Growing Area Program: Water Quality


  • Bryant Lewis - Western Maine Growing Area Program Supervisor (Kittery to Dice Head, Castine)
  • David W. Miller - Eastern Maine Growing Area Program Supervisor (Dice Head, Castine to Calais)

Program Description

Because molluscan shellfish (those that have a hinged shell, such as clams, mussels, oysters, quahogs, 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.

The Water Quality Component evaluates all shellfish growing areas in the state of Maine to determine their suitability for harvest. This program is guided by the NSSP standards. Please select this link to find the 2019 NSSP Guide for the Control of Molluscan Shellfish (PDF, 502 pages, 4.4 MB) (commonly called the "Model Ordinance").

Growing Area Sanitary Surveys

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 marine water; and
  • Analysis of how weather conditions, tides, currents, and other factors may affect the distribution of pollutants in the area.

Growing Area Classifications

Each commercially harvested growing area is assigned a "classification" according to the results of its evaluation. A growing area may be classified as Approved, Conditionally Approved, Restricted, Conditionally Restricted, or Prohibited.

Once classified, all shellfish growing areas are regularly monitored. Marine water samples are collected throughout the year. Shoreline surveys are conducted less frequently, but each year some portion of the Maine coast (47 shellfish growing areas) are surveyed. During those surveys, all actual and 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.

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