4:30 p.m.After the shocking Interstate bridge collapse in Minneapolis, Napa public works officials are thanking their stars for the Napa River-Napa Creek flood control.

Because of flood control, Napa’s list of deficient bridges is shrinking fast, city officials said Thursday.

Six of Napa’s 25 city-owned bridges were considered deficient in 2003. When the flood project is completed, there will be just one problematic bridge left, said Graham Wadsworth, an engineer who heads the city’s bridge division.

Napa made national news in December 2003 when a worker was killed and seven injured during construction of the new Maxwell bridge over the Napa River at Imola Avenue. A partially completed section of the bridge came down when wooden supports collapsed.

“Construction is a very risky time for bridges,” Wadsworth said.

Flood control has been the catalyst for replacing the 1932 Third Street bridge over the Napa River and  the 1862 First Street bridge over Napa Creek.

Next year, the 1914 First Street bridge over the river will be demolished to make room for a replacement. Later, two stone bridges over Napa Creek at Coombs Street and Behrens Street will be removed.

Flood control also spurred the replacement of the antiquated state-owned Maxwell bridge on Imola Avenue. The two-lane lift bridge, built in 1949, was replaced with a soaring four-lane span.

When flood control is finished, “we will have solved all of our bridge inadequacies with the exception of the Main Street bridge,” said Larry Pollard, the city’s assistant public works director.

The Main Street bridge at Napa Creek dates back to 1860. It’s not only the city’s oldest span, but the oldest stone arch bridge in California, Wadsworth said.

This bridge gets a low score from Caltrans because of its vulnerability to collapse in a major earthquake, Pollard said. The city has no plans to replace this landmark structure, he said.

The lowest-rated bridge in the city was the Civil War-era bridge over Napa Creek at First Street. It scores a 30 on the state’s 100-point fitness scale, Wadsworth said. The slightly older stone bridge on Main Street scores a 48, he said.

The Behrens bridge, with a score, of 37, is considered so fragile that the city lowered its carrying capacity five years ago to five tons. It will be replaced with a pedestrian-only bridge when flood control moves up the creek.

The rest of the city’s bridges are considered in good shape, Wadsworth said. The one exception is the Trancas Street bridge over the river where dirt has begun to wash out around a center pier, he said.

This does not present any immediate threat, Wadsworth said. Repairs are scheduled for next summer, he said.

Caltrans is responsible for inspecting every bridge over 20 feet long in California every year or two, he said.

Napa County has 79 bridges in the unincorporated areas, some of them old stone bridges a century old. Barring earthquakes or a serious damage from a flood, they continuing to function well, said Bob Peterson, the county’s public works director.

The county has just two problem bridges, Peterson said. Caltrans recently discovered a cracked abutment to the Oakville Cross Road bridge at the Napa River.

Design of a new span is nearly finished, with construction to occur next year. In the meantime, the speed limit has been lowered to reduce bridge vibrations and the carrying capacity has been dropped to 12 tons, he said.

In Calistoga, the county is studying how to reinforce a bridge culvert on Greenwood Avenue where there has been erosion, Peterson said. This not a safety hazard, he said.

Caltrans also owns bridges on state highways in Napa County. The largest state bridge locally is the Butler bridge which carries Highway 29 over the Napa River.

This span, also called the Southern Crossing, is relatively new, built in 1978. It is nearly a half-mile long and 100 feet high.

A Caltrans representative was not available Thursday to comment on the condition of state-owned bridges in Napa County.