From the Central Valley Water Board:
The Central Valley Regional Water Quality Control Board’s Surface Water Ambient Monitoring Program (SWAMP) team has completed monitoring for a microbial source tracking study along Nevada County’s Wolf Creek, which is listed as impaired on California’s 303(d) list due to the presence of fecal indicator bacteria.
Nine sampling sites were selected to evaluate the status of Wolf Creek specific to Escherichia coli (E. coli) – an indicator of fecal pollution and potential pathogens. The SWAMP team conducted sampling along Wolf Creek and select tributaries for 12 weeks from mid-June 2024 to early September 2024. Samples were analyzed for E. coli to better understand the presence or absence of fecal pollution. Samples will also be genetically analyzed (microbial source tracking) to identify potential sources of detected E. coli.
The draft E. coli results indicate exceedances of the Statewide Bacteria Water Quality Objectives at eight of the monitoring sites during the 12-week study period. However, for the last two weeks of the study, seven of the nine sites met the statewide objectives.
The Statewide Bacteria Objectives have been developed to evaluate whether the water quality supports recreational uses (such as swimming, fishing, etc.). Recreation in waterways exceeding the objectives has been statistically associated with increased risk of illness (examples include digestive, intestinal and other illnesses). A full data report for the study, including source identification, is anticipated in spring 2025.
While the microbial source tracking results are still pending, a summary table and an interactive web map of the draft Wolf Creek E. coli results can be found on the SWAMP Recreational Water Quality Monitoring webpage.
