ST. LOUIS • Five design teams competing for a chance to reshape the Arch grounds and riverfront spoke Thursday of visionary connections and then answered nuts-and-bolts questions from the jury of experts who will pick a winner.

The teams are finalists in the competition for a plan to improve the Jefferson National Expansion Memorial with better connections to downtown, more attractions and an expansion to East St. Louis.

After each team described its plans in sweeping phrases, jurors asked about everything from parking and traffic to how to get the work done by Oct. 28, 2015, the 50th anniversary of the topping of the Arch.

That is the ambitious goal of the National Park Service and CityArchRiver2015, a local foundation. The eight-person jury will announce a winner Sept. 24.

The National Park Service estimates the project at $305 million, warning it could be more. No money is set aside, but several area members of Congress have pledged support.

About 150 people attended the day-long session at America's Center. Team leaders offered graphics and computerized "fly-through" videos to show what their ideas would look like.

CityArchRiver2015 plans to put the presentations on its website (cityarchrivercompetition.org) soon. Donald G. Stastny, an architect from Portland, Ore., and competition manager, said the presentations are a good way to look beyond images on exhibit now at the Arch.

"It's always good to hear firsthand from the designers what their ideas are," Stastny said.

He plans to work with the winner to prepare a budget by December. Following are summaries of their presentations:

Weiss/Manfredi of New York

Michael Manfredi and Marion Weiss, the principals, said they welcomed the task of reconnecting the park and downtown despite the busy swirl of traffic on the highways, streets and Mississippi River.

"We find this incredible Gordian knot to be intriguing and incredibly challenging," Manfredi said.

Their plan, called "Full Circle," envisions wide pedestrian pathways across the Eads Bridge, through a new east side park and back across a new walkway built onto the Poplar Street Bridge. It also proposes a new glass-filled entrance to an underground museum at the Arch that would face the Old Courthouse and a grass walkway over the depressed lanes.

It also would use the top floor of the Arch garage for such things as a beer garden and ice rink, build an underground garage at Luther Ely Smith Park in front of the Old Courthouse, and build an amphitheater and other activities on the south end and beneath the snarl of ramps to the Poplar Street Bridge — a maze Weiss spun as "fabulously dynamic architecture for free."

Michael van valkenburgh associates of new york

The team studied the Arch park and was "very troubled by the benign way the grounds reached out to the city," said leader Michael Van Valkenburgh. His team proposes a big new museum entrance on the west, with an atrium.

"St. Louis will once again become a pioneer city on a new kind of frontier," he said of MVVA's plan.

Although the competition didn't require it, Van Valkenburgh offered a budget estimate, projecting the team's plan at slightly more than $300 million.

It would demolish the Arch garage, replacing it with activity fields, an earthen amphitheater, ecology center and a new entrance to Laclede's Landing. It would build garages beneath Smith Park and above ground on the south end of the park.

Juror Carol Ross Barney, an architect in Chicago, wondered whether MVVA contemplates enough activities on the east side. Van Valkenburgh said the team's plans for bird sanctuaries and elevated walkways allows for using the area without expensive remediation of the land, which has been damaged by decades of use by railroads and industry.

Behnisch Architekten of Los Angeles and Germany

Behnisch principal Stefan Behnisch said its River Circle plan connects the riverfronts by making the Eads Bridge a pedestrian path and operating a gondola above the river.

"We want to create a beautiful place that is sustainable and interwoven with the city," Behnisch said. "We want this to be more of an event place and not just a monument."

Juror Gerald Early, a professor at Washington University, asked whether the gondola, music museum and other elements would "compete with the Arch" for attention.

"I don't perceive it to be competing," Behnisch said. "Honestly, the Arch is great, but you've been there, you go up, and then you go again. I'm sorry, but something needs to change."

Oliver Schulze of Gehl Architects in Copenhagen, a design partner on the team, talked about "activating" links through multiple entry points — at Washington Avenue, across the depressed lanes, at a Poplar Street sports park and with a botanical area on the east side.

SOM, Hargreaves, BIG of Chicago

The day's fourth presentation opened with a sleek video set to a soundtrack of "St. Louis Breakdown" by Oliver Sain and interwoven with snippets of quotes from St. Louis residents. Called "Relaunch: St. Louis Can Soar," the proposal centers on preserving and enhancing most of the current Arch grounds while adding new structural elements to its edges.

Skidmore, Owings & Merrill partner Phil Enquist unveiled a 17-point plan that ranged from general goals ("1. Improvements") to ambitious projects ("6. Magic Carpet"). Of the latter, judges seemed most interested in the cap that will go over Interstate 70 to link the city with the Arch grounds — a walkway that flares at the ends like a flying carpet — as well as an 11,000-seat performance space on the east side of the river.

Other major elements of the plan would reshape Leonor K. Sullivan Boulevard into a terraced promenade and add a floating pool where people could take a dip in filtered Mississippi River water. "It would be an island of new urban life," said Bjarke Ingels of Copenhagen-based Bjarke Ingels Group.

Juror David Leland, managing partner of Leland Consulting Group in Portland, Ore., asked which of the 17 items on the proposed to-do list were highest priorities.

"I hope I'm not being naïve," Enquist responded, "but to us, the idea that nothing is impossible is so inspirational."

PWP LANDSCAPE ARCHITECTURE, FOSTER + PARTNERS, CIVITAS OF BERKELEY, CALIF.

The team stressed that it wanted to continue the vision of Arch designer Eero Saarinen and landscape architect Dan Kiley. A part of that vision would be removing the 43-foot-tall overlook that opened last year as the centerpiece of a new park in East St. Louis.

"The walkway gets you up and a nice view but it doesn't work with anything else over there," said Peter Walker, a PWP partner. The Gateway Geyser, however, would remain, he said.

PWP wants to replace the overlook with a 65-foot-tall earthen mound surrounded by agricultural fields and greenhouses. The design team leaders said an agriculture center could be used for education and as a home to harvest celebrations and a farmers market. Water taxis would shuttle park visitors across the river.

Like the other design teams, PWP proposes a lid over I-70 and reconfiguring many downtown streets, including narrowing Memorial Drive.

Garages would be built under Kiener Plaza and Luther Ely Smith Park — 1,110 spaces in all. The existing garage north of the Arch would be replaced with a cultural center, although the design plans offer nothing specific. Walker said that was intentional.

Also left open is a spot on the south side of the grounds for another possible cultural center. As the park redesign progresses, existing cultural institutions could partner with the National Park Service to best utilize those spaces, Walker suggested.