600 RIVERSIDE RD Geotech Report 2022-10-25

i Landau Associates to be below the site cleanup action levels, the soil may remain onsite. If the contaminant levels are determined to be above the site cleanup action level, they may require offsite disposal at an approved landfill. As part of this project, LAI prepared a Soil and Groundwater Management Plan (LAI 2017) that specifically addresses the recommended handling and disposal of arsenic -affected soil and groundwater during site development. This document should be reviewed for additional information related to the handling and disposal of arsenic -affected soil and groundwater during site development. 3.3 Health and Safety Considerations Construction of the proposed site infrastructure will involve working with soil and groundwater that in some areas will have elevated arsenic concentrations. Furthermore, soil and groundwater affected by petroleum hydrocarbons, polychlorinated biphenyls, carcinogenic polycyclic aromatic hydrocarbons, and pentachlorophenol are present on the site and could be encountered during construction. Therefore, the contractor should be required to prepare and submit a site -specific health and safety plan meeting applicable regulatory requirements prior to the start of construction. The contractor should also identify a Health and Safety Officer whose responsibility will be health and safety monitoring and oversight. Additionally, because the pathways by which site contaminants have migrated are not clearly defined, the contractor should exercise due caution when excavating existing soil to minimize the health hazard posed to all onsite project participants. Construction personnel who will be in direct contact with existing site soil and/or groundwater, such as pipe layers, should be health and safety trained for work on contaminated sites in accordance with OSHA and Washington State requirements. Construction personnel who will not come in direct contact with the existing onsite soil and groundwater, probably do not need to be health and safety trained to meet OSHA and Washington State requirements. However, all onsite construction personnel should receive a detailed project briefing and be familiar with the requirements of the contractor's site -specific health and safety plan. 3.4 Site Preparation and Earthwork All existing structures, foundations, vegetation, man-made debris, and other deleterious material should be cleared and stripped from all areas to be occupied by the proposed access road and trails. All excavations should be conducted in accordance with the Soil and Groundwater Management Plan (LAI 2017). Prior to placement of any structural fill to raise site grades for the proposed access road and trails, the exposed subgrade should be proof rolled to a dense and unyielding condition. Proof, rolling should be accomplished with a loaded dump truck, large self-propelled vibrating roller, or equivalent piece of equipment so that the upper 12 inches of exposed subgrade is compacted to at least 95 percent of its maximum dry density, as determined using test method ASTM D 1557 (modified Geotechnical Engineering Report 0121030.010.011 Riverside Business Park March 22, 2018 Public Access Trails and Roadway Improvements 3-3 I 1 1 1 1