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