Consultant updates commission on long-running cleanup at 549 Cedar Street; injections reduced TCE, more work planned under DEEP permit

At an April 21 meeting, the Newington Conservation Commission received an update on remediation work at 549 Cedar Street — the former Atlantic/Textron manufacturing site — where a multi-year cleanup has focused in recent years on volatile organic compounds (VOCs) in groundwater.

A presenter identified during the meeting as Dan described the site's regulatory and remediation history: earlier PCB cleanups (2012 and 2018) removed and consolidated contaminated soils into a capped engineered control that remains under long-term maintenance. The current priority is dissolved-phase VOCs (primarily PCE/TCE) that migrated into shallow bedrock fractures; the Property Transfer Act required environmental assessment and cleanup when the property changed hands.

Dan said pilot-scale injections (2018 and later tests) informed a larger 2024 program that installed a grid of monitoring wells and conducted geophysics to map fracture networks and contamination hot spots. The remediation approach uses injections of emulsified soybean oil (an organic carbon amendment) and cultured dechlorinating bacteria to promote reductive dechlorination of chlorinated solvents in bedrock fractures. “The TCE we are seeing that decrease,” Dan said, describing results from baseline sampling in 2024 through a sampling event in late 2025; he added that some daughter products (DCE/vinyl chloride) still persist in pockets and that additional injections will be made this spring to support continued biodegradation.

Commissioners and staff asked technical questions about bedrock depth, well construction and monitoring. The presenter said bedrock is shallow in places (a few feet in some locations) and that monitoring wells typically extend to about 50 feet; geophysical and well-grid data helped target injection locations. He said much of the historic soil contamination was removed and consolidated on-site under Connecticut DEEP oversight, while the groundwater treatment is managed under a DEEP permit.

The presenter said the team aims to schedule injections in May–June to complete planned work before the current DEEP permit lapses at the end of June 2026; if more work is needed after that window, the team will need to reapply for another permit, a process that can take a year. He invited commissioners to request site visits and offered to return with another update in the future.

The commission recorded the presentation as informational; no formal action was required or taken.