Two major Twin Cities developers, Doran Cos. and CSM Corp., purchased 9 acres near downtown Minneapolis from General Mills and announced plans Monday to build a 20-story apartment tower with about an acre of outdoor space.

The transaction, valued at $15.8 million, includes a building called the General Mills Riverside Technical Center, its last corporate facility near the former mills along the Mississippi where the company got its start 151 years ago.

The company said it will lease back the building, which it built in the late 1960s. Doran wouldn't comment on how long General Mills will remain in the building.

The site is between SE. 2nd Street and University Avenue SE., stretching three blocks between 2nd Avenue SE. and 5th Avenue SE. Doran will design and build the apartment tower on land between 2nd and 3rd avenues that is now a surface parking lot.

The 350- to 375-unit apartment tower will include ground-level townhouses and upscale amenities such as club rooms and a pet spa, said Doran founder and principal Kelly Doran.

"It's a great site," Doran said. "It's a walkable area. You are a block from the river. [You've] got all of the commercial space there along Central [Avenue SE]."

Planners aim to submit plans for the building to the city in the next couple months, with construction targeted to begin by the end of the year.

Both Doran and CSM have properties in the riverfront area. Doran developed six student housing properties in the area and built Mill & Main, a 338-unit luxury apartment building, just a block away from the General Mills property.

CSM owns the Renaissance Minneapolis Hotel-The Depot and Residence Inn by Marriott on the edge of downtown, just across the Mississippi River from the purchase site.

"We are excited to work with someone as iconic as Gary Holmes and his CSM team," Doran said.

The Marcy-Holmes neighborhood has been a hotbed for development with several pending projects, including plans for Alatus LLC to build a 40-story luxury condo tower and Schafer Richardson Co.'s purchase of Nye's Polonaise Room to make way for a 72-unit apartment building.

In addition to product research and testing, General Mills has its corporate archives at the Riverside Technical Center.

Nicole Norfleet • 612-673-4495

Twitter: @nicolenorfleet