Current through February, 2024
(a)
General Requirements.
(1) The requirements of
this section constitute national primary drinking water regulations. The
regulations in this section 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.
(2) Applicability. You are
subject to these requirements if your system is a community water system or a
nontransient noncommunity 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.
(3) Schedule. You must comply with
the requirements in this section on the schedule in the following table based
on your system type.
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If you are this type of system
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You must comply with Stage 2 Disinfection Byproduct
monitoring by:1
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Systems that are not part of a combined distribution
system and systems that serve the largest population in the combined
distribution system
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System serving >=100,000
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April 1, 2012
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System serving 50,000-99,999
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October 1, 2012
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System serving 10,000-49,999
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October 1, 2013
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System serving <10,000
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October 1, 20132 or
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October 1, 20143
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If you are this type of system
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You must comply with Stage 2 Disinfection Byproduct
monitoring by:1
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Other systems that are part of a combined
distribution system
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Consecutive or wholesale system
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-at the same time as the system with the earliest
compliance date in the combined distribution system
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1The State may grant up to an
additional 24 months for compliance with MCLs and operational evaluation levels
if you require capital improvements to comply with an MCL.
2If no Cryptosporidium monitoring
is required under section
11-20-46.2(b)(1)(D).
3If no Cryptosporidium monitoring
is required under section
11-20-46.2(b)(1)(D)
or (F).
(A) Your monitoring frequency
is specified in subsection (b)(1)(B).
(i) If
you are required to conduct quarterly monitoring, you must begin monitoring in
the first full calendar quarter that includes the compliance date in the table
in this paragraph.
(ii) If you are
required to conduct monitoring at a frequency that is less than quarterly, you
must begin monitoring in the calendar month recommended in the IDSE report
prepared under section
11-20-45.2(b)
or (c) or the calendar month identified in the Stage 2 Disinfection Byproduct
monitoring plan developed under subsection (c) no later than 12 months after
the compliance date in this table.
(B) If you are required to conduct quarterly
monitoring, you 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 you are required to conduct
monitoring at a frequency that is less than quarterly, you must make compliance
calculations beginning with the first compliance sample taken after the
compliance date.
(C) For the
purpose of the schedule in this paragraph, the State 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 State 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.
(4) Monitoring
and compliance
(A) Systems required to
monitor quarterly. To comply with this section MCLs in section
11-20-4.1(b)(2),
you 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 you
fail to complete four consecutive quarters of monitoring, you must calculate
compliance with the MCL based on the average of the available data from the
most recent four quarters. If you take more than one sample per quarter at a
monitoring location, you must average all samples taken in the quarter at that
location to determine a quarterly average to be used in the LRAA
calculation.
(B) Systems required
to monitor yearly or less frequently. To determine compliance with this section
MCLs in section
11-20-4.1(b)(2),
you must determine that each sample taken is less than the MCL. If any sample
exceeds the MCL, you must comply with the requirements of subsection (f). If no
sample exceeds the MCL, the sample result for each monitoring location is
considered the LRAA for that monitoring location.
(5) Violation. You are in violation of the
monitoring requirements for each quarter that a monitoring result would be used
in calculating an LRAA if you fail to monitor.
(b) Routine Monitoring.
(1) Monitoring.
(A) If you submitted an IDSE report, you must
begin monitoring at the locations and months you have recommended in your IDSE
report submitted under section
11-20-45.2(f)
following the schedule in subsection (a)(3), unless the State requires other
locations or additional locations after its review. If you submitted a 40/30
certification under section
11-20-45.2(d)
or you qualified for a very small system waiver under section
11-20-45.2(e)
or you are a nontransient noncommunity water system serving <10,000, you
must monitor at the location(s) and dates identified in your monitoring plan in
section
11-20-45.1(c)(6),
updated as required by subsection (c).
(B) You must monitor at no fewer than the
number of locations identified in this paragraph.
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Source water type
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Population size category
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Monitoring
frequency1
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Distribution system monitoring location total per
monitoring period
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Subpart H
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<500
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per year
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2
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500-3,300
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per quarter
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2
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3,301-9,999
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per quarter
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2
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10,000-49,999
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per quarter
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4
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50,000-249,999
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per quarter
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8
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250,000-999,999
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per quarter
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12
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1,000,000-4,999,999
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per quarter
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16
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>5,000,000
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per quarter
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20
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Ground
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<500
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per year
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2
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water
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500-9,999
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per year
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2
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10,000-99,999
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per quarter
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4
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100,000-499,999
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per quarter
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6
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>500,000
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per quarter
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8
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1All systems must monitor during
month of highest DBP concentrations.
