Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 809 - Safe Drinking Water
Subchapter I - Maximum Contaminant Levels, Monitoring and Analytical Requirements for Primary Drinking Water Contaminants
Section NR 809.30 - Distribution system microbiological contaminant maximum contaminant levels

Universal Citation: WI Admin Code § NR 809.30

Current through August 26, 2024

The following are the maximum contaminant levels for coliform bacteria applicable to public water systems.

(1) MCL FOR ESCHERICHIA COLI ( E. Coli).

(a) The MCL for E. coli is exceeded if any of the following occurs:

1. The public water system has an E. coli-positive repeat sample following a total coliform-positive routine sample.

2. The public water system has a total coliform-positive repeat sample following an E. coli-positive routine sample.

3. The public water system fails to take all required repeat samples following an E. coli-positive routine sample.

4. The public water system fails to test for E. coli when any repeat sample tests positive for total coliform.

(b) For purposes of public notification requirements in subch. VI, this is a violation that may pose an acute risk to health.

(2) DETERMINING COMPLIANCE. The water supplier for a public water system shall determine compliance with the MCL for E. coli in sub. (1) for each monitoring period in which the public water system is required to monitor for total coliforms.

(3) CORRECTIVE ACTION. The water supplier shall initiate action to identify the cause of the positive bacteriological sample results and to eliminate potential health hazards which may exist in the public water system when monitoring pursuant to sub. (1) shows the presence of any coliform organisms.

(4) HETEROTROPHIC BACTERIA LIMITS. If heterotrophic bacterial plate counts on water distributed to the consumer exceed 500 organisms per milliliter, the department shall determine if the bacterial count is of public health or nuisance significance and may require appropriate action.

(5) BEST AVAILABLE TREATMENT TECHNIQUES. Any of the following are best technology, treatment techniques, or other means available for achieving compliance with the maximum contaminant level for E. coli in sub. (1):

(a) Protection of wells from fecal contamination by appropriate placement and construction.

(b) Maintenance of a disinfectant residual throughout the distribution system.

(c) Proper maintenance of the distribution system including appropriate pipe replacement and repair procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, cross connection control, and continual maintenance of positive water pressure in all parts of the distribution system.

(d) Filtration and disinfection of surface water, or disinfection of groundwater using strong oxidants such as chlorine, chlorine dioxide or ozone.

(e) The development and implementation of a department-approved wellhead protection program.

Note: The basic purpose of a wellhead protection program is to restrict potentially polluting activities near wells and well fields and within recharge areas of aquifers supplying water to these wells. In general, activities are more restricted close to the well and less so farther away.

(6) AFFORDABILITY DETERMINATION. The EPA identifies the technology, treatment techniques, or other means available identified in sub. (5) as affordable technology, treatment techniques, or other means available to systems serving 10,000 or fewer people for achieving compliance with the maximum contaminant level for E. coli in sub. (1).

The basic purpose of a wellhead protection program is to restrict potentially polluting activities near wells and well fields and within recharge areas of aquifers supplying water to these wells. In general, activities are more restricted close to the well and less so farther away.

Disclaimer: These regulations may not be the most recent version. Wisconsin may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.

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