Bacteria Data Collected by SYRCL

Introduction and Sampling History

SYRCL’s River Monitoring program has been involved in the collection of bacteria data in the Yuba River watershed since 2000. The goal of bacteria data collection is to build an understanding of the levels of particular bacterial parameters in the river system. The data, which requires laboratory processing of water samples, can be compared to standards set by water quality authorities. This analysis is relevant to SYRCL’s overall interest in the health of the watershed and in particular to SYRCL’s interest in monitoring the suitability of the river for swimming and other forms of contact recreation during the warmest months of the year.

SYRCL’s first bacteria sampling took place in October 2000 at two sites: Oregon Creek above the Middle Yuba (Site 5) andMiddle Yuba at Foote’s Crossing (Site 9). Beginning in January 2001, monthly bacteria sampling occurred at multiple sites throughout the watershed, but this monthly sampling ceased in October 2003. Subsequent sampling was primarily during the highest recreation months. Since 2007 budget constraints more severely limited the frequency of sampling for bacterial tests. SYRCL has never possessed the capability to process bacterial samples without the use of a laboratory service. Cranmer Engineering of Grass Valley or the Friends of Deer Creek processed all samples used for bacterial analysis before 2008.


In 2008, SYRCL began participating in the Central Valley Regional Water Quality Control Board’s annual SWAMP Safe-to-Swim study. Table 1 outlines the Yuba basin data collected by the Safe-to-Swim study since 2008:

Table 1

Year # of days # of sites
2008 3 1
2009 1 3
2010 0 0
2011 3 9
2012 4 10

As shown, the number of sampling occasions varied year-to-year, with as many as four in 2012. All these All Safe-to-Swim sampling dates fell in the warmer months, ranging from June to September. The study has included Sampling for the Safe-to-Swim studies has taken place at a total of fourteen Yuba basin sites since it came to the watershed.

Parameters Measured and Relevance

Since the original SYRCL bacteria sampling in 2000, almost all samples taken have been consistently tested for total coliform and Escherichia coli (E. coli). Total coliform measurements include some species of bacteria that occur naturally in plant material and soil, and so do not always give a clear indication of water quality; but the particular species E. coli is only found in the feces of warm blooded mammals, so it provides a more valuable indication of potential contamination issues. However, E. coli is only an indicator, and even when measurements exceed the water quality objective, they do not necessarily demonstrate the presence of an immediate health risk.

When possible, other parameters that more directly identify public health concerns have been tested. SYRCL’s pre-2008 sampling program frequently tested for Enterococcus, a bacteria that is commonly found in the feces of humans and other warm blooded mammals, is unrelated to coliforms, and is a good indicator of fecal pollution. SYRCL published a report in 2006 on issues concerning Enterrococcus.

The 2008 Safe-to-Swim study tested only for E. coli, but all sites from 2009’s Safe-to-Swim study were also tested for E. coli O157:H7, a particular illness-causing strain of the bacterium, and Site 15: Purdon Crossing was also tested for Cryptosporidium, Giardia, and Salmonella. Salmonella, like E. coli O157:H7, is a bacterium that can be transferred between humans and animals. Cryptosporidium and Giardia are parasites that live in the intestines of infected humans and animals. None of these four parameters have water quality guidelines in the Sacramento Basin, of which the Yuba watershed is a component.

2011’s Safe-to-Swim study sampled E. coli and total coliform at six sites in the South Yuba sub-basin and three on the Middle Yuba; the Middle Yuba sites were also tested for E. coli O157:H7, Cryptosporidium, Giardia, and Salmonella. 2012’s Safe-to-Swim study sampled only E. coli and total coliform from ten sites in the South and Middle Yuba sub-basins.

Table 2 summarizes the water quality guidelines for each constituent monitored.

Table 2

Constituent Water Quality Guideline
E. coli (MPN/100mL) <235 MPN/100 mL (EPA Contact Recreation Guideline)
Total Coliform (MPN/100mL) NA
E. coli O157:H7 (positive/negative) NA
Crypotosporidium (oocyst/L) NA
Giardia (cyst/L) NA
Salmonella (MPN/100 mL) or (positive/negative) NA
Enterococcus – Enterolert (MPN/100 mL) 61 MPN/100 mL (EPA Contact Recreation Guideline)
Enterococcus – MF (CFU/100 mL) 61 MPN/100 mL (EPA Contact Recreation Guideline)
Enterococcus – MTP (MPN/100 mL) 61 MPN/100 mL (EPA Contact Recreation Guideline)
***MPN=most probable number


Data collected under the Safe-to-Swim studies are collected in accordance with the Central Valley Water Board’s San Joaquin River Basin Bacteria Monitoring Procedures Manual. The process for collecting a grab water sample begins by finding moving, well mixed water at the designated collection site. A sampling bottle, provided by the State Water Resources Control Board, comes sealed sterile with trace amounts of sodium thiosulfate in powder form. Then by either wading into the main channel or using a sampling arm, a grab sample is taken with the sterile 125 mL bottle. The trained river monitor uses latex gloves to ensure minimal contamination. If wading, the bottle is submerged in mid-channel and filled to at least the 100 mL line. If using the sampling arm, the river monitor will still use gloves and be sure to make a clean connection between the sampling arm and sterile bottle. Samples are collected between 12 p.m. and 2:30 p.m. on the designated day and kept chilled until testing can take place. Details on testing methods and quality assurance for each particular parameter can be found in the 2009 Safe-to-Swim report.

Field sampling methods for bacteria prior to 2008 followed procedure in the SYRCL River Monitoring Training Manual, and are very similar to those for the Safe-to-Swim program. Quality control followed procedures in the Yuba Watershed Council Quality Assurance Program Plan.