WESTBROOK — The owner of six dams along the Presumpscot River has agreed to a plan that would reopen the industrial river to herring, alewives and Atlantic salmon.

Sappi Fine Paper North America, owner of the former S.D. Warren paper mill in downtown Westbrook, will remove the Cumberland Mills Dam by 2011 as part of the preliminary agreement announced here just before noon today.

The dam is adjacent to the paper mill and is the lowest dam on the river and the first obstacle for fish swimming from the sea.

Restoring fish to the river will provide new recreational opportunities, such as striped bass fishing in downtown Westbrook, as well as strengthening ocean fisheries.

Before the agreement was reached, the Friends of the Presumpscot had asked the state to mandate fish passage at the dam, a step that would eventually force the company to install fish passage at five upstream hydroelectric dams.

Sappi and the Friends of the Presumpscot, together with other groups and state and federal agencies, signed onto the preliminary river restoration agreement. It will require changes in state and federal permits and is to be finalized over the next six months.

Along with removing the Cumberland Mills Dam, Sappi has agreed to install a fish passage at the Saccarappa Dam by 2016 and set up a process for capturing and trucking fish even further upstream. That first phase of the plan is expected to cost about $10 million.