Section 611.1351  Applicability of Corrosion Control

a)         Corrosion Control Required.  A supplier must complete the applicable corrosion control treatment under Section 611.1352 on or before the deadlines in this Section.

1)         Large Systems.  Each large system supplier (one regularly serving more than 50,000 persons) must complete the corrosion control treatment steps subsection (d) specifies, unless subsection (b)(2) or (b)(3) deems the supplier to have optimized corrosion control.

2)         Small and Medium-Sized Systems.  Each small system supplier (one regularly serving 3,300 or fewer persons) and each medium-sized water system (one regularly serving 3,301 to 50,000 persons) must complete the corrosion control treatment steps subsection (e) specifies, unless subsection (b)(1), (b)(2), or (b)(3) deems the supplier to have optimized corrosion control.

b)         Suppliers Deemed to Have Optimized Corrosion Control.  Subsection (b)(1), (b)(2), or (b)(3) deems a supplier to have optimized corrosion control treatment if the supplier satisfies the criterion the subsection specifies, freeing the supplier from the obligation to complete the applicable corrosion control treatment steps in this Section.  Any system subsection (b)(1), (b)(2), or (b)(3) deems to have optimized corrosion control having treatment in place must continue operating and maintaining optimal corrosion control treatment and meeting any requirements the Agency determines are appropriate to ensure that the supplier maintains optimal corrosion control treatment.

1)         Small and Medium-Sized Systems Meeting Action Levels.  Meeting the lead and copper action levels during each of two consecutive six-month monitoring periods under Section 611.1356 deems a small or medium-sized system supplier to have optimized corrosion control.

2)         SEP for Activities Equivalent to Corrosion Control.  The Agency must issue a SEP deeming a supplier to have optimized corrosion control treatment upon determining that the supplier conducts activities equivalent to the corrosion control steps under this Section.  In making this determination, the Agency must specify the water quality control parameters representing optimal corrosion control under Section 611.1352(f).  A water supplier the Agency deems as having optimized corrosion control under this subsection (b)(2) must operate in compliance with the Agency-designated optimal water quality control parameters under Section 611.1352(g) and must continue to conduct lead and copper tap and water quality parameter sampling under Sections 611.1356(d)(3) and 611.1357(d).  A supplier must provide the Agency with the following information to support the Agency issuing a SEP under this subsection (b)(2):

A)        The results of all test samples the supplier collected for each of the water quality parameters in Section 611.1352(c)(3);

B)        A report explaining the test methods the supplier used to evaluate the corrosion control treatments in Section 611.1352(c)(1), the results of all tests conducted, and the basis for the supplier selecting the optimal corrosion control treatment;

C)        A report explaining how the supplier installed corrosion control and how the supplier maintains the corrosion control to insure minimal lead and copper concentrations at consumers’ taps; and

D)        The results of tap water samples the supplier collected under Section 611.1356 at least once every six months for one year after the supplier installed corrosion control.

3)         Results Less Than Practical Quantitation Level (PQL) for Lead.  Monitoring results deem supplier to have optimized corrosion control if the supplier submits results of tap water monitoring under Section 611.1356 and source water monitoring under Section 611.1358 demonstrating that for two consecutive six-month monitoring periods the difference between the 90th percentile tap water lead level, computed under Section 611.1350(c)(3), and the highest source water lead concentration is less than the PQL that Section 611.1359(a)(2)(A) specifies.

A)        Having a highest source water lead level below the MDL deems a supplier to have optimized corrosion control under this subsection (b)(3) if the 90th percentile tap water lead level is less than or equal to the lead PQL for two consecutive six-month monitoring periods.

B)        Any supplier this subsection (b)(3) deems to have optimized corrosion control must continue tap water monitoring for lead and copper no less frequently than once every three calendar years using the reduced number of sites Section 611.1356(c) specifies and collecting the samples at times and locations Section 611.1356(d)(4)(D) specifies.

C)        Any supplier this subsection (b)(3) deems to have optimized corrosion control must notify the Agency in writing under Section 611.1360(a)(3) of any upcoming long-term change in treatment or the addition of a new source, as that Section describes.  The Agency must review and approve the addition of a new source or any long-term change in water treatment before the supplier adds the source or implements the long-term change.

D)        A supplier is not deemed to have optimized corrosion control under this subsection (b)(3) and must implement corrosion control treatment under subsection (b)(3)(E), unless the supplier meets the copper action level.

E)        Any supplier this subsection (b)(3) no longer deems to have optimized corrosion control must implement corrosion control treatment under subsection (e).  Any large system supplier this subsection (b)(3) no longer deems to have optimized corrosion control must adhere to the schedule that subsection (e) specifies for a medium-sized water system supplier, with the time periods for completing each step being triggered by the date the supplier is no longer deemed to have optimized corrosion control under this subsection (b)(3).

c)         Suppliers Not Required to Complete Corrosion Control Steps for Having Met Both Action Levels

1)         Any small or medium-sized water system supplier, otherwise required to complete the corrosion control steps because it exceeded the lead or copper action level, may cease completing the treatment steps after fulfilling specific conditions:

A)        The supplier meets both the copper and lead action levels during each of two consecutive six-month monitoring periods under Section 611.1356; and

B)        The supplier submits the results for those two consecutive six-month monitoring periods to the Agency.

