TAMPA — In a deal that will sweep away one of downtown Tampa's last vestiges of heavy industry, the development company for Jeff Vinik and Cascade Investment on Friday paid $13 million to buy the ConAgra flour mill just north of their 50-acre Water Street Tampa project.

The transaction clears the way for the 80-year-old flour plant to move, "in all likelihood, to the port," Mayor Bob Buckhorn said, and for developers with Strategic Property Partners (SPP) to expand Water Street Tampa's footprint and further shape the city's urban core.

The flour mill covers a little more than 3 acres and was owned by Ardent Mills, a joint venture between ConAgra and two other agri-business companies. It has long been seen as an anachronistic remnant of the waterfront's smokestack past and out of synch with Water Street's lifestyle-driven mix of high-rise hotels, apartments, condominiums and offices.

"It's the last missing piece of the puzzle," Buckhorn said. "I think all of us have recognized, including Ardent Mills, that the city had grown up around that plant and that was not the best use of the property for either them or us."

Built in 1938, the 80,000-square-foot flour mill grinds wheat around the clock, shipping 1.5 million pounds of flour a day to bakeries across Florida, the Southeastern United States and the Caribbean.

Discussions about the future of the mill have taken place on and off for four or five years, Buckhorn said.

"This has been a very long time coming," he said, and it took "a lot of prodding, a lot of cajoling, a lot of asking, a lot of negotiating" before "SPP and Jeff (Vinik) stepped up to the plate."

In announcing the purchase, SPP said it's looking at expanding its plans for Water Street Tampa, which already has a development cost estimated at $3 billion, onto the flour plant property. But SPP gave no indication of what it is thinking about putting there or when development could occur.

Ardent Mills said it plans to move from its current location and built a new mill at an unannounced location that will be in operation by 2021.

"We are committed to our expert Tampa team, the opportunity to continue to delight our customers and serve our great neighbors in Tampa and Central Florida," Ardent Mills CEO Dan Dye said in a statement. "We have enjoyed this privilege for more than three decades and look forward to supporting the Tampa community, Central Florida and customers across the state for many decades to come with a new state-of-the-art mill capable of growing with our customers."

Buckhorn, who sits on the port's board, said Port Tampa Bay would make sense as a new home for the flour plant because it has 5,000 acres of land with ready access to rail, shipping, and truck routes.

"That gives them three opportunities to move that product," he said. "It will allow Ardent Mills to build a modern, far more efficient facility that's more conducive to the work that they do."

A spokeswoman for the port would not discuss the matter Friday.

"There's nothing I can tell you about that issue," Port Tampa Bay director of public relations Samara Sodos said.

Nor is Ardent Mills ready to say where it's going when it moves.

"Ardent Mills is looking at several sites in Tampa and the surrounding area for our new community mill location," spokeswoman Mary Ann Strombitski said in an email Friday evening to the Tampa Bay Times. "We are excited to continue to serve the Tampa community from our current facility and our future new facility. We have not selected or finalized a site location yet."

In addition to the purchase, SPP announced that it had reached an agreement with Ardent Mills, the city of Tampa and the Tampa Hillsborough Expressway Authority to resolve a long-standing problem:

How to extend Cumberland Avenue east across a set of railroad tracks to S Meridian Avenue?

For Water Street's developers, making that connection would create a needed east-west route through the project as well as a long-sought entry point for people coming to Water Street Tampa. But until now they were unable to negotiate a resolution to the problem.

"Literally, I've been working on this since the day I started working for the Lightning in 2013," said SPP executive vice president and general counsel Jim Shimberg, who joined Vinik's team after serving as Buckhorn's first city attorney.

The amount of land at issue is tiny — less than a sixth of an acre — and is at the southern end of the Old Tampa Rail Yard, which has been in use since at least World War I. It is owned by the Tampa Hillsborough Expressway Authority and leased to the flour mill.

It has one set of railroad tracks on it and is used to switch trains carrying wheat from track to track in the rail yard. Putting a road across it and limiting its use by trains would be highly disruptive and costly, Ardent Mills has said previously.

Under the agreement struck in conjunction with the land sale:

• Cumberland will be connected from Meridian to Brorein Avenue.

• Ardent Mills will terminate its leasing rights to the tracks south of Cumberland as of Nov. 1, 2020 to allow for the extension of Cumberland.

• The city of Tampa, which at one point filed and later dropped an eminent domain lawsuit to secure rights to the parcel, will pay Ardent Mills $2.25 million in exchange for the mill giving up its rights to using the track south of Cumberland.

Developers said untangling this knot will help them create the connected, walkable and transformative neighborhood they envision.

"Restoring a downtown street network has been a priority of ours," SPP chief executive officer James Nozar said in a statement, "and the Cumberland crossing is an important milestone. With the acquisition of the property, we can now look towards the future and plan for additional points of connection for pedestrians, cyclists, and motorists."

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Contact Richard Danielson at rdanielson@tampabay.com or (813) 226-3403. Follow @Danielson_Times