Yarmouth residents filled the town’s log cabin on August 13 to hear about the impact the demolition of the Bridge Street Dam and the partial demolition of the East Elm Street Dam would have on the Royal River. Eloise Goldsmith / The Forecaster

A plan to remove two dams on the Royal River in Yarmouth would result in lower water levels and narrow the river in several places, according to an Army Corps of Engineers presentation. However, residents would still be able to use the river for canoeing upstream from the town’s canoe launch.

On August 13, about 40 Yarmouth residents filled the town’s Log Cabin meetinghouse to hear the results of a hydrologic and hydraulic study outlining how the dam’s demolition would affect water levels, appearance and flow.

The Army Corps is helping the city restore the Royal River ecosystem and earlier this year put forward a proposal to completely remove the Bridge Street Dam and remove a portion (i.e., 120 feet) of the East Elm Street Dam.

The plan also addresses a third site of interest, a series of waterfalls called Middle Falls, which Councilwoman Karin Orenstein said are difficult for fish to pass through.

It didn’t make sense to find a solution to the existing dams and not address this problem, Orenstein said. That’s why the Army Corps’ tentatively selected plan also calls for building a structure at the upper end of Middle Falls that would divert water flow into a side channel.

The Bridge Street Dam is located between Route 1 and Bridge Street, and the East Elm Street Dam is located just below East Elm Street, adjacent to Gooch’s Island. Neither dam is in use, although they served several industrial functions during their lifetime, including hydroelectric power production at the Bridge Street Dam. Both structures have fish ladders that are not efficient at transporting fish upstream, according to the Army Corps.

“The water level above the Bridge Street Dam would drop by about 3 feet,” said Tom Mihlbachler, an engineer with the Army Corps of Engineers. The water level just beyond Elm Street is expected to drop by about 4 feet.

As for velocity, their model calculations show “that the largest increases in flow velocity are expected to occur generally in the steep section between Elm Street and Bridge Street, while only minor increases are expected throughout the East Elm Street reservoir,” Mihlbachler said.

A diagram from the Army Corps of Engineers shows how the Royal River’s water level around the city’s canoe launch would drop if the dam were removed. The right side shows the water level after the dam is removed. Orange represents depths under 1 foot and red represents depths under 6 inches. Article / City of Yarmouth

At the Bridge Street location, water would become more concentrated if the dam is removed, but flow patterns would remain largely the same. At the Beth Condon Memorial Bridge, dam removal would cause water levels to drop from 2.5 feet to less than 1 foot. The tentatively selected plan would also expose a new ledge above the Beth Condon Memorial Bridge.

Around Middle Falls, depths are expected to remain largely the same at 1 foot.

In the stretch of the Royal River where residents launch canoes, near the Yarmouth Historical Society, dam removal could result in low water levels that could pose a hazard to recreational activities downstream from the canoe launch, Mihlbachler’s presentation said. However, the river will still be deep and wide enough to launch a canoe and paddle upstream.

“We do not recommend anyone to turn downstream in a canoe because there are even greater dangers there – there are waterfalls,” Orenstein said in a follow-up interview.

“What you see is a river that is still paddleable. It’s still wide enough, it’s still deep enough,” she said.

Mihlbachler said about 300 feet of the Gooch Island back channel would be “interrupted” and water would likely be diverted south of the island. The Army Corps’ plan would also likely reduce flooding risks for properties near the island.

The preliminary proposal is the precursor to a much larger project – a “feasibility study” – in which the Army Corps assesses the various problems facing a water resource, develops possible solutions, compares them, and makes recommendations.

In September, the Army Corps plans to submit a draft detailed project report/environmental impact assessment, which will be open to public comment during a public review period and a public meeting.

“I want to be very clear: There is no preconceived conclusion about what will happen. The city has not made up its mind yet. We are really waiting for the Army Corps report and for public opinion,” said Orenstein, who also said that under the current proposal, the city would cover about $2.1 million of the project’s cost. She said the city will try to raise that money through grants.

Both dams were built in the 19th century and are now owned by the city.

When the Army Corps first considered this project, it was concluded that restoring the Royal River could transform up to 135 miles (217 kilometers) of the river into a breeding ground and habitat for juvenile fish species such as herring, shad, shad, eel and seatrout.

But over the years, there have been some concerns about removing the dams. A 2013 report by Stantec, an outside environmental and engineering consultant, listed numerous concerns that could affect recreational use of the river, increased sediment input into Yarmouth Harbor, and potential environmental contaminants in the sediments at the East Elm Street Dam impoundment.

Orenstein acknowledged that there had been concerns about sediment, but in February the Army Corps presented the results of a sediment study that found that very little sediment builds up behind the dams, the sediments generally have low chemical values, and that there is little threat to aquatic life in the Royal River Estuary and Casco Bay if the city moves forward with its plan to remove the dams.

And while the actual demolition of the dam is still a long way off, it has taken many years to get to this point. In 2008, a Royal River Corridor Study examined the history, recreational use, and future development of the river corridor and surrounding areas. The final report included a recommendation to conduct a study weighing the pros and cons of demolishing the Bridge Street and East Elm Street dams.

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