406 PECKS DR Geotech Report 2025-07-14

December 30th, 2021 G-5593 4730— Seahurst Ave, Washington 98203 Page 7 Temporary excavation slopes should not be greater than the limits specified in local, state and federal government safety regulations. We recommend that temporary cuts greater than 4 feet in height be sloped at inclinations up to 1H:1V (Horizontal: Vertical) in loose to medium dense soils. Temporary excavations in the very dense, hardpan soils can be sloped near vertical under the observation of the geotechnical engineer. Permanent cut and fill slopes should be inclined no steeper than 2.5H:1V. Steeper permanent fill slopes can be achieved with the use of geogrid for lateral reinforcement. Slopes that are to be maintained or mowed should be sloped at 3H:1 V, or less. Fill slopes should consist of granular material compacted to a minimum of 90 percent of the material's maximum dry density. If supporting structural elements, the fill should be compacted to the structural fill specification of 92 percent. Based on the subsurface findings, groundwater seepage is not anticipated. If water seepage or other adverse conditions are encountered, excavation should be halted, and the geotechnical engineer should be contacted to review the site conditions. Structural Fill Structural fill is defined as fill soil supporting building foundations, floor slabs,pavements, sidewalks or other structures. Structural fill should be free of organic and other deleterious substances and have a maximum fragment size of 3 inches. The site soils contain appreciable proportions of fines and may be difficult to achieve compaction during wet weather, depending on the material's moisture content. Therefore, during wet weather, we recommend using a free- draining granular material containing no more than 5 percent fines content (silt and clay-size particles passing the No. 200 mesh sieve). Structural fill material used for foundation subgrades should consist of 1-to 2-inch crushed rock. Structural fill should be placed and compacted at or near the material's optimum moisture content and in lifts that are 10 inches thick or less. Below slab-on-grade floors, foundations, and other structural elements, structural fill should be compacted to a minimum of 92 percent of the material's maximum dry density, as determined by ASTM Test Designation D-1557 (Modified Proctor). For driveways, structural fill should be compacted to 90 percent, with the exception of the top 12 inches which should be compacted to 95 percent. Fill behind retaining walls and next to building foundation walls should be compacted to a minimum of 90 percent(92 percent if supporting structural elements; if supporting pavements, the top 12 inches should be compacted to 95 percent). GEO Group Northwest,Inc.