Target Field already is the capital of Minnesota baseball. Now it may spawn Minneapolis' answer to Grand Central Station.

Plans for what's being called the Interchange -- a transit hub next to the ballpark through which thousands of commuter rail, light rail and bus passengers would pass each day -- are being publicly aired, another step in preparing for various transit lines that could someday run through downtown.

On Tuesday night, Hennepin County held an open house to display plans for the commuter and regional rail segment of the project. They include a third track, an additional passenger platform and an extension of the existing Northstar rail platform. Two possible layover yard sites for parked trains also are identified.

The designs were prepared by engineering consultants from Parsons Brinckerhoff with help from officials with Burlington Northern Santa Fe Railway, which owns the tracks.

The plans involve a different part of the Interchange from the light-rail area, which also is being prepared for a redesign. There, the county is contemplating an $80 million project to build a new light-rail platform, a large plaza and elevated tracks to accommodate more light-rail lines.

Hennepin County Commissioner Peter McLaughlin, chair of the county's Regional Railroad Authority, says the long-term goal is to make Target Field one of the metro area's two major transportation hubs, along with Union Depot in St. Paul.

Ultimately, officials hope the area will attract private-sector investment.

The heart of the Interchange would be across 5th Street from Target Field, where a large depot structure would be built to enclose platforms and escalators headed down to the trains or up to street level. From there they could reach nearby parking garages, bus stops, light-rail platforms, even a city-suburban bike trail.

The design makes room for regional rail lines that may one day find a home at Target Field, including the proposed Red Rock Corridor from Hastings and the Northern Lights Express high-speed line from Duluth.

A stop also could be added for Amtrak, which has its Twin Cities station in St. Paul's Midway district.

Kevin Duchschere • 612-673-4455