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February 2008 Update

Creek soil excavations/restoration

Photos of the excavations and restorations (PDF) (29pp, 2.9MB, About PDF) Exit EPA Disclaimer

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Groundwater migration controls & investigations

GM currently samples approximately 40 spring locations on a quarterly basis. Groundwater seeps or springs where PCBs have been detected are being collected at 17 locations and treated at a newly constructed treatment facility on the GM property.

Locations of the monitored springs and control systems are in the Site Source Control Work Plan Addendum No. 6 (September 2007) (PDF) (41pp, 19.7MB, About PDF) Exit EPA Disclaimer

These individual groundwater collection systems were installed to collect impacted groundwater until a groundwater collection trench is cut into the competent bedrock surrounding the eastern portion of the facility. This groundwater collection trench will intercept bedrock groundwater flowing horizontally from the east portion of the facility.The design of the collection trench is in progress and GM is installing new bedrock cores along the southeast side of the GM property to guide trench installation in that area.

GM also continues to investigate a larger spring to the south of Broomsage Road (Spring 18 Area) and is developing a proposal to address this spring. The investigation work plan for Spring 18 are in the Site Source Control Work Plan Addendum No. 5 (November 2006) (PDF) (34pp, 9.6MB, About PDF) Exit EPA Disclaimer

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On-site activities

GM is implementing the Interim Measure (IM) for the property east of GM Drive (East Plant Area). The East Plant Area was historically used for plant waste management activities.

Components of the IM include

GM has started installing the multi-layer cover system at the East Plant Area. The clean clay layer has been placed over areas which are at final grade and will continue as remaining areas are completed.

A work plan to install a system of active groundwater source recovery wells in the former process pond 4 area is being developed. This area formerly held two cascading water ponds which collected the PCB hydraulic fluid from the plant. PCB oils have been found in a few bedrock cores in this area and the recovery wells will be installed to attempt to remove as much oil and affected groundwater as possible.

Additional soil testing was completed on the GM property west of GM drive (West Plant Area) to further delineate PCB concentrations. An IM for portions of the West Plant Area is being developed. Project progress reports, electronic documents and work plans can be found at the online document repository Exit EPA Disclaimer

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