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August 29, 2019 G-4971 Mr. Jeff Davis Page 4 Subarade Preparation Soils in areas to receive structural fill, or concrete slabs, should be prepared to a firm, unyielding condition. The prepared subgrade should be observed and approved by the geotechnical engineer. Any detected soft spots or disturbed areas should be compacted or excavated and replaced with compacted structural fill or crushed rock as directed by the geotechnical engineer. Structural Fill Structural fill is typically defined as earthen material that is placed below buildings (including foundations and on -grade slab floors) or other structures, and provides support to those structures. Soils that meet the material specifications for structural fill as presented below in this report, or are otherwise approved by the geotechnical engineer, can be used for structural fill. Material which is stored on site for later use as structural fill should be covered, underlain, and bermed with plastic sheeting to protect it from moisture if its usability is sensitive to its moisture content. Structural fill material should be placed and compacted in accordance with the recommendations provided below or as otherwise approved by the geotechnical engineer during construction. Fill Material Specifications All materials to be used as structural fill should not contain rocks or lumps larger than 3 inches in its greatest dimension. During wet weather, the material should be granular in character, with a fines content (passing a #200 sieve) of less than 5 percent. All material should be placed at or near its optimum moisture content. If the material is too wet to be compacted to the required degree, it will be necessary to dry the material by aeration (which may be difficult) or replace the material with an alternative suitable material, in order to be capable of achieving the required compaction. The sandier site soils might be usable as structural fill during dry weather conditions but may be subject to degradation if left exposed or unprotected. Relatively silty soils and topsoils are unlikely to be useable under most conditions due to their silty character and high moisture content. Compaction Specifications Structural fill material should be compacted to at least 92 percent of its maximum dry density as determined by ASTM D 1557 (Modified Proctor Test), unless otherwise authorized by the geotechnical engineer, and with the following exceptions. GE4 Group Northwest, Inc.