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FDA dye study traced Norwalk WPCA effluent through river and harbor; final report months away
Summary
WPCA staff briefed commissioners on an FDA and state aquaculture dye field study conducted the week of May 17 that traced plant effluent through the Norwalk River and harbor; staff said samples and drone monitoring showed dye movement to island areas and that data processing and a final report will take several months.
WPCA staff told the commission that field work for an FDA and Connecticut Department of Agriculture aquaculture flow-tracing dye study was performed during the week of May 17 and that laboratory analysis and data processing will take several months before a final report is available.
Staff said preliminary observations surprised some participants with how far the dye moved: monitoring by drones, DEEP boats and buoys showed dye movement in the Norwalk River that extended northward in the estuary and diluted as it flowed into the harbor and the sound. "I think the FDA ... at the treatment plant, they were all surprised how much of an influence the dye really made in the Norwalk River," staff recounted. Staff emphasized monitoring included automated sampling and laboratory analysis so dye presence could be detected even when not visible to the naked eye.
Commissioners asked whether the study was new and how often it is done; staff said the last full study in Norwalk had been in 1989 and that a 2016 attempt did not proceed to field testing. Staff said the work required FDA coordination because the results relate to shellfishing and aquaculture regulation. Initial anecdotal observations noted visible dye in areas as far as Eversley and Greens Ledge; staff cautioned that definitive findings await laboratory results and the final report.
During the operations briefing staff also reviewed May plant performance: collections completed 3.3 miles of CCTV inspection, 1.33 miles of sewer cleaning, 23 manhole inspections, five service calls, 32 IPP inspections, average flow 10.4 MGD and nitrogen performance around 535 lb/day, and that required permit reports (DMR, MOR, NAR, sludge) were submitted to CT DEEP and EPA for May.
Commissioners praised staff cooperation with FDA and CT DEEP and welcomed the planned final report; staff said they will share the FDA report with the commission when available.
