What Type of Water Quality Pollution is Measured?
Runoff from creeks, rivers and stormdrains is the largest source of pollution to California beaches. Runoff may contain toxic heavy metals, pesticides, petroleum hydrocarbons, animal waste, trash and even human sewage. The Beach Report Card includes an analysis of shoreline (ankle-deep) water quality data collected by more than 20 different county and city public agencies for fecal indicator bacteria. At present, the report card contains no information on toxins or trash in the water.
This year, there were 492 shoreline monitoring locations analyzed in the California Beach Report Card from Humboldt County at Trinidad State Beach near Mill Creek to San Diego County at the Border Field State Park (border fence). Shoreline water samples were analyzed for three indicator bacteria: total coliform, fecal coliform (or E.coli) and Enterococcus. Total coliform, which contains coliform of all types, originates from many sources, including soil, plants, animals and humans. Fecal coliform and enterococcus bacteria are found in the fecal matter of mammals and birds. This fecal matter does not necessarily come from humans, although numerous prior studies have demonstrated that there is a significant possibility of human sewage contamination in stormdrain runoff at any given time.
The amount of indicator bacteria present in runoff, and consequently in the surfzone, is currently the best indication of whether or not a beach is safe for recreational contact. Indicator bacteria are not usually the microorganisms that cause bather illness. Instead, their presence indicates the potential for water contamination with other pathogenic microorganisms such as bacteria, viruses and protozoa that do pose a health risk to humans. The link between swimming in waters containing elevated levels of bacteria indicators and health risk was confirmed in the groundbreaking 1996 epidemiological study conducted by USC, the Sanitation District of Orange County, the City of Los Angeles, and Heal the Bay, under the auspices of the Santa Monica Bay Restoration Project.
Most sample locations are selected by monitoring, health, and regulatory agencies to specifically target popular beaches and/or those beaches frequently affected by runoff. Water quality samples are collected by the appropriate agency at a minimum of once a week from April through October, as required under the California Beach Bathing Water Quality Standards (AB411) or the Environmental Protection Agency’s National Beach Guidance and Performance Criteria for Recreational Waters (EPA’s BEACH program). Some agencies conduct year-round sampling, while others scale back their monitoring programs from November through March. All counties that have beach monitoring programs, and provide the data to the public, are included in the Beach Report Card.
Heal the Bay's Grading System
Heal the Bay’s grading system takes into consideration the magnitude and frequency of an exceedance above indicator thresholds over the course of a year. Furthermore, those beaches that exceed multiple indicator thresholds in a given day received lower grades than those beaches that exceeded just one indicator threshold.
The grades are based on a 100-point scale. For each monitoring location, points are subtracted from a perfect score of 100 depending on the severity of bacterial count exceedances of state single sample standards, and/or exceedances of the 30-day geometric mean standards. As the magnitude or frequency of bacteria density threshold exceedances increases, the number of points subtracted increases. The threshold points and grading system can be found in Appendix A.
Water quality drops dramatically during and immediately after a rainstorm, but often rebounds to its previous level within a few days. For this reason, wet weather data were analyzed separately in order to avoid artificially lowering a location’s grade. Wet weather data are comprised of samples collected during or within three days following the cessation of a rainstorm. Heal the Bay's annual report card and weekly report cards utilize a definition of a ‘significant rainstorm’ as precipitation greater than or equal to one tenth of an inch (>0.1"). The BRC analyzes dry weather water quality data for two time periods, April 2006 through October 2006 (summer dry weather), and April 2006 through March 2007 (year-round dry weather).
What Does This Mean to the Beach User?
Simply put, the higher the grade a beach receives, the better the water quality at that beach. The lower the grade, the greater the health risk. Potential illnesses include stomach flu, ear infection, upper respiratory infection and major skin rash (full body). The known risks of contracting illnesses associated with each threshold are based on a one-time, single day of exposure (head immersed while swimming) to polluted water. Increasing frequency of exposure or the magnitude of bacteria densities may significantly increase an ocean user’s risk of contracting any one of a number of these illnesses.
It is important to note that the grades from the Beach Report Card represent the most current information available to the public, but they do not represent real-time water quality conditions. Currently, laboratory analyses of beach water quality samples take 18 to 48 hours to complete, then the data must be entered into a database before they are sent to Heal the Bay for a grade calculation. However, www.healthebay.org/brc/closures provides real-time information on beach closures due to sewage spills. The BRC is designed to give the beachgoer historical information on the water quality at a given beach. The public can then make informed decisions about which beach to visit safely.
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