Environmental officials released Wednesday their findings regarding the Gowanus Canal, backing claims that the former Brooklyn industrial site is a public health threat.

The Environmental Protection Agency's investigation revealed the water has numerous contaminants dating back more than a century, including PCBs, as well as high levels of mercury, lead and copper.

The agency says three former gas plants contributed to the contamination, and that sewage discharge and storm water continue to cause problems today. The EPA plans to get the responsible companies still in existence to help pay for the cleanup.

"It has been an open sewer, it has been an industrial dumping area for generations," said EPA Regional Administrator Judith Enck. "We now have a roadmap to figure out what's the best technology to use to get these contaminants out of the waterway."

The canal was declared a superfund site in March 2010. When the EPA stepped in, the city objected, saying that it was in a better position to know what needed to be done.

Now, city officials say they are cooperating with the federal agency.

The Gowanus Canal Community Development Corporation also initially opposed the takeover, saying it feared the work would delay needed development. Now the group says it is satisfied with the EPA's timetable for the cleanup.

"The EPA has make a commitment to set a new tone, to set a new precedent in terms of how fast they work, how communicative they can be with the community," said David Krieger of the GCCDC.

The EPA will now begin a study to determine the best way to clean it up, and says the cleanup effort will take at least a decade.

According to the EPA, the water poses a health risk to those who either eat fish or crabs caught on site, or for those who come into frequent contact with the sediment.

That is in part because 300 million gallons of sewage and industrial waste still spew into the waterway each year. Fixing that source of pollution is a separate project spearheaded by the city.

The Department of Environmental Protection says when that is finished in two years, annual waste dumped in the canal should drop by more than a third.

A public hearing on the EPA's findings will be held at P.S. 32 in Brooklyn on February 23.