ST. LOUIS — The political leaders with the influence to reshape the riverfront Arch grounds generally spoke well Friday of the new federal plan for its future.

St. Louis Mayor Francis Slay, for example, called it "terrific news for St. Louis." East St. Louis Mayor Alvin Parks Jr. said it is "something we could be very receptive to."

On Friday morning, the National Park Service released its 298-page "General Management Plan" as an official guide for the future of the 91-acre Jefferson National Expansion Memorial. It seeks a mix of preserving parkland, especially the grand lawn beneath the Arch, and developing more activities on the north and south ends of the grounds.

It calls for expanding the park across the Mississippi River to the East St. Louis riverfront. And it seeks to solve the old issue of trying to more closely connect the Arch grounds to downtown — specifically by getting people more easily across Memorial Drive and over the noise of the Interstate 70 depressed lanes.

The last piece of the Arch was fitted into place on Oct. 28, 1965. Many local and federal leaders would like to make improvements by the 50th anniversary of the Arch, in 2015.

The document calls for giving serious thought to closing as many as three blocks of Memorial Drive downtown to clear the way for wide, safe and easy walkway to the Arch grounds. Any such design probably would include the long-discussed lid over a stretch of the depressed lanes.

The Missouri Department of Transportation maintains Memorial Drive. Ed Hassinger, the agency's district engineer, said preliminary studies suggest closing part of Memorial could work. "We'd have to do a lot more work on new traffic patterns, but I've seen nothing yet that says, 'This is impossible,'" Hassinger said.

Assuming Park Service regional administrators sign the plan in 30 days, as expected, the federal agency likely will seek an international design competition next year. A similar effort in 1947 led to choosing architect Eero Saarinen's design for the Arch.

U.S. Sens. Christopher "Kit" Bond, R-Mo., and Claire McCaskill, D-Mo., both endorsed the document in general terms. So did U.S. Reps. William Lacy Clay, D-Mo., whose district includes the Arch grounds, and Jerry Costello, D-Ill., who represents East St. Louis.

There's still much work to do. A jury of specialists would run the design competition and the Park Service would pick a plan. Then Congress and local sources would have to find money. The plan estimates a cost of about $305 million but warns that detailed design work could boost the sticker substantially.

Still out of the picture is former Sen. John C. Danforth, who in 2007 urged area leaders to "think big" and redevelop the Arch grounds with more visitor-friendly attractions, such as an aquarium and restaurants. In April, Danforth withdrew from the project, saying the Park Service study was falling far short. On Friday, his spokesman said Danforth hadn't changed his mind.

McCaskill said in a statement, "I'm happy that the process is moving forward and the National Park Service is working with the community to advance this important project." Bond's statement said in part, "St. Louis deserves a world-class riverfront and I will support whatever final plan the community comes together on."

Bond also urged the Park Service to include a connection to the Great Rivers Greenway Trails System.

Clay commended the Park Service for "expanding the horizons of what the Gateway Arch can be" and for including East St. Louis. Clay called fixing the pedestrian issue at Memorial Drive "one of my top priorities."

Costello said he has favored adding the Metro East riverfront since 1991, when he pushed for it in federal legislation. "I will support any reasonable plan supported by city and (St. Clair) county officials to get that done," he said.

Slay had joined Danforth in 2007 in calling for big changes. But Jeff Rainford, Slay's chief of staff, said Friday the mayor believes the Park Service document allows for designing "Arch grounds that are as great as the Arch itself. What seemed doomed a year ago is still possible. We are charging full speed ahead."