Stanford scientists confirm that polluted groundwater flows from coastal septic systems to the sea

Daniel Strain in the Stanford University News: Faulty septic systems have long been blamed for polluting some of California's most popular beaches. Yet few scientific studies have established a direct link between septic systems and coastal contamination.

Now, in the first study of its kind, Stanford University researchers have tracked a plume of polluted groundwater from a septic system to one of Northern California's top recreational beaches. The researchers say their findings could be an important step toward improving wastewater management in coastal communities throughout the United States.

… Since 2008, Boehm and her Stanford colleagues have been studying the flow of groundwater from a large septic system at Stinson Beach, a favorite destination of swimmers and surfers about 20 miles north of San Francisco that's managed by the National Park Service. The study is supported by an Environmental Venture Projects grant from Stanford's Woods Institute for the Environment.

…Prior to this study, scientists had never observed in detail a plume of contaminated groundwater flowing from a septic system to the sea. To track groundwater pollution at Stinson Beach, the research team obtained a permit from the National Park Service to install a network of 120 monitoring wells near a large septic system close to a beach parking lot that collects wastewater from nearby homes and public toilets.

…"Our results will provide valuable insight into the fate and transport of contaminants from septic systems along the California coastline and elsewhere," Boehm said. "Predicting where, when and what magnitude of environmental pollution can be expected will help guide regulators in deciding which coastal settings are appropriate for septic systems."…

Bolinas Bay (left) and Stinson Beach (right) as seen from California State Route 1 looking northwest. Shot by Stepheng3, who has released the image into the public domain