February 2007 Update
Work continues along the Bailey's Branch stream channel to remove impacted soil and sediment from the creek channel and floodplain. The upstream removal contractor has advanced removal of soil and sediment, along the creek channel and floodplain, to approximately 6,300 feet downstream of the Outfall 002 to Broomsage Road. Restoration is nearly complete to 3,800 feet of creek downstream of Outfall 002 to just south of Broomsage Road. The contractor for the cleanup in the downstream section (north of Broomsage Road), has advanced removal of soil and sediment, along the creek channel and floodplain, to approximately 5,300 feet north of Broomsage Road and will continue in a northerly and westerly direction toward Peerless Road. The culvert bridge over the creek at Broomsage Road has been removed, the creek in the area excavated, and the bridge replaced. The road in the area will be repaved once the asphalt plants reopen in the spring. To date, more than 909,497 tons of soil, rock and sediment exceeding the cleanup criteria have been removed, tested, and disposed off-Site to permitted landfills, or transferred into the East Plant Area as part of the Interim Measure. Restoration activities will follow behind these removal activities as work progresses downstream. Excavation of impacted soil was completed on the Western Tributary on the west side of the plant and those excavations have been restored. Excavation of impacted soil on the Northern Tributary (North of Breckenridge Road) is expected to begin soon.
GM is in the process of designing and implementing the Interim Measure (IM) for the GM 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 soil removal of areas with greater than 50 ppm PCBs (the soil to be placed in an on-Site vault), a cover system to prevent contact with the remaining soil materials and limit rain water infiltration, the use of low-level (less than 50 ppm) PCB soil from the off-Site creek removal work as grading soil below the low permeability cover system, a groundwater collection trench installed downgradient into the bedrock around the northern, eastern, and southern perimeter of this area, and a groundwater source removal system in the former process pond 4 area. Long-term maintenance and monitoring are also part of the selected remedy. Excavation and placement of greater than 50 ppm PCBs soil into the vault was initiated in May 2006 and completed in January.
GM also has been conducting additional investigations related to the East Plant Area remedy. These investigations have involved new groundwater well installation and water sampling, dye trace studies, and bedrock coring. Additional soil testing was completed on the GM property west of GM drive (West Plant Area) to further delineate PCB concentrations. An Interim Measure for the West Plant Area will soon be proposed. An investigative study of one of the larger springs on the creek has begun. This study involves installation of coreholes into bedrock and the performance of dye trace studies.