NORRIDGEWOCK – Machines on Friday began removing a granite and concrete dam that has blocked the Sandy River between Norridgewock and Starks for more than a century.

Removal of the 313-foot Sandy River Dam will allow passage of salmon and other sea-run fish that swim upstream from the Kennebec River. The project is expected to cost $500,000.

Two excavators were at the scene Friday morning taking down the structure, starting a process that is expected to take about two months, Calvin Ames of Madison Electric Works said as he observed the project.

The dam, which was built in 1897, used to provide all of the power used in the town of Madison, but in recent years that has been reduced to less than 2 percent. Removal of the dam will restore a natural 6-foot waterfall in the river.

“This is another step in a long-term project [of] restoring sea-run fish to the Kennebec watershed,” said Jeff Reardon of Trout Unlimited. “It’s a great day for the river.”

Removal of the Sandy River Dam will allow for 52 miles of unimpeded passage for Atlantic salmon and other migratory fish, according a study by the Maine Atlantic Salmon Commission.