NR 810.38(1)(f)(f) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value shall be recorded each day, except that if there is a failure in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of continuous monitoring, but for no more than 5 working days following the failure of the equipment, and systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the following prescribed frequencies:

NR 810.38(1)(g)(g) The day’s samples to meet par. (f) cannot be taken at the same time. The sampling intervals are subject to department review and approval. If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling in lieu of continuous monitoring, the water supplier for the system shall take a grab sample every 4 hours until the residual concentration is equal to or greater than 0.2 mg/l.

NR 810.38(1)(h)(h) The residual disinfectant concentration of the water in the distribution system shall be measured as follows:

NR 810.38(1)(h)1.1. The residual disinfectant concentration shall be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled, except that the department may allow the water supplier for a public water system which uses a groundwater source, to take disinfectant residual samples at points other than the total coliform sampling points if the department determines that the points are more representative of treated (disinfected) water quality within the distribution system. Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in s. NR 809.311 (1), Table F, may be measured in lieu of residual disinfectant concentration, when approved by the department.

NR 810.38(1)(h)2.2. If the department determines, based on site specific considerations, that a system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified by s. NR 809.311, Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply to that system.

NR 810.38(2)(2) Monitoring requirements for systems using filtration treatment. Water suppliers for a public water system that uses a surface water source or a groundwater source under the direct influence of surface water and provides filtration treatment shall monitor in accordance with all of the following:

NR 810.38(2)(a)(a) Turbidity measurements as specified in s. NR 810.29 shall be performed on representative samples of the system’s combined filter effluent water every 4 hours, or more frequently, that the system serves water to the public. A water supplier may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous measurement for accuracy on a regular basis using a protocol approved by the department. For any systems using slow sand filtration or filtration treatment other than conventional filtration treatment, direct filtration or diatomaceous earth filtration, the department may reduce the sampling frequency to once per day if it determines that less frequent monitoring is sufficient to indicate effective filtration performance. For systems serving 500 or fewer persons, the department may reduce the turbidity sampling frequency to once per day, regardless of the type of filtration treatment used, if the department determines that less frequent monitoring is sufficient to indicate effective filtration performance.

NR 810.38(2)(b)(b) Water suppliers for systems using conventional filtration treatment or direct filtration shall conduct continuous monitoring of turbidity for each individual filter using a method approved in s. NR 809.113 (1), Tables A and B and shall calibrate turbidimeters using the procedure specified by the manufacturer. Water suppliers shall record the results of individual filter monitoring every 15 minutes. If there is a failure in the continuous monitoring equipment, the water supplier shall conduct grab sampling every 4 hours in lieu of continuous monitoring, until the turbidimeter is repaired and back on-line. The water supplier shall repair the equipment no later than 5 working days after the failure or the system is in violation.

NR 810.38(2)(c)(c) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value shall be recorded each day, except that if there is a failure in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of continuous monitoring, but for no more than 5 working days following the failure of the equipment. Water suppliers for systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the frequencies each day prescribed as follows:

If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling in lieu of continuous monitoring, the water supplier shall take a grab sample every 4 hours until the residual disinfectant concentration is equal to or greater than 0.2 mg/l.

NR 810.38(2)(d)(d) The residual disinfectant concentration in the distribution system shall be measured as follows:

NR 810.38(2)(d)1.1. The residual disinfectant concentration shall be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled. The department may allow a public water system which uses both a surface water source or a groundwater source under direct influence of surface water, and a groundwater source to take disinfectant residual samples at points other than the total coliform sampling points if the department determines that the points are more representative of treated or disinfected water quality within the distribution system. Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in s. NR 809.311 (1), Table F, may be measured in lieu of residual disinfectant concentration, when approved by the department.

NR 810.38(2)(d)2.2. If the department determines, based on site specific considerations, that a system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified in s. NR 809.311 (1), Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply to that system.

NR 810.39(1)(1) Water suppliers shall report sampling schedules under s. NR 809.332 and source water monitoring results under s. NR 809.336 to the department unless they notify the department that they will not conduct source water monitoring due to meeting the criteria of s. NR 809.331 (4).

NR 810.39(4)(4) Water suppliers for filtered and unfiltered systems shall report disinfection profiles and benchmarks to the department as described in s. NR 810.32 prior to making a significant change in disinfection practice.

NR 810.39(5)(5) Water suppliers for filtered and unfiltered systems shall report to the department in accordance with the following table for any microbial toolbox options used to comply with treatment requirements under s. NR 810.35 or 810.36. Alternatively, the department may approve a system to certify operation within required parameters for treatment credit rather than reporting monthly operational data for toolbox options.