LYNNWOOD — The Edmonds School District’s former bus barn property near Alderwood mall is valued at nearly $12 million.

But before any development occurs there, petroleum contamination on a portion of the 9.17-acre site must be cleaned up — work estimated to cost $6 million.

Cleanup work is expected to begin in June and be completed in the fall.

The school district has known for more than five years of the need for an environmental cleanup at the site, said Stewart Mhyre, the district’s executive director of business and operations.

Insurance policies obtained when the school district bought the property in the 1950s included the potential for an environmental cleanup.

The school district is working with insurance companies to help pay for an investigation of what it will take to clean up the property as well as the cost, Mhyre said.

Soil has been contaminated with petroleum products and hydraulic fluid on a portion of the property near the former bus maintenance area. The soil will be dug up and hauled away.

Once that’s complete, the state Department of Ecology is requiring groundwater monitoring on the site for a year.

That means no development on the site will likely occur before the fall of 2018.

The school district has been negotiating for a few weeks with a developer to buy the property.

“I’m not at liberty to talk about our negotiations,” Mhyre said. “After we finish the negotiations, then it will be public.”

The property, at 2927 Alderwood Mall Blvd., is adjacent to both the mall and I-5.

Although the county Assessor’s Office has valued the property at $11.9 million, its selling price depends on what a developer can put on it, Mhyre said.

The land has a sewer easement and sewer lift station on it. The easement prevents part of the property from being developed. “You can’t put a building on top of it,” Mhyre said.

The school district opened a new bus barn and maintenance facility in August on 52nd Avenue W in Lynnwood. The $30.3 million project was paid for with the district’s 2014 bond issue.

Money from the sale of the Alderwood Mall Boulevard property will go to the district’s capital fund for construction projects.

Sharon Salyer: 425-339-3486 or salyer@heraldnet.com.