Bolinas Beach closed as wastewater descends from bluff

Bolinas Beach, a popular surf spot, has been closed indefinitely because of wastewater contamination believed to be emanating from the gridded Big Mesa area of the town.

Sarah Jones, director of the Marin County Community Development Agency, said members of her staff spotted effluent coming out of Big Mesa’s eroding cliff face above the beach when visiting the town to inspect a site for a permit application on Sept. 5.

Jones said the staff members identified wastewater coming off the bluffs at a couple of dozen spots. “In some areas the water was seeping and in others it was flowing,” she said.

“Our staff observed some high volume flows of up to 10 gallons a minute or more, so that is a lot of liquid coming out and going into the ocean,” Jones said. “This would not be what we would expect to see from one person’s septic system failing. There seems to be something bigger going on.”

The effluent is pooling in some spots on the beach, forming white crystals, which indicates it contains urine.

“Testing of samples taken showed high levels of bacteria, including coliform, E. coli and enterococcus, indicating that the liquid is likely wastewater and could pose health risks,” a notice issued by the county says.

The Bolinas Community Public Utility District has confirmed that its water is safe to use from the tap, according to the county notice. The district told county officials that it tests the water weekly and that it comes from a source outside the mesa.

County health officials, however, recommend that residents living in the Big Mesa area refrain from using well water for drinking, bathing or irrigating food gardens at this time. They advise residents to use bottled water or, alternatively, test their water and treat it if necessary.

“The well water hasn’t been tested just yet,” Myisha Hogan, a spokesperson for the county, wrote in an email. “However, CDA is working with our health officer and the folks at Health and Human Services to develop a plan for testing.”

Jones said ocean water in Bolinas has been tested.

“We didn’t find that the levels were above the safe recreation levels, but there is still sewage on the beach so the beach needs to stay closed,” she said.

Health officials are struggling to determine the exact cause of the pollution.

“It seems clear that it’s somehow related to the septic systems up on top of the hill,” Jones said, referring to the Big Mesa area. “But we don’t know which ones, whether it’s connected to the overall septic load or what relationship it might have to the erosion of the bluffs.”

The people living in the Big Mesa area are not connected to the utility district’s septic system and use private septic systems. These systems consist of tanks that temporarily store solid waste and pipes that disperse liquid waste into leach fields. The soil in the leach fields is designed to strip the bacteria from the waste before it gets to the water table.

During a community meeting in Bolinas on Wednesday, Dr. Lisa Santora, the county’s public health officer, suggested that sea-level rise might be contributing to the spillage. Sea-level rise caused by climate change can raise groundwater levels, thus reducing the area of the drainfield where waste is treated.

During the meeting, members of the public said pools of water accompanied by white crystals have been evident on the beach for some time now.

“We’ve heard anecdotally from people that it’s been going on for a while,” Jones said Friday.

She said the county lacks permit records for all of the private septic systems in use in Bolinas.

“So we don’t know that the systems are or whether they’re adequate for the houses,” she said. “Some of them are really old. They might even use redwood tanks or something that’s definitely not a modern septic system.”

Marin County has struggled for decades to get residents to upgrade their septic systems. The process is expensive and often more difficult in coastal areas with shallow soils.

In 2021, county supervisors approved the installation of class II septic systems, which require a minimum separation of 2 feet between the highest level of groundwater and the bottom of the dispersal systems, instead of class I systems, which are typically required and mandate a minimum separation of 3 feet.

One of the reasons for the change was that the class I systems were considerably more costly than the class II systems. It was hoped the lower cost would spur more residents to install a permitted system.