Section 327IAC8-2.6-2. Disinfection profiling and benchmarking for systems serving a population of at least 10,000 individuals

   (a) A public water system subject to this section will determine its TTHM annual average using the procedure in subdivision (1) and its HAA5 annual average using the procedure in subdivision (2). The annual average is the arithmetic average of the quarterly averages of four (4) consecutive quarters of monitoring. A public water system subject to this section shall meet the following monitoring requirements to determine its TTHM annual average and its HAA5 annual average:

(1) The TTHM annual average must be the annual average during the same period as is used for the HAA5 annual average. Those Subpart H systems serving a population of at least ten thousand (10,000) individuals that:

(A) collected data under 40 CFR 141* must use the results of the samples collected during the last four (4) quarters of required monitoring under 40 CFR 141.142*;

(B) use grandfathered HAA5 occurrence data that meet the provisions of subdivision (2)(B) must use the TTHM data collected at the same time under 327 IAC 8-2-5(a) and 327 IAC 8-2-5.3; and

(C) use HAA5 occurrence data that meet the provisions of subdivision (2)(C)(i) must use the TTHM data collected at the same time under 327 IAC 8-2-5(a) and 327 IAC 8-2-5.3.

(2) The HAA5 annual average must be the annual average during the same period as is used for the TTHM annual average. Those Subpart H systems serving a population of at least ten thousand (10,000) individuals that:

(A) collected data under 40 CFR 141* must use the results of the samples collected during the last four (4) quarters of required monitoring under 40 CFR 141.142*;

(B) have collected four (4) quarters of HAA5 occurrence data that meets the routine monitoring sample number and location requirements for TTHM in 327 IAC 8-2-5(a) and 327 IAC 8-2-5.3 and handling and analytical method requirements of 40 CFR 141.142(b)(1)* may use those data to determine whether this section applies; and

(C) have not collected four (4) quarters of HAA5 occurrence data that meets the provisions of clause (A) or (B) by March 16, 1999, must either:

(i) conduct monitoring for HAA5 that meets the routine monitoring sample number and location requirements for TTHM in 327 IAC 8-2-5(a), 327 IAC 8-2-5.3, and handling and analytical method requirements of 40 CFR 141.142(b)(1)* to determine the HAA5 annual average and whether subsection (b) applies. This monitoring must be completed so that the applicability determination can be made no later than March 31, 2000; or

(ii) comply with all other provisions of this section as if the HAA5 monitoring had been conducted and the results required compliance with subsection (b).

(3) Subpart H systems serving a population of at least ten thousand (10,000) individuals may request that the commissioner approve a more representative annual data set than the data set determined under subdivision (1) or (2) for the purpose of determining applicability of this section.

(4) The commissioner may require that a system use a more representative annual data set than the data set determined under subdivision (1) or (2) for the purpose of determining applicability of this section.

(5) Subpart H systems serving a population of at least ten thousand (10,000) individuals shall submit data to the commissioner based on the following schedules:

(A) Those Subpart H systems serving a population of at least ten thousand (10,000) individuals that collected TTHM and HAA5 data under 40 CFR 141*, as required by subdivisions (1)(A) and (2)(A), shall submit the results of the samples collected during the last twelve (12) months of monitoring required under 40 CFR 141.142* not later than December 31, 1999.

(B) Those Subpart H systems serving a population of at least ten thousand (10,000) individuals that have collected four (4) consecutive quarters of HAA5 occurrence data that meets the routine monitoring sample number and location for TTHM in 327 IAC 8-2-5(a), 327 IAC 8-2-5.3, and handling and analytical method requirements of 40 CFR 141.142(b)(1)*, as allowed by subdivisions (1)(B) and (2)(B), must submit those data to the commissioner not later than April 15, 1999. Until the commissioner has approved the data, the system shall conduct monitoring for HAA5 using the monitoring requirements specified under subdivision (2)(C).

