A long-awaited cleanup of the old Waste Disposal Engineering (WDE) Landfill in Andover — one of Minnesota’s two most high-risk closed landfills — is shifting into gear.

Workers will start to level and prepare the site on May 15, state pollution officials told legislators this week, with a goal of completing the cleanup by the end of the year.

The task: excavating and hauling away an estimated 6,600 rotting drums and barrels of hazardous gunk buried in a one-third-acre pit at the site. Record keeping at the former dump was lousy, and state pollution regulators running the cleanup aren’t sure what they’ll find when they dig in.

“There’s a lot of unknowns,” said Hans Neve, manager of the state’s Closed Landfill Program. “This is the No. 1 priority for the program right now.”

On Tuesday, about 40 people met for a preconstruction meeting, including representatives from the state Department of Health and the main contractor, Massachusetts-based Clean Harbors Inc. and its subcontractors.

In June, work crews will build a temporary structure to house workers and protect nearby residents from fumes. Excavation starts in July.

Most of the toxic soil, sludge and rotting drums will be placed in new containers or lined dumpsters and shipped by rail to an incinerator in El Dorado, Ark. The resulting ash will be disposed of in Long Mountain, Okla.

Workers will then repair the cap over the pit, which prevents rainwater from percolating through it, and install a well to pump out residual water that may be contaminated for treatment.

The WDE Landfill is one of more than 100 dumps in the Minnesota Pollution Control Agency’s (MPCA) Closed Landfill Program, which was created by the Legislature in 1994 to manage old landfills and reduce health and environmental risks. The WDE site is the only dump in the program that was permitted to take hazardous waste. It vies with the Freeway Landfill in Burnsville in terms of posing the greatest risk to humans and the environment.

Today, the WDE Landfill looks like a very large elevated athletic field, grassed over and fenced off. But in the early 1970s it took hazardous materials such as barrels of solvents, plating sludge and cyanides, and they weren’t handled properly.

Local manufacturers such as Thermo King, Ford, Onan and FMC Corp. disposed of toxic waste at WDE, according to a 1983 report the county gave to the Minnesota Pollution Control Agency (MPCA).

According to the MPCA, “The pit is leaking and contaminating the groundwater below with polychlorinated biphenyls (PCBs), paint wastes, heavy metals, solvents, and other volatile organic compounds.”

Short-term protection systems have been in place at the site, and the agency says the drinking water of local residents has not been contaminated, including nearby private wells. Nearby Coon Creek is OK too, officials said.

The cleanup had stalled in recent years amid controversy over where to get the last piece of funding for the project, now estimated to total $22.3 million. After much wrangling, the final $10.3 million was included in the bonding bill Gov. Tim Walz signed into law last month.

The MPCA will host a community meeting about the cleanup at Andover City Hall on May 8 at 6:30 p.m.

Next, the Closed Landfill Program will tackle the Freeway Landfill in Burnsville, which is an Environmental Protection Agency Superfund site. That closed garbage site abuts the Minnesota River, but the MPCA says that local groundwater and the river have been protected because a quarry next to the landfill has been pumping out groundwater.

Crews are wrapping up an investigation of the landfill’s contents and will soon start designing a cleanup plan.