Longstanding issues with the Ashuelot River’s West Street Dam in Keene were met with new-age solutions Tuesday night at the city’s recreation center.

A team of six researchers and graduate students from the Rhode Island School of Design drove up from Providence to present community members with five potential fixes to the dam, which the state has deemed deficient.

The RISD team’s work is part of a wider, National Science Foundation-funded project. The researchers are operating solely in an advisory capacity, Keene Public Works Director Kurt D. Blomquist said, adding that the placeholder for any work to begin is 2024.

“It’s not something that’s going to happen next week,” Blomquist said at the outset of the presentation.

The forum also included small group sessions and surveys, which the RISD team will incorporate into a broader study.

The Future of Dams project, a multi-state, interdisciplinary research initiative, uses the responses to develop new decision-making methods for dam issues in the Elm City and other New England communities.

The roughly two-dozen attendees Tuesday were dispersed among color-coded tables, with a RISD representative recording their responses to oral and written questions at various points between phases of the presentation.

At the orange table, Peter Hansel, co-owner of Filtrine Manufacturing Co. in Keene, sat with Charles DeCurtis, a Concord-based freshwater manager, and Jim Rousmaniere, a Roxbury selectman who recently wrote a book called “Water Connections: What fresh water means to us; what we mean to water.”

DeCurtis drove from the capital out of an interest in RISD’s approach, while Rousmaniere said his primary concerns going into the evening were around preserving the historical character of the dam.

Hansel said he was of “two minds” on the issue: weighing the historical importance of the dam with a desire to see fish be able to migrate upstream in a potential fix.

All three men also agreed that the upstream and downstream ecosystems are important to them, with wetlands and other ecosystems currently relying on the dam as is.

Anchoring the orange table was Sheri Fultineer, dean of the architecture and design program at RISD.

As Fultineer steered the group discussion in between slides, Emily Volger, director of the landscape architecture department, presented the five options.

Each of the proposals, with the exception of removing it entirely, would fix the current issues with the dam that led it to be deemed deficient.

Repair the dam

Volger started with the most basic of the options.

Sealing off seepage on the sides of the dam, along with restoring the upstream dike to its original configuration, are the main priorities at the base of any fixes to the West Street Dam — aside from removing it altogether — Volger said.

Blomquist and Tara Kessler, a senior planner in the city’s community development department, gave a brief overview of the history of the dam, which the N.H. Department of Environmental Services declared deficient in letters in 2008 and 2011.

Projections for repair costs have ranged from $425,000 to $450,000, while removing the dam is estimated between $300,000 and $360,000, according to figures previously provided by the city.

Volger noted that while there would be long-term costs in maintaining the dam, this option would be cheaper than any of the other proposals, aside from removing it altogether.

Fish ladder

While the West Street Dam is not tall enough to warrant a fish lift — essentially an elevator in the form of a canal lock enclosure that closes shut and brings water to the top of a dam before releasing the fish upstream — one option for restoring the dam is to implement a fish ladder.

Fish are unable to migrate beyond the West Street Dam, but before it was installed, diadromous fish — such as the American shad — were able to move to and from saltwater through the Connecticut River and Long Island Sound.

Shad can spend up to four or five years of their adult lives in the Atlantic Ocean before coming back to freshwater rivers to spawn. The long-term impacts of dams on the populations of fish and aquatic foodchains are unknown, but scientists estimate that the disappearance of diadromous fish from ecosystems poses long-term threats to the survival of other species, including mammals such as manatees and dolphins.

Volger showed a design with a concrete slab tacked onto the side of the dam, with gradually inclining pools that would allow fish to jump up to the next level and, eventually, clear the dam and continue their journey.

The structure would add expense to the project, with a comparable one in Durham costing $1.9 million, according to a slide shown by Volger.

And only about 30 to 50 percent of the critters would end up finding the ladder and clearing the dam, Volger said.

‘Nature-like fishway’

One of the more popular options of the night, a “nature-like fishway” has the same premise as a fish ladder or elevator, but is much more elaborate in scope and would change the visibility of the dam.

By placing rocks, logs or other objects in rows slowly ramping up to the dam, the fishway would create resting pools that could be easily vaulted upstream.

Volger added that when the river is flowing more fervently, people would be able to kayak over the dam, which would disappear beneath the rapids.

Without relying on a narrow passageway, this option tends to have a 60 to 70 percent passage rate, Volger said.

One 5-foot dam Volger showed cost $1.14 million to be fitted with a fishway.

However, with the slowly increasing levels of the resting pools, the dam’s peak and waterfall would fall out of view, as would its historical character.

Bypass channel

Another way to bring fish migration back to the Ashuelot River could come in a bypass channel — essentially a new, concrete-reinforced creek that would cut through a marshy island behind the Starbucks in Ashuelot River Park.

This option — the most costly of the five — would preserve the historical character of the dam as well as the upstream wetlands while allowing fish to move through.

However, Volger noted that along with the intensive construction costs of regrading the soil to make way for the man-made creek, at 30 to 50 percent, the passage rate for the bypass channel is no better than the fish ladder and worse than the fishway.

The placement of the bypass channel would also be a challenge, Volger said, because of how hard it would be for the fish to find and for it to be placed in a way that would allow for enough flow to bring them through.

Another complication would be grading the bypass so as not to defeat the purpose of the dam, which would essentially involve the same kind of step-up pools entailed in the fish ladder and fishway.

Torpedo the dam

Getting rid of the dam is not only the cheapest option, but also the most fraught with variables, Volger and Blomquist said.

There would be no long-term costs, since there would be nothing to maintain, and the future coexistence of fish and humans would be natural, Volger said.

However, Blomquist noted that the city has never conducted a study on the sediment held upstream from the dam, and it is uncertain how much the water levels would change post-dam, affecting wildlife up and down the rivershed.

Historic character could still be preserved, with the buttresses on each side of the shore potentially staying in place.

By the end of the session, Rousmaniere went from valuing the dam’s preservation in its historical state to advocating for its removal altogether, as long as the buttresses remain.

Although other variables, such as the long-term cost and potential impact to the wetlands, still weighed on his mind, Rousmaniere said he was taken by the ability of his peers and the RISD experts to change his opinion.

“Even when you do live here,” Rousmaniere said to DeCurtis, “hearing everybody here makes it all the more complicated.”

Jake Lahut can be reached at 352-1234, extension 1435, or jlahut@keenesentinel.com. You can follow him on Twitter @JakeLahut.