(C) Subpart H systems serving a population of at least ten thousand (10,000) individuals that conduct monitoring for HAA5 using the monitoring requirements specified by subdivision (2)(C)(i) shall submit TTHM and HAA5 data not later than March 31, 2000.

(D) Those systems that elect to comply with all other provisions of this section as if the HAA5 monitoring had been conducted and the results required compliance with this section, as allowed under subdivision (2)(C)(ii), shall notify the commissioner in writing of their election not later than December 31, 1999.

(E) If the system elects to represent that the commissioner approve a more representative annual data set than the data set determined under subdivision (2)(A), the system must submit this request in writing not later than December 31, 1999.

(6) Any Subpart H systems serving a population of at least ten thousand (10,000) individuals having either a TTHM annual average greater than or equal to sixty-four thousandths (0.064) milligram per liter or an HAA5 annual average greater than or equal to forty-eight thousandths (0.048) milligram per liter during the period identified in subdivisions (1) and (2) shall comply with subsection (b).

  (b) Disinfection profiling requirements are as follows:

(1) Any Subpart H system serving a population of at least ten thousand (10,000) individuals that meets the criteria in subsection (a)(6) shall develop a disinfection profile of its disinfection practice for a period of up to three (3) years.

(2) Not later than April 1, 2000, Subpart H systems serving a population of at least ten thousand (10,000) individuals shall monitor daily for a period of twelve (12) consecutive calendar months to determine the total logs of inactivation for each day of operation based on the CT99.9 values in Tables 1.1 through 1.6, 2.1, and 3.1 of 40 CFR 141.74(b)*, as appropriate, through the entire treatment plant. At a minimum, Subpart H systems serving a population of at least ten thousand (10,000) individuals with a single or multiple point of disinfectant application prior to entrance to the distribution system shall conduct the monitoring in clauses (A) through (D) for each disinfection segment. The system shall monitor the parameters necessary to determine the total inactivation ratio using analytical methods in 327 IAC 8-2-8.7 as follows:

(A) The temperature of the disinfection water shall be measured one (1) time per day at each residual disinfectant concentration sampling point during peak hourly flow.

(B) If the system uses chlorine, the pH of the disinfected water shall be measured one (1) time per day at each chlorine residual disinfectant concentration sampling point during peak hourly flow.

(C) The disinfectant contact time (T) shall be determined for each day during peak hourly flow.

(D) The residual disinfectant concentration (C) of the water before or at the first customer and prior to each additional point of disinfection shall be measured each day during peak hourly flow.

(3) Instead of the monitoring conducted under subdivision (2) to develop the disinfection profile, Subpart H systems serving a population of at least ten thousand (10,000) individuals may elect to meet either of the following requirements:

(A) Not later than March 31, 2000, Subpart H systems serving a population of at least ten thousand (10,000) individuals that have three (3) years of existing operational data may submit those data, a profile generated using those data, and a request that the commissioner approve use of those data instead of monitoring under subdivision (2). The commissioner shall determine whether these operational data are substantially equivalent to data collected under subdivision (2) and whether these data are representative of Giardia lamblia inactivation through the entire treatment plant and not just of certain treatment segments. Until the commissioner approves this request, the system is required to conduct monitoring under subdivision (2).

(B) In addition to the disinfection profile generated under subdivision (2), Subpart H systems serving a population of at least ten thousand (10,000) individuals that have existing operational data may use those data to develop a disinfection profile for additional years. Subpart H systems serving a population of at least ten thousand (10,000) individuals may use these additional yearly disinfection profiles to develop a benchmark under subsection (c). The commissioner shall determine whether these operational data are substantially equivalent to data collected under subdivision (2). These data must also be representative of inactivation through the entire treatment plant and not just of certain treatment segments.

