Indian Road Quarry Dump Site Characterization and Landfill Closure

Swinomish Indian Tribal Community, Skagit County, Washington

The Swinomish Indian Tribal Community (SITC) contracted HWA to conduct a site characterization and prepare a closure design for a wood waste disposal site.

HWA performed a site characterization to provide information on fill content, native soils, and ground water conditions for closure design. This included a site survey, test pit exploration, soil borings, methane testing, and ground water monitoring. We assisted with consultations with EPA and Indian Health Services for closure design selection.

HWA evaluated closure options including wood waste extraction/recycling, site capping with geosynthetic liners, and capping with native low permeability soils. We developed cost estimates and produced bid plans and specifications for site closure using on-site low permeability soil. HWA oversaw the bidding and contractor selection, and monitored the landfill closure. HWA's evaluation and use of selected on-site low permeability soils resulted in a low cost and effective closure option.