The vision for the new Twins ballpark in the Minneapolis Warehouse District includes thousands of fans arriving by light rail and commuter trains.

The stadium site is flanked on one side by the railroad tracks that will bring Northstar commuter rail trains downtown and on another by 5th Street, on which the Hiawatha light rail line will be extended to its front door.

The problem is that two train stations and the ballpark must be shoehorned into a site barely two blocks square while leaving space for freight trains to run under a corner of the stadium. That adds up to a colossal engineering challenge for the transportation planners and ballpark designers, who hope to bring it all together by 2010.

They will have to reinforce the stadium in the event of a train derailment on the tracks that will pass beneath one section of seating. They also will have to coordinate ballpark and rail construction. Builders will have to agree who gets to stack steel where and when.

"This site has a number of advantages, the biggest one being the transit connection,'' Twins President Dave St. Peter said. "But it also has a number of challenges, the biggest one being the transit connection.''

The Northstar commuter rail service between Big Lake and Minneapolis is scheduled to begin in 2009. The ballpark is slated to open in 2010 on a roughly two-block site north of Target Center. Both projects have aggressive schedules, and bringing all the work together in such a tight spot will require precision timing, said Joe Gladke, engineering and transit planning manager for Hennepin County.