Section 611.351  Applicability of Corrosion Control

 

a)         Corrosion control treatment.  All suppliers are required to install, optimize, or re-optimize optimal corrosion control treatment (OCCT) in compliance with this section.  This section provides when a supplier must complete the corrosion control treatment steps in subsection (d) or (e) based on size, whether the supplier's system has corrosion control treatment, and whether the supplier exceeded the lead practical quantitation limit, lead action level, and/or copper action level.

 

1)         Large Suppliers (serving >50,000 people)

 

A)        A large supplier with corrosion control treatment that exceeds either the lead action level or copper action level must complete the re-optimized OCCT steps specified in subsection (d) unless the supplier:

 

i)          Has re-optimized OCCT once under subsection (d) after the compliance date in Section 611.350(a)(3);

 

ii)         Is meeting optimal water quality parameters designated by the Agency; and

 

iii)        Is continuing to operate and maintain corrosion control treatment in compliance with Section 611.352(g).

 

B)        The Agency may require a large supplier that does not have to re-optimize under subsections (a)(1)(A)(i) through (iii) to re-optimize under Section 611.352(h).

 

C)        A large supplier must meet the requirements under subsection (d) if it exceeds the lead action level at the end of a tap sampling period after completing service line replacement in compliance with Section 611.354(d) and there are no lead, galvanized requiring replacement, or lead status unknown service lines remaining in the supplier's inventory.

 

D)        Large suppliers with corrosion control treatment with 90^th percentile results as calculated in compliance with Section 611.350(c)(3) that exceed the lead practical quantitation limit of 0.005 mg/L but do not exceed the lead action level or copper action level may be required by the Agency to complete the re-optimized OCCT steps in subsection(d).

 

E)        Large suppliers without corrosion control treatment with 90^th percentile results calculated in compliance with Section 611.350(c)(3) that exceed either the lead practical quantitation limit of 0.005 mg/L or the copper action level must complete steps to study and install OCCT, as specified in subsection (e).

 

2)         Medium Suppliers (serving >10,000 and ≤50,000 people)

 

A)        Medium Suppliers with corrosion control treatment that exceed either the lead action level or the copper action level must complete the re-optimized OCCT steps specified in subsection (d) unless the supplier:

 

i)          Has re-optimized OCCT once under subsection (d) after the compliance date in Section 611.350(a)(3);

 

ii)         Is meeting optimal water quality parameters designated by the Agency; and

 

iii)        Is continuing to operate and maintain corrosion control treatment in compliance with Section 611.352(g).

 

B)        The Agency may require a medium supplier that does not have to re-optimize under subsections(a)(2)(A)(i) through (iii) to re-optimize under Section 611.352(h).

 

C)        After completing service line replacement in compliance with Section 611.354(d) and there are no lead, galvanized requiring replacement, or lead status unknown service lines remaining in the inventory, if at the end of a subsequent tap sampling period, the supplier exceeds the lead action level, a medium supplier with corrosion control treatment must meet the requirements under subsection (d).

 

D)        Medium suppliers with corrosion control treatment that do not exceed either the lead action level or the copper action level and do not have optimal water quality parameters designated by the Agency must complete the steps specified in subsection (d) starting with step 6 under subsection (d)(6) unless the supplier is deemed optimized under subsection (b)(3).

 

E)        Medium suppliers without corrosion control treatment that exceed either the lead or copper action level must complete the OCCT steps specified in subsection (e).

 

3)         Small suppliers (serving ≤ 10,000 people) and NTNCWS suppliers.

 

A)        Small and NTNCWS suppliers with corrosion control treatment that exceed either the lead action level or copper action level, must complete the re-optimized OCCT steps specified in subsection (d) unless the supplier:

 

i)          Has re-optimized OCCT once under subsection (d) after the compliance date in Section 611.350(a)(3);

 

ii)         Is meeting optimal water quality parameters designated by the Agency; and

 

iii)        Is continuing to operate and maintain corrosion control treatment as required in 611.352(g).

