Water Quality 101

Notes from a Water Quality discussion among TBF Board members and advisors

via Zoom: 5/15/2023

 By Woody Elliott, edited by Rob Carson

Here is a simple explanation of the historical background for use of various types of fecal bacteria indicating potential for human infection:

In 1986 USEPA established Public Health thresholds of E. coli and Enterococcus levels per 100 milliliters resulting in 32 illnesses per 1,000 recreators. E. coli and Enterococcus are not actual pathogens; but are bacteria that indicate pathogenic bacteria may be present. Too expensive to monitor / test for actual suit of potential pathogens.

E. coli is the best indicator for fresh water as it survives poorly in salt water.

Enterococcus is more stable in salt water so suitable for sampling tidally influenced brackish waters.

Statewide, E. coli and Enterococcus are the preferred indicator bacteria for determining Total Maximum Daily Load (TMDL): A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can accept and still meet the state’s Water Quality Standards for public health and healthy ecosystems. But not all TMDLs for pathogens in areas throughout California use these fecal indicator bacteria.

SF Bay Water Quality Control Board (SFBayWQCBoard) uses fecal coliform criteria in the Tomales Bay Watershed rather than E. coli and Enterococcus for thresholds of contaminant warnings for contact and noncontact recreation because the fecal coliform criteria were developed before the State recommended using E. coli and Enterococcus criteria. Also, the California Department of Public Health uses fecal coliform criteria for safe shellfish consumption, a major beneficial use of the water.

It is difficult to compare sites sampled for potential contamination with nonidentical indicator bacteria. Best to use same indicator bacteria analyzed by same lab for monitoring over time for best comparisons / trends.

These issues are discussed in California Bacteria Summit (Sept. 14-16, 2022) at: https://www.casqa.org/resources/water-quality-priorities/bacteria. Also, a summary of the event is available at: https://www.casqa.org/wp-content/uploads/2023/04/California-Bacteria-Summit-Short-Summary-03-27-2023.pdf

1. What are the basis for the threshold limits of Beach Water Quality Information reported as OK and Avoid at link here and shown by email from Arti Kundu as:

Figure 1 Most Probable Number Thresholds for Recreational Water Contact

TMDL for contact and noncontact recreational use of water bodies are actionable. Shellfish standards are more restrictive i.e., lower levels of contamination.

The standards are reported for Most Probable Number (MPN/100mL) .

2. Why do various entities/agencies (Marin County, Tomales Bay Foundation, NPS, Shellfish growers for Calif. Dept. Public Health) collect and report various fecal bacteria samples (total coliform, fecal coliform, E. coli, Enterococcus) from Tomales Bay as shown on the attached table?

These various fecal bacteria and associated thresholds of contamination were established and modified over time by federal, state, and local agency regulators to fit best available knowledge and changing recommendations. They are not always synchronized among agencies.

3. What is the significance and purpose of these various fecal bacteria samples (total coliform, fecal coliform, E. coli, Enterococcus).

They indicate the potential for illness in humans caused by pathogenic bacteria and can indicate other pollution (e.g., nutrients) that is a threat to the environment at large.

4. What thresholds of contamination do government agencies deem actionable and what are the remedies?

Regulatory goal: Water bodies that are safe to swim and eat shellfish using indicator bacteria from guts of warm-blooded animals. Fecal coliform is less sensitive to indicating presence of human pathogens than E. coli and Enterococcus. The goal of meeting bacteria standards is difficult if not impossible to achieve given wet weather background levels of fecal bacteria from wildlife and livestock that do not have human sources. Most monitored waters are above actional levels of contamination during wet weather events. Fecal bacteria standards are approximate at best. There is a need to develop faster methods to indicate contamination so remediation is not delayed. Need to develop quicker than one to five days and specific indicators of contamination e.g., PCR (Polymerase Chain Reaction) methods that are associated with specific sources (wildlife, livestock, humans, etc.). Bird and dog sources have a lower risk of human infection than humans and livestock. The list of PCR markers for various source species is growing.

5. What is the significance of past Fecal Coliform sampling by TB Foundation, and does it justify continued sampling on monthly, and / or 5-week sequence during high and low flow seasons?

During the early days of grant-funded sampling (2007-2012), we learned about temporal / spatial variation of sampling results. Summer, low flow, samples are predictable. Winter samples of high and low flows can show short term contamination. Long-term monitoring for trends is useful for assessing TMDL goals from accumulation of data. Marin RCD, MALT and other groups/landowners do small scale fixes with individual ranch projects. Evaluating the cumulative effects of many such projects over the years with long-term monitoring is important. Sometimes monitoring can spot “red-hot” issues needing action/remediation. Example: Millerton Point exceeded monitoring threshold which encouraged sampling at several sites upstream on Millerton Creek for chicken and livestock sources. We need to do simultaneously monitoring at Millerton Pt. and up Millerton Ck.

6. Can other entities (MALT, Marin RCD, Marin Co.) in addition to SFBayWQCBoard contribute to paying for sample analysis?

Yes. MALT and EAC have paid for lab analysis during SFBayWQCB funding hiatus when switching labs. Foundation can use SFBayWQCB labs but cannot use SFBayWQCB funding for analysis at lab not used by SFBayWQCB. Again, it would be best if the same lab and indicator bacteria are used for monitoring over time to document trends in TMDL. A five-week series of contaminant monitoring in summer and winter should continue. No criteria to trigger the start of 5-week sequential sample that theoretically would represent a winter season. During winter sampling sequence, calculation of 5-week sequence could begin from any or the first 5 weeks of a 10-week sequence as start of the Geomean calculation representing the winter season to indicate TMDL exceedances. During the summer dry season, one 5-week sequence would probably be representative. NPS does not have adequate resources to fund more analysis than it is doing.

7. How should past results from TB Foundation (fecal coliform) and Marin Co (Total Coliform, E. coli, and Enterococcus) be statistically analyzed, presented, and displayed as public information?

Do not graph various indicator bacteria (fecal coliform, total coliform, E. coli, and Enterococcus) together as simultaneous data points may not correlate /relate to contamination. Need to approximate historic trends over time using graphs of single indicator bacteria.

8. Responses to other questions.

Sampling for mercury contamination is expensive and care is needed during sample collection to avoid contamination of samples.

Turbidity sampling is correlated with levels of indicator bacteria because contaminates bind to sediment particles. Turbidity measured by light absorption is cheap and easy. Total Suspended Solids (TSS) requires filtering sample, drying, and weighting filter paper, a more complicated and costly process. Turbidity in Inverness’s 1st, 2nd and 3rd Valleys drops quickly after rainstorms while Walker Creek remains turbid longer.

Rob recommends a 5-week early summer sequence of sampling streams beginning in June 2023 because most will be still flowing. Rob will need to coordinate sampling with shellfish growers, NPS, IPUD and TB Foundation.

Arti Kundu of Marin Co. Environmental Health Services (EHS) Division has provided spreadsheets of numerical data collected 2019 through 2022 annually from April through October for fecal bacteria at Marin Co. recreational sites reported at Beach Water Quality Information.