The last of downtown Napa’s new bridges, a replacement span over the Napa River at First Street near Copia, will be the fanciest.

A ribbon of illuminated glass will run the length of the bridge under each sidewalk, casting a glow onto the piers below. There will be four overlooks with benches at the corners, with lights perched atop sleek obelisks.

And per the wishes of neighboring homeowners and the Napa City Council, the railings will be green, not gray as preferred by a larger community group.

The color of the railings was decided Tuesday by the council, which also certified the project’s environmental studies. Those moves set the stage for construction to begin, potentially this summer.

More realistically, construction won’t start until 2008, giving the city more time to negotiate right-of-way acquisitions from adjoining properties, said Graham Wadsworth, a city engineer.

The replacement bridge will be two lanes, like the current one, but with eight-foot shoulders for bicycles and wide 10-foot sidewalks with green metal railings.

The design, by T.Y. Lin International and MacDonald Architects, has elements that echo the existing bridge, a 1908 span on the National Register of Historic Places, but reflects the aesthetic of today as well, Wadsworth said.

The 1908 bridge qualified for the National Register as the first concrete and steel truss bridge in Napa County. Napa County Landmarks nominated the bridge for the National Register in an effort to save it.

Ultimately, the City Council concluded it would be too costly to try to retain the old bridge, which risks collapse in an earthquake and obstructs water in a major flood.

Eliminating this flood obstruction is necessary to make the Napa River flood control project work, officials said. The new bridge will be four feet higher than the old.

Because of greater height, the new span will require elevating the First Street approaches. This will mean retaining walls three to five feet tall in front of four houses at the southeast corner of First and Juarez Street.

These neighbors requested a green railing, saying it would be more compatible with their Victorian-era homes than a gray railing.

Gordon Huether, chair of the city of Napa Planning Commission, and Bernhard Krevet, president of Friends of the Napa River, complained Tuesday that the color had been switched from gray to green at the last moment without public notice.

This seemed like an “end run around the public process,” said Huether, who believes that gray better matched the bridge’s contemporary design.

The council was unanimous that the wishes of those living closest to the bridge should be respected. These families will bear the brunt of the project, Councilman Peter Mott said.

“Their homes are already seriously impacted,” Councilman Mark van Gorder said. “It seems the very least we can do is grant them the color they want to have.”

When construction starts, this summer or next, it will close First Street between McKinstry and Juarez streets for 18 months.

The bridge, which will be 151 feet long, is estimated to cost $8 million, with the Federal Highway Administration paying 88.5 percent of construction costs. The city will pay the remainder from gas tax revenues.

“We’re struggling to get the project built as quick as possible so construction costs don’t continue to go up,” Wadsworth said.

In 2004, the construction component was estimated to cost $5 million. Today’s estimate is $7 million.

The city slowed the project to bring the public more fully into the design process and do additional environmental studies. Several extremely modern designs were rejected because they would have cost $2 million more.