A developer is asking Ramsey County to kick in $80 million to build Riversedge, a dramatic $788 million redevelopment of a stretch of downtown St. Paul that would include a hotel, luxury housing, retail and high-end office space in four towers looming over the Mississippi River.

If built, the development on the vacant site of the former county jail and West Publishing Co. headquarters would re-sculpt St. Paul’s skyline.

County leaders agreed Tuesday to move forward with the ambitious plans, which call for building a terraced, concrete lid that turns the nearly 5-acre site into a 10-acre canvas for AECOM, the Los Angeles-based developer.

That extra acreage would provide room for outdoor public space, including a “river balcony” with prime river views.

The project would cost an estimated $788 million, with Ramsey County expected to come up with $80 million of that to cover construction of the lid. The county, in turn, would ask the state for $40 million in bonding to help cover its share of the cost.

Riversedge would be built in three phases that could span a decade.

AECOM and county officials on Tuesday shared additional details, new renderings, adjusted numbers and cost estimates with five of the seven members of the Ramsey County Board.

“This is a big, bold and ambitious project,” said Josh Olson, the county’s redevelopment manager. “This is the last key site on the [St. Paul] riverfront.”

County leaders called the project “iconic,” “transformative” and one that would attract jobs to the region. They said the network of walking paths planned throughout the property, and its panoramic waterfront views, would physically connect downtown with the Mississippi River.

“Riversedge is an opportunity to bring jobs, economic development, affordable housing and increased tax base that St. Paul, Ramsey County and the entire region needs,” said Ramsey County Board Chairman Jim McDonough, in a written statement.

Brian Dusek of AECOM said the developer would like to start construction in 2021, but laid out a lengthy to-do list to complete before then. It includes filling out an environmental work sheet, securing public financing, getting public feedback and city approvals, burying high-voltage power lines, and negotiating with the railroads and public authorities to build the concrete lid over existing tracks and Shepard Road.

According to the updated plans, Tower One on the east end would include a 168-room hotel and 56 condos, and Tower Two would have 350 apartments. Towers Three (24 stories) and Four (29 stories), if built to capacity, could include nearly 1 million square feet of Class A office space.

County commissioners nodded, asked detailed questions and on the whole gave the developer positive feedback. One sticking point: the plans include no provision for affordable housing, and AECOM has agreed to give Ramsey County $5 million for an affordable housing trust to be spent anywhere in the county.

Most of the board members present seemed open to that idea, noting that downtown St. Paul has significant affordable housing and homeless shelters. But Commissioner Victoria Reinhardt said she was uneasy over the prospect of no affordable housing at Riversedge, especially with the county locked in a lawsuit with Arden Hills over the amount of affordable housing in the redevelopment of the 427-acre Twin Cities Army Ammunition Plant (TCAAP) site.

“You put in $5 million for affordable housing and build it elsewhere?” Reinhardt asked AECOM officials. “If that’s the case, we should offer that to Arden Hills, too. ... I don’t want this [downtown] project to be treated differently than the other.”

Reinhardt represents the Seventh District, which includes the county’s eastern suburbs. Arden Hills is in the neighboring First District on the county’s north end, the board seat for which was vacated in June with the resignation of Commissioner Blake Huffman.

Commissioners left the workshop session saying the affordable housing issue was still open for discussion.

Afterward Joe Spencer, president of the St. Paul Downtown Alliance, echoed county staffers that the Riversedge project would transform downtown. He said he supported building up the number of downtown residents, currently about 8,900.

Riversedge “makes that connection between downtown and the river, which we have been talking about for a generation,” Spencer said.