Rail improvements aimed at helping Volkswagen deliver cars made at its Chattanooga plant around the country are slated to start in August.

The $6 million in taxpayer-funded work is likely the biggest rail overhaul in and around the former Volunteer Army Ammunition Plant complex at least since the Vietnam War and potentially World War II.

"We're taking it from those eras to the current day," said Tim Andrews, who directs the Hamilton County Railroad Authority, about the rail infrastructure that's publicly owned but ties into that of private carriers.

Mr. Andrews said the work includes expanding the key rail overpass at Bonny Oaks Drive near the Hickory Valley Road entrance to Enterprise South industrial park where VW is building its $1 billion plant.

The railroad span will go from a single track to a three-track bridge, he said. Also, the bridge will be widened to permit the possible future addition of lanes to Bonny Oaks Drive, Mr. Andrews said.

"The bridge is narrow and low," he said. "We're trying to take into account what the vision is for that area five, 10, 15 years down the road."

Mr. Andrews said Bonny Oaks will stay open during the work, except for a possible occasional nighttime closing.

The city and county are seeking a $3 million federal grant to help pay for the rail projects.

Mr. Andrews said project work should take 10 months at the longest.

"We want all this done and in place to support (VW's) startup," he said.

The company plans to begin production in early 2011 and produce 150,000 vehicles annually.

Workers for paint shop builder Walbridge on Thursday placed the last steel truss into place, VW spokeswoman April Wortham said.

The paint shop should be weather tight by September and equipment then ready to be installed, she said.

Don Huff, an area director in Atlanta for the U.S. Commerce Department's Economic Development Administration, said the grant money for the rail project would come from the federal stimulus package.

"Within two months, we could have approval," he said. "It's a high priority for processing."

Mr. Andrews said if the grant comes though in September, the plan is to get most of the other bids out shortly thereafter.

He said the rail improvements aren't just for VW, but also for other companies such as Gestamp Corp., which announced this summer it will build a $90 million plant to supply VW.

Other rail improvements include:

* Upgrading a Hickory Valley Road bridge to accommodate three rail tracks, adding two of the tracks.

* Fix a failing timber box culvert between Noah Reid Road and Hickory Valley Road.

* Proposed grading work for VW lead track approaches that will enter the VW facility.

VW will build its own loading ramps and whatever it needs for handling finished cars, Mr. Andrews said.

"That will be within its plant facility area and by design match up to what we're doing," the rail authority official said.

He said it's typical for auto assembly plants to transport by rail a large percentage of the vehicles produced.