 

B)        The Agency may require a small supplier that does not have to re-optimize under subsection(a)(3)(A)(i) through (iii) to re-optimize under Section 611.352(h).

 

C)        After completing service line replacement in compliance with 611.354(d) and there are no lead, galvanized requiring replacement, or lead status unknown service lines remaining in the inventory, if at the end of a subsequent tap sampling period, the supplier exceeds the lead action level, a small supplier with corrosion control treatment must meet the requirements in subsection (d).

 

D)        Small and NTNCWS suppliers without corrosion control treatment that exceed either the lead action level or copper action level must complete the corrosion control treatment steps specified in subsection (e).

 

b)         Suppliers deemed to have optimized corrosion control.  A supplier without corrosion control treatment is deemed to have OCCT as defined in Section 611.350(b) if the supplier's system meets the requirements of either subsection (b)(1)or (3).  A supplier with corrosion control treatment is deemed to have OCCT as defined in Section 611.350(b) or re-optimized OCCT if the supplier meets the requirements of either subsection (b)(1) and (4) or (b)(3) and (4).  Suppliers must submit documentation of meeting applicable requirements to the Agency in compliance with Section 611.360(c)(1) by the deadline for submitting tap sampling results under Section 611.360(a)(2).

 

1)         A medium supplier without corrosion control treatment or a small supplier is deemed to have OCCT if the supplier does not exceed the lead action level and copper action level during two consecutive six-month tap monitoring periods and then remains at or below the lead action level and copper action level in all tap sampling periods conducted in compliance with Section 611.356.

 

A)        A small supplier with corrosion control treatment is not eligible to be deemed to have OCCT under this subsection (b)(1) where the Agency has set optimal water quality parameters (OWQPs) under subsection (d) or (e).

 

B)        If a medium supplier without corrosion control treatment or a small supplier deemed to have OCCT under this subsection (b)(1) exceeds the lead action level or copper action level, the supplier must follow the requirements in subsection (a).

 

2)         This subsection (b)(2) corresponds with 40 CFR 141.81(b)(2), which USEPA marked "Reserved".  This statement maintains structural consistency with USEPA's rule.   

 

3)         A supplier is deemed to have optimized or re-optimized corrosion control treatment if it submits tap sampling results in compliance with Section 611.356 demonstrating that the 90^th percentile lead level is less than or equal to the lead PQL of 0.005 mg/L for two consecutive six-month tap monitoring periods, it does not exceed the copper action level for two consecutive six-month tap monitoring periods, and it does not have OWQPs designated by the Agency under subsection (d) or (e).

 

A)        A supplier with 90^th percentile tap sampling results that later exceeds the lead practical quantitation limit of 0.005 mg/L or copper action level during any tap sampling period is not eligible to be deemed to have optimized OCCT in compliance with this subsection (b)(3) until the supplier completes the treatment steps specified in subsection (d) or (e).

 

B)        A supplier deemed to have OCCT in compliance with this subsection (b)(3) must continue monitoring for lead and copper at the tap no less frequently than once every three calendar years using the reduced number of sites specified in 611.356(d)(1) and collecting samples at times and locations specified in 611.356(d)(2)(C).

 

4)         A supplier with corrosion control treatment deemed to have OCCT under this subsection (b) must continue to operate and maintain the corrosion control treatment and also meet any additional requirements that the Agency determines are appropriate to ensure OCCT is maintained.

 

c)         This subsection (c) corresponds with 40 CFR 141.81(c), which USEPA marked "Reserved".  This statement maintains structural consistency with USEPA's rule.

 

d)         Treatment steps and deadlines for suppliers re-optimizing OCCT.  Suppliers with corrosion control treatment required to re-optimize OCCT under subsection (a) must complete the following steps (described in Sections 611.352, 611.356, and 611.357) by the indicated time periods.  Suppliers must conduct tap sampling for lead and copper in compliance with the requirements of Section 611.356 while they complete the corrosion control steps in this section.

