WESTBROOK – Sappi Fine Paper North America plans to remove the Cumberland Mills Dam near its mill along the Presumpscot River under a tentative agreement with conservation groups.

The dam, which has blocked the Presumpscot since the late 18th century, would be removed by 2011 under a preliminary agreement between Sappi and Friends of the Presumpscot River and other conservation groups.

The removal would open another section of one of the country’s first industrial waterways to migratory fish. The dam is the first obstacle for blueback herring, alewives and other fish that swim upriver from Casco Bay.

Also under the agreement, the company would install a fish passageway such as a ladder or lift at the next dam upriver, the Saccarappa Falls Dam, within five years after the Cumberland dam is removed.

Migrating fish also would be trapped and trucked farther upstream, and the company would install fish passageways at four more dams as fish populations re-establish themselves, according to the agreement.

The dam-removal plan faces reviews by state and federal regulatory agencies, but is expected to be finished by the end of this year. Gov. John Baldacci called the agreement a good compromise and balance between the industrial and ecological uses of the river.

The president of Friends of the Presumpscot River also said the agreement marks a new beginning for the river.

“Today is the beginning of a chance to bring back some of the things that were lost on the Presumpscot River,” said Dusti Faucher, whose group was formed in 1991 when the river’s native fish runs were widely considered a lost cause by conservationists and government agencies.

Sappi officials say the removal and site engineering work will cost about $6 million.

The Westbrook dam’s blockage of sea-run fish to upper portions of the river has long been a matter of controversy.

Last year, the U.S. Supreme Court issued a ruling requiring Sappi to install future fish passageways at five hydro dams upriver of its mill, the former S.D. Warren mill.

Friends of the Presumpscot continued to push the state to mandate a fish passage at Cumberland Mills Dam, which is not federally regulated because it does not generate power.