Section 611.352  Corrosion Control Treatment

 

Description of corrosion control treatment requirements.  This section provides the requirements for suppliers and the Agency designating optimal corrosion control treatment (OCCT) for a supplier that is optimizing or re-optimizing OCCT.  All suppliers must complete the corrosion control treatment requirements in this Section as applicable under Section 611.351.

 

a)         Supplier recommendation regarding corrosion control treatment.

 

1)         Any supplier without corrosion control treatment that is required to recommend a treatment option in compliance with Section 611.351(e)(1)(C) must, based on the results of lead and copper tap sampling and water quality parameter monitoring, recommend designating one or more of the corrosion control treatments in subsection(c)(1) to the Agency as the optimal corrosion control treatment for that supplier.  The Agency may require the supplier to conduct additional water quality parameter monitoring to assist the Agency in reviewing the supplier's recommendation.

 

2)         Any supplier with corrosion control treatment that exceeds the lead action level that is required to recommend a treatment option to the Agency in compliance with Section 611.351(d)(1)(C) must recommend designating one or more of the corrosion control treatments listed in subsection (c)(2) as the optimal corrosion control treatment for that supplier.

 

3)         The Agency may waive the requirement for a supplier to recommend OCCT if the Agency requires the supplier, in writing, to complete a corrosion control study within three months after the end of the tap sampling period in which the lead or copper action level exceedance occurred.  These suppliers must proceed directly to subsection (c) and complete a corrosion control study.

 

b)         Agency-decision to require studies to identify initial OCCT under Section 611.351.(e)(2) and re-optimized OCCT under Section 611.351(d)(2).

 

1)         The Agency may require any small or medium supplier without corrosion control treatment that exceeds either the lead action level or copper action level to perform corrosion control treatment studies under subsection (c)(1) to identify OCCT for the supplier's system.

 

2)         The Agency may require any small or medium supplier with corrosion control treatment exceeding either the lead or copper action level to perform corrosion control treatment studies under subsection (c)(2) to identify re-optimized OCCT for its system (i.e., OCCT after a re-optimization evaluation).

 

c)         Performing corrosion control studies.

 

1)         Suppliers without corrosion control treatment required to conduct corrosion control studies under subsection 611.351(e) must evaluate the effectiveness of each of the following treatments, and if appropriate, combinations of the following treatments to identify OCCT for the system:

 

A)        Alkalinity and pH adjustment;

 

B)        The addition of an orthophosphate- or silicate-based corrosion inhibitor at a concentration sufficient to maintain an effective corrosion inhibitor residual concentration in all test samples;

 

C)        The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 1 mg/ L (as PO₄) in all test samples; and

 

D)        The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 3 mg/ L (as PO₄) in all test samples.

 

2)         Suppliers with corrosion control treatment required to conduct corrosion control studies under Section 611.351(d) must evaluate the effectiveness of the following treatments, and if appropriate, combinations of the following treatments, to identify re-optimized OCCT for the system:

 

A)        Alkalinity and/or pH adjustment or re-adjustment;

 

B)        The addition of an orthophosphate- or a silicate-based corrosion inhibitor at a concentration sufficient to maintain an effective corrosion inhibitor residual concentration in all test samples if no such inhibitor is currently utilized;

 

C)        The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 1 mg/ L (PO₄) in all test samples unless the current inhibitor process already meets this residual; and

 

D)        The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 3 mg/L (as PO₄) in all test samples unless the current inhibitor process already meets this residual.

 

3)         Suppliers must evaluate each of the corrosion control treatments in subsection (c)(1) or (2) individually or, if appropriate, in combinations, using pipe rig/loop tests, metal coupon tests, partial-system tests, and/or analyses based on documented analogous treatments with similar size systems that have a similar water chemistry, and similar distribution system configurations.  Large and medium suppliers with lead service lines and other systems as required by the Agency, that exceed the lead action level must conduct pipe rig/loop studies using harvested lead service lines from their distribution systems to assess the effectiveness of corrosion control treatment options on the existing pipe scale.  Metal coupon tests can be used as a screen to reduce the number of options evaluated in the pipe rig/loop studies to the current water quality and at least two additional treatment options.

 

4)         Suppliers must measure the following water quality parameters in any tests conducted under subsection (c)(3) both before and after evaluating the corrosion control treatments listed in subsections (c)(1) or (c)(2):

 

A         Lead;

 

B)        Copper;

 

C)        pH;

 

D)        Alkalinity;

 

E)        Orthophosphate as PO₄ (when an orthophosphate-based inhibitor is used);

 

F)         Silicate (when a silicate-based inhibitor is used); and

 

G)        Any additional parameters necessary to evaluate the effectiveness of a corrosion control treatment as determined by the Agency.

