Coho salmon will soon swim free again thanks to dam-removal agreement

A dam that for decades prohibited coho salmon from reaching its spawning habitat in the Santa Cruz Mountains will be taken down starting this summer after building materials company Cemex and the Sempervirens Fund reached an agreement, the environmental group announced Wednesday.

The dam, which is located on Mill Creek, is on the 8,532-acre San Vicente Redwoods property, which was formerly owned by Cemex. The company sold the property to conservation organizations Sempervirens Fund, Peninsula Open Space Trust, Save the Redwoods League and Land Trust of Santa Cruz County in 2011. Cemex has retained water and infrastructure rights on the property.

The 86,000-acre CZU Lightning Complex wildfires in August and September of 2020 burned all of San Vicente Redwoods and destroyed water lines situated on top of the dam. The lines supplied water to the community of Davenport in Santa Cruz County. The cement company funded rerouting and replacement of their water lines earlier this year and agreed to remove the dam.

Sempervirens Fund expects dam removal to begin late this summer. In March, the group received a $550,000 grant made through the Open Rivers Fund, a program of Resources Legacy Fund supported by the Menlo Park-based William and Flora Hewlett Foundation. The grant will be supplemented by support from individual donors for ongoing restoration work at San Vicente, Sempervirens Fund leaders said.

San Vicente Redwoods is the largest privately held redwood forest in the Santa Cruz Mountains. The property, which contains logged and old-growth redwoods and eight creeks, provides habitat for many wildlife and plant species important to the region, including the endangered coho salmon. Habitat for salmon is scarce and barriers such as dams diminish their access to critical waters and gravelly sediment needed for their spawning grounds, according to the Sempervirens Fund.

While rare in the Santa Cruz Mountains, dams like the one on Mill Creek were built in the early 20th century to support redwood logging. Their utility has long since expired and removal is the best option for repairing the ecosystem, the organization said.

“The dam has impeded coho salmon from reaching desperately needed spawning habitat for decades. Removing the dam will restore not only the creek flow, but improve sediment conditions critical for spawning. A restored creek is also essential to the health and resilience of the surrounding redwoods and other nearby and downstream habitats at San Vicente,” Sempervirens Fund Executive Director Sara Barth said in the statement.

The Resources Conservation District of Santa Cruz County is also partnering with the Sempervirens Fund on the project’s restoration efforts.

“This project, identified as a priority action for recovery of salmonids in the San Vicente Watershed, is an important step forward in helping threatened and endangered steelhead and coho salmon along the Central Coast of California,” district Executive Director Lisa Lurie said in the statement.

The Sempervirens Fund and its partners will monitor and survey fish populations in Mill Creek and the greater San Vicente watershed, including coho salmon, steelhead trout and lamprey eels, with help from environmental DNA techniques. In the past, researchers introduced large woody debris, which has already reinvigorated steelhead populations by creating cover and shallow pools for breeding. The fish have been seen in the creek this season, they said.

People as well as salmon will benefit from the dam removal and restoration, Santa Cruz County Supervisor Ryan Coonerty said in the statement.

“Mill Creek is part of a critical watershed on the North Coast, which provides drinking water for the town of Davenport and habitat for coho. The Mill Creek dam removal project is truly a win-win project as it will improve water quality both for the residents and the coho,” he said.