2Systems on quarterly monitoring
must take dual sample sets every 90 days at each monitoring location, except
for subpart H systems serving 500-3,300. Ground water systems serving 500-9,999
on annual monitoring must take dual sample sets at each monitoring location.
All other systems on annual monitoring and subpart H systems serving 500-3,300
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. For systems serving fewer than 500 people, 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).
(C) If you are
an undisinfected system that begins using a disinfectant other than UV light
after the dates in section
11-20-45.2
for complying with the Initial Distribution System Evaluation requirements, you
must consult with the State to identify compliance monitoring locations for
this subpart. You must then develop a monitoring plan under subsection (c) that
includes those monitoring locations.
(2) Analytical methods. You must use an
approved method listed in section
11-20-45.1(b)
for TTHM and HAA5 analyses in this section. Analyses must be conducted by
laboratories that have received certification by EPA or the State as specified
in section
11-20-45.1(b).
(c) Monitoring plan.
(1) You must develop and implement a
monitoring plan to be kept on file for State and public review. The monitoring
plan must contain the elements in this paragraph and be complete no later than
the date you conduct your initial monitoring under this section.
(A) Monitoring locations;
(B) Monitoring dates;
(C) Compliance calculation procedures;
and
(D) Monitoring plans for any
other systems in the combined distribution system.
(2) If you were not required to submit an
IDSE report under either section
11-20-45.2(b)
or (c), and you do not have sufficient section
11-20-45.1
monitoring locations to identify the required number of this section compliance
monitoring locations indicated in section
11-20-45.2(f)(2),
you 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. You must also provide the
rationale for identifying the locations as having high levels of TTHM or HAA5.
If you have more section
11-20-45.1
monitoring locations than required for this section compliance monitoring in
section
11-20-45.2(f)(2),
you must identify which locations you will use for this section compliance
monitoring by alternating selection of locations representing high TTHM levels
and high HAA5 levels until the required number of this section compliance
monitoring locations have been identified.
(3) If you are a subpart H system serving
> 3,300 people, you must submit a copy of your monitoring plan to the State
prior to the date you conduct your initial monitoring, unless your IDSE report
submitted under section
11-20-45.2
contains all the information required by this section.
(4) You may revise your 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 State-approved reasons, after consultation with the State
regarding the need for changes and the appropriateness of changes. If you
change monitoring locations, you 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 State
may also require modifications in your monitoring plan. If you are a subpart H
system serving > 3,300 people, you must submit a copy of your modified
monitoring plan to the State prior to the date you are required to comply with
the revised monitoring plan.
(d) Reduced monitoring.
(1) You may reduce monitoring to the level
specified in the table in
40 C.F.R. §
141.623(a) any time the LRAA
is <= 0.040 mg/L for TTHM and <= 0.030 mg/L for HAA5 at all monitoring
locations. You may only use data collected under the provisions of this section
or section
11-20-45.1
to qualify for reduced monitoring. In addition, the source water annual average
TOC level, before any treatment, must be <= 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 section
11-20-45.1(c)(2)(A)(iii)
or section
11-20-45.1(c)(4).
(2) You may remain on reduced
monitoring as long as the TTHM LRAA <= 0.040 mg/L and the HAA5 LRAA <=
0.030 mg/L at each monitoring location (for systems with quarterly reduced
monitoring) or each TTHM sample <= 0.060 mg/L and each HAA5 sample <=
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 <=
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 section
11-20-45.1(c)(2)(A)(iii)
or section
11-20-45.1(c)(4).
(3) 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, >4.0 mg/L at any
treatment plant treating surface water or ground water under the direct
influence of surface water, you must resume routine monitoring under subsection
(b) or begin increased monitoring if subsection (f) applies.
(4) The State may return your system to
routine monitoring at the State's discretion.
