2505 57TH ST SW Geotech Report 2022-10-25

August 29, 2019 Mr. Jeff Davis G-4971 Page 3 recommendations regarding geotechnical aspects of the project are presented in the following sections of this report. Grading and Earthwork Site Clearing and Erosion Control Grading work for the proposed addition should be restricted to the minimum needed to achieve proposed final grades. The area where construction work will be performed should be cleared of vegetation, topsoil, organics, debris, and any other deleterious materials that are found. These materials should be hauled off site or used for landscaping, as appropriate; they should not be used as structural fill or retaining wall backfill for the project. Temporary erosion and sedimentation controls (TESCs) should be installed as part of site clearing activities. TESCs for the project can include using silt fences, check dams, straw mulch, hay bales, and a stabilized construction entrance. Exposed soils, including stockpiled soils, should be covered with plastic sheeting when they are not being worked. Excavations and Slopes Temporary excavation slopes should not be greater than the limits specified in local, state and federal government safety regulations. Temporary excavation into very dense native soils such as those found in boring HA -I near the garage can be sloped to inclinations up to near -vertical, if completed under the observation of the geotechnical engineer. Permanent unreinforced slopes at the site should be inclined no steeper than 2.5H:IV. Based on the findings from our subsurface investigation, water seepage is not anticipated in excavations up to approximately 1.5 feet below existing grades. However, if water seepage or other adverse conditions are encountered, temporary cuts in these soils may need to be made at shallower inclinations where recommended by the geotechnical engineer. Also, if adequate space is not available to maintain open cuts per the recommendations in this report, engineered support may be required to provide lateral support to such excavations. During construction, water should not be allowed to stand in areas where footings are to be constructed. Surface runoff should not be allowed to flow over the top of slopes into excavations. During wet weather, exposed slopes should be covered with plastic sheeting to prevent erosion or softening. GEO Group Northwest; Inc.