The St. Paul City Council is expected Wednesday to launch a plan to transform, over the next 30 to 50 years, the city’s long Mississippi River shoreline into a continuous parkland that can be easily seen and reached from its many neighborhoods.

“This plan lays out the river as a huge asset to St. Paul,” Council President Kathy Lantry said. “Trends change, people change, but the course of the river is not going to change.”

The council will vote on the Great River Passage master plan, a 300-page land-use blueprint that spells out projects along St. Paul’s 17-mile river corridor aimed at conserving natural areas, adding rivershore amenities and making them all more accessible to people.

Whitney Clark, executive director of the Friends of the Mississippi River, said the plan shows that the Mississippi “is becoming the heart of St. Paul,” and fills out “the Great River Park” vision first set for the city more than 20 years ago by Boston architect Ben Thompson.

“It’s a landmark, a road map, a list of high priorities that future councils, mayors, residents and park users can look to as we go about the job of implementation,” Clark said.

Officials pledge that this won’t be just another eye-crossing document that lands on a shelf and is quickly forgotten. They compare it instead to the century-old plans that preserved and designed Como Park, the Grand Rounds trail system in Minneapolis and the river boulevards in both cities.

St. Paul’s focus on the river isn’t new. For more than two decades, city leaders — notably Mayor Norm Coleman — promoted the river as a recreational asset and a vehicle for downtown development. In 2006, the city developed a framework similar to the Great River Passage plan.

But much of that work was done in piecemeal fashion, said Don Ganje, project manager with St. Paul’s Parks and Recreation Department, which oversaw the plan’s development for three years by a Denver-based consulting team and a 56-member advisory board drawn from across the city.

“This looks at where those connections are to neighborhoods that are missing and how we can accomplish that,” he said. “It’s a big unifying plan.”

St. Paul used $1 million from a state grant to fund the process. It’s estimated that the plan may cost $300 million to $500 million to implement over the next 50 years, most of it with state and federal funds.

Ganje said the plan is conceptual rather than concrete, in terms of the facilities and attractions described in it. But it does offer several interesting ideas for riverfront projects.

One is to create a preserve at Pig’s Eye Lake, the heart of a large natural area in the city’s southeast corner. Another is to turn fast-moving Shepard Road into a leafy parkway, or to create a “river balcony” stretching behind buildings on Kellogg Boulevard.

At least two other projects the master plan promotes have drawn some criticism.

One is the Watergate marina, an unsightly river landmark that the city has wanted to improve for years.

To do just that — and to draw state funding for it — the plan contemplates locating an environmental education center at the marina, a project costing between $20 million and $30 million.

Ganje said the site is among the most natural in the river corridor, that it adjoins Crosby Farm Regional Park and would offer public access to anglers, canoeists and kayakers.

Peggy Lynch, executive director of the Friends of the Parks and Trails of St. Paul and Ramsey County, pointed out the site also is prone to flooding. “They can get more interest at the State Capitol to spruce up the marina if they roll it into an environmental learning center,” she said.

Ganje affirmed that was the strategy, but said the area hadn’t flooded in years.

The master plan also proposes to renovate Island Station, a vacant power plant on the river that the National Park Service is interested in converting into its headquarters for the Mississippi National River and Recreation Area.

Unlike the marina, the city doesn’t own Island Station, which is currently for sale by owners who would like a free hand to demolish it.

Recently it was found ineligible for placement on the National Register of Historic Places, eliminating hopes for redevelopment tax credits.

But interest remains high in reusing Island Station. “If we had a nickel for every idea for Island Station, we’d be rich,” said Tonya Nicholie, president of the West 7th/Fort Road Federation district council and a member of the advisory board. “It’s a compelling structure that hasn’t been utilized in four decades.”

Lantry said some anxiety was expressed at last week’s public hearing about resources being diverted from other city parks to carrying out the Great River Passage plan. She said projects will go through the regular public processes as they arise, and that nothing is set in stone.

But she underscored the importance of using the river to improve the lives of residents and visitors.

“You go all over the world, and people may not know where Minnesota is or St. Paul, but if you tell them you live on the Mississippi, they know. That’s a huge thing,” she said.