NR 809.31(2)(b)2.a.a. If a dual purpose repeat sample taken at the monitoring location required for triggered source water monitoring is E. coli-positive, the public water system has violated the E. coli MCL and shall also comply with s. NR 809.325 (2) (e). If a water supplier takes more than one repeat sample at the monitoring location required for triggered source water monitoring, the water supplier may reduce the number of additional source water samples required under s. NR 809.325 (2) (e) by the number of repeat samples taken at that location that were not E. coli-positive.

NR 809.31(2)(b)2.b.b. If a water supplier takes more than one repeat sample at the monitoring location required for triggered source water monitoring under s. NR 809.325 (2). and more than one repeat sample is E. coli-positive, the public water system has violated the E. coli MCL and shall comply with s. NR 809.327.

NR 809.31(2)(b)2.c.c. If all repeat samples taken at the monitoring location required for triggered source water monitoring are E. coli-negative and a repeat sample taken at a monitoring location other than the one required for triggered source water monitoring is E. coli-positive, the public water system has violated the E. coli MCL, but is not required to comply with s. NR 809.325 (2) (e).

NR 809.31(2)(b)3.3. The department may review, revise, and approve, as appropriate, repeat sampling proposed by water suppliers under subds. 1. and 2. The water supplier shall demonstrate that the sample siting plan remains representative of the water quality in the distribution system. The department may determine that monitoring at the entry point to the distribution system, especially at ground water systems without disinfection is effective to differentiate between potential source water and distribution system problems.

NR 809.31(2)(c)(c) Water suppliers at ground water systems may use a repeat sample, taken at the source or all of the sources serving the location of each routine positive sample, to meet the requirements of both this paragraph and s. NR 809.325 (2) (d). In cases where more than one source serves the location of the routine positive sample or samples, repeat samples shall be taken from each of the sources to satisfy the requirements of this paragraph and s. NR 809.325 (2) (d).

NR 809.31(2)(d)(d) The water supplier shall collect all repeat samples on the same day, except that the department may allow a water supplier for a public water system with a single service connection to collect the required set of repeat samples over a 3-day period or to collect a larger volume repeat sample in one or more sample containers of any size, as long as the total volume collected is at least 300 mL.

NR 809.31(2)(e)(e) If one or more repeat samples in the set is total coliform-positive, the water supplier shall collect an additional set of repeat samples in the manner specified in pars. (a) to (d). The additional set of samples shall be collected within 24 hours after the water supplier is notified of the positive result, unless the department extends the limit as provided in par. (a). The water supplier shall repeat this process until either total coliforms are not detected in one complete set of repeat samples or the water supplier determines that the coliform treatment technique trigger specified in s. NR 809.313 has been exceeded and the water supplier notifies the department as specified in s. NR 809.80 (2). If a trigger identified in s. NR 809.313 is exceeded as a result of a routine sample being total coliform-positive, water suppliers are required to conduct only one round of repeat monitoring for each total coliform-positive routine sample.

NR 809.31(2)(f)(f) Water suppliers collecting samples on a quarterly or annual frequency shall conduct additional routine monitoring the month following one or more total coliform-positive samples regardless of whether the positive samples resulted in a Level 1 treatment technique trigger. Water suppliers shall collect at least three routine samples during the next month, after consultation with the department, except that the department may waive this requirement if the conditions of subd. 1., 2., or 3. are met. Water suppliers may either collect samples at regular time intervals throughout the month or may collect all required routine samples on a single day if samples are taken from different sites. Water suppliers shall use the results of additional routine samples in coliform treatment technique trigger calculations under s. NR 809.313 (1).

NR 809.31(2)(f)1.1. The department may waive the requirement to collect 3 routine samples during the next month the public water system provides water to the public if the department performs a site visit before the end of the next month the public water system provides water to the public. Although a sanitary survey need not be performed, the site visit shall be sufficiently detailed to allow the department to determine whether additional monitoring or any corrective action is needed. The department may not approve an employee of the public water system to perform this site visit, even if the employee is an agent approved by the department to perform sanitary surveys.

NR 809.31(2)(f)2.2. The department may waive the requirement to collect 3 routine samples during the next month the public water system provides water to the public if the department has determined why the sample was total coliform positive and establishes that the water supplier has corrected the problem or will correct the problem before the end of the next month the public water system serves water to the public. In this case, the decision to waive the following month’s additional monitoring requirement will be documented in writing, signed by a qualified department official, and made available to the public. The written documentation shall describe the specific cause of the total coliform positive sample and what action the water supplier has taken or will take to correct this problem.

