1. (1) Following completion of the initial round of source water monitoring under section 5-1.81(a)(1) of this Subpart, filtered systems shall calculate an initial Cryptosporidium bin concentration for each plant for which monitoring was required, such calculation shall be done in accordance with 40 CFR 141.710(b)(1) through 40 CFR 141.710(b)(5). Calculation of the bin concentration shall use the Cryptosporidium results reported under section 5-1.81 of this Subpart.

2. (2) Filtered systems shall determine their initial bin classification from the following table and using the Cryptosporidium bin concentration calculated under paragraph (1) of this subdivision:

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3. (3) Following completion of the second round of source water monitoring required under section 5-1.81(a)(2) of this Subpart, filtered systems shall recalculate their Cryptosporidium bin concentration using the Cryptosporidium results reported under section 5-1.81(a)(2) of this Subpart, and following the procedures in 40 CFR 141.710(b)(1) through 40 CFR 141.710(b)(4). Systems shall then reevaluate their bin classification using the bin concentration from the second round of monitoring and the table in paragraph (2) of this subdivision.

   1. (i) Filtered systems shall report their initial bin classification under paragraph (2) of this subdivision to the State for approval no later than six months after the system is required to complete initial source water monitoring based on the schedule referenced in section 5-1.81(a)(3) of this Subpart.
   2. (ii) Systems shall report their bin classification under paragraph (3) of this subdivision to the State for approval no later than six months after the system is required to complete the second round of source water monitoring based on the schedule referenced in section 5-1.81(a)(3) of this Subpart.

   3. (iii) The bin classification report to the State shall include a summary of source water monitoring data and the calculation procedure used to determine bin classification.

      (b) Filtered system additional Cryptosporidium treatment requirements.

   (4)

4. (1) Filtered systems shall provide the level of additional treatment for Cryptosporidium specified in this paragraph based on their bin classification as determined under subdivision (a) of this section and according to the schedule in subdivision (d) of this section.

   1. (i) Filtered systems shall use one or more of the treatment and management options, as approved by the State, to comply with the additional Cryptosporidium treatment required in paragraph (1) of this subdivision.
   2. (ii) Systems classified in Bin 3 and Bin 4 shall achieve at least 1-log of the additional Cryptosporidium treatment required under paragraph (1) of this subdivision using either one or a combination of the following, as approved by the State: bag filters, bank filtration, cartridge filters, chlorine dioxide, membranes, ozone, or UV.

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   (2)

5. (3) Failure by a system in any month to achieve treatment credit at least equal to the level of treatment required in paragraph (1) of this subdivision is a violation of the treatment technique requirement.

6. (4) If the State determines during a sanitary survey or an equivalent source water assessment that, after a system completed the monitoring conducted under section 5-1.81(a)(1) or (2) of this Subpart, 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 State to address the contamination.

   (c) Unfiltered system Cryptosporidium treatment requirements.

7. (1) Determination of mean Cryptosporidium level.

   1. (i) Following completion of the initial source water monitoring required under section 5-1.81(a)(1) of this Subpart, unfiltered systems shall calculate the arithmetic mean of all Cryptosporidium sample concentrations reported for such monitoring. Systems shall report this value to the State for approval no later than six months after the month the system is required to complete initial source water monitoring based on the schedule referenced in section 5-1.81(a)(3) of this Subpart.
   2. (ii) Following completion of the second round of source water monitoring required under section 5-1.81(a)(2) of this Subpart, unfiltered systems shall calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under that monitoring. Systems shall report this value to the State for approval no later than six months after the month the system is required to complete the second round of source water monitoring based on the schedule referenced in section 5-1.81(a)(3) of this Subpart.
   3. (iii) If the monthly Cryptosporidium sampling frequency varies, systems 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 subparagraph (i) or (ii) of this paragraph.
   4. (iv) The report to the State of the mean Cryptosporidium levels calculated under subparagraphs (i) and (ii) of this paragraph shall include a summary of the source water monitoring data used for the calculation.

8. (2) Cryptosporidium inactivation requirements. Unfiltered systems shall provide the level of inactivation for Cryptosporidium specified in this paragraph, based on their mean Cryptosporidium levels as determined under paragraph (1) of this subdivision and according to the schedule in subdivision (d) of this section.

   1. (i) Unfiltered systems with a mean Cryptosporidium level of 0.01 oocysts/L or less shall provide at least 2-log Cryptosporidium inactivation.
   2. (ii) Unfiltered systems with a mean Cryptosporidium level of greater than 0.01 oocysts/L shall provide at least 3-log Cryptosporidium inactivation.
9. (3) Inactivation treatment technology requirements. Unfiltered systems shall use chlorine dioxide, ozone, or UV to meet the Cryptosporidium inactivation requirements of this section.

10. (4) Use of two disinfectants. Unfiltered systems shall meet the combined Cryptosporidium inactivation requirements of this section and Giardia lamblia and virus inactivation requirements of section 5-1.30(c)(3) of this Subpart using a minimum of two disinfectants, and each of two disinfectants must separately achieve the total inactivation required for either Cryptosporidium, Giardia lamblia, or viruses. Systems that fail to install a second disinfectant to treat for Cryptosporidium are in violation of the treatment technique requirement.

    (d) Schedule for compliance with Cryptosporidium treatment requirements.

11. (1) Following initial bin classification under subdivision (a) of this section, filtered systems shall provide the level of treatment for Cryptosporidium required under subdivision (b) of this section, on a schedule approved by the State.
12. (2) Following initial determination of the mean Cryptosporidium level under subparagraph (c)(1)(i) of this section, unfiltered systems shall provide the level of treatment for Cryptosporidium required under subdivision (c) of this section.
13. (3) If the bin classification for a filtered system changes following the second round of source water monitoring, as determined under paragraph (a)(3) of this section, the system shall provide the level of treatment for Cryptosporidium required under subdivision (b) of this section on a schedule approved by the State.
14. (4) If the mean Cryptosporidium level for an unfiltered system changes following the second round of monitoring, as determined under subparagraph (c)(1)(ii) of this section, and if the system shall provide a different level of Cryptosporidium treatment under subdivision (c) of this section due to this change, the system shall meet this treatment requirement on a schedule approved by the State.

(a) Bin classification for filtered systems.