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permeability characteristics in the undisturbed state. It typically develops a "weathered" zone where <br /> seasonal groundwater perches on top of the relatively impermeable unweathered till and the perched <br /> groundwater occurs as seepage following the site topography. <br /> Advance outwash deposits are mostly clean, gray, pebbly sand with increasing amounts of gravel higher <br /> in the section deposited by meltwater flowing from the advancing front of the Vashon glacier. This unit <br /> typically has high shear strength, low consolidation and moderate permeability characteristics in the <br /> undisturbed state. <br /> S.B. Subsurface Conditions <br /> 3.3.1.Soil Conditions <br /> Two typical soil types (fill and glacial advance outwash) were encountered below the pavement/gravel <br /> base in the borings completed at the project site. Our observations included the following. <br /> 3.3.1.L Asphalt PavemenVBase Course: <br /> Approximately 21/2 inches of asphalt concrete pavement and 2 inches of sand and gravel base course <br /> were observed in the borings completed in the asphalt pavement area. <br /> 3.3.1.2.Fill/Weather Outwash Deposits <br /> Up to 5 feet of medium dense to dense silty fine to medium sand with occasional gravel was encountered <br /> below the asphalt pavement in borings B-2-19 and-B-4-19. These soils may consist of reworked outwash <br /> that was placed as fill during previous grading activities or weathered native advance outwash deposits. <br /> 3.3.1.3.Advance Outwash Deposits <br /> Advance outwash was encountered within the upper five feet in each of the borings completed for this <br /> study and extended to the,depths explored. The advance outwash generally consisted of dense to very <br /> dense sand with variable silt content. Occasional interbedded silt seams are present within the advance <br /> outwash deposits. <br /> - 3.3.2.Groundwater Conditions <br /> Isolated zones of wet soil were encountered in borings previously completed at the site, indicating the <br /> presence of perched groundwater.Groundwater was also observed at a depth of approximately 24 feet in <br /> boring B-2-19. Groundwater, as well as perched groundwater, should be expected to vary as a function of <br /> season, precipitation and other factors. Seepage zones should also be expected to develop in the upper <br /> fill material, perched above the denser native glacial soils. <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the results of our subsurface exploration program, geotechnical laboratory testing, analyses, <br /> and experience on other projects within the vicinity of the project site, we conclude that the proposed LRC <br /> project can be constructed satisfactorily as planned with respect to geotechnical elements. The primary <br /> geotechnical considerations for the project are summarized below: <br /> m The LRC Building can be designed as Site Class C per the 2015 International Building Code(IBC). <br /> GEOENGINEERsr 1uly22,2019 Page3 <br /> File No.583fi-011-00 <br />