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Whipple Creek septic systems eyed after human markers found in tests

For years, bacteria levels in the Whipple Creek watershed have exceeded state standards for fecal contamination.

The question always has been: Is the fecal bacteria coming from humans, pets, livestock or wildlife?

“Traditional measures of bacteria, they tell you that bacteria is there, but they don’t tell you what it’s from,” said Jeff Schnabel, stormwater infrastructure manager with Clark County Public Works.

Advanced molecular testing completed this year found human markers in bacteria from five tributaries feeding Whipple Creek, a strong indication that neglected, failing septic systems are contributing to the pollution.

Clark County used microbial source tracking to try to pinpoint the sources of fecal contamination in the Whipple Creek watershed, which encompasses urban and rural areas primarily west of Interstate 5, north and south of 179th Street.

Water samples were taken during dry weather in August and September 2018 and during wet weather, October 2018 to April 2019.

The samples were sent overnight to Source Molecular, a laboratory in Miami Lakes, Fla., specializing in molecular testing to identify sources of contamination.

“What we got at the end of the day was kind of a mixed bag,” Schnabel said. “But we did find evidence of human DNA at all five sites, more at some, less at others.”

Schnabel said microbial source tracking actually is an umbrella term for a range of techniques used to help determine bacteria sources. This was the first time the county used what’s known as quantitative polymerase chain reaction, a relatively new technique to search for molecular markers specific to humans, dogs, birds and other animals, he said.

“It’s good enough now that you can get a sense of whether you are dealing with a horse or dealing with a person,” Schnabel said.

Testing from all five sampling sites revealed fecal bacteria from dogs, which means programs such as Canines for Clean Water still have a ways to go in persuading all dog owners to pick up what their pets leave behind.

Elevated levels of optical brighteners, which are added to laundry detergents to make clothes look whiter and brighter, also were found at the five sites.

Inspection requirements

County code requires basic gravity septic systems to be inspected every three years by a county-certified inspector who records the results in a county database. Pressurized systems need to be inspected every two years, and more complex systems need to be tested annually.

An October 2017 analysis determined that 30 percent of the 961 septic systems in the Whipple Creek watershed were “non-compliant,” meaning there are not records indicating the systems have been inspected within the required periods.

That alone does not mean these septic systems are releasing harmful bacteria into the environment. But the October 2017 assessment, coupled with the microbial source tracking findings, raises questions about the actual condition of these systems and their effect on clean water.

Chuck Harman, on-site septic program manager for Clark County Public Health, said his department has previously received data for fecal coliform and E. coli, but this is the first time it’s had access to DNA information.

“We are going to move forward in using this data to focus our efforts and work with property owners,” he said.

Neither Harman nor Schnabel believes the human markers are coming from another source than septic systems, in part because there haven’t been problems with homeless camps in the area.

“There are limited ways you can get human bacteria into a stream,” Schnabel said.

The bacteria itself is enteric, meaning it’s from the intestines, he said.

“There always been this suspicion out there that septic systems must be contributing to these problems,” he said.

Clark County seeks voluntary compliance to septic system inspection and maintenance and sends reminders to property owners. Harman said compliance with county-mandated inspections has increased from 50 percent to 70 percent.

“We have made a lot of gains throughout the county just through notification,” he said.

What’s next?

Harman said county health officials will be working closely with the Clark County Council, acting in its capacity as the Clark County Board of Health, and County Manager Shawn Henessee.

Not many Washington counties have an operations and maintenance program, often referred to as “O&M,” for septic systems, he said. Although there has been discussion of a statewide requirement, the decision is left to individual counties, he said.

“There is a lot of resistance to an O&M program politically because it is the regulation of individuals,” Harman said.

That resistance might be best illustrated from an interview 10 years ago, when then-County Commissioner Tom Mielke told a Columbian reporter that Clark County should stop requiring property owners to fix overflowing septic systems, at least until they begin to disturb their neighbors.

Janis Koch, environmental health director for Clark County Public Health, said the county always wants to work constructively with property owners.

“We have added an option for homeowners to inspect their own gravity system,” she said. “They can come take a class. That is something our county has offered to residents.”

Fecal biomarkers do not survive long in water, which means they are typically collected close to their sources. That will allow the county to reach out to property owners with noncompliant septic systems near the five sampling sites.

Koch said the county hasn’t had a chance to interact with those property owners on the microbial source tracking report.

“Chuck is working on a letter to those homes, sharing the data,” she said.


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