(4) Subpart H systems serving a population of at least ten thousand (10,000) individuals shall calculate the total inactivation ratio as follows:

(A) If the system uses only one (1) point of disinfectant application, the system may determine the total inactivation ratio for the disinfection segment by using either of the following methods:

(i) Determine one (1) inactivation ratio (CTcalc/CT_99.9) before or at the first customer during peak hourly flow.

(ii) Determine successive CTcalc/CT_99.9 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 system must calculate the total inactivation ratio by determining (CTcalc/CT_99.9) for each sequence and then adding the (CTcalc/CT_99.9) values together to determine (Σ (CTcalc/CT_99.9)).

(B) Subpart H systems serving a population of at least ten thousand (10,000) individuals that use more than one (1) point of disinfectant application before the first customer 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/CT_99.9) value of each segment and (Σ (CTcalc/CT_99.9) shall be calculated using the method in clause (A).

(C) Subpart H systems serving a population of at least ten thousand (10,000) individuals shall determine the total logs of inactivation by multiplying the value calculated in clause (A) or (B) by three and zero-tenths (3.0).

(5) Subpart H systems serving a population of at least ten thousand (10,000) individuals that use either chloramines or ozone for primary disinfection shall also calculate the logs of inactivation for viruses using a method approved by the commissioner.

(6) Subpart H systems serving a population of at least ten thousand (10,000) individuals shall retain disinfection profile data in graphic form, as a spreadsheet, or in some other format acceptable to the commissioner for review as part of sanitary surveys conducted by the commissioner.

  (c) Disinfection benchmarking requirements are as follows:

(1) A Subpart H system serving a population of at least ten thousand (10,000) individuals required to develop a disinfection profile under subsections (a) and (b) that decides to make a significant change to its disinfection practice shall consult with the commissioner before making the change. As used in this subdivision, "significant changes" means changes to the following:

(A) Point of disinfection.

(B) Disinfectants used in the treatment plant.

(C) Disinfection process.

(D) Any other modification identified by the commissioner.

(2) A Subpart H system serving a population of at least ten thousand (10,000) individuals that is modifying its disinfection practice shall calculate its disinfection benchmark using the following procedures:

(A) Subpart H systems serving a population of at least ten thousand (10,000) individuals shall determine the lowest average monthly Giardia lamblia inactivation for each year of profiling data collected and calculated under subsection (b). The system shall determine the average Giardia lamblia inactivation for each calendar month for each year of profiling data by dividing the sum of daily Giardia lamblia inactivation by the number of values calculated for that month.

(B) The disinfection benchmark is the lowest monthly average value (for Subpart H systems serving a population of at least ten thousand (10,000) with one (1) year of profiling data) or average of lowest monthly average values (for Subpart H systems serving a population of at least ten thousand (10,000) individuals with more than one (1) year of profiling data) of the monthly logs of Giardia lamblia inactivation for each year of profiling data.

(C) Subpart H systems serving a population of at least ten thousand (10,000) individuals that use either chloramines or ozone for primary disinfection shall also calculate the disinfection benchmark for viruses using a method approved by the commissioner.

(D) The system shall submit the following information to the commissioner as part of its consultation process:

(i) A description of the proposed change in disinfection practice.

(ii) The disinfection profile for Giardia lamblia (and, if necessary, viruses) under subsection (b) and benchmark as required by this subsection.

(iii) An analysis of how the proposed change will affect the current levels of disinfection.

  *40 CFR 141, 40 CFR 141.142, 40 CFR 141.142(b)(1), and 40 CFR 141.74(b) are incorporated by reference and are available for copying at the Indiana Department of Environmental Management, Office of Water Quality, 100 North Senate Avenue, Room N1255, Indianapolis, Indiana 46204. (Water Pollution Control Division; 327 IAC 8-2.6-2; filed May 1, 2003, 12:00 p.m.: 26 IR 2854; filed Jun 13, 2005, 2:30 p.m.: 28 IR 3248; errata filed Jul 6, 2005, 3:15 p.m.: 28 IR 3583)