Scotland — The operator of the hydroelectric dam on the Shetucket River has requested a 90-day extension of a federal licensing deadline to file plans for upstream and downstream fish ladders, saying it needs more time to resolve issues relating to how it is operating the facility.

In a May 14 letter to the Federal Energy Regulatory Authority, FirstLight Hydro Generating Co. said it is considering modifying the existing turbine so that it can generate power in a manner that would be more acceptable to state regulators, but must conduct an engineering analysis first.

Earlier this month, the state Department of Energy and Environmental Protection warned FirstLight that it may revoke a water quality permit it has issued for the dam because it is not generating power from “run of river” natural flows, but from impound-and-release flows in which water levels widely fluctuate.

DEEP said the company is obligated under its FERC license and the state permit to operate the dam as a “run of river” facility, which is better for the river environment than impound-and-release operations.

Steve Gephard, supervising fisheries biologist for DEEP, said Friday that the agency recommended to FirstLight that it request the extension so that the run-of-river issue could be resolved before the fish ladder design is decided. The 40-year FERC license FirstLight received two years ago required that fish ladder plans be developed in consultation with state and federal agencies and be submitted by May 21.

In its letter to FERC, FirstLight said it has scrapped plans to install a low-flow turbine needed for a run-of-river operation because it would cost $5 million, instead of the $2.6 million the company had estimated when it applied for the license. A low-flow turbine also generates less power than the existing equipment. Wholesale energy prices also have fallen, the company said.

“It would be a significant enough impact that it would make the project uneconomic,” said Leonard Greene, government and regulatory affairs advisor for GDS Suez, the U.S. parent company of FirstLight. “We’re trying to find a viable alternative.”

Celeste Miller, spokeswoman for FERC, said the agency is reviewing FirstLight’s request for an extension and has not yet made a decision.

In addition to the extension request, FERC also is reviewing a letter submitted this week by Trout Unlimited, an advocacy group for anglers. The group said FirstLight has failed to provide public access above or below the dam as its license requires and is out of compliance.

It asked that FERC address the issue, and suggested that given the problems with access and the fact that it is not a run-of-river operation, FERC should reopen the licensing process.

FirstLight competed with Norwich Public Utilities for the license that was granted in 2013.

j.benson@theday.com

Twitter: @BensonJudy