11625 AIRPORT RD SONRISE CHRISTIAN CENTER Geotech Report 2022-10-25

I I GEOTECHNICAL EVALUATION EVERETT,WASHINGTON IFebruary 6,2018 IThe excavated material is not suitable as fill material within parking lot but could be used as fill material in non-settlement sensitive areas such as landscaping regions.In these non-settlement sensitive areas,the I fill should be placed in maximum 12 inch thick lifts that should be compacted to at least 90 percent of the modified proctor(ASTM D 1557 Test Method)maximum dry density. The native soils below the vegetation and topsoil consist fine-grained glacial till. These soils are I considered suitable for use as structural fill provided they are within 3 percent of the optimum moisture content. The soils should be considered moisture sensitive and suitable for use as structural fill only during the summer months. I Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines(material passing the U.S. Standard No.200 Sieve). Structural fill should be placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of the modified proctor maximum dry density,as determined by the ASTM D 1557 test method. 8.1.2 Temporary Excavations 1 Based on our understanding of the project, we anticipate that the grading could include local cuts on the order of approximately 8 feet or less for detention vault placement. These excavations should be sloped no steeper than 1H:1V (Horizontal:Vertical) in medium dense to dense native soils and 3/4H:1V in very I dense native glacial till soils. If an excavation is subject to heavy vibration,extend below the groundwater, or surcharge loads, we recommend that the excavations be sloped no steeper than 1.5H:1V, where room permits. I Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N, Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified person during construction activities and the inspections should be documented in daily reports. The I contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope erosion during construction. Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather,and the I slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. Materials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes Iwill need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable,to deal with unanticipated conditions, so that the project can proceed and required deadlines Ican be met. I 1 4 PO Box 82243 Kenmore,WA 98028 (206)331-1097 ICobaltgeo ftmail.com