Current through Register Vol. 48, No. 38, September 20, 2024
Each supplier must monitor to determine compliance with the
MCL for nitrate in Section
611.301.
a) Suppliers must monitor at the following
frequencies:
1) CWSs and NTNCWSs
A) GWSs: annually;
B) SWSs and mixed systems: quarterly.
BOARD NOTE: Derived from
40 CFR
141.23(d)(1).
2) Transient non-CWSs:
annually.
BOARD NOTE: Derived from
40 CFR
141.23(d)(4).
b) Quarterly Monitoring
for GWSs
1) A CWS or NTNCWS supplier that is
a GWS must initiate quarterly monitoring in the quarter following any one
sample that has a nitrate concentration equal to or greater than 50 percent of
the MCL.
2) The Agency must grant a
SEP that reduces the monitoring frequency to annual after the supplier has
completed quarterly sampling for at least four quarters if it determines that
the sampling point is reliably and consistently below the MCL.
A) The request must include the following
minimal information: the results from four consecutive quarterly
samples.
B) In issuing the SEP, the
Agency must specify the level of the contaminant upon which the "reliably and
consistently" determination was based. All SEPs that allow less frequent
monitoring based on an Agency "reliably and consistently" determination must
include a condition requiring the supplier to resume quarterly monitoring under
subsection (b)(1) if it violates the MCL specified by Section
611.301
for nitrate.
BOARD NOTE: Derived from
40 CFR
141.23(d)(2).
c) Reduction
of Monitoring Frequency for SWSs and Mixed Systems
1) The Agency must grant a SEP that allows a
CWS or NTNCWS supplier that is a SWS or mixed system to reduce its monitoring
frequency to annually if it determines that all analytical results from four
consecutive quarters are less than 50 percent of the MCL.
2) As a condition of the SEP, the Agency must
require the supplier to initiate quarterly monitoring, beginning the next
quarter, if any one sample is greater than or equal to 50 percent of the MCL.
BOARD NOTE: Derived from
40 CFR
141.23(d)(3).
d) This subsection
corresponds with
40 CFR
141.23(d)(4), which the
Board has codified at subsection (a)(2). This statement maintains structural
consistency with USEPA rules.
e)
After completion of four consecutive quarters of monitoring, each CWS or NTNCWS
supplier monitoring annually must take samples during the quarters that
resulted in the highest analytical result.
BOARD NOTE: Derived from
40 CFR
141.23(d)(5).
