3321 52ND PL SW 2016-01-01 MF Import

C - � , Geotechnicai Engineering Investigation Schwab Residence ]uly 13, 2001 NGA File No. 329401 �'age 7 exposed subgrade should be protected from construction tra�c and surfaa: runoff. Erosion Control Measures The erosion hazard for the on-site soils in the gently-sloping portion of the site is listed as slight and as moderate to high for the steeply sloping portions of the site, depending on how the site is gr�ded and water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Measures taken may include diverting surface water away from the sVipped areas and ;iom flowing over the slope. Silt fences or straw bales should be erected to prevent muddy water from leaving the site or flowing over the top of the slope. Disturbed areas should be planted with vegetation at the end of construction. The vegetation should be maintained until established. The erosion potential of areas not stripped of vegetation should be low. Setback From t6e Slope Uncertainties related to building along steep slopes ara typically addressed by the use of building setbacks. The purpose of the setback is to establish a"buffer zone" between the dwelling areas and the slope margin, so that ample room is allowed for nortnal slope surFace regression, or if a slope failure were to occur. This setback also prutects the slope from the impacts of the development. From a geological standpoint, a reasonable setback is based on the slope's physical characteristics; e.g., slope height, surface angle, material composition, hydrology, etc. Other factors s�ch as historical slope activity, rate of regression and earthwork activity along the tce of slope, a�e important considerations as well. Based on our slope evaluation and observations, we recommend a minimum effective horizontal setback distance of 15 feet between the face of the slope and the bottom of the downhill footing line. In addition to this recommended setback distance, the downhill footing line should be embedded a minimum of 3 feet into medium dense or better native soils. The recommended setback and footing embedment values are shown on Figure 7. We should be retained to evaluate the residence foundation subgrade and effective setback prior to pouring footings. Slope and Setback Protection Protection of the setback and steep slope areas should be pe��formed as required by the City of Everett. Specifically, we recommend that the setback areas not be used for placeme�t or storage of fill materials, including "temporary" excavation spoils from building area preparation and lVELSON GEOTECHNICAL ASSOC/ATES, /NC. �