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Erosion disputes intensify: MassDEP reviews BSTEM models, peer reviews and FirstLight’s stabilization plan
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Summary
MassDEP presented competing analyses of bank erosion in the Turners Falls impoundment: FirstLight’s BSTEM modeling identifies dominant causes as high flows and boat wakes but attributes specific reaches to operations; an independent peer review found underreported operation‑attributable erosion. MassDEP is considering both peer reviews and FirstLight’s proposed monitoring and stabilization schedule.
MassDEP’s wetlands program spent the information session’s erosion block describing decades of study on bank loss in the Turners Falls impoundment and how the agency is evaluating whether operations attributed to FirstLight have caused or contributed to bank erosion.
David Hilgeman of MassDEP said erosion causation is complex and that MassDEP’s review is considering a broad literature spanning Army Corps work in 1979 and follow‑up reports into the 1990s and later. FirstLight’s 2024 BSTEM (Bank Stability and Toe Erosion Model) submission split erosion drivers into dominant (high flows, boat waves) and contributing causes, and reported operation‑attributable erosion on several sections of the impoundment — figures cited in the presentation included about 21,600 feet between Barton Cove and French King Gorge and roughly 46,100 feet upstream of the Northfield tailrace, as reported by FirstLight.
Two peer reviews are in the MassDEP record. One peer review submitted on behalf of the Connecticut River Conservancy (CRC) concluded FirstLight’s analysis underreports operations‑attributable erosion and recommended increased monitoring, reduced operational fluctuation ranges and additional bank stabilization if flow changes do not reduce erosion. MassDEP’s consultant Interflue conducted a separate peer review that concluded the BSTEM simulations were extensive and developed by competent professionals but noted model limitations in providing assurance that proposed operations would not violate surface water quality standards.
FirstLight’s application proposes a combined approach as the starting point for any certification conditions: boat‑wake restrictions coordinated with the Department of Conservation and Recreation, a shoreline erosion monitoring plan to be approved by MassDEP with surveys in years 1, 10, 20, 30 and 40, and stabilization work (if recommended) to be implemented within five years of identification. Hilgeman said MassDEP is splitting review into two buckets — existing erosion that must be remediated to reach compliance, and future erosion that must be prevented — and has not made a decision. "We have not made any decisions yet. We are here standing in front of you to provide information and some transparency, but we're also listening," he said.
On responsibility, MassDEP said it would require the applicant to carry out required repairs and that MassDEP’s watershed planning program would certify and oversee the work if included as certification conditions. Panelists also acknowledged the public requests for additional peer review but noted time constraints in a year‑long process and that MassDEP is still considering the record.
What to watch: whether MassDEP requires additional monitoring or shorter timetables for stabilization and whether peer reviewers’ recommendations change the scope of conditions MassDEP attaches to any certification decision.