 

5)         Suppliers must identify all chemical or physical constraints that limit or prohibit the use of a particular corrosion control treatment and document those constraints by providing either of the following:

 

A)        Data and documentation showing a particular corrosion control treatment has adversely affected other drinking water treatment processes when used by another supplier with comparable water quality characteristics.  Suppliers using metal coupon tests to screen and/or pipe rig/loop studies to evaluate treatment options cannot exclude treatment strategies from the studies based on the constraints identified in subsection (c)(5)(A).

 

B)        Data and documentation demonstrating the supplier previously attempted to evaluate a particular corrosion control treatment and found the treatment was ineffective or adversely affects other drinking water quality treatment processes.  Suppliers using metal coupon tests to screen and/or pipe rig/loop studies to evaluate treatment options cannot exclude treatment strategies from the studies based on the constraints identified in subsection (c)(5)(B), unless the treatment was found to be ineffective in a previous pipe rig/loop study.

 

6)         Suppliers must evaluate the effect of the chemicals used for corrosion control treatment on other drinking water quality treatment processes.  Suppliers using metal coupon tests to screen and/or pipe rig/loop/ studies to evaluate treatment options cannot exclude any of the required treatment strategies specified in subsection (c)(1) or (c)(2) from the studies based on the effects identified in this Section.

 

7)         Based on the data and analysis for each treatment option evaluated under this subsection (c), suppliers must recommend to the Agency, in writing, the treatment option that the corrosion control studies indicate constitutes OCCT for its system as defined in Section 611.350(b).  Suppliers must provide the Agency with a rationale for the OCCT recommendation, and all supporting documentation specified in subsections (c)(1) or (c)(2) and subsections (c)(3) through (c)(7).

 

d)         Agency designation of OCCT and re-optimized OCCT

 

1)         Designation of OCCT or re-optimized OCCT.  Based on available information, including, where applicable, studies conducted under subsection (c)(1) or (c)(2) and/or a supplier's recommended corrosion control treatment option, the Agency must either approve the supplier-recommended corrosion control treatment option or designate alternative corrosion control treatment(s) from among those listed in subsection (c)(1) or (c)(2), as applicable.  The Agency must notify the supplier, in writing, of its designation of OCCT or re-optimized OCCT and explain the basis for this determination.

 

A)        When designating OCCT, the Agency must consider the effects that additional corrosion control treatment has on water quality parameters and other drinking water quality treatment processes.

 

B)        If the Agency requests additional information to aid its review, the supplier must provide that information.

 

2)         This subsection (d)(2) corresponds with 40 CFR 141.82(d)(2), which USEPA marked "Reserved".  This statement maintains structural consistency with USEPA's rule.

 

e)         Installing OCCT and Re-Optimizing OCCT.  Each supplier must install and operate the OCCT or re-optimized OCCT designated by the Agency under subsection (d) throughout its distribution system.

 

f)         Agency review of treatment and designation of optimal water quality parameters for OCCT and re-optimized OCCT.  The Agency must evaluate the results of all lead and copper tap and water quality parameter sampling submitted by the supplier and determine whether the supplier has installed and operated the OCCT designated by the Agency in subsection (d).  Upon reviewing the supplier's tap and water quality parameter sampling results, both before and after the supplier installs OCCT, or re-optimized OCCT, the Agency must designate each of the following:

 

1)         A minimum value or a range of values for pH measured at each entry point to the distribution system.

 

2)         A minimum pH value measured in all distribution system samples.  This value must be equal to or greater than 7.0, unless the Agency determines that meeting a pH level of 7.0 is not technologically feasible or is not necessary for OCCT.

 

3)         If a corrosion inhibitor is used, a minimum concentration or a range of concentrations for orthophosphate (as PO₄) or silicate measured at each entry point to the distribution system.

 

4)         If a corrosion inhibitor is used, a minimum orthophosphate (as PO₄) or silicate concentration measured in all tap samples that the Agency determines is necessary to form a passivating film on the interior walls of the pipes of the distribution system. When orthophosphate is used, for OCCT designations for suppliers previously without corrosion control treatment, the orthophosphate concentration must be equal to or greater than 0.5 mg/L (as PO₄) and for OCCT designations for suppliers previously with corrosion control treatment, the orthophosphate concentration must be equal to or greater than 1.0 mg/L, unless the Agency determines that meeting the applicable minimum orthophosphate residual is not technologically feasible or is not necessary for OCCT.

