6107 BERKSHIRE DR 2018-01-02 MF Import

ADaPT Engineering, Inc. Western Wireless Corporation ADaPT Job No, WA98-992 April I, 1998 Page 9 soil mixtures of silt, sand, and gravel. Recycled concrete, asphalt, and glass, derived from pulverized parent materials may also be used as structural fill. Placement and Compaction: Generally, CDF, and lean -mix concrete do not require special placement and compaction proccdu-es. In contrast, pit -run, sand, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Using the modified Proctor maximum dry density (ASTM:D-1557) as a standard, we recommend that structural fill used for various on -site applications be compacted to the following r.tinimum densities: Fill Air rlicalion Minimum Cnm action Slab/Footing subgrade 90 percent Gravel drive subgradc (upper I foot) 95 perecut Gravel drive subgradc (below I foot) 90 percent Subgrades and Testing: Regardless of location or material, all structural fill should be placed over firm, unyielding subgradc soils. We recommend that a reprewmative from ADaPT be retained to observe the condition of subgradc soils before fill placement begins. and to perform a series of in -place density tests during soil fill placement. In this way, the adequacy of soil compaction efforts may be evaluated as earthwork progresses. Fill Content: Soils used for structural fill should not contain individual panicles greater than about 6 inches in diameter and should be free of organics, debris, and other deleterious materials. Given these prerequisites, the suitability of soils used for structural fill depends primarily on the grain -size distribution and moisture content of the soils when they are placed. When the "lines" content (that soil fraction passing the U.S. No. 200 Sieve) increases. soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding conditon when the moisture content is more than about 2 percentage points above optimum. "1'he use of "clean" soil is necessary for fill placement during wet -weather site work. Clean soils are defined as granular soils that have a fines content of less than 5 percent (by weight) based on the soil fraction passing the U.S. No.314-inch Sieve. CLOSURE The conclusions and recommendation; presented in this report are based, in part, on the explorations that tvc perforated for this study. If variations in subsurface conditions are discovered during earthwork, we may need to modify this report. Because the future performance and integrity of the tower foundations