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 809.325 - Groundwater source microbiological monitoring requirements

Universal Citation: WI Admin Code ยง NR 809.325

Current through August 26, 2024

(1) SAMPLING LOCATION.

(a) Any groundwater source sample required under sub. (2) shall be collected at a location prior to any treatment of the groundwater source unless the department approves a sampling location after treatment.

(b) If the public water system's configuration does not allow for sampling at the well itself, the water supplier may collect a sample at a department-approved location to meet the requirements of par. (a), if the sample is representative of the source water quality of that well.

(c) Source water samples taken in response to positive total coliform samples collected under s. NR 809.31 shall be referred to as triggered source water samples.

(2) TRIGGERED SOURCE WATER MONITORING.

(a) Water suppliers for groundwater systems shall conduct triggered source water monitoring if all of the following conditions exist:
1. The public water system does not provide at least 4-log treatment of viruses before or at the first customer for each groundwater source.

2. The public water system is notified that a sample collected under s. NR 809.31 (1) is total coliform-positive and the sample is not invalidated under s. NR 809.31 (3).

(b) The following sampling requirements apply:
1. No later than 24 hours after notification of a total coliform-positive distribution system sample, a water supplier for a groundwater system shall collect at least one groundwater source sample, for each total coliform-positive sample, from each groundwater source in use at the time the total coliform-positive sample was collected, except as provided in par. (c).

2. The department may extend the 24-hour time limit on a case-by-case basis if the water supplier cannot collect the groundwater source water sample within the 24-hour time limit due to circumstances beyond the water supplier's control. In the case of an extension, the department shall specify, in writing, how much time the water supplier has to collect the sample.

3. If approved by the department, water suppliers for groundwater systems with more than one groundwater source may meet the requirements of this paragraph by sampling a representative groundwater source or sources if they have an approved triggered source water monitoring plan.

(c) A triggered source water monitoring plan shall evaluate each sample site in the sample siting plan for the public water system under s. NR 809.31 (1) (a) and identify the sources that are representative of each monitoring site. If directed by the department, a water supplier for a public water system shall submit for department approval a triggered source water monitoring plan that identifies one or more groundwater sources that are representative of each monitoring site in the sample siting plan for the public water system and that the water supplier intends to use for representative sampling under par. (b).

(d) A water supplier for a groundwater system serving 1,000 people or fewer may use a repeat sample collected from a groundwater source to meet both the requirements of s. NR 809.31 (2) and to satisfy the monitoring requirements of par. (b) for that groundwater source. If the repeat samples collected from the groundwater source are E. coli positive, the water supplier shall comply with the requirements of par. (e) unless the department requires immediate corrective action under s. NR 809.327 (2) (b).

(e) If the department does not require corrective action under s. NR 809.327 (2) (b) for an E. coli-positive source water sample collected under par. (b), the water supplier shall collect five additional source water samples from the same source no later than 24 hours after being notified of the E. coli positive sample. If any of the 5 samples collected under this paragraph is E. coli-positive, the water supplier shall conduct a corrective action as outlined in s. NR 809.327 (2).

(3) CONSECUTIVE AND WHOLESALE SYSTEMS.

(a) In addition to the other requirements of this section, a water supplier for a consecutive groundwater system that has a total coliform-positive sample collected under s. NR 809.31 (1) shall notify any wholesale system from which it receives water no later than 24 hours after being notified of the total coliform-positive sample.

(b) A water supplier for a wholesale groundwater system that receives notice from a water supplier for a consecutive system served by the wholesale system that a sample collected under s. NR 809.31 (1) was total coliform-positive shall, no later than 24 hours after being notified, collect samples from its groundwater sources under sub. (2) and analyze them for E. coli under s. NR 809.323 (1) (b) Table G. The department may extend the 24-hour time limit on a case-by-case basis if the public water system cannot collect the groundwater source water sample within the 24-hour time limit due to circumstances beyond the water supplier's control. In the case of an extension, the department shall specify, in writing, how much time the water supplier has to collect the sample.

(c) If the sample collected under par. (b) is E. coli-positive, the water supplier for the wholesale groundwater system shall notify all water suppliers for the consecutive systems served by that groundwater source no later than 24 hours after being notified of the groundwater source sample monitoring result and shall meet the requirements of sub. (2) (e) unless the department requires immediate corrective action under s. NR 809.327 (2) (b).

(4) EXCEPTION TO THE TRIGGERED SOURCE WATER MONITORING REQUIREMENTS. A water supplier for a groundwater system is not required to comply with the triggered source water monitoring requirements of sub. (2) if the department determines, and documents in writing, that the total coliform-positive sample collected under s. NR 809.31 (1) was caused by a distribution system deficiency.

(5) FAILURE TO MEET MONITORING REQUIREMENTS. If a water supplier fails to meet any of the monitoring requirements of subs. (1) to (3), the public water system is in violation and is required to complete public notification requirements under s. NR 809.953.

(6) PUBLIC NOTIFICATION. A water supplier for a groundwater system with a groundwater source sample collected under subs. (2) or (3) that is fecal indicator-positive and that is not invalidated under s. NR 809.323, including consecutive systems served by the groundwater source, shall conduct public notification under s. NR 809.951 (1) (b) 9.

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