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How Shellfish Areas are Classified

A growing area's classification is determined by conducting a "sanitary survey," which is a three-fold process consisting of:

  • A shoreline survey, which identifies pollution sources that may impact water quality. The program evaluates sewage treatment plants, onsite sewage systems, animal farms, drainage ways, and wildlife;
  • Marine water sampling to determine fecal coliform bacterial levels in the marine water; and
  • 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 growing area may be classified as one of these five:

Classification
Status
Shellfish Harvesting Activity
Approved
Open
Harvesting allowed
Conditionally Approved
Open
Harvesting allowed except during specified conditions (rainfall, STP bypass or seasonal)
Closed
Harvesting NOT allowed
Restricted
Open
Depuration and/or Relay harvesting only
Conditionally Restricted
Open
Depuration and/or Relay harvesting allowed except during specified conditions (rainfall, STP bypass or seasonal)
Closed
Harvesting NOT allowed
Prohibited
Closed
No harvesting allowed or water use allowed for processing (administratively imposed precautionary closure)

 

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 shellfish harvest for direct marketing.

A growing area may be classified as Conditionally Approved when it meets Approved criteria, but only during predictable and manageable 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 determined 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 the water quality returns to Approved criteria, 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. Shellfish harvested from Restricted growing areas cannot be marketed directly. They must be “relayed” or “depurated”. Shellfish that are “relayed” are moved 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. Shellfish that are “depurated” are moved to a depuration facility to cleanse themselves in sterile seawater under strict controls and are tested before they are released to the market. Shellfish harvesting in a Restricted area requires a permit: for an application, go to Maine DMR, Public Health Division - Shellfish Program and look under Forms.

A growing area may be classified as Conditionally Restricted when it meets Restricted criteria, but only during predictable and manageable periods. For example, a Restricted area that is adjacent to a sewage treatment plant Prohibited area may meet Restricted water quality standards, but after a malfunction at the sewage treatment plant the water quality declines. In this example, the Conditionally Restricted area is temporarily closed to harvest after a sewage treatment plant malfunction. The length of closure is determined for each Conditionally Restricted area, and is based on water and shellfish tissue sample data that show the amount of time it takes for water quality and the shellfish to recover and again meet Restricted criteria. Once the water quality and shellfish return to Restricted criteria, the area is reopened.

Shellfish harvested from Conditionally Restricted growing areas cannot be marketed directly. They must be “relayed” or “depurated”. Shellfish that are “relayed” are moved 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. Shellfish that are “depurated” are moved to a depuration facility to cleanse themselves in sterile seawater under strict controls and are tested before they are released to the market. Shellfish harvesting in a Restricted area requires a permit: for an application, go to Maine Department of Marine Resources, Public Health Division - Shellfish Program and look under Forms.

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, licensed overboard discharges, 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. Shellfish harvests are not allowed from Prohibited areas.

The completion of a sanitary survey is of paramount importance in making the distinction between acceptable and unacceptable growing areas, and is the key to accurate growing area classification as approved, conditionally approved, restricted, conditionally restricted, or prohibited. Under the NSSP Model Ordinance, a sanitary survey is required for each growing area prior to its approval by the state as a source of shellfish for human consumption or as a source for shellfish to be used in a depuration or relay operation.

Keeping the sanitary survey current consists primarily of routinely evaluating major pollution sources, collecting water quality data from sampling stations under the selected NSSP water quality monitoring strategy (systematic random sampling), and analyzing the data to assure that the classification continues to represent current sanitary conditions in the growing area. The sanitary survey must be repeated fully every 12 years. When a written sanitary survey report is not completed, the area must be placed in the closed status.

For more information:

red dye from failing septic system

 

 

The photo illustrates a malfunctioning septic system which was dye tested by ME DEP during shoreline survey work in May 2008. The red dye on the ground is where the malfunction was suspected. After flushing the dye in the toilet, the water came out of the ground and into the growing area waters; the red dye in the water in the background. The malfunction was found in an area that was previously approved for shellfish harvest.

Photo: Phil Garwood, ME DEP