Businesses have recently committed to clean up more than half of the heavily contaminated 10-mile portion of the Willamette River in Portland, according to the U.S. Environmental Protection Agency.

The agency announced Monday that it reached agreements with nearly two dozen companies, including Chevron, Exxon and Shell Oil, between December and last Wednesday to restore eight portions of the Portland Harbor Superfund site.

Portland officials said the new contracts account for 140 contaminated acres or 57% of the superfund site.

The affected portion of the river flows from near the Broadway Bridge downstream to Sauvie Island. The site includes portions of the sediment of the Willamette River that have been contaminated with hazardous substances over the last century from industrial use in the area.

A state and federal study found in 1997 that the river sediments were heavily contaminated posing human health and environment risks. Three years later, the environmental protection agency designated the area a federal superfund site and placed it on its list of national priorities, requiring a long-term cleanup plan. Federal officials in 2017 released a final plan to clean up the harbor’s contaminated soil and toxic materials, which they estimate will take around 30 years and cost $1.05 billion.

According to the Environmental Protection Agency, there are around 150 parties believed to be partly responsible for releasing hazardous substances into the river, including the Oregon Department of Transportation, Department of State Lands and City of Portland. The federal agency group also estimates around 3 million cubic yards of contaminated sediment need to be removed from the river bottom and banks.

Before the latest batch of agreements, some of the agreements the environmental protection agency already reached included the Port of Portland to clean up its marine Terminal 4 site near Sauvie Island; NW Natural for its Gasco property; and the City of Portland, electric power company PacifiCorp and four other companies to be responsible for River Mile 11 East, which stretches between the Broadway and Fremont bridges.

Last May, the City of Portland and the State of Oregon agreed to provide up to $24 million in reimbursement funds as an incentive to any group suspected of taking part in the contamination to sign agreements with the Environmental Protection Agency to submit blueprints for the cleanup effort. The city and state would provide $12 million each.

Before then, the federal agency hoped to have cleanup plans that accounted for the entire superfund site to be submitted to them by the end of 2019.

The agency said Monday that the funds “bolstered” its negotiations toward the new agreements. More than $11 million of the reimbursement fund has been claimed, according to the Portland Bureau of Environmental Services.

“This is a unique and bold approach by public agencies and it’s resulting in the most significant progress we have seen since the site was listed 20 years ago,” Mayor Ted Wheeler said in a statement.

The companies that have signed the latest agreements also include BP Products North America Inc., General Electric Co., and Phillips 66.

-- Everton Bailey Jr; ebailey@oregonian.com | 503-221-8343 | @EvertonBailey

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