Removal of Potter Hill Dam Would Improve Pawcatuck River Fish Passage, Reduce Flooding Risks
March 20, 2021
Rhode Island residents, state legislators, and municipal officials were recently presented with several options regarding the future of the deteriorating Potter Hill Dam, which once powered Westerly’s Potter Hill Mill.
During a March 18 online public information meeting, participants applauded the proposal to remove the only remaining dam on the Pawcatuck River, but some residents worried that removing the dam would significantly lower the water level of the river, draining wetlands and impacting wells and property values.
Funded by a $100,000 grant, the first funding of a multiyear award from the National Oceanic and Atmospheric Administration (NOAA), the project has received additional monetary and in-kind donations totaling $112,500.
Participating groups, in addition to NOAA, are The Nature Conservancy, the Westerly Town Council, the Westerly Conservation Commission, the U.S. Fish & Wildlife Service (USFWS), the U.S. Geological Survey, the Rhode Island Department of Environmental Management, the Southern Rhode Island Conservation District, and the Wood-Pawcatuck Watershed Association (WPWA). (The town of Hopkinton borders the river on the other side, however, the study doesn’t have a Hopkinton representative.)
The derelict Potter Hill Mill, recently the focus of a failed private redevelopment plan, continues to crumble into the river. The Potter Hill Dam, first built in the 1780s and rebuilt in the early 1900s, is also failing. Both the dam and the mill are currently in receivership.
Westerly director of development services Lisa Pellegrini described the site as “a big, expensive problem,” which, in addition to posing a public safety hazard, puts the town at an increased risk for flooding.
“If the dam fails, there will be a devastating flood that will greatly affect Westerly,” she said.
Water resources engineer Nils Wiberg, of the Providence-based environmental engineering firm Fuss & O’Neill, presented a technical overview of the study, which evaluated several options for removing part or all of the dam.
The project will be the final step in an initiative that began a decade ago with fish passage enhancements at the Lower Shannock, Horseshoe Falls and Kenyon Mill dams, followed by the removals of the White Rock and Bradford dams.
“So here we are at Potter Hill dam, which is, I’ll say, the last significant barrier to upstream migration,” Wiberg said. “There is a fish ladder there. That fish ladder is probably on the order of 30 or 40 years old.”
The existing fish ladder is outdated and largely ineffective. Migrating fish, such as river herring, crowd together as they attempt to navigate several millrace channels searching for the fish ladder, and become easy prey for cormorants and gulls.
The dam’s spillway also poses a hazard to paddlers, who must portage their kayaks and canoes, but the greatest threat, Wiberg said, is the dam suddenly collapsing altogether.
“If those gates were to give way during a storm or a flood, the whole upstream region of the river could be drained in an uncontrolled manner,” he said.
Engineers and scientists have analyzed every aspect of the river and the dam, from water flow to the river bottom, sediment transport, and nearby bridges and wetlands. They considered several options before arriving at their preferred course of action: removing the dam and returning the river to its natural state with a low-flow channel created for fish passage.
During the meeting’s public comment period, several residents said they were concerned that their shallow wells might run dry when the water level drops by a projected 3-5 feet.
Sen. Dennis Algiere, R-Westerly, and Rep. Brian Patrick Kennedy, D-Hopkinton, said they had received calls from constituents afraid that their shorelines will become several feet of muck.
“They’re very concerned that this will not only take away their current riverfront location, but also significantly lower the value of their homes,” Kennedy said.
Hiscox Road resident Brian Tarpey said he worried about losing the wetlands.
“These are going to disappear,” he said. “You can say you’re turning it into scrubland or whatever you want, but you’re taking several hundred acres of wetlands and destroying them.”
Before the recent meeting, WPWA executive director Christopher Fox told ecoRI News that the objective was to restore the river and wetlands to their natural state, which would, in turn, mitigate flooding.
“You’re restoring the floodplain of the river to its natural characteristics,” he said. “Think of it this way: the dam is flooding the floodplain as though we were experiencing heavy rainfall, because it’s a manmade block across the river. Take the block out, and now the floodplains are no longer just standing water. They’re dry land waiting for flood waters to come.”
USFWS biologist Suzanne Paton said the removal of the dam would improve fish passage and help turtles.
“The whole Wood-Pawcatuck watershed is a high priority for the Fish and Wildlife Service because we know it’s such an important river for fish passage, and also for wood turtles and spotted turtles, which right now are being proposed for federal listing,” she said. “We’re really concerned about turtle populations and we have really good habitat for wood turtle and spotted turtle in the Wood-Pawcatuck watershed. It’s a nice healthy river system for the most part. Just having the river connected and open and flowing naturally so that species can move up and down river at will and not have to get out and cross the road is always just fantastic.”
Project planning is expected to continue through the fall. Questions and comments can be submitted online.