DEQ completes Santosh landfill cap

The Oregon Department of Environmental Quality (DEQ) has completed the installation of a new state of the art landfill cap at Santosh Landfill. The impermeable cap prevents precipitation from coming into contact with the waste, and reduces the risk of groundwater contamination. The 15-acre landfill accepted waste from 1970 to 1983.

This year’s construction involved regrading the landfill with about 43,000 tons of imported soil to promote drainage. The impermeable cap is a geocomposite clay liner, consisting of a layer of processed clay sandwiched between two layers of geotextile fabric. The landfill improvements also include a landfill gas venting system and a storm water collection system. The site was covered with 48,000 tons of topsoil and seeded with native grasses. Soil and rock for the project were obtained from the nearby Glacier Northwest facility, which minimized related truck traffic.

The $3.5 million dollar project was funded by the Solid Waste Orphan Account.

The DEQ has monitored environmental conditions at the site since 2004, when contaminated water was observed leaching out of the south side of the landfill. This portion of the landfill was regraded and capped in the fall of 2007 to eliminate the most obvious leachate seeps. A small strip of wetland adjacent to the landfill was covered as a result of this construction. To compensate for this, DEQ constructed and fenced an enhanced wetland area nearby. About 700 native trees, shrubs and ground cover species were planted in the enhanced wetland area.