 

5)         If alkalinity is adjusted as part of OCCT, a minimum concentration or a range of concentrations for alkalinity, measured at each entry point to the distribution system and in all tap samples.

 

6)         The values for the applicable water quality parameters in subsections (f)(1) through (f)(5) must be the values the Agency determines reflect OCCT or re-optimized OCCT for the supplier's water system. The Agency may designate values for additional water quality parameters the Agency determines reflect OCCT or re-optimized OCCT for the supplier's water system. The Agency must notify the supplier, in writing, of these determinations and explain the basis for its decisions.

 

g)         Continued operation and monitoring for OCCT and re-optimized OCCT.  All suppliers, including those optimizing or re-optimizing OCCT, must continue to operate and maintain OCCT, including maintaining water quality parameters at or above the minimum values or within the ranges designated by the Agency under subsection (f), in compliance with this subsection (g) for all water quality parameter samples collected under Section 611.357(b)(4) through (d).  The requirements of this subsection (g) apply to all suppliers, including suppliers with consecutive systems that distribute water that has been treated to control corrosion by another supplier, and any supplier system with corrosion control treatment,OCCT, or re-optimized OCCT that is not required to monitor water quality parameters under Section 611.357.  

 

1)         The supplier must determine whether it complies with this subsection (g) every six months, as specified in Section 611.357(b)(4).  A supplier is out of compliance with this subsection (g) for a six-month period if it has excursions for any Agency-specified parameter on more than nine days, cumulatively, during the period. An excursion occurs whenever the daily value for one or more of the water quality parameters measured at a sampling location is below the minimum value or outside the range designated by the Agency.  Daily values are calculated as set out in subsection (g)(2).  The Agency has discretion to not include results of obvious sampling errors from this calculation. The supplier must record sampling errors even when not included in calculations.

 

2)         Water quality parameter daily value.

 

A)        On days when the supplier collects more than one measurement for a water quality parameter at a sampling location, the daily value must be the average of all results collected at that sampling location during the same day, regardless of whether they are collected through continuous monitoring, grab sampling, or a combination of both.

 

BOARD NOTE:  Corresponding 40 CFR 141.82(g)(2)(i) further provides as follows:  If USEPA approves an alternative formula under 40 CFR 142.16(d)(1)(ii) in the State's application for a program revision submitted under 40 CFR 142.12, the approved formula must be used to aggregate multiple measurements at a sampling point for the water quality parameters in lieu of the formula in this subsection (g)(2).

 

B)        On days when the supplier collects only one measurement for a water quality parameter at a sampling location, the daily value must be the result of that measurement.

 

C)        On days when the supplier collects no measurement for a water quality parameter at a sampling location, the daily value must be the daily value calculated on the most recent day on which the supplier measured the water quality parameter at the sampling location.

 

h)         Modification of Agency treatment determination for OCCT and re-optimized OCCT.  Upon its own initiative or in response to a request by a supplier or other interested party, the Agency may modify its determination of OCCT under subsection (d), or the optimal water quality parameters under subsection (f).  A request for modification by a supplier or other interested party must be in writing, explaining why the modification is appropriate, and providing supporting documentation.  The Agency may require a supplier to conduct a CCT study to support modification of the determination of OCCT or re-optimized OCCT.  The Agency may modify its determination where it concludes that such a change is necessary to ensure that the supplier continues to optimize corrosion control treatment.  A revised designation must be made in writing, set forth the new treatment requirements and/or optimal water quality parameters, explain the basis for the Agency's determination, and provide an implementation schedule for completing the treatment modifications for re-optimized corrosion control treatment.

 

i)          Treatment decisions by USEPA in lieu of the Agency on OCCT and re-optimized OCCT. Under the procedures in 40 CFR 142.19, USEPA may review OCCT determinations made by the Agency under subsections (d),(f), or (h) and issue federal corrosion control treatment determinations consistent with the requirements of 40 CFR 141.82(d), (f), or (h) where USEPA finds that:

 

1)         The Agency failed to issue a treatment determination by the applicable deadlines in Section 611.351 (corresponding with 40 CFR 141.81);

 

2)         The Agency abused its discretion; or

 

3)         The technical aspects of the Agency's determination would be indefensible in a federal enforcement action taken against a supplier.

