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)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(2)(2) Water suppliers for filtered systems shall report the Cryptosporidium bin classification of their system to the department as described in s. NR 810.34.

NR 810.39(3)(3) Water suppliers for unfiltered GWUDI systems shall report the mean source water Cryptosporidium level of their system to the department as described in s. NR 810.36.

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.

NR 810.40(1)(1) Public water systems shall keep results from the initial round of source water monitoring under s. NR 809.331 (1) and the second round of source water monitoring under s. NR 809.331 (2) until 3 years after bin classification under s. NR 810.34 for filtered systems or determination of the mean Cryptosporidium level under s. NR 810.35 for unfiltered GWUDI systems for the particular round of monitoring.

NR 810.40(2)(2) Public water systems shall keep any notification to the department that the systems will not conduct source water monitoring due to meeting the criteria of s. NR 809.331 (4) for 3 years from the date of notification.

NR 810.40(3)(3) Public water systems shall keep the results of treatment monitoring associated with microbial toolbox options under ss. NR 810.42 to 810.46 for 3 years from the date of monitoring.

NR 810.41(1)(a)(a) Public water systems receive the treatment credits listed in the table in sub. (2) by meeting the conditions for microbial toolbox options described in ss. NR 810.42 to 810.46. Systems apply these treatment credits to meet the treatment requirements in s. NR 810.35 or 810.36, as applicable.