Dozens of Washington Grove and Gaithersburg residents told officials from CSX Corporation that is should lower its railroad under the East Deer Park Bridge rather than raise the historic span to make room for double-decker trains.

At issue is 17 inches — the difference between the height of the bridge's understructure and the 21 feet needed to fit the taller rail cars.

CSX project leaders met Dec. 2 with more than 50 residents to explain four alternatives for the Gaithersburg-to-Washington Grove bridge, one of 61 structures in six states that need to be cleared as part of the rail giant's $840 million "National Gateway" project to enable its rail lines to ports in Baltimore, Hampton Roads, Va., northern New Jersey and Wilmington, N.C. to handle the double-decker cars.

Though work on the bridge could begin next year, CSX has not decided, officials said, whether to raise, lower, replace or eliminate the 63-year-old span — also known as "Humpback Bridge" — extending East Deer Park Drive over the CSX tracks and into Railroad Street. So far, CSX favors replacing the bridge and has deemed lowering the tracks as the most expensive and disruptive choice, officials said.

Lowering "a couple thousand feet" of track would take up to six weeks and cost as much as $4 million, Mike Hoey, CSX's National Gateway project manager, said at last week's forum at the Activity Center at Bohrer Park in Gaithersburg.

One of the two tracks would be closed while equipment dug more than three feet to build a new railway bed. That would disrupt trains along the Brunswick line and spill onto other rail branches, Hoey said.

The work would be complicated by the narrow gulch under the bridge, a MARC passenger platform and the at-grade crossing.

The predominantly Washington Grove audience said that the inconvenience was worth it.

Given the promise of greater revenues from carrying more freight in double-decker cars, residents argued that the company can afford to lower the tracks.

"I'm convinced that if there's a will, there's a way. If you put your engineers to work creatively, you all can come up with something," said Nancy Helme, who has lived in Washington Grove for 26 years. "Whatever drop in the bucket it is to lower the tracks, we as a community think it's worth it. You've got to give a little; we're giving up a lot."

CSX will review all four options over the next few months, ahead of another forum in Gaithersburg, said CSX spokesman Bob Sullivan.

Monday night, the Washington Grove town council passed a resolution in support of lowering the tracks. Gaithersburg city leaders want to see what CSX comes back with before taking a position, said Mayor Sidney A. Katz.

After a CSX assessment in 2007, the preferred option was to replace the bridge, Hoey said. CSX can build a bridge that expresses historical and cultural characteristics of the existing bridge.

Raising the bridge will wreak less environmental damage and disrupt less traffic than lowering the tracks, Hoey said — but would cost up to $2 million.

The defense of the bridge in Washington Grove is driven by residents' belief that it embodies the community's railroad-linked past. The town started as a Methodist camp founded a few yards from the B&O Railroad in the 1870s.

A few years ago, Washington Grove residents fought off a county proposal to replace the bridge with a two- or four-lane span. The county settled on a $450,000 project this summer to replace elements of the bridge's timber support structure.

Last month, the Maryland Historic Trust determined that the bridge is eligible for the National Register of Historic Places, which requires the applicant to consider — but is not prevented from — the possibility of disturbing the area. Washington Grove is on the register, so MHT will make sure impacts there are weighed, said Tim Tamburrino, an MHT preservation officer.