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The Cumberland Mills Dam at the Sappi paper mill in Westbrook will have a fish passage installed as the result of Monday’s order by the commissioner for the Maine Department of Inland Fisheries and Wildlife.

Presumpscot River advocates say Monday's decision ordering Sappi Fine Paper North America to install a fish passage on one of its Westbrook dams is significant because it could open the entire river to several species of anadromous fish.

The decision by Roland D. Martin, commissioner for the Maine Department of Inland Fisheries and Wildlife, came nearly three years after river advocates asked the state to intervene.

Martin ordered the company, owner of the former S.D. Warren Paper Mill, to install the fish passage on the Cumberland Mills Dam – one of six dams Sappi operates on the Presumpscot.

Cumberland Mills is the only dam that does not produce electricity, which means that the federal government could not require that it have a fish passage.

The state was the only agency with that authority, but Martin had to rely on a Maine statute that has not been used in more than century.

"Cumberland Mills Dam is the key to unlocking the rest of the Presumpscot River," said Will Plumley, a former president and founder of Friends of the Presumpscot River. "We are very happy. It's good news for the river, for the fish and for the people who live in the watershed."

In October 2006, Friends of the Presumpscot and American Rivers requested that the state consider ordering construction of a fishway on the dam.

Hearings were held in December 2008.

Those organizations, which were represented by the Conservation Law Foundation, argued that a fishway would restore river access to species such as alewives, shad, salmon and sturgeon.

The river flows for 25 miles from Sebago Lake in Standish to the ocean in Falmouth.

In his ruling, Martin concluded that "there is convincing evidence in the record that the Presumpscot River historically supported large quantities of anadromous and migratory fish, including Atlantic salmon, American shad and river herring. Over time, these species were eliminated from the river by the construction of dams that blocked passage and by pollution."

Martin said he believes that if a fish passage is installed on the Cumberland Mills Dam, those fish can be restored "in substantial numbers" to the Presumpscot River watershed.

Sean Mahoney, an attorney for the Conservation Law Foundation's Maine Advocacy Center, said it made no sense to install passages on the upriver dams owned by Sappi because fish access to the upper reaches of the river was blocked at Cumberland Mills.

He said Sappi fought the fish passage "at every turn." Passageways on all of the dams, Mahoney estimates, could cost "in the millions."

Attempts to reach Sappi's spokeswoman, Amy Olson, were unsuccessful.

Staff Writer Dennis Hoey can be contacted at 791-6365 or at: dhoey@pressherald.com