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KLEIN FELDER In areas where moisture transmission through floor slabs will be undesirable, the gravel or sand should be covered with a moistureproofing membrane, such as "Moiststop," or equivalent, to act as a vapor barrier. Care should be taken to ensure that the membrane extends to all perimeter foundations and no exposed area exists between the foundations and membrane. If the membrane should be damaged during construction, it should be removed and patched or completely replaced in order for it to perform its intended function. All openings in_the membrane to accommodate plumbing should be carefully sealed after the membrane is placed. The membrane should be covered with approximately 1 to 2 inches of moist sand to protect it during construction and to aid in curing the concrete. We recommend that floor slabs be a minimum of 4 inches in thickness and be reinforced with at least wire mesh. The actual floor slab thickness and reinforcing design should be provided by the structural engineer. 6. Site Preparation and Grading Site preparation for most of the parcels will include only the stripping of vegetation, and debris from the areas of construction. Where existing structures exist, site preparation should include removal of all structures and their foundations, underground irrigation lines and utilities. Vegetation and debris should not be incorporated in any of the structural fills. The actual depth of stripping should be determined in the field by a representative of our firm. Voids left by the removal of foundations, tree root systems, underground irrigation lines and/or utilities, and any other buried objects should be cleaned of all loose soils and debris to stable soil and properly backfilled with Engineered Fill placed as described below. Depending on the finished site grades and method of floor slab support, it may be necessary to overexcavate some of the existing soils to provide for nonexpansive Engineered Fill beneath floor slabs. We recommend that overexcavations to provide for Engineered Fill beneath floor slabs extend a minimum of 5 feet beyond the structure outlines. After all excavations are completed and before any fill is placed beneath the structures, we recommend that the exposed soils be scarified to a minimum depth of 6 inches and be recompacted to between 85 and 95 percent of the maximum dry density as determined by the ASTM D-1557 test method, at a moisture content near optimum. If moisture conditioning of the existing soils is to be performed at a later date, we caution that overcompaction be avoided since higher densities will reduce the permeability of the soils. Just prior to placing floor slabs or nonexpansive Engineered Fill beneath floor slabs, the moisture content of the existing soils should be increased to at least 3 percent over optimum to the depths recommended in the previous subsection. After any required excavations are completed and before any fill is placed beneath proposed pavement areas, we recommend that the exposed soils be scarified to a minimum depth of 6 inches and be recompacted to a minimum of 95 percent of the above referenced maximum test dry density. 20-4280-0I.G012019RI50 Page 6 of 12 April 14, 1999 Copyright 1999 Kleinfelder,Inc.