A proposal to replace the Belmont Bridge with an underpass that would travel below the CSX railroad would cost nearly twice as much as building another bridge, according to a report from Charlottesville staff.

The bridge would cost just under $15 million, whereas the underpass option would cost $27.3 million. The city hired the construction management firm Barton Malow to develop the cost comparisons after a February public meeting.

The City Council decided in 2008 to replace the bridge, which was built in 1962, rather than to repair it. The Virginia Department of Transportation’s six-year program contains $14.6 million in funding for the project.

MMM Design was hired to develop a design, but the process was reopened after some residents lobbied for alternative designs.

Filmmaker and Belmont resident Brian Wimer held a design contest called Project Gait-way to solicit new ideas, a process that coincided with the first all-school project by the University of Virginia School of Architecture.

The winning entry envisioned an at-grade pedestrian crossing, but that option was a non-starter because permission from the railroad would be required.

After the contest, the city looked at all of the entries and advanced an underpass concept to serve as an alternative to the bridge replacement project. A schematic was created by Siteworks Studios and architect Jim Rounsevell.

Rounsevell placed second for his design that featured an iconic pedestrian bridge that connected to the nTelos Wireless Pavilion.

The public was invited to weigh in on the two concepts at a meeting in February. However, many of the underpass proponents expressed skepticism about the city’s original $30 million cost estimate.

Since then, city officials commissioned Barton Malow to develop a new cost estimate for both projects to allow for a better cost comparison.

“In order to provide an equal comparison both were reviewed under the assumption that vehicular traffic along Ninth Street would not be stopped except for minor interruptions at non-peak times,” wrote Chris Weatherford, project manager for Barton Malow, in a letter to the city.

The budget assumes a 5 percent contingency because the MMM Design plans are only partially completed. The underpass option assumes a 15 percent design contingency because the project has yet to be fully reviewed by the city or the state.

“Like the bridge replacement, the underpass construction plan starts with the idea that two lanes of vehicular traffic will be maintained throughout,” wrote Jim Tolbert, the city’s director of neighborhood development services, in a staff report. “The first phase of construction for the underpass will start with the new bridges for the railroad, Avon Street and Water Street, respectively.”

Barton Malow and the city also corresponded with neighboring businesses and CSX to determine if they would support an underpass. Railroad officials would have to give permission, and will only do so if 24-hour-a-day operations are not affected by construction.

The city also said that the underpass option would eliminate the current tunnel that provides a link between the Pavilion and the LexisNexis building. Lexis has a ground-lease from the Charlottesville Economic Development Authority that lasts through 2016, and Lexis can reduce certain payments if the tunnel is closed.

“LexisNexis strongly prefers the Belmont Bridge replacement, and not the underpass option, for the project,” said Jack Colasurdo, vice president of real estate for the firm.

Rounsevell said in an email that he believes the cost comparisons are flawed.

“What we have after seven months is an updated cost for a replacement highway overpass that the public categorically rejected,” Rounsevell said. He said he believes the city is artificially lowering the bridge’s cost estimate, and that the underpass option’s true cost could be reduced if developed through a design-build approach.

Rounsevell acknowledged that the underpass would be more expensive and challenging, but he said it’s a better long-term solution.

The council will be briefed on the matter at its meeting at 7 p.m. Monday at City Hall.