 

1)         Step 1:  Initiate mandatory pipe rig/loop or CCT study or treatment recommendation.

 

A)        Large or medium suppliers with lead service lines that exceed the lead action level must harvest lead service lines from its distribution system and construct flowthrough pipe rigs/loops and operate the rigs/loops with finished water within one year after the tap sampling period in which they exceed the lead action level.  These suppliers must proceed to Step 3 under subsection (d)(3) and conduct the corrosion control studies for re-optimization under subsection (d)(3)(A) using the pipe rigs/loops.

 

B)        Large suppliers without lead service lines that exceed the lead action level or copper action level must conduct the corrosion control studies for re-optimization under subsection (d)(3)(B) (step 3).

 

C)        A supplier other than those covered in subsection (d)(1)(A) or (B) must recommend re-optimized optimal corrosion control treatment (Section 611.352(a)) within six months after the end of the tap sampling period in which the supplier exceeded the lead action level or copper action level.

 

D)        Suppliers may make an existing corrosion control treatment modification recommendation to the Agency within six months after the end of the tap sampling period in which the supplier exceeded the lead action level.  The Agency must evaluate a supplier's past corrosion control treatment study results prior to approving an existing treatment modification.  When the Agency approves existing treatment modifications, the Agency must specify re-optimized OCCT within 12 months after the end of the tap sampling period in which the supplier exceeded the lead action level.  The supplier must complete modifications to corrosion control treatment to have re-optimized OCCT installed within six months of the Agency specifying re-optimized OCCT.  These suppliers must proceed to step 6 in subsection (d)(6) and conduct follow-up monitoring.

 

2)         Step 2:  Agency requires CCT study or Agency designates re-optimized OCCT.  Within one year after the end of the tap sampling period in which a medium supplier without lead service lines or a small supplier exceeded the lead action level or copper action level, the Agency may require the supplier to perform corrosion control studies for re-optimization (Section 611.352 (c)(2)).  If the Agency does not require the supplier to perform such studies, the Agency must specify re-optimized optimal corrosion control treatment (Section 611.352(d) within the timeframes in subsections (d)(2)(A) and (d)(2)(B).  The Agency must provide its determination to the supplier in writing:

 

A)        For a medium supplier, within one year after the end of the tap sampling period during which the supplier exceeded the lead action level or copper action level.

 

B)        For a small supplier, within 18 months after the end of the tap sampling period in which the supplier exceeded the lead action level or copper action level.

 

3)         Step 3:  Study duration.  

 

A)        Any supplier with lead service lines that exceeds the lead action level in subsection (d)(1)(A) must complete the pipe rig/loop corrosion control treatment studies and recommend re-optimized OCCT within 30 months after the end of the tap sampling period in which the supplier exceeded the lead action level.

 

B)        If the supplier is required to perform corrosion control studies under subsection (d)(1)(B) or (d)(2), the supplier must complete the studies (Section 611.352(e)) and recommend re-optimized OCCT within 18 months after the end of the tap sampling period in which the supplier exceeded the lead or copper action level or after the Agency requires the supplier to conduct the studies.

 

4)         Step 4:  Agency designation of re-optimized OCCT based on CCT study results.  The Agency must designate re-optimized OCCT (Section 611.352(d)) within six months after the supplier completes subsection (d)(3)(A) or (B) (step 3).

 

5)         Step 5:  Re-optimized OCCT installation deadlines.  Suppliers must install re-optimized OCCT (611.352(e)) within one year after the Agency completes subsection (d)(4) (Step 4) or the Agency completes subsection (d)(2)(A) or (B) (Step 2)

 

6)         Step 6:  Follow-up monitoring.  Suppliers must complete standard monitoring for at least two consecutive tap monitoring periods under Section 611.356(c)(2)(C)(iv) and water quality parameter monitoring under Section 611.357(b)(3) after completing subsection (d)(5) (step 5).  The first tap monitoring period for standard monitoring must begin on January 1 or July 1, whichever is sooner, after completing subsection (d)(5) (step 5).

