4801 HARBOR LN 2018-01-02 MF Import

Geotechnical Engineering ( ort Johnson Residence Addition Everett, Washington J 1280 27 February 2002 Page 9 It is exceedingly difficult under the variable circumstances to pre -establish a safe and "maintenance -free" temporary cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since the contractor is continuously at the job site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater conditions encountered. It may be necessary to drape temporary slopes with plastic or to otherwise protect the slopes from the elements and minimize sloughing and erosion. We do not recommend vertical slopes or cuts deeper than 4 feet if worker access is necessary. The cuts should be adequately sloped or supported to prevent injury to personnel from local sloughing and spalling. The excavation should conform to applicable Federal, State, and local regulations. Based upon our review of WAC 296-155-650, Part N (Excavation, Trenching, and Shoring), we have interpreted the site soils disclosed by the explorations to meet the following type definitions: • Type B: Dense to very dense clean granular soils; • Type C: Existing fill, loose to medium dense granular soils. We recommend that temporary excavations below the existing foundations be inclined no steeper than 1.5HAV (Horizontal:Vertical), and that permanent slopes below the existing foundations be no steeper than 2H: IV. The bearing splay of existing foundations may be taken as beginning 1 foot outside the foundation limits and extended below the foundation at a 1.5H:1V inclination. Lateral and vertical support for existing underground utilities should be maintained during construction of the proposed dwelling and deck foundations. Temporary foundation support will be required in cases where temporary excavations intrude into the bearing splay of the existing foundations. Erosion Control The proposed residential construction will take place adjacent to a steep slope, and as such, surface water runoff should be controlled to reduce the potential for erosion. We recommend that stripping of existing vegetation only occur within the construction limits. Straw bale barriers or coir logs installed along the top of the steep slope will reduce the potential for surface water flowing from the construction area onto the steep slope. Maintaining plastic sheet covering over excavation slopes will also reduce the potential for sediment generation. Water from impervious surfaces should be collected and tightlined to the bottom of the slope below the dwelling; surface water should not be disposed of at the top of the slope or on the slope. Recommendations for Further Study This report presents design phase geotechnical recommendations for site improvements exclusive of the reinforced rockeries or walls proposed that may be needed along a portion of the Ztooer Zeman Associates, Inc. 18905 33" Avenue West. Suite 117 L)nnw wd. Washington 98036 (425) 771 - 3304 �t