What Type of Water Quality Pollution is Measured?
Runoff from creeks, rivers or storm drains 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 various county and city public agencies for fecal indicator bacteria.
At present, the report card contains no information on toxins or trash in the water.
Currently, there are approximately 460 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 are 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 storm drain 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 were 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 conducted 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 were included in the Beach Report Card.
Water Quality Thresholds
Densities of total coliform, fecal coliform and enterococcus bacteria are typically measured in colony-forming units (cfu) per 100 milliliters of ocean water. Colony-forming units are the number of bacteria that are capable of reproduction during the course of sample analysis. The Beach Report Card methodology utilizes four thresholds, or specific levels of exposure, that are associated with increased health risks. These thresholds were derived from California Department of Health Services standards set forth in AB411, findings from the 1996 SMBRP Epidemiological Study on swimmers at urban runoff polluted beaches, and recent amendments to the California Ocean Plan. The four exceedance thresholds for various indicator bacteria can be found in Appendix A.
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 where the data falls within the designated thresholds. As the magnitude or frequency of bacteria density threshold exceedance 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 was analyzed separately in order to avoid artificially lowering a location's grade. A wet weather data point is any sample collected during or within three days following the cessation of a rainstorm. Heal the Bay's annual report card and weekly report cards utilized a definition of a significant rainstorm as precipitation more than or equal to one tenth of an inch (=0.1"). Also, in response to requests from health agency officials, the BRC now analyzes dry weather water quality data for two time periods, 1) April 2004 through October 2004 (summer dry weather), and 2) April 2004 to March 2005 (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 derived for the California 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 it is sent to Heal the Bay for a grade calculation. However, www.healthebay.org provides real-time information on beach closures due to sewage spills that most health agencies close immediately after a spill. The report card 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.
|