 

7)         Step 7:  Agency sets optimal water quality parameters.(OWQPs) The Agency must review the supplier's re-optimized OCCT and designate OWQPs (611.352(f)) within six months after completing subsection (d)(6) (Step 6).

 

8)         Step 8:  Suppliers meet OWQPs to demonstrate compliance.  Suppliers must comply with the Agency-designated OWQPs (Section 611.352(g)) and conduct tap sampling under Section 611.356(c)(2)(C)(v) and water quality parameter monitoring under Section 611.357.(b)(4).

 

e)         Treatment steps and deadlines for suppliers without corrosion control treatment. Except as provided in subsection (b) suppliers without corrosion control treatment must complete the following corrosion control treatment steps (described in the referenced portions of Sections 611.352, 611.356, and 611.357) by the indicated time periods.  Suppliers must conduct tap sampling for lead and copper in compliance with the requirements of Section 611.356 while completing the corrosion control steps in this section.

 

1)         Step 1:  Initiate mandatory pipe rig/loop or CCT study or treatment recommendation.

 

A)        A medium or large supplier with lead service lines that exceeds the lead action level must harvest lead pipes from the distribution system and construct flowthrough pipe rigs/loops and operate the rigs/loops with finished water within one year after the end of the tap sampling period during which the supplier exceeded the lead action level.  These suppliers must proceed to step 3 in subsection (e)(3) and conduct the corrosion control studies for optimization under subsection (e)(3)(A) using the pipe rigs/loops.

 

B)        Large water suppliers under subsection (a)(1)(E) must conduct the corrosion control studies for optimization under subsection (e)(3) (step 3).

 

C)        A supplier other than those covered in subsection (e)(1)(A) or (B) must recommend optimal corrosion control treatment (OCCT) (Section 611.352(a)) within six months after the end of the tap sampling period during which the supplier exceeded either the lead action level or copper action level.

 

2)         Step 2:  Agency requires CCT study or designates OCCT.  Within one year after the end of the tap sampling period in which the supplier exceeded the lead or copper action level, the Agency may require the supplier to perform corrosion control studies (Section 611.352(b)(1)) if those studies are not otherwise required by this subpart.  The Agency must notify the supplier in writing when a corrosion control study is required.  If the Agency does not require the supplier to perform corrosion control studies, the Agency must specify OCCT (Section 611.352(d)) within the timeframes established in subsections (e)(2)(A) and (e)(2)(B).  The Agency must provide its determination to the supplier in writing:

 

A)        For a medium supplier, within 18 months after the end of the tap sampling period in which such supplier exceeds the lead action level or copper action level; or

 

B)        For a small supplier, within 24 months after the end of the tap sampling period in which the supplier exceeds the lead action level or copper action level.

 

3)         Step 3:  Study duration.

 

A)        Large and medium suppliers with lead service lines that exceed the lead action level must complete the corrosion control treatment studies and recommend OCCT within 30 months after the end of the tap sampling period in which they exceeded the lead action level.

 

B)        If a supplier is required to perform corrosion control studies under subsection (e)(1)(B) or (e)(2), the supplier must complete the studies (Section 611.352(c)) and recommend OCCT within 18 months after the end of the tap sampling period in which the supplier exceeded the lead or copper action level or the Agency notifies the supplier in writing, that such studies must be conducted.

 

4)         Step 4:  Agency designation of OCCT based on CCT study results.  The Agency must designate OCCT (Section 611.352(d)) within six months after the supplier completes subsection (e)(3)(A) or (B) (Step 3).

 

5)         Step 5:  OCCT Installation deadlines.  Suppliers must install OCCT (Section 611.352(e)) within 24 months after the Agency designates OCCT under subsection (e)(2) or (e)(4) (Step 2 or Step 4).

