In under 48 hours, SPAWN staff, interns and Clif Bar & Company volunteers built a rain garden at the San Geronimo Golf Course to stop a rush of pollution and sediment from cascading into key endangered coho salmon habitat.

The rain garden intercepts golf course runoff allowing water to settle and filter out sediment and any toxins before entering San Geronimo Creek.  This easy, simple, “bio-engineering” technique can be used anywhere to capture stormwater runoff from roofs, driveways, parking lots, etc.

SPAWN and the Golf Course worked together to design a plan to slow the flow of the stormwater by hole No. 6, and allow it to infiltrate into the ground in a more natural manner. The entire project was completed in under two days.

Thanks to Clif Bar and its employees for volunteering!

First the golf course and SPAWN staff designed the dimensions and features of the bioswale, then the Golf Course used their backhoe to excavate the swale and level the area near hole no. 6. Second, SPAWN staff, interns, and volunteers shaped the terrain, laid erosion control fabric, and seeded the area with native bunch grasses. Lastly, the corporate volunteer crew from Clif Bar & Company planted over 45 native wetland plants in one day.

The stormwater which once rushed directly into the creek, now spills into a rocky-bathtub of sorts, and then into a 15 by 30 ft basin filled with native wetland plants whose roots soak up the water over a gradual uphill slope that allows for the water to gradually enter the creek, guarding against erosion.

“This project is a low-tech, cheap solution that is extremely effective,” explained Preston Brown, watershed biologist. “If everyone in the San Geronimo Valley built a rain garden that allowed stormwater from a roof or driveway to sink into the ground rather than rush into the creek it would make a huge difference for the coho,” he added.

If you are thinking of building a rain garden, now is the time to start planting native vegetation, because the plants will have time to stabilize the ground prior to strong down pours. If you’d like more information about rain gardens, please email