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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 470 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 illness in swimmers.
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). Many
agencies conducted year-round sampling, while others
scaled 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
Concentrations
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 and findings from the
1996 SMBRP Epidemiological Study on swimmers at urban
runoff polluted beaches. 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 for 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 2003 to October 2003 (AB411 time period),
and 2) April 2003 to March 2004.
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,
the Report Card on the Heal the Bay web site includes
real-time information on beach closures because most
closures are due to sewage spills and nearly all
health agencies close beaches 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.
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