1033 51ST PL SW Geotech Report 2022-10-28

• 8.0 CONSTRUCTION 8.1 SITE PREPARATION 8.1.1 Grubbing and Stripping Stripping and grubbing will be required at.the site to remove vegetation that is at the ground surface. Where present, the existing root zone material should be stripped and removed from all proposed building and pavement areas. We anticipate a stripping depth of approximately 6 inches to 1 foot over areas of the site where native vegetation has grown. Greater depths may be necessary to remove localized zones of organic material or deeper root zones in loose upper material. The actual stripping depth should be based on field observations at the time of construction. Stripping depths shouldextend at least 5 feet beyond the limits of proposed structural areas. Stripped material should be transported off site for disposal or used as fill in landscaped areas. 8.1.2 Subgrade Verification A member of our geotechnical staff should observe the exposed footing, foundation,floor slab, pavement, and driveway subgrade after stripping, excavation, scarifying and compaction, and placement of structural fill have been completed to confirm that there are no areas of unsuitable or unstable soil. The subgrade should be evaluated using moisture-density testing or a hand probe. If soft, loose, or otherwise unsuitable soil is found at the subgrade level,we recommend the soil be over-excavated and replaced with structural fill or stabilization material. We recommend the upper 24 inches of subgrade beneath footings, foundations, pavement, and floor slabs be properly compacted to 95 percent of the maximum dry density, as determined by ASTM D1557. 8.1.3 Permanent Slopes Permanent cut or fill slopes should not exceed a.gradient of 2H:1V, unless specifically evaluated for stability. Upsiope buildings, access roads, and pavement should be set back a minimum of 5 feet from the crest of such slopes. Alternatively, the setback at the top of the slopes can be determined on a case-by-case basis by the geotechnical engineer. Slopes should be planted with appropriate vegetation to provide protection against erosion as soon as possible after grading. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face of the slope. 8.2 •DRAINAGE CONSIDERATIONS • 8.2.1 Surface Drainage The finished ground surface should be sloped away from the structures at a minimum 2 percent gradient for a distance of at least 5 feet. Roof drainage from the structures should be directed into solid, smooth-walled drainage pipes that carry the collected water to the storm drain system. Pavement surfaces and open space areas should be sloped such that surface water runoff is colie'eted.and-routed°to suitable•discharge points, Runoff water should not be directed to the top of slopes. 8.2.2 Subsurface Drainage in our opinion, perimeter footing drains should be required considering the proposed below- grade,tuck-under structures will be embedded into the very dense glacial till material. G EODESIGNi 9 NWHome-1.01:101618