A plan to increase the capacity of the Burnsville Sanitary Landfill was unanimously approved Tuesday night by the Burnsville City Council, with the state poised to make decisions about another essential permit as soon as September.

The council's approval allows the landfill — owned by Waste Management, the nation's largest trash firm — to take in an additional 26 million cubic yards of household waste and grow 268 feet taller over the next 40 years, while also shrinking its footprint by a dozen acres.

"I understand that there are some community members that don't want the landfill to expand," said Burnsville Mayor Elizabeth Kautz. "However, the landfill is here and it's not going away."

At 1,082 feet above sea level, the resulting trash mountain near the Minnesota River would tower over landmarks like U.S. Bank Stadium in Minneapolis. The Federal Aviation Administration will require lights on top to prevent interference with airplanes.

The next 10 years of expansion received a draft permit from the Minnesota Pollution Control Agency (MPCA) in July and the state finalized two other steps — the certificate of need process and an environmental review — in April. Agency officials will accept public comment through Sept. 4.

The project's opponents, including Bloomington city officials, cite visual and environmental concerns.

"The more we learn about the project, the more concerns we have," Bloomington Mayor Tim Busse said last month.

Busse cited worries about the portions of the Burnsville landfill that are unlined and whether trash from those areas might eventually interact with groundwater when water levels rise at the nearby Kraemer Quarry and when the Minnesota River floods.

Bloomington officials have requested that Burnsville require Waste Management to line the landfill's unlined portions.

The MPCA's environmental review found that the agency doesn't anticipate the expansion to contaminate groundwater or air, though it is expected to produce 87,000 tons of new greenhouse gases a year. Over 80% of the waste entering the landfill comes from Hennepin and Dakota counties, the MPCA said.

Burnsville officials are hoping that the expansion will help them clean up the nearby Freeway Landfill and Freeway Dump, a polluted Superfund site. Both accepted waste beginning in the 1960s, when landfills weren't required to have liners.

The Freeway site is a concern because the trash could come in contact with groundwater or the Minnesota and contaminate them. Right now, the quarry is keeping water tables artificially low by pumping out millions of gallons of groundwater a day.

Officials are looking at two options — known as "dig and line" and "dig and haul" — to remediate the situation. Both would dig out all the waste. The first alternative would add liners and then put the garbage back in, while the second would take it elsewhere.

The MPCA has not yet chosen between the two concepts. Burnsville officials are pinning their hopes on "dig and haul," which would most likely move the resulting 6 million cubic yards of trash to the Burnsville landfill.

City leaders would like the waste to be removed so the land can be developed, said Deb Garross, a Burnsville city planner. "If the dig and line option is done, there's not very much land available for any type of redevelopment," she said.

Waste Management has said the Burnsville landfill would take that trash, Garross said, and the city's expansion permits include space for it. The MPCA accounts for that trash in its draft permit as well, though officials said they don't have a preference on where it ends up.

Even if the landfill expansion is approved, there is no guarantee that the Legislature — which must eventually approve the project's funding — will choose the "dig and haul" plan.

Waste Management must still collaborate with the Department of Natural Resources on habitat requirements for the protected Blanchard's cricket frog, and work with the U.S. Army Corps of Engineers and the Federal Emergency Management Agency on measures that will remove the area from the flood plain.

Julie Ketchum, a spokeswoman for Waste Management, called the council's action Tuesday "a significant milestone" toward "providing much needed disposal capacity for Twin Cities metro area residents and businesses."