BANGOR, Maine — Slightly behind schedule, the removal of coal tar deposits from the Penobscot River is expected to begin on Monday, a three-week process that will create quite a stink on the city’s waterfront.
Site preparation of the area known as Dunnett’s Cove already has begun, but the dredging of about 7,000 cubic yards of sediment was delayed a week while the city’s consulting firm waited for materials.
That firm, Wisconsin-based RMT Inc., will finish installing what are known as turbidity curtains, which are installed in the water to keep soils contained but keep fish out of the dredging area. Then the dredging begins.
Once that is complete, RMT will install a cap of crushed stone, clay and boulders to ensure that any further migration of coal tar from sediment to surface is permanently prevented. That process is expected to last six to eight weeks, but the foul odors caused by the dredging should be gone after three weeks.
The cleanup effort is a collaboration among city, state and federal regulatory agencies. It’s the culmination of a decadelong effort to address the scope of the problem and come up with a remedy.
Coal tar, byproduct of gas manufacturing and a known carcinogen, was deposited in the Penobscot River by Bangor Gas Works, which operated from 1881 to 1963 on land where Shaw’s supermarket now sits.
Chemically, coal tar is similar to creosote and roofing tar in that it contains naphthalene, the same substance used in mothballs. The safe exposure level of naphthalene, according to the U.S. Department of Labor, is 100 times higher than what the average person can smell. Once the dredging begins, air will be monitored to ensure that the public is not at risk.
The $7 million project will be paid 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 will cover any additional costs.
Once the coal tar-contaminated materials are removed from the water, they will be taken to a warehouse on Main Street for treatment. From there, they will be shipped to one of two area landfills.