Environmental monitoring includes efforts before, during, and after construction - or pre-construction, construction, and post-construction.
Pre-Construction Monitoring
Since the early 1990s, Arconic (formerly Alcoa) has monitored water column and resident fish samples from the lower Grasse River in order to assess the long-term changes in water quality and PCB levels in the river, and to identify what impacts naturally occurring events (such as high flow events and ice jams) and major pilot studies have had on the recovery of the lower Grasse River.
Construction Monitoring
Monitoring during construction included water and air from 2017 to 2022 and 2024.
Long-Term Monitoring and Maintenance
Monitoring and maintenance will be performed to assess progress toward the remedial goals established by EPA in the April 2013 Record of Decision for PCB concentrations in water and fish and to verify the performance of the installed cap.
The long-term program will include:
- Water quality testing in the river for PCBs
- Fish sampling for smallmouth bass, brown bullhead, and spottail shiner and testing for PCBs (other adult fish species will be added in the future)
- Cap monitoring through bathymetric surveys and PCB measurements in the water immediately above the cap using passive samplers
- Cap maintenance, as needed
Cap repair work started in 2022 in the small area impacted by the March 2022 ice jam that formed upstream of the Route 131 Bridge. A project update is available that provides additional details about the 2022 activities. Cap repairs resumed in 2024 and will be completed in 2025 and result in the extension of the armored cap to just downstream of the Route 131 bridge. Additional details are available in EPA’s August 2024 update. Cap repairs were also intiated due to impacts from Hurricane Debby and will continue in spring 2025. Details are provided in the October Community Update. Contruction monitoring (air, water, and noise) is performed during the cap repair work.