A major effort to restore the habitat for endangered coho salmon in Lagunitas Creek has received a $4.6 million infusion from the state.

The Marin Municipal Water District plans to use the grant to hire a contractor to do restoration work for phase one of the project, staff said at a presentation to the finance and administration committee Thursday.

“The grant also includes funding for a natural resources technician position here at the district,” said Jonathan Koehler, the district fisheries program manager. The position is for two years.

The committee recommended that the board accept the funds and authorize the district general manager to sign the grant agreement. A resolution is expected to be presented to the full board next month.

“$4.6 million is really an incredible amount of resources to bring to the district to help do really important work,” said committee member Monty Schmitt, president of the water district board.

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, the agency said.

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.

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.

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.

The district plans to make the improvements in two phases over a period of four to six years beginning next summer. The grant is funding project phase one, which will involve installing the habitat structures and augmenting spawning gravel at six out of 13 planned sites. The grant will fund construction management and monitoring support, Koehler said.

The first phase is expected to take three years. 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.

“What a lucky organization we are to have this tremendous staff that is protecting Lagunitas Creek, one of the great coho habitats in the North Coast of California,” said Jed Smith, chair of the finance committee and a member of the district board. “This is just another phase in a long project, but super proud to be associated with it.”