Engineers warn Coventry Reservoir dam needs $5.9 million in repairs, council told

Engineers from Fuss & O’Neill told the Coventry Town Council on March 11 that Coventry Reservoir Dam (Dam 176) is in poor condition, may overtop in moderate flood events and will require millions of dollars in repairs to avoid catastrophic failure.

The town’s contracted engineers presented dive-inspection findings and hydrology modeling showing the masonry embankment and spillway cannot safely pass a 10- to 50-year storm without risk of overtopping. “Between the 10 year storm and the 50 year storm, the spillway is not able to pass that amount of water, which means that the dam is going to overtop on one of its embankments,” Justin Deschen, project manager at Fuss & O’Neill, said. He said the modeling shows overtopping begins at roughly the 25-year event.

Why it matters: the spillway and embankment back a larger downstream impoundment (Johnson’s Pond). Engineers and town officials warned that a breach could send a sudden release of water and accumulated sediments and contaminants into Johnson’s Pond and downstream neighborhoods, exposing homes and public infrastructure to flood damage and environmental risk.

What the engineers recommended: Fuss & O’Neill proposed a conceptual repair that would armor the embankment so it can overtop safely without failing. The package includes embankment armoring, spillway improvements and repairs to the low‑level outlet. The consultant’s current opinion of probable cost for full repairs is roughly $5,900,000 (present-day dollars), with a substantial contingency.

“We found missing stones, depressions and voids behind the masonry wall, and the data show the spillway is not sized to pass design storms,” Dean Odette, senior resource for the project, said during the presentation. Divers reported that voids behind the stonework are enlarging — a sign of ongoing internal erosion — and geotechnical work confirmed concerns.

Short‑term actions and risks: engineers and the solicitor told the council there are interim measures the town must consider to reduce near‑term risk. Those include removing trees growing in the dam face, installing temporary sandbag armoring (large, tonnage‑scale sandbag protection at the masonry face), and restoring a functioning low‑level outlet so operators can draw down the impoundment when flows are predicted. Solicitor Steven Angel said an administrative order from the Department of Environmental Management (DEM) already requires the town to supply plans and timelines.

On timing and probability: the consultant said the dam’s spillway would overtop between the 10‑ and 50‑year events; the consultants described a 10‑year rainfall as having a 10 percent chance of occurring in any given year and a 50‑year event as having a 2 percent chance. “An inch of water over the top of the dam is not a big deal,” Fuss & O’Neill said. “Three feet of water is really bad.” The engineers said the structure shows signs of previous overtopping and that failure could occur during an intense storm.

Funding outlook: the consultants and town staff said the most likely funding sources are competitive federal programs such as FEMA’s BRIC (Building Resilient Infrastructure and Communities) grants and other state or federal dam mitigation programs, and that these are competitive. The town will seek phased work and pursue grant opportunities while planning short‑term stabilization. The town manager and engineers said they will coordinate with DEM on an acceptable phasing plan and apply for grants, but emphasized that DEM is likely to require immediate mitigation steps before long‑term work.

Council next steps: Fuss & O’Neill will complete a 30% design package and deliver a draft 30% design report (including dive and geotechnical reports) to the town and to Bridal (a referenced stakeholder) by the end of next month. Town staff said they will meet with DEM and the consultants to develop a prioritized schedule and a funding strategy. No council vote was taken on funding at the March 11 meeting.

Ending: The presentation made clear the town faces a complex decision that combines public‑safety urgency, environmental permitting and highly competitive grant timelines. The council asked that staff return with clearer budget options and a proposed phasing plan after meeting with DEM and completing the 30% design deliverable.