BANGOR, Maine — An expensive and heavily monitored coal tar removal and remediation project on the Bangor Waterfront is nearing completion a little behind schedule but a little under budget, City Engineer Jim Ring said.

Ring updated members of the City Council earlier this week about the $7 million project, which involved removing 7,000 cubic yards of foul coal tar deposits from the river, then capping the targeted area. Work began early last September and will continue through the spring with cleanup, but the major elements are complete, Ring said.

“This is as unique a project as I’ve been involved with,” he said. “I’ve certainly learned a great deal.”

Coal tar is a byproduct of gas manufacturing and a known carcinogen. It was deposited in the Penobscot River by Bangor Gas Works, which operated from 1881 to 1963 on land where Shaw’s supermarket now sits.

The cleanup effort was a collaborative effort among city, state and federal regulatory agencies, and it climaxed more than a decade of planning to address the scope of the problem and come up with a remedy. Combined with a comprehensive plan to overhaul the city’s waterfront, the coal tar cleanup has dramatically changed the landscape.

The $7 million project was funded primarily through a settlement with Citizens Communications Co., a group of third parties a federal judge ruled was responsible for a majority of the cleanup. Bangor’s downtown tax increment financing district funds covered any additional costs.

Work was done primarily by Wisconsin-based RMT Inc., an environmental consulting firm. The first part involved dredging contaminated soil. The second phase involved the installation of a cap of crushed stone, clay and boulders to ensure that any further migration of coal tar from sediment to surface is permanently prevented.

Ring said the weather proved to be the biggest variable. Ice began forming in the Penobscot River earlier than usual. Some odors were emitted from the dredging, but Ring said they were actually not as bad as expected. Other than that, the project went smoothly and the engineer said state and federal environmental regulatory agencies have monitored the project closely from the beginning.

Coal tar-contaminated materials that were removed from the water were taken to a warehouse on Main Street for treatment, then shipped to one of two area landfills.