NR 809.31(2)(f)3.3. The requirement to collect 3 routine samples during the next month the public water system provides water to the public shall not be waived solely on the grounds that all repeat samples are total coliform-negative. The water supplier shall collect at least one routine sample before the end of the next month the public water system serves water to the public and use it to determine compliance with the treatment technique trigger for total coliforms in s. NR 809.31, unless the department has determined that the water supplier corrected the contamination problem before the water supplier collected the set of repeat samples required in pars. (a) to (e) and all repeat samples were total coliform negative.

NR 809.31(2)(g)(g) After a water supplier collects a routine sample and before learning the results of the analysis of that sample, if the water supplier collects another routine sample from within 5 adjacent service connections of the initial sample, and the initial sample after analysis is found to contain total coliforms, then the water supplier may count the subsequent sample as a repeat sample instead of as a routine sample.

NR 809.31(2)(h)(h) Results of all routine and repeat samples not invalidated by the department shall be included in determining whether any coliform treatment technique triggers specified in s. NR 809.313 have been exceeded. If any trigger has been exceeded, water suppliers shall complete assessments as required in s. NR 809.313.

NR 809.31(2m)(a)(a) Increased monitoring requirements for public water systems on quarterly or annual monitoring. Except as specified in pars. (d) and (e), water suppliers at public water systems on quarterly or annual monitoring that experience any of the events identified in subds. 1. to 4. shall begin monthly monitoring the month following the event. A water supplier at a public water system on annual monitoring that experiences the event identified in subd. 5. shall begin quarterly monitoring the quarter following the event. The water supplier shall continue monthly or quarterly monitoring until the requirements in par. (b) for quarterly monitoring or par. (c) for annual monitoring are met. A public water system on monthly monitoring for reasons other than those identified in subds. 1. to 4. is not considered to be on increased monitoring for the purposes of pars. (b) and (c).

NR 809.31(2m)(a)4.4. The public water system has two coliform monitoring violations in a rolling 12-month period, or is a non-community public water system and has one coliform monitoring violation and one Level 1 assessment under the provisions of s. NR 809.313 in a rolling 12-month period for a public water system on quarterly monitoring.

NR 809.31(2m)(a)5.5. The public water system has one coliform monitoring violation for a public water system on annual monitoring. For transient non-community public water systems, the department may elect to not count monitoring violations under sub. (9) if the missed sample is collected no later than the end of the monitoring period following the monitoring period in which the sample was missed. The water supplier shall collect the make-up sample in a different week than the routine sample for that monitoring period and shall collect the sample as soon as possible during the monitoring period, except that this is not allowed under par. (c). This authority does not affect the provisions of sub. (9) and s. NR 809.312 (2).

NR 809.31(2m)(b)(b) Requirements for public water systems on increased monitoring to return to quarterly monitoring. The department may reduce the monitoring frequency for a public water system on monthly monitoring triggered under par. (a) to quarterly monitoring if the public water system meets the criteria in subds. 1. and 2.

NR 809.31(2m)(b)1.1. Within the last 12 months, the public water system shall have a completed sanitary survey or a site visit by the department or a voluntary Level 2 assessment by a party approved by the department, be free of sanitary defects, and have a protected water source.

NR 809.31(2m)(b)2.2. The public water system shall have a clean compliance history for a minimum of 12 months. For transient non-community public water systems, the department may elect to not count monitoring violations, as allowed under sub. (9), if the missed sample is collected no later than the end of the monitoring period following the monitoring period in which the sample was missed. The water supplier shall collect the make-up sample in a different week than the routine sample for that monitoring period and should collect the sample as soon as possible during the monitoring period, except that this is not allowed under par. (c). This authority does not affect the provisions of sub. (9) and s. NR 809.312 (2).

NR 809.31(2m)(c)(c) Requirements for systems on increased monitoring to qualify for annual monitoring. The department may reduce the monitoring frequency for a transient non-community public water system on increased monitoring under par. (a) if the transient non-community public water system meets the criteria in par. (d) and the criteria in subds. 1. and 2.

NR 809.31(2m)(c)1.1. The department shall conduct an annual site visit and the water supplier shall correct all identified sanitary defects. The water supplier may substitute a voluntary Level 2 assessment conducted by a party approved by the department in place of the department’s annual site visit in any given year.