HWA was lead geotechnical engineer for the design team developing plans for the proposed relocation of the permanent facilities at the Cedar Hills Landfill in order to construct the proposed Area 9 portion of the landfill. The project included performing explorations at the selected facility location to provide information regarding subsurface conditions. Geotechnical design included analyses for foundation, wall, and pavement design.

HWA provides assistance with three Seattle Public Utilities landfill sites. Assistance provided includes quarterly gas and groundwater monitoring, preparation of data validation reports, baseline landfill cap inspection, installation of dewatering wells via sonic drilling and piezometers via hand tools, support with preparation of annual landfill reports including senior review, hydrogeological assessments, and material testing services.

HWA served as environmental consultant lead for over 20 years on numerous technical and regulatory issues at this 280-acre site which includes a closed landfill, former industrial properties, wetlands, river, parks & trails. HWA managed numerous investigations of municipal landfill and surrounding sites, supported remedial investigation and feasibility studies including groundwater, surface water, soil gas, chemical and hydrological data and leachate evaluations.