Sixty miles of prime spawning ground in the Napa River and its tributaries are now open.

On Friday, representatives from the county and environmental groups celebrated the completion of a $1 million project that eliminated a concrete apron under the Zinfandel Lane bridge. The apron was blocking Chinook salmon and steelhead trout from swimming upstream to their preferred spawning grounds.

Over the years, erosion formed a ledge and the jump necessary to get upstream became so daunting that all but the very strongest fish were stranded on the downstream side.

“A lot of Chinook salmon would spawn just downstream, right on top of each other,” said Jonathan Koehler, a fish biologist from the Napa County Resource Conservation District whom officials credited with bringing the barrier to the county’s attention about seven years ago.

“I have video of fish bashing their heads against the old concrete apron,” he said. “It was heartbreaking.”

The new passageway is “not even going to be a blip on their radar screen,” Koehler said.

The barrier also interfered with younger fish swimming downstream toward the ocean, said Rick Thomasser, watershed and flood operations manager for the county.

The new structure, completed in October, includes a fishway, a bypass channel and a trough to dissipate the energy of the water and prevent downstream erosion. 

Sam Schuchat, executive director of the California Coastal Conservancy, said the Napa River was recently identified as one of eight “anchor watersheds” for Chinook and steelhead in the Bay Area.

“This project frees up 50 percent more habitat for fish,” he said. “So it’s a lot of bang for our fish buck.”

The project was financed by county Measure A funds, a $400,000 grant from the California Coastal Conservancy, and design and engineering funding from the U.S. Army Corps of Engineers and the Gasser Foundation.

The county will monitor fish passage and spawning behavior to verify that the fish are using the new passage.

The project should also please history buffs interested in preserving the Zinfandel Lane bridge, which was built in 1913.

Geotechnical studies raised doubts about the stability of the bridge’s central pier, Thomasser said. So in addition to the fishway and bypass channel, an underwater cutoff wall was installed to tie the pier into the bedrock and prevent erosion from destabilizing the bridge.

“We got a two-fer here,” said District 3 Supervisor Diane Dillon. “We got wonderful fish passage and we helped this old bridge.”

Dillon thanked vintner and vineyard manager Davie Pina for championing river restoration on behalf of landowners, and Kohler for identifying the barrier and working on a solution.

The bridge apron was the most serious fish barrier in the watershed, but the county is seeking funding from the National Oceanic and Atmospheric Administration to fix another 20 barriers, said Leigh Sharp, executive director of the Napa County Resource Conservation District.

In addition to the $400,000 grant for the Zinfandel Lane bridge project, Schuchat announced that staff from the California Coastal Conservancy will ask their board for another $1 million for further restoration work along the Napa River.

Officials planted eight oak trees along the eastern bank of the river to commemorate the project’s completion.

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