7500 HARDESON RD Geotech Report 2022-10-25

I I Geotechnical Engineering Report SSGC Hardeson Road Retail Everett,Washington SSGC Project No. 18072 ISeptember 18,2018 Table 5.Preliminary Pavement Sections Minimum Recommended Pavement Section Thickness(inches) 1 Traffic Area Asphalt Portland Aggregate Subbase Concrete Cement Base t 2 3,4 Aggregate' Surface Concrete Course I Access Drives 3 6 612 Parking 2 5 4 12 t 1i2—inch nominal aggregate hot-mix asphalt(HMA)per WSDOT 9-03.8(I) I 2 A 28 day minimum compressive strength of 4,000 psi and an allowable flexural strength of at least 250 psi Crushed Surfacing Base Course per WSDOT 9-03.9(3) I 4Although not required for structural support under concrete pavements,a minimum four-inch thick base course layer is recommended to help reduce potentials for slab curl,shrinkage cracking,and subgrade "pumping'through joints `Native granular soils compacted to 95%of the ASTM D1557 test method,or Gravel Borrow per IWSDOT 9-03.14(1)or Crushed Surfacing Base Course WSDOT 9-03.9(3) I Conventional Pavement Maintenance The performance and lifespan of pavements can be significantly impacted by future maintenance. The above pavement sections represent minimum recommended thicknesses and,as such,periodic I maintenance should be completed. Proper maintenance will slow the rate of pavement deterioration,and will improve pavement performance and life. Preventive maintenance consists of both localized maintenance(crack and joint sealing and patching) and global maintenance (surface I sealing). Added maintenance measures and reduced pavement life should be expected if any existing fill is left in-place beneath pavement sections. Lateral Earth Pressures Below grade and retaining walls will be subject to lateral earth pressures. Subgrade walls are typically I designed for "active" or"at-rest" earth pressure conditions. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes lateral movement at the top of the wall of around 0.002H to 0.004H, where H is the height of the wall. The at-rest condition assumes no wall Imovement. The following recommended earth pressures (Table 6) should be applied as a triangular distribution Istarting at the top of the wall(for active and at-rest)and bottom of wall (for passive)and assume: ■ Backfill behind walls is level and no surcharge loads will be applied; ■ Drainage is provided behind the wall to prevent the development of hydrostatic pressures. I 11