Rule 391-3-5-.53. Stage 2 Disinfection Byproducts Rule (Stage 2 DBPR)

Purpose. The Stage 2 Disinfection Byproducts Rule (DBPR) (40 CFR, Subpart V § 141) builds on existing regulations by requiring water systems to meet disinfection byproduct (DBP) maximum contaminant levels (MCLs) at each monitoring site in the distribution system to better protect public health. The Stage 2 DBPR includes a provision requiring all community water systems (CWS) and only non-transient non-community water systems (NTNCWS) serving more than 10,000 people to conduct an initial distribution system evaluation (IDSE) (40 CFR, Subpart U § 141). NTNCWS serving less than 10,000 are exempted from IDSE requirements, but will need to comply with the Stage 2 DBPR compliance monitoring requirements. The goal of the IDSE is to characterize the distribution system and identify monitoring sites where customers may be exposed to high levels of total trihalomethanes (TTHM) and haloacetic acids (HAA5).

1. (1) Initial Distribution System Evaluations.

   1. (a) General requirements: The requirements of 40 CFR Part 141Su bpart U constitute national primary drinking water regulations. The regulations in 40 CFR Part 141 Subpart U establish monitoring and other requirements for identifying 40 CFR Part 141 Subpart V compliance monitoring locations for determining compliance with maximum contaminant levels for total trihalomethanes (TTHM) and haloacetic acids (five) (HAA5). A system must use an Initial Distribution System Evaluation (IDSE) to determine locations with representative high TTHM and HAA5 concentrations throughout its distribution system. IDSEs are used in conjunction with, but separate from, compliance monitoring per 40 CFR Part 141 Subpart L, to identify and select compliance monitoring locations per 40 CFR Part 141 Subpart V.
   2. (b) Applicability: Public water systems are subject to these requirements if the water system is a community water system that uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light; or if the water system is a non-transient non-community water system that serves at least 10,000 people and uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light.
   3. (c) Schedule: 40 CFR Subpart U § 141.600(c), in its entirety, is hereby incorporated by reference. Systems required to comply with Initial Distribution System Evaluations - Subpart U, must comply with the schedule specified in the table 40 CFR § 141.600(c)(1). A wholesale system or a consecutive system must comply with the specified schedule at the same time as the system with the earliest compliance date in the combined distribution system.
   4. (d) 40 CFR Subpart U § 141.600(d) through (f), in its entirety, is hereby incorporated by reference.

   5. (e) Standard Monitoring: 40 CFR Subpart U § 141.601 is hereby incorporated by reference.

      1. 1. Standard monitoring plan: 40 CFR Subpart U § 141.601(a) through (c), in its entirety, is hereby incorporated by reference.
      2. 2. System specific studies: 40 CFR Subpart U § 141.602(a) through (b), in its entirety, is hereby incorporated by reference.
      3. 3. 40/30 Certification: 40 CFR Subpart U § 141.603(a) through (b), in its entirety, is hereby incorporated by reference.
      4. 4. Very small system waivers: 40 CFR Subpart U § 141.604(a) through (b), in its entirety, is hereby incorporated by reference.
   6. (f) 40 CFR Part 141 Subpart V Compliance Monitoring Location Recommendations: 40 CFR Subpart U § 141.605(a) through (e), in its entirety, is hereby incorporated by reference. Water system's IDSE report must include the recommendations and justification for where and during what month(s) TTHM and HAA5 monitoring for Subpart V of part 141 should be conducted. Water system must base its recommendations on the criteria in paragraphs (b) through (e) of this section.

