1707 SCENIC DR SNO CO PUD Geotech Report 2022-10-25

Weather Considerations The on-site soils contain a high percentage of fines (silt) and are moisture sensitive. When the moisture content of these soils is appreciably above the optimum moisture content, the soils become muddy and unstable. Operation of equipment on these soils will be difficult, and it will be difficult to meet the required compaction criteria. Additionally, disturbance of these near surface soils should be expected if earthwork is completed during periods of wet weather. The wet weather season generally begins in October and continues through May in the Puget Sound region; however, periods of wet weather may occur during any month of the year. The optimum earthwork period for these types of soiis is typically June through September. If wet weather earthwork is unavoidable, we recommend that: ■ Structural fill piaced during the wet season or during periods of wet weather consist of Gravel Borrow with less than 5 percent fines (material passing the U.S. No. 200 sieve). � The ground surface in and around the work area be sloped so that surface water is directed away from the work area. The ground surface should be graded such that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. Excavations General Cuts up to 10 feet deep may be needed to accomplish site grading. Excavations are also required for retaining walls, fill benched into slopes, and underground utilities. The stability of open cut slopes is a function of soil type, groundwater seepage, slope inclination, slope height and nearby surface loads. The use of inadequately designed open cuts could impact the stability of adjacent work areas, existing utilities, and endanger personnel. The contractor perForming the work has the primary responsibility for protection of workmen and adjacent improvements. In our opinion,the contractor will be in the best position to observe subsurFace conditions continuously throughout the construction process and to respond to variable soil and groundwater conditions. Therefore,the contractor should have the primary responsibility for deciding whether or not to use open cut slopes for much of the excavations rather than some form of temporary excavation support, and for establishing the safe inclination of the cut slope. Acceptable slope inclinations for utilities and ancillary excavations should be determined during construction. Because of the diversity of construction techniques and available shoring systems, the design of temporary shoring is most appropriately left up to the contractor proposing to complete the installation. Temporary cut slopes and shoring must comply with the provisions of Title 296 (of the Washington State Administrative Code [WAC]), Part N, "Excavation, Trenching and Shoring." Based on the subsurFace soil conditions encountered in the explorations, we expect that the soils at � ihe site may be excavated using conventional heavy duty construction equipment. The materials encountered generally include loose fill to very dense native till consisting of sand with variable silt, gravels, and cobbles. The native glacial till deposits may require a large excavator to accomplish the excavations. Glacial deposits in the area commonly contain cobbles and boulders that may be encountered during excavation. Concrete debris and buried foundations and slabs were encountered GEOENGINEER� October24,2014 Page 10 Fle No.0482-027-02