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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 waters in which 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-fold process consisting of:
Each commercially harvested growing area is assigned a "classification" according to the results of its evaluation. A commercial growing area may be classified as one of these: A growing area may be classified as 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.
A growing area may be classified as 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.
A Restricted classification is used for areas that do not meet 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.
A growing area must be classified as 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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