They’ve taken the plunge.

After more than five years of discussion, Lawrence city commissioners Tuesday agreed to sign the necessary documents for ownership of the 467-acre Farmland Industries property to be transferred to the city so that it can be converted into an industrial park.

“There is probably nothing you are going to vote on in terms of economic development, or perhaps anything else, that will be bigger than this,” Mayor Mike Amyx told fellow commissioners before the vote.

As part of the deal, the city will become responsible for cleaning up the environmental issues left behind by Farmland Industries when it used the site as a fertilizer plant. The city will receive $8.5 million in trust fund money that had been set aside to clean the property. The city will not pay a purchase price for the land, but does have to pledge the taxing authority of the city to cover any cleanup costs that go above the $8.5 million amount.

Commissioners have said they don’t think that is likely.

“There is nothing scary about this site environmentally,” Commissioner Aron Cromwell said. “It is a mildly contaminated site. We’re able to acquire a mildly contaminated site and turn it into something that will be a positive impact on the city’s economic base for a long time.”

The property’s main environmental issue is groundwater that is contaminated by nitrogen. The cleanup of the property involves pumping the groundwater through an existing pipeline system to North Lawrence, where it is spread on farm fields.

The city should take possession of the property in 60 to 90 days. While city commissioners are optimistic the cleanup can be done with the $8.5 million trust, the site will need millions of dollars in infrastructure improvements.

City Manager David Corliss said he will recommend that $3 million in new debt be included in the city’s 2011 budget to provide infrastructure upgrades at the site. Corliss said street projects to extend O’Connell Road and create a new frontage road between the site and the adjacent East Hills Business Park may be some of the first projects undertaken.

Corliss is recommending that $1 million of the money come from general obligation bonds. The remaining $2 million would be paid off through special assessments placed on the property. The city, though, will be responsible for paying off those assessments if the property isn’t sold as part of a future development.

City leaders hope to begin selling some portions of the site to business tenants sooner rather than later. The Lawrence-Douglas County Bioscience Authority has hired a consultant to begin providing recommendations on how to convert the site into a biosciences park, Corliss said.

About 225 acres of the property are clean enough to be developed immediately.

Commissioners approved the project on a 4-0 vote. Commissioner Rob Chestnut was absent.

In other city commission news:

• Commissioners approved modifications to the city’s Mixed Use Zoning District category. The change will allow bars to be included in the districts, if they receive a special use permit. But commissioners did include language that does not allow the property at 1420 Crescent Road, the site of the Jayhawk Bookstore, to apply for the special use permit. The site currently is the only mixed use district in the city, and commissioners had promised neighbors when it was approved that bars would not be an allowable use in the district.

• An ordinance making the city’s smoking ban fit with the new statewide smoking ban was approved. The biggest change will be that outdoor areas within 10 feet of a business’ entrance now will be nonsmoking.