Current through Register Vol. 48, No. 38, September 20, 2024
a) A supplier's IDSE report must include its
recommendations and justification for where and during what months it will
conduct TTHM and HAA5 monitoring for Subpart Y. The supplier must base its
recommendations on the criteria set forth in subsections (b) through
(e).
b) The supplier must select
the number of monitoring locations specified in the applicable of subsections
(b)(1) through (b)(13), subject to the limitations of subsections (b)(14) and
(b)(15). The supplier will use these recommended locations as Subpart Y routine
compliance monitoring locations, unless the Agency requires different or
additional locations. The supplier should distribute locations throughout the
distribution system to the extent possible.
1) A Subpart B system supplier that serves
fewer than 500 persons must annually collect samples from two monitoring
locations: one sample from the highest TTHM location and one sample from the
highest HAA5 location.
2) A Subpart
B system supplier that serves 500 to 3,300 persons must quarterly collect
samples from two monitoring locations: one sample from the highest TTHM
location and one sample from the highest HAA5 location.
3) A Subpart B system supplier that serves
3,301 to 9,999 persons must quarterly collect samples from two monitoring
locations: one sample from the highest TTHM location and one sample from the
highest HAA5 location.
4) A Subpart
B system supplier that serves 10,000 to 49,999 persons must quarterly collect
samples from four monitoring locations: two samples from the highest TTHM
locations, one sample from the highest HAA5 location, and one sample from an
existing Subpart I compliance location.
5) A Subpart B system supplier that serves
50,000 to 249,999 persons must quarterly collect samples from eight monitoring
locations: three samples from the highest TTHM location, three samples from the
highest HAA5 locations, and two samples from existing Subpart I compliance
locations.
6) A Subpart B system
supplier that serves 250,000 to 999,999 persons must quarterly collect samples
from 12 monitoring locations: five samples from the highest TTHM location, four
samples from the highest HAA5 locations, and three samples from existing
Subpart I compliance locations.
7)
A Subpart B system supplier that serves 1,000,000 to 4,999,999 persons must
quarterly collect samples from 16 monitoring locations: six samples from the
highest TTHM location, six samples from the highest HAA5 locations, and four
samples from existing Subpart I compliance locations.
8) A Subpart B system supplier that serves
more than 5,000,000 persons must quarterly collect samples from 20 monitoring
locations: eight samples from the highest TTHM location, seven samples from the
highest HAA5 locations, and five samples from existing Subpart I compliance
locations.
9) A groundwater system
supplier that serves fewer than 500 persons must annually collect samples from
two monitoring locations: one sample from the highest TTHM location and one
sample from the highest HAA5 location.
10) A groundwater system supplier that serves
500 to 9,999 persons must annually collect samples from two monitoring
locations: one sample from the highest TTHM location and one sample from the
highest HAA5 location.
11) A
groundwater system supplier that serves 10,000 to 99,999 persons must quarterly
collect samples from four monitoring locations: two samples from the highest
TTHM locations, one sample from the highest HAA5 location, and one sample from
an existing Subpart I compliance location.
12) A groundwater system supplier that serves
100,000 to 499,999 persons must quarterly collect samples from six monitoring
locations: three samples from the highest TTHM locations, two samples from the
highest HAA5 locations, and one sample from an existing Subpart I compliance
location.
13) A groundwater system
supplier that serves more than 500,000 persons must quarterly collect samples
from eight monitoring locations: three samples from the highest TTHM locations,
three samples from the highest HAA5 locations, and two samples from existing
Subpart I compliance locations.
14)
The supplier must monitor during the month of highest DBP
concentrations.
15) A supplier on
quarterly monitoring must take dual sample sets every 90 days at each
monitoring location, except for a Subpart B system supplier that serves 500 to
3,300 persons. A groundwater system supplier that serves 500 to 9,999 persons
which is on annual monitoring must take dual sample sets at each monitoring
location. Any other supplier that is on annual monitoring or which is a Subpart
B system supplier that serves 500 to 3,300 persons is 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 a
supplier that serves fewer than 500 people, only one location with a dual
sample set per monitoring period is needed if the highest TTHM and HAA5
concentrations occur at the same location and month.
c) The supplier must recommend Subpart Y
compliance monitoring locations based on standard monitoring results,
system-specific study results, and Subpart I compliance monitoring results. The
supplier must follow the protocol in subsections (c)(1) through (c)(8). If
required to monitor at more than eight locations, the supplier must repeat the
protocol as necessary. If the supplier does not have existing Subpart I
compliance monitoring results or if the supplier does not have enough existing
Subpart I compliance monitoring results, the supplier must repeat the protocol,
skipping the provisions of subsections (c)(3) and (c)(7) as necessary, until
the supplier has identified the required total number of monitoring locations.
1) The location with the highest TTHM LRAA
not previously selected as a Subpart Y monitoring location.
2) The location with the highest HAA5 LRAA
not previously selected as a Subpart Y monitoring location.
3) The existing Subpart I average residence
time compliance monitoring location (maximum residence time compliance
monitoring location for a groundwater system) with the highest HAA5 LRAA not
previously selected as a Subpart Y monitoring location.
4) The location with the highest TTHM LRAA
not previously selected as a Subpart Y monitoring location.
5) The location with the highest TTHM LRAA
not previously selected as a Subpart Y monitoring location.
6) The location with the highest HAA5 LRAA
not previously selected as a Subpart Y monitoring location.
7) The existing Subpart I average residence
time compliance monitoring location (maximum residence time compliance
monitoring location for a groundwater system) with the highest TTHM LRAA not
previously selected as a Subpart Y monitoring location.
8) The location with the highest HAA5 LRAA
not previously selected as a Subpart Y monitoring location.
d) The supplier may recommend
locations other than those specified in subsection (c) if the supplier includes
a rationale for selecting other locations. If the Agency approves the
alternative locations, the supplier must monitor at these locations to
determine compliance under Subpart Y.
e) The supplier's recommended schedule must
include Subpart Y monitoring during the peak historical month for TTHM and HAA5
concentration, unless the Agency approves another month. Once the supplier has
identified the peak historical month, and if the supplier is required to
conduct routine monitoring at least quarterly, the supplier must schedule
Subpart Y compliance monitoring at a regular frequency of every 90 or fewer
days.
BOARD NOTE: Derived from
40 CFR
141.605
(2016).
