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.

• Water Column Monitoring
• Resident Fish Monitoring
• Historical Results
  
  

Construction Monitoring

Monitoring during construction included water and air from 2017 to 2022.

• Construction Monitoring Data
  
  

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. The 2022 cap repairs included placing sand, gravel and/or cobble and activated carbon mix. A project update is available that provides additional details about the 2022 activities. Starting September 2024, cap repairs will continue, and the armored cap will be extended to just downstream of the Route 131 bridge. The armored cap will consist of sand and activated carbon, gravel, and larger stone. The cap repair is anticipated to continue in spring 2025. Additional details are available in EPA’s August 2024 update. Air, water, and noise monitoring will be performed during the cap repair work.