| (V) Systems must monitor at the frequency indicated
in the following table titled "Frequency of Initial Distribution System
Evaluation (IDSE) Monitoring:"
(VI) The IDSE monitoring frequency and locations may
not be reduced.
(iii) The IDSE report must comply with the elements
in this clause.
(I) The IDSE report must include all TTHM and HAA5
analytical results from Stage 1 compliance monitoring under §290.113
of this title and all IDSE sample results and locational running annual
averages presented in a tabular or spreadsheet format acceptable as
described in Texas Commission on Environmental Quality regulatory
guidance number 384: "How to Develop a Monitoring Plan for a Public
(II) If changed from the IDSE plan submitted under
clause (ii) of this subparagraph, the IDSE report must also include
an updated distribution system map, documentation verifying the population
served, and an updated list of sources including their water type.
(III) The IDSE report must include an explanation of
any deviations from the approved IDSE plan.
(IV) The IDSE report must recommend and justify Stage
2 compliance monitoring locations consistent with paragraph (1) of
this subsection. The recommended Stage 2 compliance monitoring locations
must be listed in a Stage 2 sample plan as part of the system's monitoring
(V) The IDSE report must include recommendations and
justification for when Stage 2 samples should be collected.
(iv) The executive director may approve a system specific
study that meets the requirements in 40 CFR §141.602 to comply
with IDSE sampling requirements. The commission hereby adopts the
requirements of 40 CFR §141.602 by reference.
(D) The executive director may require a system to
perform IDSE sampling or a system specific study for any reason. The
executive director may require a system to perform IDSE sampling or
a system specific study even if the system meets the criteria for
an IDSE waiver. The executive director may require new systems and
systems with a change in population or system type to perform IDSE
sampling or a system specific study.
(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. Public
water systems must submit reports related to TTHM and HAA5 to the
executive director. Reports must be mailed to the Water Supply Division,
MC 155, Texas Commission on Environmental Quality, P.O. Box 13087,
Austin, Texas 78711-3087.
(1) 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.
(A) The owner or operator of a public water system
is responsible for reporting the following information for each monitoring
location to the executive director within ten days of the end of any
quarter in which monitoring is required:
(i) number of samples taken during the last quarter;
(ii) date and results of each sample taken during the
(iii) arithmetic average of quarterly results for the
last four quarters for each monitoring location (LRAA), beginning
at the end of the fourth calendar quarter that follows the compliance
date and at the end of each subsequent quarter;
(iv) whether the MCL was violated at any monitoring
(v) any OELs that were exceeded during the quarter
and, if so, the location and date, and the calculated TTHM and HAA5
(B) If the LRAA based on fewer than four quarters would
cause the MCL to be exceeded regardless of the monitoring results
of subsequent quarters, the system must report a potential MCL violation
as part of the first report due following the compliance date or anytime
thereafter that this determination is made. A system required to conduct
monitoring at a frequency that is less than quarterly must make compliance
calculations beginning with the first compliance sample taken after
the compliance date, unless the system is required to conduct increased
monitoring under subsection (c)(4) of this section.
(C) A system that treats surface water or groundwater
under the direct influence of surface water that seeks to qualify
for or remain on reduced TTHM and HAA5 monitoring must measure and
report TOC monthly in accordance with §290.112 of this title
and distribution system disinfection levels in accordance with §290.110
of this title (relating to Disinfectant Residuals).
(2) A system that exceeds an OEL described in subsection
(b)(2) of this section must conduct an operation evaluation and submit
a written operation evaluation report that meets the requirements
of this paragraph.
(A) The operation evaluation report must be submitted
to the executive director no later than 90 days after being notified
of the analytical result that causes the exceedance of the OEL.
(B) The operation evaluation report must document an
examination of system treatment and distribution operation practices
that may contribute to TTHM and HAA5 formation, including:
(i) storage tank operations;
(ii) excess storage capacity;
(iii) distribution system flushing;
(iv) changes in sources or source water quality;
(v) treatment changes or problems; and
(vi) what steps could be considered to minimize future
(C) If the cause of the OEL exceedance is identifiable
the scope of the report may be limited with the approval of the executive
director. A request to limit the scope of the evaluation does not
extend the schedule in subparagraph (A) of this paragraph for submitting
the written report. The executive director's approval to limit the
scope of the operation evaluation report must be in writing. The system
must keep a copy of the executive director's approval with the completed
operation evaluation report.
(D) The operation evaluation report must be submitted
and approved in writing.
(f) Compliance determination for TTHM and HAA5. Compliance
with the provisions of this section shall be determined as follows.
(1) A public water system violates the MCL for TTHM
if any locational running annual average for TTHM exceeds an MCL specified
in subsection (b)(1)(A) of this section. A public water system violates
the MCL for HAA5 if any locational running annual average for HAA5
exceeds the MCL specified in subsection (b)(1)(B) of this section.
(A) Compliance with the MCLs for TTHM and HAA5 shall
be based on the LRAA of all samples collected during four consecutive
quarters of monitoring. If a single quarterly sample would cause an
LRAA exceedance regardless of the results of subsequent quarters,
compliance may be based on fewer than four quarters of data. Should
a system fail to collect all required samples, compliance will be
based on the available data. 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.
(B) Stage 2 MCL compliance determination with LRAAs
will start after Stage 2 samples are collected.
(i) For systems required to conduct routine quarterly
monitoring, compliance calculations will be made starting at the end
of the fourth calendar quarter that follows the compliance date in
subsection (a)(2) of this section and at the end of each subsequent
(ii) For systems on quarterly monitoring, where the
LRAA based on fewer than four quarters would exceed the MCL regardless
of the monitoring results of subsequent quarters, compliance will
be calculated beginning with the first sample that causes that exceedance.
(iii) For systems that are required to monitor less
frequently than quarterly, compliance shall be calculated beginning
with the first compliance sample taken after the compliance date.
(iv) For systems monitoring annually or triennially
that start monitoring quarterly in the quarter following an LRAA exceedance,
compliance shall be calculated based on the results of all available
(C) 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.
(D) The executive director may choose to perform calculations
and determine MCL exceedances in lieu of having the system report
(E) IDSE results will not be used for the purpose of
determining compliance with MCLs.
(2) A system that fails to monitor in accordance with
this section commits a monitoring violation. A system on a quarterly
monitoring schedule is in violation of the monitoring requirements
for each quarter that it fails to monitor.
(3) A system that fails to perform a required operation
evaluation under subsection (e)(2) of this section commits a monitoring
(4) 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.
(5) A system that fails to submit an operation evaluation
report as required under subsection (e)(2) of this section commits
a reporting violation.
(6) A system that fails to perform a required public
notification commits a public notification violation.
(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
(1) A public water system that commits an MCL violation
described in subsection (f)(1) 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
(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.
(3) Any IDSE compliance documents required under subsection
(c)(5) of this section must be made available to the executive director
or the public upon request.
(4) Any operation evaluation report required under
subsection (e)(2) of this section must be made available to the executive
director or the public upon request.
(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 CFR §141.64(b)(2)(ii) and
|Source Note: The provisions of this §290.115 adopted 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