Two sets of water quality tests point to human waste


Water quality tests commissioned by the San Geronimo Valley Planning Group have largely confirmed the county’s continued findings that human waste makes its way into San Geronimo and Woodacre Creeks. 

Yet the planning group, which has long questioned the need for a large-scale solution to the contamination problem, continues to call for more testing before the county moves ahead with a proposed community wastewater system.

Meanwhile, the county’s agreement to purchase the former San Geronimo Golf Course has thrown a wrench into its plans for the wastewater system, whose treatment plant was proposed to be located on the course. Now county officials say they will conduct a comprehensive re-evaluation of the proposed alternatives after pending litigation around the county’s conversion of the golf course to a park is resolved.

Last week, Dr. Gary Anderson of the Lawrence Berkeley National Laboratory, which carried out the planning group’s tests last year, and Ken Naffziger, chair of group’s water quality committee, presented the new data. The results offered insight into where and when the contamination is occurring, and largely paralleled recent tests by the county.

“We want to know where exactly the hotspots are, if there are more localized problems,” Mr. Naffziger said. “Maybe we don’t need a whole new system.”

The problem of leaky septic systems in the valley was first identified in 2005 in response to anecdotal accounts from residents, who banded together to form the Woodacre and San Geronimo Flats Wastewater Group. 

Total maximum daily load requirements prohibit discharges of human waste into Lagunitas Creek tributaries, which the San Francisco Bay Regional Water Quality Control Board identifies as impaired water bodies.

Last March, the county released a feasibility study that presented possible remedies. The preferred alternative was a $14 million option that would transition 370 homes and businesses in Woodacre and San Geronimo from individual septic systems to a community wastewater system.

Though many residents favored the plans, the planning group had for years expressed concern that a community system would lead to greater development in the valley, as septic capacity remains the largest impediment to increasing square footage for many homeowners. To confirm the sources of contamination and the prevalence of pollution, the group zeroed in on the county’s efforts to conduct water testing.

“To justify the proposed treatment plant, supporters of the project frequently claimed that the Woodacre Flats was heavily contributing to contaminants in the Lagunitas Creek Watershed,” the planning group’s analysis of the new study out of Berkeley Labs states. “It therefore became critical that the [planning group] definitively determine the sources of any creek contaminants.”

As the county began working to secure funding from the regional water quality control board for microbial testing—taking over a proposal that originated with the Tomales Bay Watershed Council—the planning group took matters into its own hands. They looked to Lawrence Berkeley Labs for a new, cutting-edge technology and commissioned an independent study. Both studies began in the summer of last year. 

Dr. Anderson and his team used PhyloChip technology, which evaluates tens of thousands of microbes simultaneously in order to locate fecal contamination, to test water samples collected by the Marin Municipal Water District. (Most technologies only look at two or three microbes.)  

The $9,000 project, funded by the planning group and a $6,000 donation from the Nicasio-based Endurance Fund, examined samples from four dates from December 2016 through July 2017 at 13 different sites across the valley. Dr. Anderson said the lab afforded the planning group a large discount, as its contribution did not even cover the cost of materials.

Meanwhile, during the same time period, the county pressed ahead with its own water testing using a different kind of microbial testing called qPCR, or quantitative polymerase chain reaction. 

The county conducted multiple tests at three sites: one in Woodacre Creek just above the confluence of San Geronimo Creek and the others in San Geronimo Creek, above the confluence with Woodacre Creek and under the Meadow Way Bridge.

During last week’s planning group meeting, Dr. Anderson and Lorene Jackson, project manager with the county, disputed which scientific method was more “sensitive.” 

“While PhyloChip is an exciting technology with many uses, one of its best uses is trying to understand unknown sources of contamination,” Ms. Jackson explained in an email last week. “It was extremely valuable to know there were no sources of contamination that we’ve missed. Human waste was the primary source of contamination.”

Both the county’s and planning group’s studies showed markers of feces from birds, dogs, horses, ruminants and humans. The county’s study found markers for human waste at each of the testing sites, with the marker appearing at the Woodacre Creek site each of the four testing times, at Meadow Way three out of the four testing times and at San Geronimo above Woodacre Creek two out of the four testing times.

Markers for horses followed in prevalence, showing up three out of four times at two of the sites and half the time at the other location, whereas markers for cows and deer showed up less than horses, and dogs were of the least concern.

The Berkeley Lab showed a more fluid picture.

In December 2016, the first month in their study, all three of the sites tested were positive for human waste. (There was also exceptionally heavy rainfall that month.) In February, just two sites out of the 13 tested showed strong human markers, one at the mouth of Woodacre Creek and the other in San Geronimo Creek near Forest Knolls.

In both December and February, the strength of the human source signal at the mouth of Woodacre Creek became diluted as it traveled, leading to a marginal signal by the time the water reached a testing site at Meadow Way, across from Lagunitas School.

The tests found no human source signals in May and July, with the exception of what Dr. Anderson characterized as an anomaly at Montezuma Creek in May that was so high it likely indicated raw sewage from a single septic failure, he said.

Mr. Naffziger said the results proved that contamination was occurring in areas outside of the San Geronimo and Woodacre flats, the area that the proposed wastewater system would address.

“I’m not surprised at all that there are problems in septics in these other parts of the valley,” Ms. Jackson said to the Light last week. “We are very happy to work with other communities to upgrade their systems. From the beginning, we have been responding to a desire from property owners to do something.”

As far as the planning group’s call for further testing, Ms. Jackson was somewhat exasperated.

“Future testing would be great, though we would have to generate the funds. The results of these two tests confirmed what our concerns are. We’ve known this was a problem for over a decade and, from a human health perspective, as well as from a point of concern for the watershed, this has to be addressed.” 

The county had been on track to finish an environmental impact report for the wastewater system by January of this year, but the purchase of the golf course by the Trust for Public Land and the county’s agreement to buy it from that group derailed the process. 

Now, before the county can write an impact report, it will have to conduct a new feasibility study to adjust to the changed circumstances. In particular, the location of the treatment plant and how the water it generates would be used are up in the air.  

Though the different alternatives presented in the county’s 2017 study varied on the number of homes the system would serve, they shared a plan to send wastewater through a series of underground gravity and pressure lines to a 10,000-square-foot treatment plant, housed at the golf course. There, waste would be filtered and disinfected with ultraviolet radiation and then piped to one or two lined ponds large enough to accommodate a 100-year rainfall event.

Whatever its final size, the system has “some exciting potential,” Ms. Jackson said. 

Treated water from the communities in the valley would be clean enough to provide ongoing irrigation for a number of purposes—including community gardens or farms, landscaping or ball fields. Ongoing uses such as these might be preferable over seasonal irrigation for the golf course, she said, because that would have required larger ponds to contend with heavier flow in the winter months. 

It’s also possible the defunct golf course will no longer be the best site for the system at all, since an important factor was that it would irrigate the course, she said.

Though Ms. Jackson emphasized that it was not the main reason for a new feasibility study, she also said that after the first study was released last spring, the county had realized there was conflict with an upcoming Salmon Protection and Watershed Network salmon enhancement project located at the same spot as the proposed wastewater facility. 

SPAWN recently secured $3 million from California Fish and Wildlife to conduct that project, which will likely begin next summer.