NR 810.36(1)(b)(b) Following completion of the second round of source water monitoring required under s. NR 809.331 (2), water suppliers for unfiltered systems shall calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under s. NR 809.331 (2). Water suppliers shall report this value to the department for approval no later than 6 months after the month the system is required to complete the second round of source water monitoring based on the schedule in s. NR 809.331 (3).

NR 810.36(1)(c)(c) If the monthly Cryptosporidium sampling frequency varies, water suppliers shall first calculate a monthly average for each month of monitoring. Systems shall then use these monthly average concentrations, rather than individual sample concentrations, in the calculation of the mean Cryptosporidium level in par. (a) or (b).

NR 810.36(1)(d)(d) The report to the department of the mean Cryptosporidium levels calculated under pars. (a) and (b) shall include a summary of the source water monitoring data used for the calculation.

NR 810.36(1)(e)(e) Failure to comply with the conditions of this subsection is a violation of the treatment technique requirement.

NR 810.36(2)(2) Cryptosporidium inactivation requirements. Unfiltered systems shall provide the level of inactivation for Cryptosporidium specified in this subsection, based on their mean Cryptosporidium levels as determined under sub. (1) and according to the schedule in s. NR 810.37.

NR 810.36(2)(a)(a) Unfiltered systems with a mean Cryptosporidium level of 0.01 oocysts/L or less shall provide at least 2-log Cryptosporidium inactivation.

NR 810.36(2)(b)(b) Unfiltered systems with a mean Cryptosporidium level of greater than 0.01 oocysts/L shall provide at least 3-log Cryptosporidium inactivation.

NR 810.36(3)(3) Inactivation treatment technology requirements. Unfiltered systems shall use chlorine dioxide, ozone, or UV as described in s. NR 810.46 to meet the Cryptosporidium inactivation requirements of this section.

NR 810.36(3)(a)(a) Unfiltered systems that use chlorine dioxide or ozone and fail to achieve the Cryptosporidium inactivation required in sub. (2) on more than one day in the calendar month are in violation of the treatment technique requirement.

NR 810.36(3)(b)(b) Unfiltered systems that use UV light and fail to achieve the Cryptosporidium inactivation required in sub. (2) by meeting the criteria in s. NR 810.46 are in violation of the treatment technique requirement.

NR 810.36(4)(4) Use of two disinfectants. Unfiltered systems shall use a minimum of 2 disinfectants to meet the combined Cryptosporidium inactivation requirements of this section along with the Giardia lamblia and virus inactivation requirements of s. NR 810.31 (1). Each of the 2 disinfectants shall separately achieve the total inactivation required for either Cryptosporidium, Giardia lamblia, or viruses.

NR 810.37(1)(1) Following initial bin classification under s. NR 810.34 (3), filtered systems shall provide the level of treatment for Cryptosporidium required under s. NR 810.35 according to the schedule in sub. (3).

NR 810.37(2)(2) Following initial determination of the mean Cryptosporidium level under s. NR 810.36 (1) (a), unfiltered systems shall provide the level of treatment for Cryptosporidium required under s. NR 810.36 according to the schedule in sub. (3).

1The department may allow up to an additional 2 years for complying with the treatment requirement for systems making capital improvements.

NR 810.37(4)(4) If the bin classification for a filtered system changes following the second round of source water monitoring, as determined under s. NR 810.34, the system shall provide the level of treatment for Cryptosporidium required under s. NR 810.35 on a schedule approved by the department.

NR 810.37(5)(5) If the mean Cryptosporidium level for an unfiltered GWUDI system changes following the second round of monitoring, as determined under s. NR 810.36, and if the system is required to provide a different level of Cryptosporidium treatment under s. NR 810.36 due to this change, the system shall meet this treatment requirement on a schedule approved by the department.

NR 810.38(1)(1) Monitoring requirements for groundwater systems under the direct influence of surface water that do not provide filtration. A public water system that uses a groundwater source under the direct influence of surface water and does not provide filtration treatment shall begin monitoring as specified in this subsection on December 31, 1990, or 6 months after the department determines that the groundwater source is under the direct influence of surface water, whichever is later.

NR 810.38(1)(a)(a) Fecal coliform or total coliform density measurements as required by s. NR 810.30 (1) (a) shall be performed on representative source water samples immediately prior to the first or only point of disinfectant application. The water supplier shall sample for fecal or total coliforms at the following minimum frequency each week the system serves water to the public:

NR 810.38(1)(b)(b) The samples in par. (a) shall be taken on separate days. In addition, one fecal or total coliform density measurement shall be performed every day the system serves water to the public and the turbidity of the source water exceeds one NTU. These samples count toward the weekly coliform sampling requirement.

NR 810.38(1)(c)(c) Turbidity measurements as required by s. NR 810.30 (1) (b) shall be performed on representative grab samples of source water immediately prior to the first or only point of disinfectant application every 4 hours, or more frequently, that the system serves water to the public. A public water system 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.

NR 810.38(1)(d)(d) The total inactivation ratio for each day that the system is in operation shall be determined based on the CT values in ss. NR 810.47 to 810.62, as appropriate. The parameters necessary to determine the total inactivation ratio shall be monitored as follows: