The U.S. Army Corps of Engineers plans to spend at least $350 million more over 10 years to dig up and haul away nuclear waste from a dump site about 35 miles northeast of Pittsburgh.

The Army Corps halted the cleanup - originally estimated to cost $44.5 million - after crews discovered unanticipated amounts of “complex” materials, like uranium and plutonium, at the Parks Township site in 2011.

The site was once owned by Nuclear Materials and Equipment Corp., which operated fuel plants for nuclear submarines in Parks and nearby Apollo. NUMEC owned the dump site from 1957 until the 1980s, but Babcock & Wilcox Co. most recently owned the land.

The Army Corps already spent $62 million on the cleanup, meaning the final cost will be $412 million - nearly 10 times the original amount.

“Presuming that this this goes forward - and barring any other sidesteps at the political or legal levels - I am hoping that all agencies that are involved will work in concert to effectuate a safe and comprehensive cleanup of this site,” said Patricia Ameno, a 63-year-old local environmental activist who has led the fight to clean up the related waste dump since 1988.

Ameno spearheaded litigation over airborne pollution from the nuclear plants that has led to $92 million in legal settlements from Atlantic Richfield Co. (NUMEC’s parent for part of the time the plants operated) and Babcock & Wilcox, for scores of nearby residents who claimed they developed cancer.

But Ameno, who has had two brain tumors and growths on her breast and cervix, has concentrated her fight in recent years on uncovering the truth about what was dumped at the site and by whom - both of which remain mysteries.

U.S. Sen. Bob Casey, D-Pa, has joined that fight in recent years and, after the cleanup was halted by the discovery of the more serious, complex pollutants, pushed for the Nuclear Regulatory Commission’s Office of Inspector General to investigate the site and how the NRC had handled the cleanup.

That report, issued in March, concluded the companies that operated the nuclear plants and later maintained the dump kept shoddy records and that the NRC and Army Corps couldn’t be sure what’s there as a result.

That’s one reason why the Army Corps now proposes to dig up all of whatever waste remains and ship it to an undisclosed location out of state that is approved to accept hazardous, nuclear waste.

Casey spokesman John Rizzo called Monday’s announcement “a step in the right direction toward resuming cleanup” of the site, but he said the senator continues to push for other documents to be publicized that more clearly spell out all the government agencies with links to the project.

The amended plan was posted online Monday and will remain there through Feb. 4 for public comment. A public hearing will be held Jan. 27 at the Parks Township fire hall.

Assuming the plan is approved, the Corps hopes to award a contract in August. The contractor must then develop a cleanup plan for approval by the Corps, Corps spokesman Dan Jones said. The cleanup should begin in late 2016 or early 2017 and take about 10 years, with the Corps having to get congressional appropriations each year for the project to continue.

“We’re still early in the process, but this is a giant step forward,” Jones said.