PORTLAND, Ore. (AP) — A 10-mile stretch of the Willamette River — the iconic body of water flowing directly through one of America’s most environmentally-conscious cities — could soon be teeming with massive equipment and crews tasked with cleaning up more than a century’s-worth of hazardous contaminants from industrial use.

The federal government’s $746 million-cleanup plan for Portland Harbor was revealed two weeks ago, ending a 16-year wait after the polluted area gained status as a Superfund site by the U.S. Environmental Protection Agency.

But the long-awaited proposal — a 30 year process that’d involve cleaning up a tiny portion of the area, while leaving the rest to recover naturally — was blasted by environmentalists and community leaders, who say it’ll take too long and won’t be enough to make the water and riverbed safe for the area’s families and wildlife.

Just before the EPA’s first public hearing downtown Portland Friday, protesters gathered urged residents to voice their opposition over the next 90 days, the window for public comment that the EPA extended earlier that morning.

“Allowing these toxins to even remain in the river, to be covered up or to be washed down into the Columbia River is unacceptable, and even more than being unacceptable, it’s a violation of human rights,” said Rose Longoria, regional superfund cleanup projects coordinator with Yakama Nation Fisheries. “And on top of that, it’s a violation of the Yakima Nation’s treaty rights.”

Under the proposal, roughly 200 acres of the site’s most toxic parts would be under construction for seven years. Sediment polluted with heavy metals and various carcinogenic chemicals would be removed or covered by a man-made barrier, called dredging and capping. Less severe contamination in the remaining 2,000 or so acres would be left to recover on its own, which will take an estimated 30 years overall.

EPA officials say the current proposal is much cheaper and less disruptive to the environment than some of the other options they were considering. The agency could finalize its proposal before year-end.

The Port of Portland, which owns much of the land in the Superfund site, and some of the companies considered potentially responsible for the pollution and financing some costs are also opposing the project.

Seven companies who’ve agreed to take some of that responsibility — including Union Pacific Railroad, Chevron and TOC Holdings Co. — filed a legal dispute this week with the EPA. They criticized the plan in 22-page letter as a “rushed” decision.

The letter said the end-goal isn’t achievable, “requires unnecessary treatment, and will be far more disruptive than described by EPA. Further, the cleanup will take much longer to implement than predicted by EPA and will likely cost far more than estimated by EPA.”

Port of Portland officials took issue with some of the areas target for the cleanup and also the cost estimates, which they called “overly optimistic.”

“While we were intrigued by the more than $600 million drop in the cost of EPA’s preferred remedy, a closer look left us perplexed,” Curtis Robinhold, Port deputy director, wrote to federal regulators this week. “Costs dropped, but there was little actual change in the plan for cleanup … meaning the public is not informed about the true higher anticipated cost of the cleanup or the benefits that different cleanup alternatives would achieve.”