A $539,590 project to boost tidal flow and enhance the habitat in Greenbrae marsh is set to launch next week.

The effort to improve the area at Hal Brown Park along Corte Madera Creek is “important for the health of the marsh,” said Christopher Bramham, superintendent of capital projects with Marin County Parks.

“The goal is to improve tidal exchange in and out of Creekside Marsh from Corte Madera creek so more wetland vegetation can expand into some of the low-lying areas that are now a bad soil where plants have difficulty growing,” he said.

Water flow should improve once the single 60-inch culvert, immediately upstream from the Bon Air Bridge, is replaced with three culverts of the same size.

Thompson Builders Corp., of Novato, is expected to begin construction on the culverts sometime next week, Bramham said.

Construction crews cannot begin until they have completed environmental training, he said. The project is expected to be finished in late October.

“It’s very exciting,” said Sandra Guldman, vice president of Friends of Corte Madera Creek Watershed, which helped push through the project and obtain grant funding. “When you put a lot of effort into planning, you hate to see the plans go belly-up or be dragged out. It’s very nice to actually do it.”

Increased tidal flow will enhance the marshlands by replacing its hard, gravelly soil —which does not support vegetation — with more fertile soil that can be replanted with native species.

The project also will benefit the species that inhabit the marshlands, including the Ridgeway’s rail and salt marsh harvest mouse, which are both listed on the federal endangered species list, according to Marin County Parks. Paths too close to habitat will be closed and replanted.

A portion of the pathway also will be repaved. A detour will be available, Bramham said.

“From the signal light on Bon Air Road, there’s a small pedestrian bridge you can take to Hal Brown Park,” he said. “We’re detouring users over the pedestrian bridge and along the bike path on Bon Air Road and then they can go on the street.”

The project is being financed by mitigation funds, grants and contributions from the Ross Valley Sanitary District, the California Regional Water Quality Control Board, Transportation Authority of Marin, Friends of Corte Madera Creek Watershed and Marin County Parks.