Design planning for the renovation of the Union Depot in downtown St. Paul is on budget and ahead of schedule, officials said Tuesday.

If the pace holds up, it means construction could begin a month earlier this fall.

Ramsey County Regional Rail Authority board members got an update Tuesday on the nearly $240 million project, which is envisioned to transform the historic depot into a regional transit hub for trains, buses, taxis and bicycles.

"Being ahead is always good," said Jolly Mangine, the county's director of property management. The goal is to complete the project in September 2012 because of federal funding guidelines, he said.

Dan Mehls, project leader for Mortenson Construction, led the presentation. Mortenson is the lead contractor and has been working with engineering firm URS Corp. and architecture company HGA.

The Rail Authority granted a $5.7 million design contract to Mortenson in January.

A second contract will need to be signed before construction can begin, and that's expected to happen as soon as August.

Bid packages are set to begin going out in May.

A new significant feature is a planned entrance to the depot's rear concourse from Kellogg Boulevard with a separate lane for automobile access. That would allow for drop-offs, taxis and baggage check-in. Vehicles won't be able to go to the front of the depot because of a light-rail station.

The depot will be the terminus of the Central Corridor light-rail line, and Amtrak is expected to move there after the renovation is done. Advocates for high-speed rail to Chicago also want trains to stop there.

The building was put on the National Register of Historic Places in 1974 and, because of that, project officials have had to meet regularly with a variety of historic preservationist agencies and groups.

Many of the design ideas so far call for cleaning and restoring the existing structure and trying not to overpower the historic features.

Officials hope to have even more detailed designs in another two months.

An animated look at the updated designs can be seen at blog.regionalrail.org.

Chris Havens • 612-673-4148