Section 611.970  General Requirements

a)         General.  The requirements of this Subpart Y constitute NPDWRs.  The regulations in this Subpart Y establish monitoring and other requirements for achieving compliance with MCLs based on LRAAs for TTHM and HAA5, and for achieving compliance with MRDLs for chlorine and chloramine for certain consecutive systems.

b)         Applicability.  A supplier is subject to these requirements if its system is a CWS or a NTNCWS that uses a primary or residual disinfectant other than ultraviolet light or which delivers water that has been treated with a primary or residual disinfectant other than ultraviolet light.

c)         A supplier must comply with the requirements in this Subpart Y as follows:

1)         The supplier's monitoring frequency is specified in Section 611.971(a)(2).

A)        If a supplier is required to conduct quarterly monitoring, it must begin monitoring in the first full calendar quarter that includes the applicable compliance date set forth in this subsection (c).

B)        If a supplier is required to conduct monitoring less frequently than quarterly, it must begin monitoring in the calendar month recommended in the IDSE report prepared under Section 611.921 or Section 611.922 or in the calendar month identified in the Subpart Y monitoring plan developed under Section 611.972, but in no instance later than 12 months after the applicable compliance date set forth in this subsection (c).

2)         If a supplier is required to conduct quarterly monitoring, it 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 a supplier is required to conduct monitoring less frequently than quarterly, it must make compliance calculations beginning with the first compliance sample taken after the compliance date.

3)           The  Agency may, by a SEP, determine that the combined distribution system does not include certain consecutive systems based on factors such as receipt of water from a wholesale system only on an emergency basis or receipt of only a small percentage and small volume of water from a wholesale system.  The Agency may also determine that the combined distribution system does not include certain wholesale systems based on factors such as delivery of water to a consecutive system only on an emergency basis or delivery of only a small percentage and small volume of water to a consecutive system.

BOARD NOTE:  Implementation of this Subpart Y occurred in stages during October 1, 2012 through October 1, 2014, depending on population served.  See 40 CFR 141.620(c)(1) through (c)(5).  The Board removed the now-obsolete implementation dates.

d)         Monitoring and Compliance

1)         Suppliers Required to Monitor Quarterly.  To comply with Subpart Y MCLs in Section 611.312(b)(2), the supplier must calculate LRAAs for TTHM and HAA5 using monitoring results collected under this Subpart Y, and it must determine that each LRAA does not exceed the MCL.  If the supplier fails to complete four consecutive quarters of monitoring, it must calculate compliance with the MCL based on the average of the available data from the most recent four quarters.  If the supplier takes more than one sample per quarter at a monitoring location, it must average all samples taken in the quarter at that location to determine a quarterly average to be used in the LRAA calculation.

2)         Suppliers Required to Monitor Yearly or Less Frequently.  To determine compliance with Subpart Y MCLs in Section 611.312(b)(2), the supplier must determine that each sample taken is less than the MCL.  If any sample exceeds the MCL, the supplier must comply with the requirements of Section 611.975.  If no sample exceeds the MCL, the sample result for each monitoring location is considered the LRAA for that monitoring location.

e)         Violation for Failure to Monitor.  A supplier is in violation of the monitoring requirements for each quarter that a monitoring result would be used in calculating an LRAA if the supplier fails to monitor.

BOARD NOTE:  Derived from 40 CFR 141.620.

(Source:  Amended at 44 Ill. Reg. 6996, effective April 17, 2020)