As part of an environmental overhaul of Muir Woods National Monument, crews have started work on a half-mile segment of Redwood Creek to restore habitat for endangered coho salmon and rainbow trout. And park visitors will get to witness it.

“A big decision for us was to keep the park open during this period of time because we think a really important part of our story is for the public to see restoration in action,” said Mia Monroe, a spokeswoman for Golden Gate National Recreation Area.

This month, crews will begin preparing to remove young coho salmon from sections of the creek before water is removed. Once the water is removed, crews will work to remove large concrete rip-rap structures built by the Civilian Conservation Corps during the Great Depression to prevent erosion and flooding in the area, Monroe said.

“The result was a straight channel with no vegetation, no hiding spots and very little food,” Monroe said.

Since then, coho salmon populations on the creek have reached critically low levels but have shown some signs of recovery. Redwood Creek salmon are so endangered that conservationists have resorted to “heroic efforts,” including captive rearing, said Todd Steiner of the Salmon Protection and Watershed Network. The Olema-based organization has partnered with state and national park officials to restore coho salmon populations in Marin watersheds.

“Muir Woods and the National Park Service are at the forefront of improving critical habitat for salmon and steelhead, and these current efforts are a welcome addition to repairing the historical mistakes of the past,” Steiner said. “These efforts give these species a fighting chance at survival and recovery.”

Crews will now work to recreate the natural habitat by digging deep pools, installing large pieces of wood in the creek and planting vegetation. Crews plan to return in 2022 to restore another half-mile of creek.

The project is estimated to cost less than $1 million, with the California State Coastal Conservancy providing a $155,000 grant to the project, Monroe said. Other partners on the project include California State Parks, the North Bay Conservation Corps and One Tam.

The work will require the temporary closure of some trails in Muir Woods as well as the Alice Eastwood Group Camp site and nearby trails in Mount Tamalpais State Park, according to Alexis Jones, supervising park ranger. The closure will last until Aug. 15 to allow for equipment to move in. Another closure will take place from Oct. 31 to Nov. 7.

Redwood Creek’s restoration is just one piece of the national monument’s “redwood renewal” project, which seeks to protect sensitive habitat by relocating and enhancing trails, bridges, parking lots, sewage and wastewater systems in the national monument. The project began in 2017 with the implementation of the parking reservation system and is expected to last into 2023.

More information about the project and trail closures can be found online at bit.ly/2WgV1Bf.