(e) Additional requirements for consecutive
systems. If you are 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, you must comply with analytical and monitoring
requirements for chlorine and chloramines in section
11-20-45.1(b)(3)
and section
11-20-45.1(c)(3)(A)
and the compliance requirements in section
11-20-45.1(d)(3)(A)
beginning April 1, 2009, unless required earlier by the State, and report
monitoring results under section
11-20-45.1(e)(3).
(f) Conditions requiring increased
monitoring.
(1) If you are required to
monitor at a particular location annually or less frequently than annually
under subsection (b) or (d), you 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) You are in violation of the MCL when the
LRAA exceeds this section's MCLs in section
11-20-4.1(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). You are
in violation of the monitoring requirements for each quarter that a monitoring
result would be used in calculating an LRAA if you fail to monitor.
(3) You may return to routine monitoring once
you have 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.
(g) Operational evaluation levels.
(1) You have 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.
(2) If you exceed the operational evaluation
level, you must conduct an operational evaluation and submit a written report
of the evaluation to the State no later than 90 days after being notified of
the analytical result that causes you to exceed the operational evaluation
level. The written report must be made available to the public upon request.
(A) Your 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 exceedances.
(B)
You may request and the State may allow you to limit the scope of
your evaluation if you are able to identify the cause of the operational
evaluation level exceedance. Your request to limit the scope of the evaluation
does not extend the schedule in paragraph (2) for submitting the written
report. The State must approve this limited scope of evaluation in writing and
you must keep that approval with the completed report.
(h) Requirements for remaining on
reduced TTHM and HAA5 monitoring based on section
11-20-45.1
results. You may remain on reduced monitoring after the dates identified in
section (a)(3) for compliance with this section only if you qualify for a 40/30
certification under section
11-20-45.2(d)
or have received a very small system waiver under section
11-20-45.2(e),
plus you meet the reduced monitoring criteria in subsection (d)(1), and you do
not change or add monitoring locations from those used for compliance
monitoring under section
11-20-45.1.
If your monitoring locations under this section differ from your monitoring
locations under section
11-20-45.1,
you may not remain on reduced monitoring after the dates identified in
paragraph (a)(3) for compliance with this section.
(i) Requirements for remaining on increased
TTHM and HAA5 monitoring based on section
11-20-45.1
results. If you were on increased monitoring under section
11-20-45.1(c)(2)(A),
you must remain on increased monitoring until you qualify for a return to
routine monitoring under subsection (f)(3). You must conduct increased
monitoring under subsection (f) at the monitoring locations in the monitoring
plan developed under subsection (c) beginning at the date identified in
subsection (a)(3) for compliance with this section and remain on increased
monitoring until you qualify for a return to routine monitoring under
subsection (f)(3).
(j) Reporting
and recordkeeping requirements.
(1)
Reporting.
(A) You must report the following
information for each monitoring location to the State within 10 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 last quarter.
(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. 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,
you must report this information to the State as part of the first report due
following the compliance date or anytime thereafter that this determination is
made. If you are required to conduct monitoring at a frequency that is less
than quarterly, you must make compliance calculations beginning with the first
compliance sample taken after the compliance date, unless you are required to
conduct increased monitoring under subsection (f).
(iv) Whether, based on subsection
11-20-4.1(b)(2)
and this section, the MCL was violated at any monitoring location.
(v) Any operational evaluation levels that
were exceeded during the quarter and, if so, the location and date, and the
calculated TTHM and HAA5 levels.
(B) If you are a subpart H system seeking to
qualify for or remain on reduced TTHM/HAA5 monitoring, you must report the
following source water TOC information for each treatment plant that treats
surface water or ground water under the direct influence of surface water to
the State within 10 days of the end of any quarter in which monitoring is
required:
(i) The number of source water TOC
samples taken each month during last quarter.
(ii) The date and result of each sample taken
during last quarter.
(iii) The
quarterly average of monthly samples taken during last quarter or the result of
the quarterly sample.
(iv) The
running annual average (RAA) of quarterly averages from the past four quarters.
(v) Whether the RAA exceeded 4.0
mg/L.
(C) The State may
choose to perform calculations and determine whether the MCL was exceeded or
the system is eligible for reduced monitoring in lieu of having the system
report that information.
(2) Recordkeeping. You must retain this
section's monitoring plans and this section's monitoring results as required by
section
11-20-19.
