1. (a) Systems shall conduct an initial and a second round of source water monitoring for each plant that treats water from a surface water source or ground water source directly influenced by surface water. This monitoring may include Cryptosporidium, E. coli, and turbidity, as described in section 5-1.81(a) through (d) of this Subpart, to determine what level, if any, of additional Cryptosporidium treatment shall be provided. Cryptosporidium monitoring shall be done using an approved method. The following method modifications must also be followed:

   1. (1) samples must be at least 10 liters (L) or a packed pellet volume of at least 2 milliliters (mL) must be used. If a 10 L sample cannot be processed, as much sample volume as can be filtered by two filters, as described in 40 CFR 141.704(a)(1), must be processed, up to a packed pellet volume of at least 2 mL;
   2. (2) the method-required matrix spike (MS) samples must be spiked and filtered by a laboratory certified for the method;
   3. (3) if the volume of the MS is greater than 10 L, the volume greater than 10 L may be filtered in the field, and the filtered sample may be shipped with the 10 L sample to the laboratory where the 10 L sample is spiked and filtered through the filter that was used to collect the balance of the sample in the field;
   4. (4) flow cytometer-counted spiking suspensions must be used for MS samples and ongoing precision and recovery samples.
2. (b) Systems that plan to make a significant change to their disinfection practice shall develop disinfection profiles and calculate disinfection benchmarks, as described in section 5-1.82 of this Subpart.
3. (c) Filtered systems shall determine their Cryptosporidium treatment bin classification, as described in section 5-1.83(a) of this Subpart, and provide additional treatment for Cryptosporidium, if required, as described in section 5-1.83(b) of this Subpart. All unfiltered systems shall determine their mean Cryptosporidium level and provide treatment for Cryptosporidium as described in section 5-1.83(c) of this Subpart. Systems shall implement Cryptosporidium treatment according to the schedule in section 5-1.83(d) of this Subpart.

The provisions of this section, and sections 5-1.81 through 5-1.83 of this Subpart apply to all public water systems supplied by a surface water source(s) or ground water source(s) directly influenced by surface water, provided the system serves 15 or more service connections or serves 25 or more persons. The requirements in this section for filtered systems apply to any system with a surface water or GWUDI source that is required to provide filtration, regardless of whether the system is currently operating a filtration system. All treatment must comply with the requirements of the Microbial Toolbox Components as described in 40 CFR 141.715 through 40 CFR 141.720. Any unfiltered systems that are in compliance with the filtration avoidance criteria in section 5-1.30(c) of this Subpart, are subject to the requirements in sections 5-1.80 through 5-1.83 of this Subpart pertaining to unfiltered systems. Wholesale system compliance with sections 5-1.81 through 5-1.83 of this Subpart is based on the population of the largest system in the combined distribution system. The above systems shall comply with the following requirements: