granular fill containing less than 5 percent material passing the No. 200 sieve, such as sand, crushed rock, or sand and gravel. During wet weather grading operations, all excavations should be performed using a smooth-bladed, tracked backhoe working from areas where mater'al has yet to be removed or from the already placed structural fill. Subgrade areas should be cleanly cut to firm undisturbed soil. Proofrolling of excavation bottoms is likely not appropriate dw,ng wet weather grading in order to avoid disturbance of moisture-sensitive soils. Should construction take place during wet weather, we recommend that a representative of the geotechnical engineer be present to observe the subgrade in order to evaluate whether acicilional preparation is indicated Placement of crushed rock should follow immediately ;after site grading in order to provide protection of the sensitive subgrade soils during construction activities. In traffic areas, the placement of a one-foot thick granular working base is generally recommended with thicker sections and/or geotextile fabrics recommended in heavily traveled areas. Generally, three to six inches of crushed rock is sufficient in foot traffic areas 5.2 Excavations Excavation and construction operations may expose the on-site soils to inclement weather conditions. The stability of exposed soils may rapidly deteriorate due to precipitation or the action of heavy or repeated construction traffic. Accordingly, foundation area excavations should be adequately protected from the elements, and from the action of repetitive or heavy construction loadings. V