 

6)         Step 6:  Follow-up monitoring.  Suppliers must complete standard monitoring for at least two consecutive tap monitoring periods under Section 611.356(c)(2)(C)(iv) and water quality parameter monitoring under Section 611.357(b)(3) after completing subsection (e)(5) (step 5).  The first tap monitoring period for standard monitoring must begin on January 1 or July 1, whichever is sooner, after completing subsection (e)(5) (step 5).

 

7)         Step 7:  The Agency sets optimal water quality parameters (OWQPs).  The Agency must review the supplier's installation of treatment and designate OWQPs.  (Section 611.352(f)) within six months after completing subsection (e)(6) (Step 6).

 

8)         Step 8:  Suppliers meet OWQPs to demonstrate compliance.  Suppliers must comply with the Agency-designated OWQPs (Section 611.352(g)) and conduct tap sampling under Section 611.356(c)(2)(C)(v) and water quality parameter monitoring under Section 611.357(b)(4).

 

f)         Suppliers with lead or galvanized requiring replacement service lines that can complete full service line replacement in five years or less.

 

1)         A supplier with one or more lead or galvanized requiring replacement service lines is not required to complete the steps under subsection (d) or (e) if the supplier meets all the following requirements:

 

A)        Deadline to complete mandatory service line replacement.

 

i)          A supplier must complete the service line replacement requirements under Section 611.354(d) in five years or less from the date of the end of the tap sampling period in which the supplier first exceeds the lead action level; or

 

ii)         A large supplier without corrosion control treatment must complete the service line replacement requirements under Section 611.354.(d) in five years or less from the date of the end of the tap sampling period in which the supplier's 90^th percentile results first exceed the lead practical quantitation limit; and

 

iii)        For a supplier with less than five years remaining to complete mandatory service line replacement in compliance with Section 611.354(d), the supplier must complete the service line replacement requirements under subsection (f)(1)(A) by that deadline

 

B)        At a minimum, a supplier must replace the total number of lead and/or galvanized requiring replacement service lines each year, as identified in that supplier's inventory on the date of the end of the tap sampling period in which the supplier first exceeds the lead action level or in which the supplier's 90^th percentile first exceeds the lead practical quantitation limit, whichever applies, at an annual rate equally divided by the total number of years for service line replacement provided in subsection (f)(1)(A).  For purposes of calculating the annual rate, the supplier must replace all lead and galvanized requiring replacement service lines within the least number of years feasible not to exceed five years from the date of the end of the tap sampling period in which the supplier first exceeds the lead action level or in which the supplier's 90^th percentile first exceeds the lead practical quantitation limit, whichever applies.  If the Agency determines a replacement deadline less than five years is feasible for a supplier, the supplier must replace service lines by that deadline and establish an annual replacement rate based on that number of years until that deadline.

 

C)        By the end of the five-year-or-less period in subsection (f)(1)(A), the supplier must have replaced all lead and galvanized requiring replacement service lines calculated in compliance with Section 611.354(d)(6) (i.e., no lead, galvanized requiring replacement or lead status unknown service lines remain in the inventory), and identified the material of all lead status unknown service lines, completed the inventory validation requirements in compliance with Section 611.354(b)(5), and replaced all unknowns found to be lead or galvanized requiring replacement service lines.

 

D)        Except as provided in this section, all other requirements in Section 611.354(d) apply.

 

2)         Throughout the five-year-or-less period in subsection(f)(1)(A), suppliers with corrosion control treatment must continue to operate and maintain corrosion control treatment in addition to completing the mandatory service line replacement requirements under this section.

 

3)         A supplier that does not replace lead and/or galvanized requiring replacement service lines calculated in compliance with Section 611.354(d)(6) at the minimum annual rate provided in subsection (f)(1)(B) in any one year of the five-year-or-less period in subsection (f)(1)(A) or complete the service line replacement requirements under Section 611.354(d) in compliance with subsection (f)(1)(C), must meet the requirements in subsection (d) or (e), as applicable, starting immediately after the supplier fails to meet the annual removal requirement in subsection (f)(1)(B).