2)         A supplier that ceases completing the corrosion control steps under subsection (c)(1) (or the Agency, if appropriate) must resume completion of the applicable treatment steps, beginning with the first treatment step that the supplier previously did not complete in its entirety, if the supplier thereafter exceeds the lead or copper action level during any monitoring period.

3)         The Agency may issue a SEP requiring a supplier to repeat treatment steps the supplier previously completed if the Agency determines that this is necessary to properly implement the treatment requirements of this Section.  The Agency must explain the basis for its decision in any SEP.

4)         A small or medium-sized water system supplier exceeding the lead or copper action level triggers the requirement to implement corrosion control treatment steps under subsection (e) (including systems deemed to have optimized corrosion control under subsection (b)(1)).

d)         Treatment Steps for Large Systems.  Except as subsections (b)(2) and (b)(3) provide otherwise, a large system must complete certain corrosion control treatment steps as specific rules provide).

1)         Step 1:  Initial monitoring during two consecutive six-month monitoring periods (under Sections 611.1356(d)(1) and 611.1357(b)).

2)         Step 2:  Corrosion control studies (under Section 611.1352(c)).

3)         Step 3:  The Agency approving optimal corrosion control treatment in a SEP (under Section 611.1352(d)).

4)         Step 4:  Installing optimal corrosion control treatment (under Section 611.1352(e)).

5)         Step 5:  Completing follow-up sampling (under Sections 611.1356(d)(2) and 611.1357(c)).

6)         Step 6:  The Agency reviewing installed treatment and approving optimal water quality control parameters (under Section 611.1352(f)).

7)         Step 7:  Complying with the Agency-specified optimal water quality control parameters (under Section 611.1352(g)) and continuing tap sampling (under Sections 611.1356(d)(3) and 611.1357(d)).

e)         Treatment Steps and Deadlines for Small and Medium-Sized Water Systems.  Except as subsection (b) provides otherwise, a small and medium-sized system supplier must complete certain corrosion control treatment steps as specific rules provide before the indicated time periods.

1)         Step 1:  The supplier must conduct initial tap sampling (under Sections 611.1356(d)(1) and 611.1357(b)) until the supplier either exceeds the lead or copper action level or becomes eligible for reduced monitoring under Section 611.1356(d)(4).  A supplier exceeding the lead or copper action level must recommend optimal corrosion control treatment (under Section 611.1352(a)) within six months after the end of the monitoring period during which the exceedance occurred.

2)         Step 2:  Within 12 months after the end of the monitoring period during which a supplier exceeds the lead or copper action level, the Agency may require the supplier to perform corrosion control studies (under Section 611.1352(b)).  If the Agency does not require the supplier to perform corrosion control studies, the Agency must issue a SEP specifying optimal corrosion control treatment (under Section 611.1352(d)) within the appropriate of specific timeframes:

A)        For a medium-sized water system, within 18 months after the end of the monitoring period during which the supplier exceeded the lead or copper action level; or

B)        For a small system, within 24 months after the end of the monitoring period during which the supplier exceeded the lead or copper action level.

3)         Step 3:  If the Agency requires a supplier to perform corrosion control studies under step 2 (subsection (e)(2)), the supplier must complete the studies (under Section 611.1352(c)) within 18 months after the Agency requires the supplier to conduct the studies.

4)         Step 4:  If a supplier performs corrosion control studies under step 2 (subsection (e)(2)), the Agency must issue a SEP approving optimal corrosion control treatment (under Section 611.1352(d)) within six months after the supplier completes step 3 (under subsection (e)(3)).

5)         Step 5:  The supplier must install optimal corrosion control treatment (under Section 611.1352(e)) within 24 months after the Agency approves that treatment.

6)         Step 6:  The supplier must complete follow-up sampling (under Sections 611.1356(d)(2) and 611.1357(c)) within 36 months after the Agency approves optimal corrosion control treatment.

7)         Step 7:  The Agency must review the supplier’s installation of treatment and issue a SEP approving optimal water quality control parameters (under Section 611.1352(f)) within six months after the supplier completes step 6 (under subsection (e)(6)).

8)         Step 8:  The supplier must comply with the Agency-approved optimal water quality control parameters (under Section 611.1352(g)) and continue tap sampling (under Sections 611.1356(d)(3) and 611.1357(d)).

BOARD NOTE:  This Section corresponds with Section 611.1351 and derives from 40 CFR 141.81 (2020).

(Source:  Added at 47 Ill. Reg. 16486, effective November 2, 2023)