Los Angeles-based AECOM aims to begin construction next year on its massive $788 million Riversedge project, a redevelopment of the former West Publishing site overlooking the Mississippi River in downtown St. Paul.

But first the development team has to finish design and engineering work and clear additional hurdles that include regulatory approvals, a development agreement with Ramsey County, and an air-rights deal with two railroads.

After a six-month due diligence process, and years of on-again, off-again proposals for the county-owned site at 50 W. Kellogg Blvd., the Ramsey County Board on Tuesday sealed the deal with AECOM.

In doing so, the board elected to move forward with a redevelopment plan that will bring a mix of Class A offices, apartments, retail, entertainment and hospitality uses to the riverfront in four towers.

“It was a good day. The county board is fully behind moving forward on this project. I am encouraged,” Jim McDonough, a county board member, said in an interview.

A linchpin of the development is a proposed land bridge over Shepard Road, a public space that will connect downtown St. Paul to the Mississippi River. Other public spaces include a river-level esplanade, an amphitheater and bandshell with views of the river.

One complicating factor: The land bridge will extend over railroad tracks along Shepard Road, which means the development team has to work out an agreement with the Union Pacific and Canadian Pacific railroads.

“The railroads have the air rights above their tracks, so any time you are going in the railroads’ right-of-way you have to work with them and … ensure there is no impact to their operations,” McDonough said.

Brian Dusek, AECOM’s managing principal for real estate development, said the wheels are already turning on that front. He anticipates an air-rights deal to be in place by the second quarter of next year.

“It’s a marathon, not a sprint,” Dusek said in an interview. “They have a very detailed process and it involves transportation engineers. Fortunately, we have transportation engineers at AECOM. We have the right expertise to navigate through this.”

Though the county’s official timeline for the start of construction is 2020 or 2021, Dusek said he expects to begin in 2020.

The $278 million first phase will deliver 132,000 square feet of public realm space and trail connections, two towers with a 168-key hotel, 56 condo units, 350 rental apartments, 11,500 square feet of retail and 500 parking spaces, according to the county.

Phases two and three will bring two office-retail towers with additional parking. In all, the redevelopment will create 1,546 parking stalls, according to AECOM.

Dusek estimates the first phase will be ready for occupancy by late 2022 or early 2023. The second phase will be roughly a year behind that schedule, and the third phase hinges on demand for offices, he said.

AECOM brings a lot of in-house expertise to the table, but Dusek said there will be ample opportunities for local building contractors and other partners to participate in the development.

“We are not doing it by ourselves,” he said.

Ramsey County says the private redevelopment could generate more than $15 million annually in new property tax.

Joe Spencer, director of the St. Paul Downtown Alliance, said Riversedge brings a needed mix of office, retail and residential uses to downtown St. Paul while also creating a long-hoped-for connection with the river.

Marrying the two is no simple matter because a steep bluff, railroad tracks and Shepard Road separate downtown from the river, Spencer noted.

“We have been talking about making that connection for generations in downtown St Paul. This lid that comes out and over and connects downtown to the river, is just a really, really exciting thing for downtown St. Paul,” Spencer said.

As Finance & Commerce previously reported, the county plans to seek $40 million in state bonding money to help pay for $80 million in public space improvements. The county and other sources would have to match those funds.

Dusek said the subsidy would be strictly for public space improvements.

“AECOM didn’t come to county hat in hand for the subsidy. What the subsidy is paying for is the public realm space,” he said.

Ramsey County spent $17 million on demolition and other work to groom the site for development. That included demolition and remediation of the former adult detention center and the Ramsey County Government West buildings.

Redevelopment has been challenging in part because of the cost of taking down the buildings with more than 700,000 square feet of space pinned into the bluffs.

Phoenix-based Cardon Development previously proposed a $225 million mixed-use development at the site in 2017, but the county and Cardon agreed to part ways after the developer said it needed public money for a parking structure.

West Publishing vacated the site when it moved to Eagan in 1992. The six buildings forming the campus were later converted to a 600,000-square-foot government office complex, which operated there until 2013. A 122,410-square-foot county jail, built in 1979, also operated on the site.