 

j)          Distribution system and site assessment for tap sampling sites with lead results that exceed 0.010 mg/L.  The supplier must conduct the following steps when the lead results from an individual tap sample site sampled under Section 611.356 exceed 0.010 mg/L and the site is included in the site sample plan under Section 611.356(a)(1):

 

1)         Step 1:  Corrosion control treatment assessment.  Within five days of receiving the tap sampling results, the supplier must sample at a water quality parameter site in compliance with subsection (j)(1)(B) that is on the same-size water main, in the same pressure zone and located within a half mile radius of the site with the lead result that exceeds 0.010 mg/L.  Suppliers without corrosion control treatment are not required to collect these samples.

 

A)        The supplier must measure the following water quality parameters:

 

i)          pH;

 

ii)         Alkalinity;

 

iii)        Orthophosphate (as PO₄), when an inhibitor containing an orthophosphate compound is used; and

 

iv)        Silica, when an inhibitor containing a silicate compound is used.

 

B)        The supplier must measure at the following locations:

 

i)          Suppliers with an existing water quality parameter site that meets the requirements in this subsection (j)(1) can conduct this sampling at that site.

 

ii)         All suppliers required to meet optimal water quality parameters but do not have an existing water quality parameter site that meets the requirements in this subsection (j)(1) must add new sites to the minimum number of sites described in Section 611.357(b)(1)(A).  Sites must be added until a supplier has twice the minimum number of sites listed in Section 611.357(b)(1)(A).  When a supplier exceeds twice the number of sites, the Agency has discretion to determine if these additional newer sites can better assess the effectiveness of the corrosion control treatment and whether to remove existing sites during sanitary survey evaluation of OCCT.

 

2)         Step 2:  Site assessment.  Within 30 days of receiving the tap sampling results, suppliers must collect and analyze a follow-up sample for lead at any tap sample site that exceeds 0.010 mg/L .  The supplier may use these follow-up sample volumes or different sample procedures to assess the source of elevated lead levels.  Samples the supplier collected under this Section must be submitted to the Agency but cannot be included in the 90^th percentile calculation for compliance monitoring under Section 611.356.  If the supplier is unable to collect a follow-up sample at a site, the supplier must provide documentation to the Agency, as specified in Section 611.360(g)(2), explaining why it was unable to collect a follow-up sample.

 

3)         Step 3:  Evaluate results and system treatment recommendation.  Suppliers must evaluate the results of the sampling conducted under subsections (j)(1) and (j)(2) to determine if either localized or centralized adjustment of OCCT or other distribution system actions are necessary and submit the recommendation to the Agency within six months after the end of the tap sampling period in which the site(s) exceeded 0.010 mg/L.  Corrosion control treatment modification may not be necessary to address every exceedance of 0.010 mg/L.  Other distribution system actions may include flushing to reduce water age.  Suppliers must note the cause of the elevated lead level, if known from the site assessment, in their recommendation to the Agency as site-specific issues can be an important factor in why the supplier does not recommend any adjustment of corrosion control treatment or other distribution system actions.  Suppliers in the process of optimizing or re-optimizing OCCT under subsections (a) through (f) do not need to submit a treatment recommendation for distribution system and site assessment.

 

4)         Step 4:  Agency approval of treatment recommendation.  The Agency must approve the supplier's treatment recommendation or specify a different approach within six months of completing Step 3, as described in subsection (j)(3) and notify the supplier in writing.

 

5)         Step 5:  Modifications to OCCT.  If the Agency-approved treatment recommendation requires the supplier to adjust the OCCT process, the supplier must complete modifications to its corrosion control treatment within 12 months of receiving notification from the Agency, as described in subsection (j)(4).  Suppliers without corrosion control treatment required to install OCCT must follow the schedule in Section 611.351(e).

 

6)         Step 6:  Follow-up sampling.  Suppliers adjusting OCCT must complete follow-up sampling in compliance with Sections 611.356(c)(2)(C)(iv) and 611.357(b)(3) within 12 months after completing Step 5, as described in subsection (j)(5) and submit sampling results to the Agency in compliance with Sections 611.356 and 611.357.

 

7)         Step 7:  Agency OWQP designation.  For suppliers adjusting OCCT, the Agency must review the supplier's modification of corrosion control treatment and designate optimal water quality parameters in compliance with subsection (f) within six months of receiving the sampling result described in subsection (j)(6).

 

8)         Step 8:  Operate in compliance.  For a supplier adjusting OCCT,the supplier must comply with the Agency-designated optimal water quality parameters in compliance with subsection (g) and continue to conduct tap sampling in compliance with Sections 611.356(c)(2)(C)(v) and 611.357(b)(4).

 

BOARD NOTE:  This Section derives from 40 CFR 141.82.

 

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