The Department of Marine Resources (DMR) Bureau of Public Health collects surface water grab samples at approximately 1,200 water quality monitoring stations along the Maine coast year-round. Samples are processed in the lab via membrane filtration and enumerated for fecal coliform bacteria. Fecal coliform results are reported as the number of colony forming units (individual bacterium capable of forming colonies) per 100mL of water. DMR scientists analyze data from each station and calculate annual summary statistics using at least 30 of the most recent samples collected under a systematic-random sampling design. These values, along with sanitary surveys of the area, help determine whether the water quality is acceptable for harvesting molluscan shellfish.

DMR's Shellfish Growing Area Classification Program classifies shellfish areas as Approved, Conditionally Approved, Restricted, Conditionally Restricted or Prohibited using standards set by the National Shellfish Sanitation Program (NSSP), a federal/state cooperative program that sets the requirements for all states involved in interstate shellfish harvest and sale. For more information about the classification of shellfish flats, visit https://www.maine.gov/dmr/fisheries/shellfish/shellfish-growing-area-classification.

All classifications are based on two factors: the results of a shoreline survey which looks for the presence of pollution sources, and fecal coliform monitoring results. Two statistical values are calculated from the most recent 30 fecal coliform scores: the geometric mean (geomean) and the 90th percentile (P90). The standards for Approved classification are 14 CFU or less (geomean) and 31 CFU or less (P90). The standards for Restricted are 88 CFU or less (geomean) and 163 CFU or less (P90). The standards for Prohibited are greater than 88 CFU (geomean) and greater than 163 CFU (P90).

End of year 2022 P90 data for all Maine active and investigative water quality stations based on the most recent 30 samples. Conditional Area stations are based on last 30 samples in the open status. Data projection is NAD 1983 UTM Zone 19N.