(a) Applicability for total trihalomethanes (TTHM) and haloacetic acids (group of five) (HAA5). All community and nontransient, noncommunity water systems shall comply with the requirements of this section for TTHM and HAA5.
  (1) Systems must comply with the initial monitoring requirements starting on the dates given in subsection (c) of this section.
  (2) Systems must comply with all of the additional requirements in this section starting on the date shown in the table entitled "Date to Start Stage 2 Compliance."
Attached Graphic
    (A) Systems required to conduct quarterly monitoring, must begin monitoring in the first full calendar quarter that includes the compliance date in the table titled "Date to Start Stage 2 Compliance."
    (B) Systems required to conduct routine monitoring less frequently than quarterly must begin monitoring in the calendar month approved by the executive director in their Initial Distribution System Evaluation (IDSE) report or revised monitoring plan identifying Stage 2 sample sites.
  (3) Systems must complete their monitoring plan for the additional Stage 2 TTHM and HAA5 requirements according to §290.121 of this title (relating to Monitoring Plans) before the date shown in the table entitled "Date to Start Stage 2 Compliance."
(b) Maximum contaminant levels (MCL) and operational evaluation levels (OELs) for TTHM and HAA5. Systems shall comply with MCLs and OELs.
  (1) The locational running annual average (LRAA) concentration of TTHM and HAA5 shall not exceed the MCLs. A public water system that exceeds a MCL shall determine compliance as described in subsection (f) of this section.
    (A) The MCL for TTHM is 0.080 milligrams/liter (mg/L).
    (B) The MCL for HAA5 is 0.060 mg/L.
  (2) The OEL at any monitoring location is the sum of the two previous quarters' results plus twice the current quarter's result, divided by 4 to determine an average. A public water system that exceeds an OEL shall perform operation evaluation monitoring and reporting described in subsection (e) of this section.
    (A) The OEL for TTHM is 0.080 mg/L.
    (B) The OEL for HAA5 is 0.060 mg/L.
(c) Monitoring requirements for TTHM and HAA5. Monitoring shall be performed at locations and frequency specified in the system's monitoring plan as approved by the executive director. The executive director may require changes to a system's sampling locations. The executive director may require sampling at additional sampling locations.
  (1) Monitoring locations. Systems must establish Stage 2 compliance monitoring sites throughout the distribution system at locations with the potential for relatively high disinfection byproduct formation. Systems must determine Stage 2 compliance monitoring locations by the dates shown in the table titled "Date to Establish Stage 2 Sites."
Attached Graphic
    (A) Systems that perform IDSE sampling in accordance with paragraph (5) of this subsection must use the IDSE and Stage 1 results to set Stage 2 compliance monitoring sites.
    (B) Systems that do not perform IDSE sampling must set Stage 2 compliance monitoring sites through consultation with the executive director in accordance with this subparagraph.
      (i) Systems required to sample at the same number of sites under Stage 1 and Stage 2, can use the Stage 1 sites for Stage 2 compliance monitoring.
      (ii) Systems required to sample at more sites under Stage 2 than Stage 1 must identify Stage 2 sites in addition to the existing Stage 1 sites. Systems must identify additional sites representing areas of the distribution system with potentially high TTHM or HAA5 levels and provide the rationale for identifying these locations as having high levels of TTHM or HAA5. The required number of compliance monitoring locations must be identified.
      (iii) Systems required to sample at fewer sites under Stage 2 than Stage 1 must identify which locations will be used for Stage 2. Stage 2 sites will be selected by alternating selection of Stage 1 locations representing the highest TTHM levels and highest HAA5 levels until the required number of compliance monitoring locations have been identified.
    (C) The protocol given in 40 Code of Federal Regulations (CFR) §141.605(c) - (e) for selecting Stage 2 sample sites is hereby adopted by reference.
    (D) To change monitoring locations, a system 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. Changes must be approved by the executive director and included in the monitoring plan.
  (2) Monitoring frequency and number of sample sites. Routine sampling frequency and number of sample sites are given in the following table, titled "Routine Stage 2 Monitoring Frequency and Number of Sites." Systems must take all routine compliance TTHM and HAA5 samples during normal operating conditions.
Attached Graphic
  (3) Reduced monitoring for TTHM and HAA5. Monitoring may be reduced when 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 Stage 2 compliance monitoring locations. The Stage 2 reduced sampling frequency and number of sample sites are given in the following table, titled "Reduced Stage 2 Monitoring Frequency and Number of Sites."
Attached Graphic
    (A) Only data collected under the provisions of §290.113 of this title (relating to Stage 1 Disinfection Byproducts (TTHM and HAA5)) and under this section may be used to qualify for reduced monitoring.
    (B) In order to remain on reduced monitoring, a system must meet the applicable conditions of this subparagraph.
      (i) Systems with annual or less frequent reduced monitoring qualify to remain on reduced monitoring as long as each TTHM sample is less than or equal to 0.060 mg/L and each HAA5 sample is less than or equal to 0.045 mg/L.
      (ii) Systems on quarterly reduced monitoring qualify to remain on reduced monitoring as long as the TTHM LRAA is less than or equal to 0.040 mg/L and the HAA5 LRAA is less than or equal to 0.030 mg/L at each monitoring location.
      (iii) To qualify for and remain on reduced monitoring, the source water annual average Total Organic Carbon (TOC) level, before any treatment, must be less than or equal to 4.0 mg/L at each treatment plant treating surface water or groundwater under the direct influence of surface water, based on monitoring conducted under §290.112(c)(2)(C) of this title (relating to Total Organic Carbon (TOC)).
    (C) Systems will be returned to routine monitoring:
      (i) if the LRAA at any monitoring location exceeds either 0.040 mg/L for TTHM or 0.030 mg/L for HAA5 based on quarterly monitoring, or
      (ii) if the annual (or triennial) sample at any location exceeds either 0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or
      (iii) if the source water annual average TOC level, before any treatment, exceeds 4.0 mg/L at any treatment plant treating surface water or groundwater under the direct influence of surface water.
    (D) The executive director may return a system on reduced monitoring to routine monitoring at any time.
    (E) A system that is on reduced Stage 1 monitoring in accordance with §290.113(c)(4) of this title that has monitoring locations for Stage 2 different from those under Stage 1 must initiate routine monitoring in accordance with paragraph (2) of this subsection on the schedule given in subsection (a) of this section.
    (F) A system that is on reduced monitoring in accordance with §290.113(c)(4) of this title may remain on reduced monitoring after the dates identified in subsection (a)(2) of this section only if the system:
      (i) received a very small system (VSS) IDSE waiver under paragraph (5)(A) of this subsection or received a 40/30 IDSE waiver under paragraph (5)(B) of this subsection,
      (ii) meets the reduced monitoring criteria in subparagraph (B) of this paragraph, and
      (iii) is approved to use the same monitoring locations under Stage 1 and Stage 2.
    (G) The executive director may choose to perform calculations and determine whether the system is eligible for reduced monitoring in lieu of having the system report that information.
  (4) Increased monitoring for TTHM and HAA5. The executive director may increase monitoring in accordance with this paragraph.
    (A) A system required to routinely monitor at a particular location annually or less frequently than annually under paragraph (2) of this subsection must increase monitoring to quarterly dual sample sets (every 90 days) at all locations if any TTHM compliance sample is greater than 0.080 mg/L or if any HAA5 compliance sample is greater than 0.060 mg/L at any location.
Cont'd...