Before the Ford plant came to St. Paul nearly a century ago, a stream cut across native prairie before it spilled over the bluff at what would become known as Hidden Falls.

The water went underground to storm sewers when the automaker moved in. But with the Ford plant gone, St. Paul officials envision a scenic stream once again carrying stormwater toward a re-energized Hidden Falls with water cleaned by vegetation and trees before it enters the Mississippi River.

The opportunity to redevelop the 120-plus-acre industrial site along the river's edge has officials planning a new way to handle stormwater. Where once the idea was to channel water quickly to underground sewers before dumping it into the river through a pipe above the falls, officials now want to make the water a centerpiece.

A recreated stream and pond would serve not only as infrastructure, but as a way to draw new residents and businesses to a vibrant urban village and, in the process, do a better job cleaning water along the way.

"We're bringing water back to St. Paul," said Bob Fossum, program manager with the Capitol Region Watershed District. "Residents have in some ways lost touch with water in St. Paul. … We need to find ways to bring water back into the consciousness of the public."

Bringing stormwater back to the surface is a key component in other proposed developments across the city, including the West Side Flats and the planned soccer stadium in the Midway neighborhood. Nearly three years ago, the city created the 42-acre Trout Brook Nature Sanctuary on the city's North End, restoring a winding stream bed to replace old stormwater pipes that ran to the river. Like a restored stream at the Ford site, Trout Brook crosses a "brownfield" covered with contaminated soil.

A family picnicked along the banks of the Mississippi in Hidden Falls Regional Park, St. Paul.

At Ford, a new stream bed would be lined with an impervious material so water could not leach through the soil to pick up pollutants. It would flow into a containment pond near the falls before falling to the river.

The "unhiding" of Hidden Falls or, more accurately, recreating the stream that once fed Hidden Falls, is perhaps the most dramatic example of what planners call "daylighting." And the most popular, judging by public reaction at a series of meetings over the past few months.

"It helps to give the site a very distinct character," said Merritt Clapp-Smith, city planner working on the Ford site project.

"Public works projects have traditionally been unseen, invisible," said Wes Saunders-Pearce, city water resource coordinator. "This makes it visible, makes it, 'Wow!' "

City officials have not yet released a firm design or cost estimate. But it's likely to be part of the site's infrastructure improvements — along with streets, sanitary sewer, water and electrical — that go in before the first building rises there, perhaps by 2020 or 2022, said Jonathan Sage-Martinson, director of Planning and Economic Development for the city.

The city also hasn't decided how to cover the costs. Most likely, there will be a system of assessments charged to either the Ford developer or to property owners in the new development, said Kristin Guild, deputy director of Planning and Economic Development.

The Ford site was once 85 percent paved, with heavy stormwater runoff plunging over and eroding the falls several times a year. The new system would create a more consistent and perhaps year-round flow of water through the stream and over the falls — serving as an attraction as well as a stormwater solution. Clapp-Smith said officials are looking at the system as a way to drain a 100-acre area to the north of the Ford site, as well as a 30-acre area to the south, which would also make the flow through the stream and falls more constant.

"The more water we can get into this, the better," Clapp-Smith said.

jim.walsh@startribune.com 651-925-5041