2710 14TH ST BLDG A Geotech Report 2023-12-29

4.5.12. Sedimentation and Erosion Control In our opinion, the erosion potential of the on -site soils is low to moderate. Construction activities including stripping and grading will expose soils to the erosion effects of wind and water. The amount and potential Impacts of erosion are partly related to the time of year that construction actually occurs. Wet weather ' construction will increase the amount and extent of erosion and potential sedimentation. Erosion and sedimentation control measures may be implemented by using a combination of interceptor swales, straw bale barriers, silt fences and straw mulch for temporary erosion protection of exposed soils. All disturbed areas should be finish graded and seeded as soon as practicable to reduce the risk of erosion. Erosion and sedimentation control measures should be installed and maintained in accordance with the ' requirements of the City of Everett. 4.6. Pavement Recommendations ' 4.6.L Subgrade Preparation We recommend the subgrade soils in new pavement areas be prepared and evaluated as described in Section 4.5.4. All new pavement and hardscape areas should be supported on subgrade soils that have been proof rolled or probed, and approved by the geotechnical engineer. If the exposed subgrade soils are loose or soft, it may be necessary to excavate localized areas and replace them with structural fill or gravel ' base course. Pavement subgrade conditions should be observed during construction and prior to placing the base course materials in order to evaluate the presence of zones of unsuitable subgrade soils and the need for over -excavation and replacement of these zones. 4.6.2. New Hot -Mix Asphalt Pavement In light -duty pavement areas (e.g., automobile parking), we recommend a pavement section consisting of ' at least a 2.5-inch thickness of 1/2-inch hot -mix asphalt (HMA) (PG 58-22) per WSDOT Sections 5-04 and 9-03, over a 4-inch thickness of densely compacted crushed rock base course per WSDOT Section 9-03.9(3). In heavy-duty pavement areas (e.g., truck traffic areas, materials delivery) around buildings, we ' recommend a pavement section consisting of at least a 4-inch thickness of 1/--inch HMA (PG 58-22) over a 6-inch thickness of densely compacted crushed rock base course. The base course should be compacted to at least 95 percent of the MDD (ASTM D 1557). We recommend that a proofroll of the compacted base ' course be observed by the geotechnical engineer of record prior to paving. Soft or yielding areas observed during proofrolling may require over -excavation and replacement with compacted structural fill. ' The pavement sections recommended above are based on our experience. Thicker asphalt sections may be needed based on the actual subgrade conditions, traffic data and intended use. ' 4.6.3. Portland Cement Concrete Pavement PCC sections should be considered for loading dock aprons, trash dumpster areas and where other concentrated heavy loads may occur. We recommend that these pavements consist of at least 6 inches of PCC over 6 inches of CSBC. A thicker concrete section may be needed based on the actual traffic data. If the concrete pavement will have doweled joints, we recommend that the concrete thickness be increased by an amount equal to the diameter of the dowels. The base course should be compacted to at least 95 percent MDD. I GEOENGINEERS� October30, 2019 Page 18 Flle No. 2'. 288-002 00