Nov 28, 2018 By Scott Beveridge for The 2 min read

MARIANNA — An environmental group that plans to demolish the deteriorating Marianna dam wants to breach it to remove pressure on its breastwork.

American Rivers is seeking permission to “poke a hole” in the century-old dam after high water flows were believed to have contributed to a landslide that closed a Marianna road in September, said Lisa Hollingsworth-Segedy, director of river restoration at the charitable organization’s Pittsburgh district office.

“It’s been a really bad summer for slopes and unstable banks,” Hollingsworth-Segedy said, referring to heavy rains that overflowed streams and washed out hillsides this year.

American Rivers should know by the end of the week whether or not the state Department of Environmental Protection will approves the plan to lower the reservoir at Marianna, she said.

The valve that controlled the water level at the dam no longer works, she added.

The low-head dam along Ten Mile Creek was built to provide a water source for the long-defunct Marianna mine. It is owned by the borough and it no longer serves that purpose. The DEP has said a dam failure would not pose a safety risk because there are no occupied buildings in its direct path.

The borough contacted American Rivers after the Sept. 26 slide exposed gas and sewer lines and forced the closing of a small section of Beeson Avenue.

Borough Council President Wes Silva said, “One or two more high flows” along Ten Mile could cause more land to shift at the 300-foot-tall hillside above the creek.

Silva said there is no odor now in the area after the sewer line was diverted into a temporary hose to a pumping system.

American Rivers plans to move the dam removal project into the design phase in the spring. The organization plans to add stream bank restoration work to the $200,000 project.