A.23 Grasse River, NY

A.23.1 Summary

Environment:	Marine
Scale:	Pilot
Contaminants of Concern:	PCBs: average concentration 11 ppm
Final Remedy:	Hydraulic cutterhead dredge

A.23.2 Site Description

Freshwater, 10–15 feet deep.

Year: 2005

A.23.3 Remedial Objectives

The remedial objective is to bring additional information to the decision-making process in key areas of uncertainty and to make progress towards cleanup of the river.

A.23.4 Remedial Approach

This event was a pilot study for different cappingTechnology which covers contaminated sediment with material to isolate the contaminants from the surrounding environment. materials and their efficiencies. A hydraulic cutterhead dredge was used. Dredged material was dewatered and disposed in an existing on-site TSCA/RCRA landfill. Water was treated and deposited back into the river. Some Geotube dewatering was used.

Only 40% of the planned area was dredged. The river bottom was rocky and uneven, resulting in slowed progress and multiple equipment failures.

A.23.5 Monitoring

RAOs/project objectives achieved? Samples outside silt curtains showed high concentrations of contaminants. Dredged areas were backfilled with different materials (sand, topsoil, and armor stone) at different locations to determine best one. Once backfilled, levels were 95% lower after dredging.

A.23.6 References

Alcoa, U.S. EPA. Superfund Program Update for the Grasse River Study Area. Jun 2004. http://www.thegrasseriver.com/pdf/Final_June_2004_Newsletter.pdf.

Major Contaminated Sediment Sites Database; Sept. 2004 as updated 2008. http://www.smwg.org/MCSS_Database/MCSS_Database_Docs.html.

Publication Date: August 2014