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Aug 14, 2023

Marin district outlines plans for salmon habitat restoration

The Marin Municipal Water District is preparing for one of its larger restoration projects on Lagunitas Creek with some new approaches in its effort to bolster endangered coho salmon populations. The

The Marin Municipal Water District is preparing for one of its larger restoration projects on Lagunitas Creek with some new approaches in its effort to bolster endangered coho salmon populations.

The project, which has an estimated cost of $10 million to $12 million, is set to begin next summer. The district plans to use both proven and new strategies to mimic the natural habitats found in the creek before the construction of dams, utility staffers told the board during a project update on Tuesday.

The Peters Dam at Kent Lake blocks large pieces of wood and gravel from moving downstream where salmon and steelhead spawn. The debris is vital for creating gravel beds and deep, cool pools in the creek where adult coho salmon spawn and juveniles grow during their 16-month stay in freshwater.

“This channel really is starving for both of those things,” Jonathan Koehler, the district fisheries program manager, told the board.

For the first time in its management of the creek, the district plans to add gravel to the channel to restore lost spawning beds. Nearly 12,300 tons of gravel — a weight about 2,000 tons heavier than the Eiffel Tower — would be added at three sites along the creek.

“We have not done that in Lagunitas Creek and it’s an exciting advancement in our restoration efforts,” Shaun Horne, the district watershed resources manager, told the board.

While a new tactic for Lagunitas Creek, supplementing gravel to restore salmon habitat has benefitted other salmon strongholds in the state such as the Trinity River, said biologist Preston Brown of the Olema-based Salmon Protection and Watershed Network, or SPAWN.

“While they are doing some exploratory testing of methods, those methods such as gravel augmentation have proven effective elsewhere,” Brown said. “It is a no-brainer to me to add gravel below a dam.”

SPAWN, which monitors and performs restoration work in San Geronimo Creek, a Lagunitas Creek tributary, is recommending that the water district create a new program to continue adding gravel and wood structures in perpetuity.

“As long as the dam is in place, gravel is still going to be held behind it,” Brown said.

Lagunitas Creek is home to the largest population of Central Coast coho salmon from Monterey Bay to the Sonoma County-Mendocino County border. Once believed to number in the thousands with a habitat stretching to tributaries on Mount Tamalpais, the population of coho salmon has significantly diminished since the construction of dams. Specifically, Peters and Seeger dams have blocked fish from accessing about half of their historic spawning grounds.

To be removed from federal endangered status, Lagunitas Creek coho must lay at least 1,600 nests for three consecutive winters. In the past 25 years of district monitoring, the counts have not reached half that amount.

In addition to gravel, the district will install nearly 300 large logs into the streams to create deep pools and riffles and hold gravel to benefit salmon and other species. Koehler said these features will be installed in areas where the creek bed has “mediocre” habitat. In these areas, salmon are more vulnerable to warmer temperatures, predators, insufficient food, strong storm flows and a lack of adequate spawning beds.

The logs will be ballasted with heavy boulders to prevent them from being moved downstream, Koehler said.

The district plans to make the improvements in two phases over a period of four to six years beginning next summer. The first phase of construction at eight sites is expected to take two to three years, Horne said. The timeline depends on what conditions the California Department of Parks and Recreation places on the project because many sites are located in Samuel P. Taylor State Park.

The project is being funded primarily by grants. The district has secured about $3.2 million in state and federal grants to complete designs and permitting of the first phase of the project. The agency is also awaiting word on a $4.6 million state grant application that would fund the construction of the first eight sites. Horne said the district has also applied for a $600,000 grant to begin designs on the second phase of the project.

The agency says the project is exempt from a full environmental review under California’s “Cutting the Green Tape” initiative, which exempts fish and wildlife restoration projects through 2024. The agency says the exemption will reduce project costs by about $200,000.

On Tuesday, district board members discussed the potential of monitoring for impacts of climate change on salmon populations and more scientific analysis of the effectiveness of the district’s restoration efforts.

“Climate projections have unfortunately shifted for the worst,” said Monty Schmitt, the board president.

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