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The Growing Area Classification
Program evaluates all commercially harvested shellfish growing areas in
Washington State to determine their suitability for harvest. See
Annual Shellfish Growing Area Reports.
Because molluscan shellfish (those that have a hinged shell, such as clams,
mussels, oysters, geoduck, etc.) are filter feeders, the quality of the
water where they grow is a key factor in determining whether they are safe to
eat.
Growing Area Classifications A growing area's classification is determined by conducting a "sanitary
survey," which is a three-part process consisting of:
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A shoreline survey, which identifies pollution sources that may impact water
quality. We evaluate sewage treatment plants, onsite sewage
systems, animal farms, drainage ways, and wildlife;
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Marine water sampling to determine fecal coliform bacterial levels in the
marine water; and
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Analysis of how weather conditions, tides, currents, and other factors may
affect the distribution of pollutants in the area.
Each commercially harvested growing area is assigned a "classification"
according to the results of its evaluation. A commercial growing area may be
classified as:
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Approved when the sanitary survey
shows that the area is not subject to contamination that presents an
actual or potential public health hazard. An Approved
classification authorizes commercial shellfish harvest for direct
marketing.
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Conditionally Approved when it meets Approved criteria, but only during
predictable periods. For example, during dry weather a growing area may meet
Approved water quality standards, but after a certain amount of rain falls
(termed a "rainfall event") the water quality declines. In this example, the
Conditionally Approved area is temporarily closed to harvest after a
rainfall event. The length of closure is predetermined for each
Conditionally Approved area, and is based on water sample data that show
the amount of time it takes for water quality to recover and again meet
Approved criteria. Once that time period has elapsed, the area is reopened.
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Restricted when water quality standards for an Approved classification,
but the sanitary survey indicates only a limited degree of pollution from
non-human sources. Shellfish harvested from Restricted growing areas cannot
be marketed directly. They must be » relayed» to Approved growing area waters
for a specified amount of time, allowing shellfish to naturally cleanse
themselves of contaminates before they are harvested for market.
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Prohibited
when the sanitary survey indicates that fecal material, pathogenic
microorganisms, or poisonous or harmful substances may be present in
concentrations that pose a health risk to shellfish consumers. Growing areas
adjacent to sewage treatment plant outfalls, marinas, and other persistent
or unpredictable pollution sources are classified as Prohibited. Growing
areas that have not undergone a sanitary survey are also classified as
Prohibited. Commercial shellfish harvests are not allowed from Prohibited
areas.
Once classified, all active commercial shellfish growing areas are regularly
monitored. Marine water samples are collected throughout the year. Shoreline
surveys are conducted less frequently, but each year dozens of commercial
shellfish growing areas are surveyed. During those surveys, all potential
pollution sources that may impact water quality are evaluated.
The purpose of continued water sampling and shoreline surveys is to ensure
that growing areas continue to meet the standards associated with their
classification, to modify classifications when needed, and to notify the
responsible agencies about identified and potential pollution sources.
Questions about growing area
classifications may be sent to:
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