Maintenance work began Wednesday on Union Pacific railroad tracks in the Downtown Sacramento railyards, while ongoing upgrades continue at the historic Sacramento Valley Station.

Union Pacific has started rail maintenance work on existing tracks. Rail cars that are part of a track replacement train known as the TRT 909 are pulling up the rail and replacing railroad ties underneath, said Aaron Hunt, public relations director for Union Pacific.

"We have track improvement projects going on throughout the state currently," he said.

The work is not part of the $60 million Downtown track relocation project, said Richard Rich, development director of Thomas Enterprises' Railyards project.

The timing was determined by the amount of train traffic and loads on the tracks, even though those tracks will be ripped out in a year or so, as track relocation work is scheduled to start by May. Railroad track relocation is the first phase of a regional transportation center being built in the 244-acre historic railyards adjacent to the existing station at Fifth and I streets.

The design and location of the future transit hub must still be determined. Two weeks ago, Thomas and another development team proposed incorporating the transportation center into a new Kings arena if the arena were built adjacent to the existing train station.

On Tuesday, the California Department of General Services closed off a dozen parking spaces next to the train station for work expected to begin soon on upgrading the station's electrical system, said Linda Tucker, spokesperson for the city's Department of Transportation.

Those spaces won't be available until May 15. The station's water system is also being updated at this time, she said.

City workers are designing new front-entry canopies for all the doors and strengthening wall and floor connections, she said.

Workers have also secured the building against pests, updated the natural gas system, repaired basement leaks, removed some lead paint and asbestos, and done other work since the city bought the building on behalf of its residents in 2006. Amtrak leases the station from the city.

Sacramento Valley Station sits on a major national trade route, the Central Corridor, whose western junction is the high-volume Port of Oakland. Freight and passenger trains share three tracks in a configuration set up about the time the Sacramento station was built in 1925.

Track relocation work will include building tracks devoted to freight, in order to allow a higher volume of freight trains to move more quickly through Sacramento. Freight and passenger tracks also will be moved at least 300 feet north and straightened to allow for longer trains.