Current through Register Vol. 48, No. 38, September 20, 2024
a)
General Requirements
1) Where compliance is
based on a running annual average of monthly or quarterly samples or averages
and the supplier fails to monitor for TTHM, HAA5, or bromate, this failure to
monitor will be treated as a monitoring violation for the entire period covered
by the annual average. Where compliance is based on a running annual average of
monthly or quarterly samples or averages and the supplier's failure to monitor
makes it impossible to determine compliance with the MRDL for chlorine or
chloramines, this failure to monitor will be treated as a monitoring violation
for the entire period covered by the annual average.
2) All samples taken and analyzed under the
provisions of this Subpart I must be included in determining compliance, even
if that number is greater than the minimum required.
3) If, during the first year of monitoring
under Section
611.382,
any individual quarter's average will cause the running annual average of that
supplier to exceed the MCL for TTHM, HAA5, or bromate or the MRDL for chlorine
or chloramine, the supplier is out of compliance at the end of that
quarter.
b) Disinfection
Byproducts (DBPs)
1) TTHMs and HAA5
A) For a supplier monitoring quarterly,
compliance with MCLs in Section
611.312
must be based on a running annual arithmetic average, computed quarterly, of
quarterly arithmetic averages of all samples collected by the supplier as
prescribed by Section
611.382(b)(1).
B) For a supplier monitoring less frequently
than quarterly, the supplier demonstrates MCL compliance if the average of
samples taken that year under the provisions of Section
611.382(b)(1)
does not exceed the MCLs in Section 611.312. If the average of these samples
exceeds the MCL, the supplier must increase monitoring to once per quarter per
treatment plant, and such a system is not in violation of the MCL until it has
completed one year of quarterly monitoring, unless the result of fewer than
four quarters of monitoring will cause the running annual average to exceed the
MCL, in which case the supplier is in violation at the end of that quarter. A
supplier required to increase to quarterly monitoring must calculate compliance
by including the sample that triggered the increased monitoring plus the
following three quarters of monitoring.
C) If the running annual arithmetic average
of quarterly averages covering any consecutive four-quarter period exceeds the
MCL, the supplier is in violation of the MCL and must notify the public under
Subpart V in addition to reporting to the Agency under Section
611.384.
D) If a PWS fails to complete four
consecutive quarter's monitoring, compliance with the MCL for the last
four-quarter compliance period must be based on an average of the available
data.
2) Bromate.
Compliance must be based on a running annual arithmetic average, computed
quarterly, of monthly samples (or, for months in which the supplier takes more
than one sample, the average of all samples taken during the month) collected
by the supplier, as prescribed by Section
611.382(b)(3).
If the average of samples covering any consecutive four-quarter period exceeds
the MCL, the supplier is in violation of the MCL and must notify the public
under Subpart V, in addition to reporting to the Agency under Section 611.384.
If a PWS supplier fails to complete 12 consecutive months' monitoring,
compliance with the MCL for the last four-quarter compliance period must be
based on an average of the available data.
3) Chlorite. Compliance must be based on an
arithmetic average of each three sample set taken in the distribution system as
prescribed by Section
611.382(b)(2)(A)(ii)
and Section
611.382(b)(2)(B).
If the arithmetic average of any three sample set exceeds the MCL, the supplier
is in violation of the MCL and must notify the public under Subpart V, in
addition to reporting to the Agency under Section 611.384.
c) Disinfectant Residuals
1) Chlorine and Chloramines
A) Compliance must be based on a running
annual arithmetic average, computed quarterly, of monthly averages of all
samples collected by the supplier under Section
611.382(c)(1).
If the average of quarterly averages covering any consecutive four-quarter
period exceeds the MRDL, the supplier is in violation of the MRDL and must
notify the public under Subpart V, in addition to reporting to the Agency under
Section 611.384.
B) In cases where
a supplier switches between the use of chlorine and chloramines for residual
disinfection during the year, compliance must be determined by including
together all monitoring results of both chlorine and chloramines in calculating
compliance. Reports submitted under Section
611.384
must clearly indicate that residual disinfectant was analyzed for each
sample.
2) Chlorine
Dioxide
A) Acute Violations. Compliance must
be based on consecutive daily samples collected by the supplier under Section
611.382(c)(2).
If any daily sample taken at the entrance to the distribution system exceeds
the MRDL, and on the following day one (or more) of the three samples taken in
the distribution system exceeds the MRDL, the supplier is in violation of the
MRDL and must take immediate corrective action to lower the level of chlorine
dioxide below the MRDL and must notify the public under the procedures for
acute health risks in Subpart V, in addition to reporting to the Agency under
Section 611.384. Failure to take samples in the distribution system the day
following an exceedance of the chlorine dioxide MRDL at the entrance to the
distribution system will also be considered an MRDL violation and the supplier
must notify the public of the violation in accordance with the provisions for
acute violations under Subpart V, in addition to reporting to the Agency under
Section 611.384.
B) Nonacute
Violations. Compliance must be based on consecutive daily samples collected by
the supplier under Section
611.382(c)(2).
If any two consecutive daily samples taken at the entrance to the distribution
system exceed the MRDL and all distribution system samples taken are below the
MRDL, the supplier is in violation of the MRDL and must take corrective action
to lower the level of chlorine dioxide below the MRDL at the point of sampling
and must notify the public under the procedures for nonacute health risks in
Subpart V, in addition to reporting to the Agency under Section 611.384.
Failure to monitor at the entrance to the distribution system the day following
an exceedance of the chlorine dioxide MRDL at the entrance to the distribution
system is also an MRDL violation and the supplier must notify the public of the
violation in accordance with the provisions for nonacute violations under
Subpart V, in addition to reporting to the Agency under Section
611.384.
d)
Disinfection Byproduct (DBP) Precursors. Compliance must be determined as
specified by Section
611.385(c).
A supplier may begin monitoring to determine whether Step 1 TOC removals can be
met 12 months prior to the compliance date for the supplier. This monitoring is
not required and failure to monitor during this period is not a violation.
However, any supplier that does not monitor during this period, and then
determines in the first 12 months after the compliance date that it is not able
to meet the Step 1 requirements in Section 611.141(b)(2) and must therefore
apply for alternate minimum TOC removal (Step 2) requirements, is not eligible
for retroactive approval of alternate minimum TOC removal (Step 2) requirements
as allowed under Section
611.385(b)(3)
and is in violation of an NPDWR. A supplier may apply for alternate minimum TOC
removal (Step 2) requirements any time after the compliance date. For a
supplier required to meet Step 1 TOC removals, if the value calculated under
Section
611.385(c)(1)(D)
is less than 1.00, the supplier is in violation of the treatment technique
requirements and must notify the public under Subpart V, in addition to
reporting to the Agency under Subpart V.
BOARD NOTE: Derived from
40 CFR
141.133.