Section 611.921  Standard Monitoring

a)         Standard Monitoring Plan.  A supplier's standard monitoring plan must comply with subsections (a)(1) through (a)(4).  The supplier must prepare and submit its standard monitoring plan to the Agency according to the appropriate of the schedules provided in Section 611.920(c).

1)         The supplier's standard monitoring plan must include a schematic of its distribution system (including distribution system entry points and their sources, and storage facilities), with notes indicating locations and dates of all projected standard monitoring, and all projected Subpart I compliance monitoring.

2)         The supplier's standard monitoring plan must include justification of standard monitoring location selection and a summary of data the supplier relied on to justify standard monitoring location selection.

3)         The supplier's standard monitoring plan must specify the population served and its system type (i.e., that it is a Subpart B or groundwater system).

4)         The supplier must retain a complete copy of its standard monitoring plan submitted under this subsection (a), including any Agency modification of the plan, for as long as the supplier is required to retain its IDSE report under subsection (c)(4).

b)         Standard Monitoring

1)         The supplier must monitor as indicated in the applicable of subsections (b)(1)(A) through (b)(1)(P), subject to the limitations of subsections (b)(1)(Q) and (b)(1)(R).  The supplier must collect dual sample sets at each monitoring location.  One sample in the dual sample set must be analyzed for TTHM.  The other sample in the dual sample set must be analyzed for HAA5.  The supplier must conduct one monitoring period during the peak historical month for TTHM levels or HAA5 levels or the month of warmest water temperature.  The supplier must review available compliance, study, or operational data to determine the peak historical month for TTHM or HAA5 levels or warmest water temperature.

A)        A Subpart B system supplier that serves fewer than 500 persons and which operates a consecutive system must collect samples once each calendar year during the peak historical month:  one near an entry point to the distribution system and one at a high TTHM location, for a total of two samples during each monitoring period.

B)        A Subpart B system supplier that serves fewer than 500 persons and which does not operate a consecutive system must collect samples once each calendar year during the peak historical month:  one at a high TTHM location and one at a high HAA5 location, for a total of two samples during each monitoring period.

C)        A Subpart B system supplier that serves 500 to 3,300 persons and which operates a consecutive system must collect samples four times each calendar year (once every 90 days):  one near an entry point to the distribution system and one at a high TTHM location, for a total of two samples during each monitoring period.

D)        A Subpart B system supplier that serves 500 to 3,300 persons and which does not operate a consecutive system must collect samples four times each calendar year (once every 90 days):  one at a high TTHM location and one at a high HAA5 location, for a total of two samples during each monitoring period.

E)        A Subpart B system supplier that serves 3,301 to 9,999 persons must collect samples four times each calendar year (once every 90 days):  one at a location in the distribution system that represents the average residence time, two at high TTHM locations, and one at a high HAA5 location, for a total of four samples during each monitoring period.

F)         A Subpart B system supplier that serves 10,000 to 49,999 persons must collect samples six times each calendar year (once every 60 days):  one near an entry point to the distribution system, two at locations in the distribution system that represent the average residence time, three at each TTHM location, and two at high HAA5 locations, for a total of eight samples during each monitoring period.

G)        A Subpart B system supplier that serves 50,000 to 249,999 persons must collect samples six times each calendar year (once every 60 days):  three near entry points to the distribution system, four at locations in the distribution system that represent the average residence time, five at high TTHM locations, and four at high HAA5 locations, for a total of 16 samples during each monitoring period.

H)        A Subpart B system supplier that serves 250,000 to 999,999 persons must collect samples six times each calendar year (once every 60 days):  four near entry points to the distribution system, six at locations in the distribution system that represent the average residence time, eight at high TTHM locations, and six at high HAA5 locations, for a total of 24 samples during each monitoring period.

I)         A Subpart B system supplier that serves 1,000,000 to 4,999,999 persons must collect samples six times each calendar year (once every 60 days):  six near entry points to the distribution system, eight at locations in the distribution system that represent the average residence time, ten at high TTHM locations, and eight at high HAA5 locations, for a total of 32 samples during each monitoring period.

