Some thoughts about shoreline bacterial monitoring and
implications for public health warning systems
Stephen B. Weisberg
Southern California Coastal Water Research Project
Friday, July 12, 2002
12:00 Noon–Pacific Forum
Implementation of Assembly Bill 411 enhanced beach water quality
monitoring programs throughout California, but it also increased reliance
on single sample bacterial standards. Use of single sample standards is
confounded by variability in bacterial measurements, and studies were
conducted to quantify temporal, spatial, and laboratory variability.
Laboratory variability was found to be high. Most samples on which health
warnings are based were within measurement error of state standards.
Spatial variability was found to be low, except near storm drain outlets
where rapid dilution away from these high concentration sources was found
to depend on oceanographic conditions. Temporal variability was also
large, with nearly 70% of high bacterial concentration events lasting less
than the 24 hours necessary for laboratory sample processing. Thus, most
public health warnings are out-of-date when they are issued. Several
research and management alternatives for improving the health warning
systems will be presented.
Next: How usability engineering broadens access to research and engineering data