| (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
exceedances.
(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
quarter.
(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
samples.
(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
that information.
(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
violation.
(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
customers.
(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
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.
(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
(iii).
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| 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 |
