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Update: May 2004

Current Massachusetts Regulatory Limit
MMCL = Treatment Technique. (Refer to 310 CMR 22.20.) ORS has adopted the MCL published by the U.S. EPA.

Federal Regulatory Limit
The MCL for heterotrophic plate count is a Treatment Technique. Under U.S. EPA's Surface Water Treatment Rule, systems using surface water or groundwater under the direct influence of surface water must achieve a heterotrophic plate count (HPC) no greater than 500 bacterial colonies per milliliter (67 FR 1811; U.S. EPA, 2002).

Basis for Criteria
The MCL for Heterotrophic plate count is based on a Treatment Technique as described above.

Critical Effects
Heterotrophic plate count is not an indicator of health effects and is not associated with disease. It is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is (67 FR 1811; U.S. EPA, 2002).

Cancer Assessment: 

Biological Pathogen

Analytical Information
: See CMR 22.20 

Analytical Methods
Standard Method 9215 B. See 310 CMR 22.20A(5).

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at US EPA Drinking Water Analytical Methods .

Federal Register. January 14, 2002. Environmental Protection Agency. Parts 9, 141 and 142. National Primary Drinking Water Regulations: Long Term 1 Enhanced Surface Water Treatment Rule. Final Rule. (67 FR 1811).

U.S. Environmental Protection Agency (U.S. EPA). July 2002. List of Contaminants and Their MCLs. EPA 816-F-02-013.