The Ramsey County Board pushed forward a proposal Tuesday that could reshape the downtown St. Paul skyline and create a walkable slope down the bluffs from Kellogg Boulevard to the Mississippi riverfront.

The board selected AECOM, a Los Angeles firm with a Minneapolis office, as its preferred developer to build up to four towers on a narrow stretch along Kellogg that once housed the county jail and West Publishing Co.

The project would be built in three phases and cost between $620 million and $900 million, according to AECOM estimates.

The towers would rise 12 to 36 stories high and include some combination of hotel rooms, apartments, condominiums, shops and offices. They would be constructed on a sloping land bridge — complete with tree-lined paths and open staircases — that would cross over Shepard Road and the railroad tracks below the bluff to connect pedestrians on Kellogg Boulevard with the river’s edge 80 feet below.

It’s that walkable bridge that could make the project iconic and stand the test of time, said Commissioner Rafael Ortega.

“To me a tower is a tower is a tower,” Ortega said. “But what they’ve done is connect downtown to the river.”

The county and AECOM will enter a six-month due diligence period when either side could back out as they come up with detailed cost estimates and timelines, and determine whether more public money would be needed to make the project happen.

Once the six months are up, the County Board and AECOM officials would negotiate a final development agreement and property sale.

The site, on Shepard Road near the Wabasha Bridge, has been one of Ramsey County’s top redevelopment priorities for years.

But other proposals have all fallen through, despite the fact that the county has spent $17 million razing the buildings there and cleaning and prepping the land.

What’s different this time is that the towers would be built over the railroad tracks, allowing people to make it down to the river from Kellogg, said Jim Thomson, a vice president and managing principal for AECOM.

“The other proposals really stopped at our Phase One,” Thomson said. “That’s not where we’re stopping.”

In the project’s first phase, to be completed by 2021, AECOM would build up to 350 apartments, 150 condos and a hotel with up to 250 rooms.

The first phase also would include up to 1,800 underground parking spots as well as an amphitheater, restaurants and storefronts built into the hill. AECOM estimates the first phase could cost as much as $280 million.

With the strong demand for apartments and housing, ground could be broken on the residential portions of the project almost immediately, said Brian Dusek, AECOM’s managing principal for real estate development.

The second phase would call for building an office tower with up to 20 floors, at a cost of up to $220 million. It could be completed by 2023, according to AECOM.

A second office tower that could reach 36 stories would be built in a third phase that also would include the extension of several roads. AECOM estimates that final phase could be completed by 2026 and cost up to $400 million.

Office demand uncertain

The demand for office space in St. Paul is more uncertain than it is for housing.

Nearly one in five downtown offices were vacant as of last month, according to a recent report from the Greater St. Paul Building Owners and Managers Association.

But Dusek said demand for new office space exists.

“We’re trying to break that stereotypical cycle in St. Paul where developers don’t build offices here and therefore office users don’t come here because there’s no development,” he said.

AECOM won’t start building the office towers until it has identified anchor tenants that would occupy 30 to 50 percent of the office space, Dusek said.

“We’re confident that what we’re going to create here in Phase One is going to drive that interest,” he said.

County Board members said they would be open to considering public financing for the project if they feel it’s required, once AECOM and county staffers study the market over the next six months. But a tax-increment finance district would be off the table, Ortega said.

Thomson said he would expect city or county help with extending roads and other public infrastructure.

All six County Board members in attendance — Commissioner Janice Rettman was absent — said they were impressed by the plans, especially the walkable corridors between the proposed towers.

“This is the third time I’ve been through this with a developer sitting right there telling us about this site,” said Board Chairman Jim McDonough.

“But this is the first time I’ve got a good sense that the developer truly realizes the potential of it and recognizes the importance of the public connection.”

County officials vowed to work closely with the city of St. Paul throughout the project. Increasing access to the riverfront is vital, said Mayor Melvin Carter.

“The vision for this development captures the exciting potential of St. Paul as a river city,” Carter said.