(2) Stage 2 Disinfection Byproducts Requirements. (a) General Requirements: The requirements of 40 CFR Part 141Su bpart V constitute national primary drinking water regulations. The regulations establish monitoring and other requirements for achieving compliance with maximum contaminant levels based on locational running annual averages (LRAA) for total trihalomethanes (TTHM) and haloacetic acids (five) (HAA5), and for achieving compliance with maximum residual disinfectant residuals for chlorine and chloramine for certain consecutive systems. (b) Applicability: Public water systems are subject to these requirements if the system is a community water system or a non-transient non-community water system that uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light. (c) Schedule: 40 CFR Subpart V § 141.620(c), in its entirety, is hereby incorporated by reference. Systems required to comply with Stage 2 Disinfection Byproducts Requirements - Subpart V, must comply with the schedule specified in the table 40 CFR § 141.620(c). A wholesale system or a consecutive system must comply with the specified schedule at the same time as the system with the earliest compliance date in the combined distribution system. 1. Systems serving 100,000 or more people: April 1, 2012 2. Systems serving 50,000-99,999 people: October 1, 2012 3. Systems serving 10,000-49,999 people: October 1, 2013 4. Systems serving fewer than 10,000 people: October 1, 2013 if no Cryptosporidium monitoring is required under 40 CFR § 141.701(a)(4) OR October 1, 2014 if Cryptosporidium monitoring is required under 40 CFR § 141.701(a)(4) or (a)(6). (d) Monitoring frequency must be in accordance with 40 CFR Subpart V § 141.621(a)(2). 1. If a water system is required to conduct quarterly monitoring, it must begin monitoring in the first full calendar quarter that includes the compliance date in the table in paragraph 40 CFR § 141.620(c). 2. If a water system is required to conduct monitoring at a frequency that is less than quarterly, it must begin monitoring in the calendar month recommended in the IDSE report prepared under 40 CFR § 141.601 or 40 CFR § 141.602 or the calendar month identified in the Subpart V monitoring plan developed under 40 CFR § 141.622 no later than twelve (12) months after the compliance date in paragraph 40 CFR § 141.620(c). 3. If a water system is required to conduct quarterly monitoring, it must make compliance calculations at the end of the fourth calendar quarter that follows the compliance date and at the end of each subsequent quarter (or earlier if the LRAA calculated based on fewer than four quarters of data would cause the MCL to be exceeded regardless of the monitoring results of subsequent quarters). If a water system is required to conduct monitoring at a frequency that is less than quarterly, it must make compliance calculations beginning with the first compliance sample taken after the compliance date. 4. For the purpose of the schedule in paragraph 40 CFR § 141.620(c), the Division may determine that the combined distribution system does not include certain consecutive systems based on factors such as receiving water from a wholesale system only on an emergency basis or receiving only a small percentage and small volume of water from a wholesale system. The Division may also determine that the combined distribution system does not include certain wholesale systems based on factors such as delivering water to a consecutive system only on an emergency basis or delivering only a small percentage and small volume of water to a consecutive system. (e) Monitoring and Compliance. 1. Systems required to monitor quarterly. To comply with Subpart V MCLs in 40 CFR § 141.64(b)(2), water systems must calculate LRAAs for TTHM and HAA5 using monitoring results collected under this Subpart and determine that each LRAA does not exceed the MCL. If a water system fails to complete four consecutive quarters of monitoring, it must calculate compliance with the MCL based on the average of the available data from the most recent four quarters. If a water system takes more than one sample per quarter at a monitoring location, it must average all samples taken in the quarter at that location to determine the quarterly average to be used in the LRAA calculation. 2. Systems required to monitor yearly or less frequently. To determine compliance with Subpart V MCLs in 40 CFR § 141.64(b)(2), water systems must determine that each sample taken is less than the MCL. If any sample exceeds the MCL, the water system must comply with the requirements of 40 CFR § 141.625. If no sample exceeds the MCL, the sample result for each monitoring location is considered the LRAA for that monitoring location. (f) Violations: A water system is in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if it fails to monitor. (g) Routine Monitoring: If a water system submitted an IDSE report, it must begin monitoring at the locations and months it has recommended in its IDSE report submitted under 40 CFR § 141.605 following the schedule in 40 CFR § 141.620(c), unless the Division requires other locations or additional locations after its review. If a water system submitted a 40/30 certification under 40 CFR § 141.603 or it qualified for a very small system waiver under 40 CFR § 141.604 or it is a non-transient non-community water system serving less than 10,000, it must monitor at the location(s) and dates identified in its monitoring plan in 40 CFR § 141.132(f), updated as required by 40 CFR § 141.622. (h) Water systems must monitor at no fewer than the number of locations identified in this paragraph: Source Water Type Population Served Monitoring Frequency⁽¹⁾ Distribution System Monitoring Locations Total per Monitoring Period⁽²⁾ Subpart H Fewer than 500 per year 2 500-3,300 per quarter 2 3,301-9,999 per quarter 2 10,000-49,999 per quarter 4 50,000-249,999 per quarter 8 250,000-999,999 per quarter 12 1,00,000-4,999,999 5,000, 000 or more per quarter per quarter 16 20 Ground Water Fewer than 500 per year 2 500-9,999 per year 2 10,000-99,999 per quarter 4 100,000-499,999 per quarter 6 500,000 or more per quarter 8 NOTES: (1) All systems must monitor during the highest month of DBP concentrations. (2) Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, except for Subpart H systems serving 500-3,300 persons. Systems on annual monitoring and Subpart H systems serving 500-3,300 persons are required to take individual TTHM and HAA5 samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. Only one location with a dual sample set per monitoring period is needed if highest TTHM and HAA5 concentrations occur at the same location (and month, if monitored annually). (i) If a water system is an undisinfected system that begins using a disinfectant other than UV light after the dates in 40 CFR Part 141 Subpart U for complying with the Initial Distribution System Evaluation requirements, it must consult with the Division to identify compliance monitoring locations for 40 CFR Part 141 Subpart V. The water system must then develop a monitoring plan under 40 CFR § 141.622 that includes those monitoring locations. (j) Analytical Methods: The water system must use an approved method listed in 40 CFR § 141.131, as stated in Rule 391-3-5-.24(4)(g) for TTHM and HAA5 analyses. Analyses must be conducted by laboratories that have received certification by EPA or the Division.