J)         A Subpart B system supplier that serves 5,000,000 or more persons must collect samples six times each calendar year (once every 60 days):  eight near entry points to the distribution system, ten at locations in the distribution system that represent the average residence time, 12 at high TTHM locations, and ten at high HAA5 locations, for a total of 40 samples during each monitoring period.

K)        A groundwater system supplier that serves fewer than 500 persons and which operates a consecutive system must collect samples once each calendar year during the peak historical month:  one near an entry point to the distribution system and one at a high TTHM location, for a total of two samples during each monitoring period.

L)        A groundwater system supplier that serves fewer than 500 persons and which does not operate a consecutive system must collect samples once each calendar year during the peak historical month:  one at a high TTHM location and one at a high HAA5 location, for a total of two samples during each monitoring period.

M)       A groundwater system supplier that serves 500 to 9,999 persons must collect samples four times each calendar year (once every 90 days):  one at a high TTHM location and one at a high HAA5 location, for a total of two samples during each monitoring period.

N)        A groundwater system supplier that serves 10,000 to 99,999 persons must collect samples four times each calendar year (once every 90 days):  one near an entry point to the distribution system, one at a location in the distribution system that represents the average residence time, two at high TTHM locations, and two at high HAA5 locations, for a total of six samples during each monitoring period.

O)        A groundwater system supplier that serves 100,000 to 499,999 persons must collect samples four times each calendar year (once every 90 days):  one near an entry point to the distribution system, one at a location in the distribution system that represents the average residence time, three at high TTHM locations, and three at high HAA5 locations, for a total of eight samples during each monitoring period.

P)         A groundwater system supplier that serves 500,000 or more persons must collect samples four times each calendar year (once every 90 days):  two near an entry point to the distribution system, two at locations in the distribution system that represent the average residence time, four at high TTHM locations, and four at high HAA5 locations, for a total of 12 samples during each monitoring period.

Q)        A dual sample set (i.e., a TTHM and an HAA5 sample) must be taken at each monitoring location during each monitoring period.

R)        The "peak historical month", for the purposes of subsections (b)(1)(A), (b)(1)(B), (b)(1)(K), and (b)(1)(L), means the month with the highest TTHM or HAA5 levels or the warmest water temperature.

2)         The supplier must take samples at locations other than the existing Subpart I monitoring locations.  Monitoring locations must be distributed throughout the distribution system.

3)         If the number of entry points to the distribution system is fewer than the specified number of entry point monitoring locations, excess entry point samples must be equally replaced at high TTHM and HAA5 locations.  If there is an odd extra location number, the supplier must take a sample at a high TTHM location.  If the number of entry points to the distribution system is more than the specified number of entry point monitoring locations, the supplier must take samples at the entry points to the distribution system that have the highest annual water flows.

4)         The supplier's monitoring under this subsection (b) may not be reduced under the provisions of Section 611.500, and the Agency may not reduce the supplier's monitoring using the provisions of Section 611.161.

c)         IDSE Report.  A supplier's IDSE report must include the elements required in subsections (c)(1) through (c)(4).  The supplier must submit its IDSE report to the Agency according to the applicable of the schedules set forth in Section 611.920(c).

1)         The supplier's IDSE report must include all TTHM and HAA5 analytical results from Subpart I compliance monitoring and all standard monitoring conducted during the period of the IDSE as individual analytical results and LRAAs presented in a tabular or spreadsheet format acceptable to the Agency.  If changed from the supplier's standard monitoring plan submitted under subsection (a), the supplier's report must also include a schematic of the supplier's distribution system, the population served, and system type (Subpart B system or groundwater system).

2)         The supplier's IDSE report must include an explanation of any deviations from the supplier's approved standard monitoring plan.

3)         The supplier must recommend and justify Subpart Y compliance monitoring locations and timing based on the protocol in Section 611.925.

4)         The supplier must retain a complete copy of its IDSE report submitted under this Section for ten years after the date on which the supplier submitted the supplier's report.  If the Agency modifies the Subpart Y monitoring requirements that the supplier recommended in its IDSE report or if the Agency approves alternative monitoring locations under Section 611.161, the supplier must keep a copy of the Agency's notification on file for ten years after the date of the Agency's notification.  The supplier must make the IDSE report and any Agency notification available for review by the Agency or the public.

BOARD NOTE:  Derived from 40 CFR 141.601.

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