Silver Lake

Project Sheet

Location: Berkshire County, Pittsfield, MA, US

Year: 2006/2013

Project Type(s): Sediment remediation/thin layer capping

Project Description: Historic discharges of PCBs and other chemicals from a GE facility resulted in moderate to high concentrations of PCBs in the Silver Lake sediments. 400 CY of “hot spot” sediment was dredged, in addition to near-shore sediment, and contaminated bank soil. A silty sand-based cap was placed on the entire bottom of the lake. A pilot scale project was conducted in 2006 which was used to develop the conceptual design of the cap and the final work plan. Full-scale remediation initiated in the summer of 2012 and was completed in December 2013. Multiple capping systems were incorporated in different areas of the site. The majority of the lake bottom was capped with a 14-in. thick layer. The near-shore portion of the lake was capped with a non-woven geotextile followed by a 10-in. thick layer of cap material (sand and topsoil with a minimum in-place TOC of 0.5%), and an armor stone layer. The placement system consisted of a conveyor system, modified mix tank, make-up water and slurry pumps, 1,800-foot slurry pipeline, floating barge structures, and a custom-designed slurry dissipator barge. In 2014, GE initiated inspection, monitoring and maintenance activities at the site to ensure that the capping systems were functioning effectively.