1. (3) Monitoring Plans for Stage 2 Disinfection Byproducts Requirements.

   1. (a) Water systems must develop and implement a monitoring plan to be kept on file for Division and public review. The monitoring plan must contain the following elements and be complete no later than the date it conducts its initial monitoring under 40 CFR Part 141 Subpart V.

      1. 1. Monitoring locations;
      2. 2. Monitoring dates;
      3. 3. Compliance calculation procedures; and
      4. 4. Monitoring plans for any other systems in the combined distribution system.
   2. (b) If a water system was not required to submit an IDSE report under either 40 CFR § 141.601 or § 141.602, and it does not have sufficient 40 CFR Part 141 Subpart L (Stage 1 DBPR) monitoring locations to identify the required number of 40 CFR Part 141 Subpart V (Stage 2 DBPR) compliance monitoring locations indicated in 40 CFR § 141.605(b), it must identify additional locations by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of compliance monitoring locations have been identified. It must also provide the rationale for identifying the locations as having high levels of TTHM or HAA5. If it has more Subpart L monitoring locations than required for Subpart V compliance monitoring in 40 CFR § 141.605(b), it must identify which locations it will use for Subpart V compliance monitoring by alternating selection of locations representing high TTHM levels and high HAA5 levels until the required number of Subpart V compliance monitoring locations have been identified.
   3. (c) A Subpart H water system serving over 3,300 people must submit a copy of its monitoring plan to the Division prior to the date it conducts its initial monitoring under this Subpart, unless its IDSE report submitted under Subpart U of this part contains all the information required by this section.
   4. (d) A water system may revise its monitoring plan to reflect changes in treatment, distribution system operations and layout (including new service areas), or other factors that may affect TTHM or HAA5 formation, or for Division-approved reasons, after consultation with the Division regarding the need for changes and the appropriateness of changes. If a water system changes monitoring locations, it must replace existing compliance monitoring locations with the lowest LRAA with new locations that reflect the current distribution system locations with expected high TTHM or HAA5 levels. The Division may also require modifications in water system's monitoring plan. A Subpart H system serving over 3,300 people must submit a copy of its modified monitoring plan to the Division prior to the date it is required to comply with the revised monitoring plan.

2. (4) Reduced Monitoring.

