NR 810.34(1)(1) Following completion of the initial round of source water monitoring required under s. NR 809.331 (1), water suppliers for filtered systems shall calculate an initial Cryptosporidium bin concentration for each plant for which monitoring was required. Calculation of the bin concentration shall use the Cryptosporidium results reported under s. NR 809.331 (1) and shall follow the procedures in sub. (2) (a) to (e).

NR 810.34(2)(a)(a) For filtered systems that collect a total of at least 48 samples, the bin concentration is equal to the arithmetic mean of all sample concentrations.

NR 810.34(2)(b)(b) For filtered systems that collect a total of at least 24 samples, but not more than 47 samples, the bin concentration is equal to the highest arithmetic mean of all sample concentrations in any 12 consecutive months during which Cryptosporidium samples were collected.

NR 810.34(2)(c)(c) For filtered systems that serve fewer than 10,000 people and monitor for Cryptosporidium for only one year, collecting 24 samples in 12 months, the bin concentration is equal to the arithmetic mean of all sample concentrations.

NR 810.34(2)(d)(d) For filtered systems with plants operating only part of the year that monitor fewer than 12 months per year under s. NR 809.331 (5), the bin concentration is equal to the highest arithmetic mean of all sample concentrations during any year of Cryptosporidium monitoring.

NR 810.34(2)(e)(e) 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 applicable calculation for bin classification in pars. (a) to (d).

NR 810.34(3)(3) Water suppliers for filtered systems shall determine their initial bin classification from the following table and using the Cryptosporidium bin concentration calculated under subs. (1) and (2):

NR 810.34(4)(4) Following completion of the second round of source water monitoring required under s. NR 809.331 (2), water suppliers for filtered systems shall recalculate their Cryptosporidium bin concentration using the Cryptosporidium results reported under s. NR 809.331 (2) and following the procedures in sub. (2) (a) to (d). Systems shall then redetermine their bin classification using this bin concentration and the table in sub. (3).

NR 810.34(5)(5) Water suppliers shall report their bin classification of the water system as follows:

NR 810.34(5)(a)(a) Water suppliers for filtered systems shall report the initial bin classification under par. (c) to the department for approval no later than 6 months after the system is required to complete initial source water monitoring based on the schedule in s. NR 809.331 (3).

NR 810.34(5)(b)(b) Water suppliers for filtered systems shall report the bin classification under sub. (4) to the department for approval no later than 6 months after the system is required to complete the second round of source water monitoring based on the schedule in s. NR 809.331 (3).

NR 810.34(5)(c)(c) The bin classification report to the department shall include a summary of source water monitoring data and the calculation procedure used to determine bin classification.

NR 810.34(6)(6) Failure to comply with the conditions of sub. (5) is a violation of the treatment technique requirement.

NR 810.35(1)(1) Filtered systems shall provide the level of additional treatment for Cryptosporidium specified in this paragraph based on their bin classification as determined under s. NR 810.34 and according to the schedule in s. NR 810.37.

NR 810.35(2)(2) Systems shall use the following treatment or management practices:

NR 810.35(2)(a)(a) Filtered systems shall use one or more of the treatment and management options listed in s. NR 810.41, termed the microbial toolbox, to comply with the additional Cryptosporidium treatment required in sub. (1).

NR 810.35(2)(b)(b) Filtered systems classified in Bin 3 and Bin 4 shall achieve at least 1-log of the additional Cryptosporidium treatment required under sub. (1) using either one or a combination of the following: bag filters, bank filtration, cartridge filters, chlorine dioxide, membranes, ozone, or UV, as described in ss. NR 810.42 to 810.46.

NR 810.35(3)(3) Failure by a filtered system in any month to achieve treatment credit by meeting criteria in ss. NR 810.41 to 810.46 for microbial toolbox options that is at least equal to the level of treatment required in sub. (1) is a violation of the treatment technique requirement.

NR 810.35(4)(4) If the department determines during a sanitary survey or an equivalent source water assessment that after a filtered system completed the monitoring conducted under s. NR 809.331 (1) or 809.331 (2), significant changes occurred in the system’s watershed that could lead to increased contamination of the source water by Cryptosporidium, the system shall take actions specified by the department to address the contamination. These actions may include additional source water monitoring or implementing microbial toolbox options listed in s. NR 810.41, or both.

NR 810.36NR 810.36 Cryptosporidium treatment requirements for groundwater under the direct influence of surface water systems that do not filter. Section NR 811.42 requires filtration for all surface water sources. The following applies only to GWUDI systems not required to filter.