Historic Crossing

Napa’s First Street Bridge gets major overhaul

By Greg Aragon

The old First Street Bridge has been demolished and the piers for its $15 million replacement are going up over the Napa River in the city of Napa.

“One of the neat things about the new bridge is that it looks like the one we are taking out,” says Jason B. Holley, acting senior civil engineer for the city of Napa. “We wanted to mimic the old bridge because of its historical value.”

Built in 1914, the old 155-ft-long by 60-ft-wide First Street Bridge was added to the National Register of Historic Places in 2004. It was constructed with reinforced concrete.

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But during the design of a 100-year flood protection plan for the Napa River started by the U.S. Army Corps of Engineers in 1999, the bridge was found to be structurally deficient, showing signs of age and standing 5 ft below the 100-yr flood elevation of 20.25 ft.

The new three-span bridge will stand 21.25 ft-high and measure 167 ft-long by 64 ft wide. When complete in August, the reinforced concrete, arch girder bridge will feature one lane of traffic in each direction, bicycle lanes and sidewalks.

The project team includes San Francisco-based MacDonald Architects; San Francisco-based TY Lin International, engineer; and Benicia-based American Civil Constructors, general contractor.

Because the bridge crosses a sensitive portion of the Napa River, crews were only allowed to construct in the water between July 1 and Oct. 15 to protect endangered fish.

Holley says during this “very tight time frame,” crews worked double shifts to demolish the old bridge, build cofferdams and construct new piers and abutments.

To beat the clock, construction documents were modified to allow pier walls and cages to be tied off-site in a nearby parking lot, while at the same time workers progressed with pier-footing construction in the water, says Chris Hodge, TY Lin deputy project manager.

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