 

4)         At the end of each year of the five-year-or-less period, the supplier must submit written documentation to the Agency about the number of lead and galvanized requiring replacement service lines removed that year and whether the minimum annual replacement rate in subsection (f)(1)(B) was met.  If a supplier reports or the Agency determines that the supplier did not meet its minimum annual replacement rate that year, the supplier is no longer eligible to defer the requirements under subsection (d) or (e) and must meet those requirements, as applicable.

 

5)         After completing service line replacement in compliance with the requirements in subsection (f), a supplier must meet the requirements under subsection (d) or (e), as applicable, if at the end of a subsequent tap sampling period, the supplier either exceeds the lead action level or the lead practical quantitation limit, whichever is applicable.

 

g)         Completing corrosion control steps for small and medium suppliers without corrosion control treatment.

 

1)         Any small or medium supplier without corrosion control treatment required to complete the steps in subsection (e) that does not exceed the lead action level and copper action level during two consecutive six-month tap monitoring periods under Section 611.356 prior to the start of step 3 in subsection (e)(3) or before or concurrent with the end of step 4 in subsection (e)(4) may stop completing the steps and is not required to complete subsection (e)(3) or (5) (step 3 or step 5), respectively, except that medium suppliers without corrosion control treatment and with lead service lines must complete a corrosion control treatment study under subsection (e)(3)(A).  A 90^th percentile level at or below the lead action level or copper action level based on less than the required minimum number of samples under Section 611.356 cannot be used to meet the requirements of this subsection (g)(1).  Eligible suppliers can only use the exception in subsection (g)(1) once.

 

2)         Any supplier that starts step 5 in compliance with subsection (e)(5) must complete the remaining steps (i.e., steps 6 through 8) in subsection (e)(6) through (8) and is not permitted to stop the steps.

 

3)         Any small or medium supplier without corrosion control treatment under subsection (g)(1) that stopped the steps in subsection (e) and subsequently exceeds either the lead action level or copper action level must complete the corrosion control treatment steps in subsection (e) beginning with the first treatment step that was not completed.

 

4)         The Agency may require a supplier to repeat treatment steps previously completed by the supplier when the Agency determines it is necessary to implement the treatment requirements of this subsection.  The Agency must notify the supplier in writing of such a determination and explain the basis for its decision.

 

h)         Notification requirements for upcoming long-term change in treatment or source.  At a time specified by the Agency, or if no specific time is designated, as early as possible but no later than six months prior to the addition of a new source or any long-term change in water treatment, a supplier must submit written documentation describing the addition of a new source or long-term change in treatment to the Agency.  Suppliers may not implement the addition of a new source or long-term treatment change without Agency approval.  The Agency must review and approve the addition of a new source or long-term change in water treatment before it can be implemented by the supplier.  The Agency may require any such supplier to take action before or after the addition of a new source or long-term treatment change to ensure that the supplier operates and maintains optimal corrosion control treatment, such as additional water quality parameter monitoring, additional lead or copper tap sampling, and re-evaluating corrosion control treatment.  Examples of long-term treatment changes include but are not limited to the addition of a new treatment process or modification of an existing treatment process.  Examples of modifications include switching secondary disinfectants, switching coagulants (e.g., alum to ferric chloride), and switching corrosion inhibitor products (e.g., orthophosphate to blended phosphate).  Long-term treatment changes can also include dose changes to existing chemicals if the system is planning long-term changes to its finished water pH or residual inhibitor concentration.  Long-term treatment changes would not include chemical dose fluctuations associated with daily raw water quality changes where a new source has not been added.

 

BOARD NOTE:  This Section derives from 40 CFR 141.81.

 

(Source:  Amended at 50 Ill. Reg. 2531, effective February 17, 2026)