NR 810.33(1)(c)(c) The requirements of this section for unfiltered groundwater systems under the direct influence of surface water apply only to unfiltered systems that timely met and continue to meet the filtration avoidance criteria in s. NR 810.30.

NR 810.33(2)(2) Requirements. Public water systems shall comply with the following requirements:

NR 810.33(2)(a)(a) Water suppliers shall conduct an initial and a second round of source water monitoring for each plant that treats a surface water or GWUDI source. This monitoring may include sampling for Cryptosporidium, E. coli, and turbidity as described in s. NR 809.331, to determine what level, if any, of additional Cryptosporidium treatment they shall provide.

NR 810.33(2)(b)(b) Water suppliers for systems that plan to make a significant change to their disinfection practice shall develop disinfection profiles and calculate disinfection benchmarks, as described in s. NR 810.32.

NR 810.33(2)(c)(c) Water suppliers for filtered systems shall determine their Cryptosporidium treatment bin classification as described in s. NR 810.34 and provide additional treatment for Cryptosporidium, if required, as described in s. NR 810.35. All unfiltered GWUDI systems shall provide treatment for Cryptosporidium as described in s. NR 810.36. Filtered systems and unfiltered GWUDI systems shall implement Cryptosporidium treatment according to the schedule in s. NR 810.37.

NR 810.33(2)(d)(d) Water systems with uncovered finished water storage facilities shall comply with the requirements to cover the facility as described in s. NR 810.28. Finished water is that water which has received all required treatment.

NR 810.33(2)(e)(e) Water systems required to provide additional treatment for Cryptosporidium shall implement microbial toolbox options that are designed and operated as described in ss. NR 810.41 to 810.46.

NR 810.33(2)(f)(f) Water suppliers for water systems shall comply with the applicable recordkeeping and reporting requirements described in ss. NR 810.39 and 810.40.

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.