HOWLAND, Maine — Town and Penobscot River Restoration Trust officials are amending an easement agreement after selectmen raised concerns about the large amount of construction debris left on the former Howland tannery site, they said Friday.

Since winter, the river restoration trust has been overseeing construction of a $3.2 million fish bypass on property adjacent to the tannery site and the Penobscot and Piscataquis rivers. The bypass is part of the Penobscot River Restoration Trust’s plan to open nearly 1,000 miles of habitat to endangered Atlantic salmon, sturgeon, American shad, alewives and seven other species of migratory, sea-run fish now blocked from going past Howland. Those species help support other commercially important species, such as cod and lobster.

Members of the Board of Selectmen became concerned starting about three weeks ago that too much debris was being left on the site for the town to clean up, said Glenn Brawn, chairman of the Board of Selectmen.

Selectmen were also concerned that the huge mound of debris there would thwart town efforts to develop the site, one of the key developable parcels of town-owned land, Brawn said.

“We are trying to come up with an amendment for the original easement to allow us more control over the site and what gets left on the site,” Brawn said Friday.

River restoration trust spokesman and Deputy Director George Aponte Clarke agreed that the piles of ash, dirt and other debris were vast, but are only going to be left on-site temporarily.

“There has never been an intention to leave all of that material there,” Clarke said Friday.

Both sides met in executive session to discuss the matter on Monday. The negotiations are ongoing, Brawn said.

Made up of a coalition of organizations, the restoration trust bought the Veazie, Great Works and Howland dams from PPL Corp. in December 2010 in a historic deal worth $24 million. Under an agreement brokered in 2004, PPL in return gained authorization to increase power generation at six other dams along the river, entirely offsetting the generation losses incurred when the three dams were decommissioned.

The Veazie Dam was breached in stages during several months of 2013. The Great Works Dam, which stretched across the Penobscot River from Bradley to Old Town, went down in 2012. The Howland Dam near the confluence of the Piscataquis and Penobscot rivers remains in place but does not generate electricity.

As of Friday, about two-thirds of the proposed bypass had been dug. The rest will be finished in several weeks before cement and other materials start getting poured, Clarke said. The project is due for completion by this fall.

Negotiations over the debris disposal plan should conclude in a few weeks, Brawn said.