A California Red-legged Frog
photo credit: NPS/Kirke Wrench

Hike through Marin’s Tennessee Valley and you’ll pass by a small duck pond set just back from the beach. Holding in the pond: a small earthen dam - whose days are numbered. 

The dam was originally built by a private landowner around 1960 according to Julian Espinoza with the National Parks Service - the same time that developers attempted to build a planned city of 30,000 called Marincello in Tennessee Valley and the surrounding Marin Headlands.

"The pond that is impound by the dam was used for duck hunting, and as you might imagine, wasn't engineered to today's standards," Espinoza said. "So the dam can't be stabilized without completely rebuilding it, but there's not any ecological reason to maintain it. So as a result, we are planning for its removal."

Tennessee Valley is part of the Golden Gate National Recreation Area, and Espinoza said the dam has been on the Park Service’s radar for some time.

"It was identified for removal as early as 2014," Espinoza said. "The most recent actions that have happened on it have had to do with the compliance work for the project. So we began the environmental assessment in August 2022 and had a 30 day public comment period in October of that same year."

Espinoza said the removal project has received broad support thanks to the improvements it will reap to the surrounding habitat and nearby trail, but he said removing the pond come at a cost.

"It is, however, breeding habitat for California red-legged frogs, but because of the way the pond was constructed and because of its age, it's filling with sediment and it eventually will not function as habitat," Espinoza said. "So as part of the project, our plan is to instead build new ponds elsewhere in the watershed to maintain that habitat."

Unique in its blend of natural and urban environments, Espinoza said projects like the dam removal are part of the balancing act maintained in the Golden Gate National Recreation Area.

"Private landowners during that period of time didn't really have the sense of the kind of destructive or harmful environmental effects that the construction of such a dam would have," Espinoza said. "This is something that would never have been built if we had always owned that land. It's really just us correcting something that someone else had constructed now more than 50 years ago."

The final dam removal and habitat restoration remain at least a year away.