(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.
  (1) Systems must comply with the Stage 1 requirements in this section until the date shown in the table entitled "Date to Start Stage 2 Compliance."
  (2) Until the date shown in the table in Figure: 30 TAC §290.113(a)(2) of this paragraph, systems must continue to monitor according to this section.
Attached Graphic
(b) Maximum contaminant level (MCL) for TTHM and HAA5. The running annual average concentration of TTHM and HAA5 shall not exceed the MCLs.
  (1) The MCL for TTHM is 0.080 milligrams/liter (mg/L).
  (2) The MCL for HAA5 is 0.060 mg/L.
(c) Monitoring requirements for TTHM and HAA5. Systems must take all TTHM and HAA5 samples during normal operating conditions. Monitoring shall be performed at locations and frequency specified in the system's monitoring plan.
  (1) The minimum number of samples required to be taken shall be based on the number of treatment plants used by the system, except that multiple wells drawing raw water from a single aquifer shall be considered as one treatment plant for determining the minimum number of samples.
  (2) All samples taken within one sampling period shall be collected within a 24-hour period.
  (3) Systems must routinely sample at the frequency and locations given in the following table entitled "Stage 1 Routine Monitoring Frequency and Locations for TTHM and HAA5."
Attached Graphic
  (4) The executive director may reduce the monitoring frequency for TTHM and HAA5 as indicated in the following table entitled "Stage 1 Reduced Monitoring Frequency and Locations for TTHM and HAA5."
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    (A) The executive director may not reduce the routine monitoring requirements for TTHM and HAA5 until a system has completed one year of routine monitoring in accordance with the provisions of paragraph (3) of this subsection.
    (B) A system that is on reduced monitoring and collects quarterly samples for TTHM and HAA5 may remain on reduced monitoring as long as the running annual average of quarterly averages for TTHM and HAA5 is no greater than 0.060 mg/L and 0.045 mg/L, respectively, and as long as it meets the requirements in subparagraph (D) of this paragraph.
    (C) A system that is on a reduced monitoring and monitors no more frequently than once each year may remain on reduced monitoring as long as TTHM and HAA5 concentrations are no greater than 0.060 mg/L and 0.045 mg/L, respectively, and as long as it meets the requirements in subparagraph (D) of this paragraph.
    (D) To remain on reduced TTHM and HAA5 monitoring, systems that treat surface water or groundwater under the direct influence of surface water must also maintain a source water annual average total organic carbon (TOC) level, before any treatment, less than or equal to 4.0 mg/L (based on the most recent four quarters of monitoring) on a continuing basis at each plant.
  (5) The executive director may require a system to return to the routine monitoring frequency described in paragraph (3) of this subsection.
    (A) A system that does not meet the requirements of paragraph (4)(B), (C) or (D) of this subsection must return to routine monitoring in the quarter immediately following the quarter in which the results exceed 0.060 mg/L or 0.045 mg/L for TTHMs and HAA5, respectively, or when the source water annual average TOC level, before any treatment, exceeds 4.0 mg/L at any plant.
    (B) A system that is on reduced monitoring and makes any significant change to its source of water or treatment program shall return to routine monitoring in the quarter immediately following the quarter when the change was made.
    (C) If a system is returned to routine monitoring, routine monitoring shall continue for at least one year before a reduction in monitoring frequency may be considered.
    (D) The executive director may return a system on reduced monitoring to routine monitoring at any time.
  (6) Systems monitoring no more frequently than once each year must increase their monitoring frequency to quarterly if either the TTHM annual average is >0.080 mg/L or the HAA5 annual average is >0.060 mg/L. The system must begin monitoring quarterly immediately following the monitoring period in which the system exceeds 0.080 mg/L or 0.060 mg/L for TTHMs or HAA5, respectively.
(d) Analytical requirements for TTHM and HAA5. Analytical procedures required by this section shall be performed in accordance with §290.119 of this title (relating to Analytical Procedures). Testing for TTHM and HAA5 shall be performed at a laboratory accredited by the executive director.
(e) Reporting requirements for TTHM and HAA5. The owner or operator of a public water system must ensure the executive director is provided with a copy of the results of any test, measurement, or analysis required by this subsection. The copies must be submitted within the first ten days following the month in which the result is received by the public water system, or the first ten days following the end of the required monitoring period as provided by this subsection, whichever occurs first. The copies must be mailed to the Water Supply Division, MC 155, Texas Commission on Environmental Quality, P.O. Box 13087, Austin, Texas 78711-3087.
(f) Compliance determination for TTHM and HAA5. Compliance with the provisions of this section shall be determined as follows.
  (1) A system that fails to monitor in accordance with this section commits a monitoring violation. Failure to monitor will be treated as a violation for the entire period covered by the annual average.
  (2) A public water system that fails to report the results of the monitoring tests required by subsection (e) of this section commits a reporting violation.
  (3) Compliance with the MCLs for TTHM and HAA5 shall be based on the running annual average of all samples collected during the preceding 12 months.
    (A) A public water system that samples for TTHM and HAA5 each quarter must calculate the running annual average of the quarterly averages.
    (B) A public water system that samples for TTHM and HAA5 no more frequently than once each year must calculate the annual average of all samples collected during the year.
    (C) All samples collected at the sampling sites designated in the public water system's monitoring plan shall be used to compute the quarterly and annual averages unless the analytical results are invalidated by the executive director for technical reasons.
  (4) A public water system violates the MCL for TTHM if the running annual average for TTHM exceeds the MCL specified in subsection (b)(1) of this section.
  (5) A public water system violates the MCL for HAA5 if the running annual average for HAA5 exceeds the MCL specified in subsection (b)(2) of this section.
  (6) If a public water system is routinely sampling in accordance with the requirements of subsection (c)(3) of this section and an individual sample or quarterly average will cause the system to exceed the MCL for TTHM or HAA5, the system is in violation of the respective MCL at the end of that quarter.
  (7) If a public water system's failure to monitor makes it impossible to determine compliance with the MCL for TTHM or HAA5, the system commits an MCL violation for the entire period covered by the annual average.
(g) Public Notification Requirements for TTHM and HAA5. A public water system that violates the treatment technique requirements of this section must notify the executive director and the system's customers.
  (1) A public water system that violates an MCL given in subsection (b)(1) or (2) of this section shall report to the executive director and the water system customers in accordance with the requirements of §290.122(b) of this title (relating to Public Notification).
  (2) A public water system which fails to conduct the monitoring required by subsection (c) of this section must notify its customers of the violation in accordance with the requirements of §290.122(c) of this title.
(h) Best available technology for TTHM and HAA5. Best available technology for treatment of violations of MCLs in subsection (b) of this section are listed in 40 Code of Federal Regulations §141.64(b)(1)(ii).

Source Note: The provisions of this §290.113 adopted to be effective September 13, 2000, 25 TexReg 8880; amended to be effective May 16, 2002, 27 TexReg 4127; amended to be effective January 9, 2008, 33 TexReg 198; amended to be effective May 15, 2011, 36 TexReg 2860; amended to be effective March 30, 2017, 42 TexReg 1466