BANGOR – The findings of an investigation into a coal tar deposit on the Penobscot River bottom – and options for remediation – were released during a public informational meeting Wednesday night at City Hall.

The session also yielded a surprise visit from an attorney representing the Stamford, Conn.-based company the city believes is responsible for the coal tar deposit.

The so-called Bangor Landing investigation focused on the nature and extent of the tar deposit, which covers roughly a 10-acre area along Dunnett’s Cove, located along the city’s waterfront redevelopment zone. Impacts on human health and the environment also were assessed.

Initial studies of the area determined that the now-defunct Bangor Gas Works was the source of the plume-shaped deposit, beginning at a former sewage outlet known locally as the “old stone,” or Davis Brook sewer, and extending 1,400 feet downstream from the Bangor landing.

The sewage outlet once began at the gas plant that operated on the city’s west side from 1881 to 1963 and emptied into the river.

When temperatures rise, the sticky, black residue found at the site sometimes bubbles up to the surface, sticking to boat hulls and creating an oily sheen on the river surface.

During the session, the results of the investigation into the tar deposit at Dunnett’s Cove were outlined by representatives of the city, the Maine Department of Environmental Protection and RMT Inc. of Madison, Wis., the private environmental contractor the city hired to conduct ecological and health assessments of the affected area.

The city hired RMT in 1999 to study the former site of the Bangor Gas Works, which generated the coal tar as a waste product of its gas manufacturing operations, officials believe, near what is now Second Street Park.

Those studies confirmed the presence of coal tar in the river and linked the pollution to the plant.

While not believed to be harmful to humans who avoid contact with it, coal tar consists of chemical components that can elevate the risk of cancer and other health problems in instances of prolonged or frequent skin contact, according to Eugene McLinn, a senior project manager for RMT.

McLinn served as a primary presenter, along with Kathy Niziolek, DEP project manager. McLinn said, however, that there were no known documented cases of cancer directly connected to the deposit.

The news for the river’s ecology was worse, McLinn said. Testing demonstrated that direct contact with tar killed the same type of organisms that live in the riverbed and ecological surveys showed fewer species able to live over the tar deposit, he said.

The next phase of the project will involve evaluating various remediation options. Each of the possible options outlined Wednesday called for dredging, capping, or a combination thereof.

While cost estimates have yet to be developed for each of the options, the cleanup is expected to cost up to $10 million.

According to Niziolek, additional investigation, including sampling sediments near shore, will be conducted this fall. The feasibility study weighing the pros and cons of remediation options will occur during the winter.

Niziolek and McLinn were among a study team that also included DEP staffers Deborah Rice, toxicologist; Troy Smith, staff geologist; and Hank Aho, acting director of the department’s remediation division.

City Engineer Jim Ring provided an introduction and brief project background statement before the presentations.

On hand to present “the rest of the story” was Martha C. Gaythwaite of the Portland firm Friedman, Gaythwaite, Wolf & Leavitt, one of several attorneys representing Citizens Communications, the company the city filed a federal lawsuit against last fall in an effort to compel it to share in the cleanup cost.

In turn, Citizens Communications has filed about a dozen third-party lawsuits against companies, some from Maine, it alleges also share responsibility for the pollution and the cleanup.

After the presentation, Gaythwaite said that company’s experts concluded that the city’s investigation was incomplete and “flawed.” As an example, she said the environmental assessment was based on only two samples, one of which did not contain tar.

She also said the city wasn’t taking the company up on its offer to help pay for additional testing.

“In our view, that’s just not right,” she said.

City Solicitor Norman Heitmann said that the purpose of Wednesday session was not to address legal issues. That, he said, will occur in court.