Two major road projects on different sides of Napa County – a Devlin Road bridge in the airport industrial area and a Silverado Trail retaining wall near St. Helena – have seen eye-catching action in recent days.
On Tuesday and Wednesday, a six-story-tall crane swung 92-foot-long steel girders into place for a Devlin Road bridge over Fagan Creek. The crane is tall enough that the Federal Aviation Administration had to clear its use because of nearby Napa County Airport.
“We’re in the flight path,” county Engineering Supervisor Graham Wadsworth said on Wednesday morning as he watched construction activities. “We had to notify pilots from the airport that the crane is going to be operating.”
The crane boom is lowered at night lest an unsuspecting pilot fly into this towering metal spike in the dark.
On Wednesday, the crane swung the last of the eight steel bridge girders manufactured in Antioch into place. The girders form the skeleton of the bridge deck and will be covered with metal plates and concrete.
Napa County for several decades has been building Devlin Road in phases. This latest 1,100-foot phase will link Airpark Road and Tower Road.
The ultimate goal is for Devlin Road to link Soscol Ferry Road and Green Island Road, a distance of 3.5 miles. Then it will serve as a parallel route to congested Highway 29 between the cities of Napa and American Canyon. American Canyon could begin the final, southernmost segment in 2020 or 2021.
As workers build the new Devlin Road bridge, they watch for the California red-legged frog, western burrowing owl and western pond turtle. A pamphlet tells them to inspect trenches for wildlife before filling. If they see a rare species, they are to stop work until the frog, owl or turtle leaves on its own.
The project is costing $8 million, with money coming from traffic impact developer fees and a CalRecycle grant. CalRecycle is providing $385,000 for the county to use 310,000 shredded tires as roadway fill adjacent to the bridge instead of imported soil.
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The Devlin Road segment is being built by Ghilotti Construction Co. of Santa Rosa. County officials said it could be finished in December.
Meanwhile, workers are stabilizing a hill adjacent to Silverado Trail at Pratt Avenue near St. Helena. The rain-saturated hill during the huge January 2017 storms sent more than 20 truckloads of compressed volcanic ash tumbling down on The Trail, some pieces as big as a Volkswagen.
Ever since, a temporary fix of stacked concrete barricades has narrowed Silverado Trail next to the hill. Workers on Tuesday did the concrete pour for the permanent wall that will keep falling debris from smacking a passing car.
This massive wall will be 280 feet long and vary in height from 5 feet to 23 feet. The slope behind the wall is to be backfilled with concreted rock extending 5 feet to 47 feet above the wall to buttress the unstable hillside, a county report said.
“The wall will have a texture that will give it a more natural feeling,” Public Works Director Steven Lederer said.
As an example, he mentioned the retaining walls along Highway 12 in Jameson Canyon. Those concrete walls as high as 55 feet were sculpted by workers with trowels and stained brown to look like rocky outcroppings.
The Silverado Trail hillside stabilization project could be done in early November, county officials said.
Construction being done by McCullough Construction Inc. of Arcata is costing $1.9 million and the total project $2.9 million. The county expects much of the cost to be reimbursed by the Federal Highway Administration.