The Connecticut Department of Energy & Environmental Protection (CT DEEP) has just released a monthly project update for the cleanup of lead impacted sediment by hydraulic dredging in the Mill River.
As noted in previous updates, the sediment dredging portion of the project has been completed. The process of dewatering the sediment is ongoing at the moment, as well as treating the filtrate water from the dewatering process, discharging treated water back to the Mill River and disposing of the dewatered sediment.
Last month, Exide Corporation and CT DEEP announced that during required waste characterization sampling, part of the trial run load‐out, polychlorinated biphenyls (PCBs) were detected, which required discussions with the regulatory agencies CT DEEP and the U.S. Environmental Protection Agency (EPA). Accordingly, loadout of the dewatered sediment was temporarily suspended pending agency direction.
A plan was submitted on May 18, 2016 and revised on May 31, 2016 to EPA for review and approval that outlined the steps and approach to manage and dispose of dewatered sediment that contains PCBs.
During the end of May, additional samples of untreated filtrate water from the dewatering of the sediment were collected and analyzed for PCBs. This is the water that is later treated in the water treatment plant (WTP). PCBs were not detected in these samples.
In June, the contractors will continue with the dewatering of sediment and treatment of filtrate. Monitoring and sampling will continue as well. Discharge monitoring will be intermittent during this period reflecting the infrequent generation of treated water.