Everett Landfill Brownfields Feasibility Study & Compliance Monitoring

Everett, Washington

The City of Everett is in the process of redevelopment of the former City of Everett Landfill located along the Snohomish River. HWA has provided hydrogeologic and geotechnical services on this project since 1995.

HWA developed a comprehensive ground water model for the site in support of the Feasibility Study and Consent Decree for the Department of Ecology. Compliance monitoring under the consent decree includes the establishment of no beneficial ground water use, a conditional point of compliance at the site boundary, area background cleanup levels for selected analytes, and the use of surface water cleanup levels for ground water. We also eliminated unnecessary monitoring wells, thus reducing monitoring requirements.

HWA performed an evaluation of background ground water quality, to establish background-based cleanup levels for compounds naturally or regionally present at elevated concentrations, yet not associated with the landfill. We also determined that elevated chloride concentrations detected in a point of compliance well were attributed to saline water from the adjacent river, and not associated with the landfill. HWA worked with City and Department of Ecology staff to successfully resolve these potential compliance issues.

HWA has also been providing landfill gas and ground water monitoring services, and prepared a ground water compliance monitoring plan for submittal to Department of Ecology. Other work has included delineation of waste, a leachate collection trench evaluation, hydraulic gradient analysis, installation of new ground water monitoring wells, a landfill gas migration study, stormwater site selection study under the US EPA Brownfields program, and supporting the design, installation, and monitoring of a perimeter gas collection system. HWA is currently providing geotechnical services to support site development, and was recently selected to provide ground water and landfill gas compliance monitoring for the next 5 years.