CA - Risky dam above Marin County beach needs to come down, park service says
It was built decades ago to create a pond in Tennessee Valley
The National Park Service is advancing its plan to remove a Tennessee Valley dam that has been classified as having a high risk of failure and threatens public safety at a nearby beach.
The California Coastal Commission voted unanimously Thursday to endorse the park service’s proposed project, which also includes restoring acres of wetland habitat that has been affected by the dam over the decades.
“We have the removal of a dam for public safety but also to restore some of this natural process in the Tennessee Valley,” Kate Huckelbridge, the commission’s executive director, said before the vote.
Built in the early 1960s by the former landowner to attract waterfowl for hunting, the earthen dam was one of the many artificial structures inherited by the National Park Service after the Golden Gate National Recreation Area was founded in 1972. The dam and its holding pond are accessible on the Tennessee Valley Trail and are about 900 feet from Tennessee Beach.
In 2017, the U.S. Bureau of Reclamation classified the dam as having a high risk of failure because of erosion, lack of compliance with seismic engineering standards and poor overall condition. The park service closes the Tennessee Valley trail during storms as a public safety measure.
Carolyn Shoulders, a project manager with the park service, said the agency has envisioned removing the dam since 2014 as part of work to restore habitat in the Tennessee Valley.
“I think that this is one more project where the Golden Gate National Recreation Area is transitioning a lot of the inherited landscapes to a natural landscape with native vegetation,” Shoulders said. “The recreation area inherited a lot of agricultural lands and we’ve been transitioning a lot of it to more natural habitat. This is one more example of that.”
By removing the dams, the agency will work to restore the area to natural wetland habitats and prevent erosion issues caused by the dam.
The estimated $10 million project would drain the pond and remove the dam. In addition to the new wetlands that would be created, three new ponds fed by groundwater and springs will be built to make up for the lost habitat for endangered red-legged frogs living in the pond. Shoulders said the existing pond has been reduced to about half of its original size due to sedimentation.