   1. (a) The water system may reduce monitoring to the level specified in table 40 CFR § 141.623(a) any time the LRAA is less than or equal to (<=) 0.040 mg/L for TTHM and less than or equal to (<=) 0.030 mg/L for HAA5 at all monitoring locations. It may only use data collected under the provisions of this Subpart or Subpart L of this part to qualify for reduced monitoring. In addition, the source water annual average TOC level, before any treatment, must be less than or equal to (<=)4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water, based on monitoring conducted under either 40 CFR § 141.132(b)(1)(iii) or § 141.132(d).
   2. (b) The water system may remain on reduced monitoring as long as the TTHM LRAA less than or equal to (<=) 0.040 mg/L and the HAA5 LRAA less than or equal to (<=) 0.030 mg/L at each monitoring location (for systems with quarterly reduced monitoring) or each TTHM sample less than or equal to (<=) 0.060 mg/L and each HAA5 sample less than or equal to (<=) 0.045 mg/L (for systems with annual or less frequent monitoring). In addition, the source water annual average TOC level, before any treatment, must be less than or equal to (<=) 4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water, based on monitoring conducted under either 40 CFR § 141.132(b)(1)(iii) or § 141.132(d).
   3. (c) If the LRAA based on quarterly monitoring at any monitoring location exceeds either 0.040 mg/L for TTHM or 0.030 mg/L for HAA5 or if the annual (or less frequent) sample at any location exceeds either 0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or if the source water annual average TOC level, before any treatment, is greater than () 4.0 mg/L at any treatment plant treating surface water or ground water under the direct influence of surface water, the water system must resume routine monitoring under 40 CFR § 141.621 or begin increased monitoring if 40 CFR § 141.625 applies.
   4. (d) The Division may return the water system to routine monitoring at its discretion.
3. (5) Additional Requirements for Consecutive Systems. A consecutive system that does not add a disinfectant but delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light must comply with analytical and monitoring requirements for chlorine and chloramines in 40 CFR § 141.131(c) and § 141.132(c)(1) and the compliance requirements in 40 CFR § 141.133(c)(1) beginning April 1, 2009, unless required earlier by the Division, and report monitoring results under 40 CFR § 141.134(c).

4. (6) Conditions Requiring Increased Monitoring.

   1. (a) A water system that is required to monitor at a particular location annually or less frequently than annually under 40 CFR § 141.621 or § 141.623 must increase monitoring to dual sample sets once per quarter (taken every 90 days) at all locations if a TTHM sample is >0.080 mg/L or a HAA5 sample is >0.060 mg/L at any location.
   2. (b) A water system is in violation of the MCL when the LRAA exceeds the Subpart V MCLs in 40 CFR § 141.64(b)(2), calculated based on four consecutive quarters of monitoring (or the LRAA calculated based on fewer than four quarters of data if the MCL would be exceeded regardless of the monitoring results of subsequent quarters). The water system is in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if it fails to monitor.
   3. (c) A water system may return to routine monitoring once it has conducted increased monitoring for at least four consecutive quarters and the LRAA for every monitoring location is <=0.060 mg/L for TTHM and <=0.045 mg/L for HAA5.

5. (7) Operational Evaluation Levels.

   1. (a) The water system has exceeded the operational evaluation level at any monitoring location where the sum of the two previous quarters' TTHM results plus twice the current quarter's TTHM result, divided by 4 to determine an average, exceeds 0.080 mg/L, or where the sum of the two previous quarters' HAA5 results plus twice the current quarter's HAA5 result, divided by 4 to determine an average, exceeds 0.060 mg/L.

      1. 1. If a water system exceeds the operational evaluation level, it must conduct an operational evaluation and submit a written report of the evaluation to the Division no later than 90 days after being notified of the analytical result that causes it to exceed the operational evaluation level. The written report must be made available to the public upon request.

      2. 2. The operational evaluation must include an examination of system treatment and distribution operational practices, including storage tank operations, excess storage capacity, distribution system flushing, changes in sources or source water quality, and treatment changes or problems that may contribute to TTHM and HAA5 formation and what steps could be considered to minimize future exceedences.

         1. (i) The water system may request and the Division may allow limiting the scope of the water system's evaluation if it is able to identify the cause of the operational evaluation level exceedance.
         2. (ii) The water system's request to limit the scope of the evaluation does not extend the schedule in paragraph (7)(a)1. for submitting the written report. The Division must approve this limited scope of evaluation in writing and the water system must keep that approval with the completed report.
6. (8) Requirements for Remaining on Reduced TTHM and HAA5 Monitoring Based on Subpart L Results. 40 CFR Subpart V § 141.627 is hereby incorporated by reference.
7. (9) Requirements for Remaining on Increased TTHM and HAA5 Monitoring Based on Subpart L Results. 40 CFR Subpart V § 141.628 is hereby incorporated by reference.
8. (10) Reporting and Recordkeeping Requirements. 40 CFR Subpart V § 141.629 is hereby incorporated by reference.
9. (11) Division Recordkeeping. The records kept by the Division shall be in accordance with 40 CFR § 142.14.

Authority: O.C.G.A. § 12-5-170et seq.

History. Original Rule entitled "Stage 2 Disinfection Byproducts Rule (Stage 2 DBPR)" adopted. F. May 27, 2009; eff. June 16, 2009.

Amended: F. Jan. 8, 2014; eff. Jan. 28, 2014.

Amended: F. Apr. 22, 2021; eff. May 12, 2021.