NR 810.32(2)(c)(c) In lieu of conducting new monitoring under par. (b), public water systems may elect to meet the following requirements:

NR 810.32(2)(c)1.1. Water suppliers for systems that have at least one year of existing data that are substantially equivalent to data collected under par. (b) may use these data to develop disinfection profiles as specified in this section if the water system has neither made a significant change to its treatment practice nor changed sources since the data were collected. Water suppliers may develop disinfection profiles using up to 3 years of existing data.

NR 810.32(2)(c)2.2. Water suppliers may use disinfection profile or profiles developed previously in lieu of developing a new profile if the water system has not made a significant change, as determined under sub. (1) (b), to its treatment practice or has not changed sources since the profile was developed. Water suppliers for systems that have not developed a virus profile shall develop a virus profile using the same monitoring data on which the Giardia lamblia profile is based.

NR 810.32(2)(d)(d) The water supplier shall calculate the total inactivation ratio for Giardia lamblia as follows:

NR 810.32(2)(d)1.1. For water systems using only one point of disinfectant application, the water supplier may determine the total inactivation ratio for the disinfection segment based on either of the following methods:

NR 810.32(2)(d)1.a.a. Determine one inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly flow.

NR 810.32(2)(d)1.b.b. Determine successive (CTcalc/CT99.9) values, representing sequential inactivation ratios, between the point of disinfectant application and a point before or at the first customer during peak hourly flow. Under this alternative, the water supplier shall calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values together to determine (∑ (CTcalc/CT99.9)).

NR 810.32(2)(d)2.2. For systems using more than one point of disinfectant application before the first customer the water supplier shall determine the CT value of each disinfection segment immediately prior to the next point of disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. The (CTcalc/CT99.9) value of each segment and (∑ (CTcalc/CT99.9)) shall be calculated using the method in subd. 1.

NR 810.32(2)(d)3.3. The water supplier shall determine the total logs of inactivation by multiplying the value calculated in subd. 1. or 2. by 3.0.

NR 810.32(2)(e)(e) Water suppliers shall determine the total logs of inactivation for viruses using a protocol approved by the department.

NR 810.32(2)(f)(f) For water systems required to calculate a disinfection benchmark water suppliers shall use the following procedure:

NR 810.32(2)(f)1.1. For each year of profiling data collected and calculated under this subsection, the water supplier shall determine the lowest mean monthly level of both Giardia lamblia and virus inactivation. The water supplier shall determine the mean Giardia lamblia and virus inactivation for each calendar month for each year of profiling data by dividing the sum of daily or weekly Giardia lamblia and virus log inactivation by the number of values calculated for that month.

NR 810.32(2)(f)2.2. The disinfection benchmark is the lowest monthly mean value, for water systems with one year of profiling data, or the mean of lowest monthly mean values, for water systems with more than one year of profiling data, of the monthly logs of Giardia lamblia and virus log inactivation in each year of profiling data.

NR 810.33(1)(1) Applicability. The requirements of this section apply to all public water systems supplied by a surface water source and public water systems supplied by a groundwater source under the direct influence of surface water.

NR 810.33(1)(a)(a) Wholesale systems shall comply with the requirements of this section based on the population of the largest system in the combined distribution system.

NR 810.33(1)(b)(b) The requirements of this section for filtered systems apply to water systems required by s. NR 810.29 to provide filtration treatment, whether or not the system is currently operating a filtration system.

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).