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Penske Truck Leasing-Proposed Service Facility,2410 Railway Ave,Everett,WA Mar.8,2019/Rev.Feb.25,2020 <br /> Geotechnical Engineering Report P1493-T18 <br /> 4_1 Site Preparation <br /> Preparation of the project site should involve erosion control, temporary drainage, clearing, <br /> stripping, excavations, dewatering, cutting, subgrade compaction, and filling. <br /> Erosion Control: Before new construction begins,an appropriate erosion control system should be <br /> installed. This system should collect and filter all surface water runoff through silt fencing. We <br /> anticipate a system of berms and drainage ditches around construction areas will provide an <br /> adequate collection system. Silt fencing fabric should meet the requirements of WSDOT Standard <br /> Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below <br /> existing grade. An erosion control system requires occasional observation and maintenance. <br /> Specifically,holes in the filter and areas where the filter has shifted above ground surface should be <br /> replaced or repaired as soon as they are identified. <br /> Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or <br /> near-surface water within the construction zones before stripping begins. Because the selection of <br /> an appropriate drainage system will depend on the water quantity, season, weather conditions, <br /> construction sequence, and contractor's methods, final decisions regarding drainage systems are <br /> best made in the field at the time of construction. Based on our current understanding of the <br /> construction plans, surface and subsurface conditions, we anticipate that curbs,berms, or ditches <br /> placed around the work areas will adequately intercept surface water runoff. <br /> Site Excavations: Based on our explorations, we expect that excavations will encounter medium <br /> dense gravelly soil or soft silty soil which can be easily excavated using standard excavation <br /> equipment. <br /> Dewatering: Our explorations encountered groundwater seepage at a depth of approximately 5 to <br /> 7 1/2 feet below existing grade. The majority of the soils encountered onsite are silty, granular <br /> alluvial soils, which could potentially be water bearing during winter months. The contractor <br /> should be prepared to deal with this condition. <br /> For shallow excavations above the water table,should groundwater be encountered,we anticipate <br /> that an internal system of ditches,sump holes,and pumps will be adequate to temporarily dewater <br /> excavations. For deeper excavations below the water table,more extensive dewatering equipment, <br /> such as well points, could be necessary in order to temporarily dewater excavations. We <br /> recommend that the appropriate dewatering system be selected during construction, when the <br /> ' specific subgrade conditions encountered are directly observable. The contractor should be <br /> prepared for more extensive dewatering at that time should it be needed. <br /> Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should <br /> be adequately inclined to prevent sloughing and collapse. Temporary cut slopes in site soils should <br /> be no steeper than 11/2H:1 V, and should conform to Washington Industrial Safety and Health Act <br /> (WISHA) regulations. <br /> Migizi Group, Inc. Page 8 of 17 <br /> r.liui:' IIiI� <br />