One commenter stated that "[t]he 12-month construction timeline for CCT re-optimization (141.81(d)(1)) is not achievable for large treatment modification projects" and noted that "[m]any times a supplier needs to install a new treatment building or chemical room and therefore go through the design, approval and construction process." The commenter also identified "state revolving funding or a short construction season" as additional constraining factors and suggested that "the deadline be dependent on the treatment change or modification scope. Minor treatment changes using existing equipment (e.g., orthophosphate dose change) should take place as soon as possible and within a maximum time limit to protect public health. However, if the treatment change is significant then up to two years should be granted."
Other commenters generally stated that "if construction of significant changes to treatment processes is required, the 12-month implementation deadline in the proposal is inadequate" and that "design and construction of corrosion control-related capital upgrades can take much longer than twelve months to complete." These commenters suggested revising the prescribed timeframe and allowing it to be extended on a case-by-case basis.
One commenter suggested EPA revise § 141.81(e)(5) to require installation of optimal corrosion control treatment within 6 months instead of 24 months on the basis that "the preceding [treatment] steps allow enough time for bidding, budgeting, etc." and that the commenter's state also had done so. Another commenter similarly suggested EPA evaluate the installation timeframe "to see if the amount of time can be shortened when possible."
Under § § 141.81(d)(6) and (e)(6), EPA proposed to require water systems to complete follow-up sampling within 12 months of completion of modifications to corrosion control treatment or installation of optimized or re-optimized corrosion control treatment. One commenter stated that "[t]he requirement to have follow-up monitoring completed within 12 months may be impractical in instances when the beginning of the next six-month monitoring period is months away from the treatment approval date." The commenter instead recommended requiring "water systems complete follow-up sampling for two consecutive six-month monitoring periods and within 18 months after initial installation or re-optimization."
Finally, a commenter sought general clarification on whether the optimization steps were intended to take "up to 4.5-5 years based on timelines given." With regard to the proposed treatment steps for systems that are re-optimizing their corrosion control treatment, a second commenter asked, "[h]ow can a large water system recommend optimal corrosion control treatment within six months after the end of the monitoring period during which it exceeds either the lead trigger level or copper action level before it conducts the corrosion control studies required under § 141.81(d)(2)" and noted that § 141.81(d)(2) "calls for completing the corrosion control studies within 18 months of the exceedance pursuant to § 141.81(d)(3)." The commenter noted the same question for the proposed requirements in § § 141.81(e)(1), (2), and (3) for systems installing optimal corrosion control treatment.
A final commenter suggested that "[t]he noncompliance time period that triggers replacement of all lead service lines needs to be lengthened by 12-18 months to allow adjustments to corrosion control to actually be seen in the distribution system." For more information  on LSLR see response comment Section 6.
Agency Response
EPA agrees the amount of time needed to complete a corrosion control study will depend on the type of study conducted and recognizes that budgeting, planning and procurement for certain studies, those using pipe loops/rigs, will require significantly more time. EPA also agrees with the importance of providing a final rule that better enables systems to make timely treatment decisions appropriate to the specifics of their situation. As discussed in the next paragraph, EPA has included modifications in the final rule to provide additional time to those systems that must conduct pipe loop/rig studies. For other types of studies  -  e.g., metal coupon tests, partial-system tests or analyses based on documented analogous treatments with other systems of similar size  -  the final rule retains the 18-month timeframe. EPA does not believe the scope and logistical complexity of these other types of studies are sufficient to justify delaying the installation of optimized/re-optimized treatment. With regard to the shorter timeframe suggested for OCCT recommendations, systems will need sufficient time to gather and analyze data, identify technical constraints and articulate a basis for which treatment option(s) the system is recommending as its OCCT. EPA does not believe it would be practical or feasible, based on the Agency's experience with implementing the current rule, for systems to do so in fewer than the six months prescribed in the final rule. With regard to the shorter timeframe suggested for CCT studies, the Agency similarly believes that the majority of systems will need 18 months not only to conduct the studies, but to complete a variety of activities related to the planning, analysis of study results and subsequent summarization of findings and conclusions when preparing the study report for the state. For those systems that are able to submit their treatment recommendations or CCT studies sooner than the timeframes prescribed in the final rule  -  6 and 18 months, respectively  -  the Agency notes that the final rule would not preclude them from doing so. Finally, the Agency disagrees with comments suggesting the proposed timeframe does not sufficiently allow systems to evaluate current or future treatment measures or options, or that it warrants a phased deadline approach for conducting in-depth studies or taking corrective actions. Prior to the start of the 18-month study period, systems that are not conducting pipe loop/rig studies are provided an additional 6 months to initiate their evaluations as they develop treatment recommendations for initial or re-optimized corrosion control in accordance with § § 141.81(d)(1)(i) or (e)(1)(i), respectively. As identified above, and discussed in the next paragraph, systems conducting pipe loop/rig studies would have up to 30 months.
With regard to the comments that more specifically suggested the proposed rule's 18-month timeframe for corrosion control studies would not be sufficient for the subset of systems required to conduct pipe loop/rig evaluations because of the additional time required to harvest, construct and stabilize the pipe loop/rig prior to commencing the study, EPA acknowledges the logistical considerations raised by commenters and agrees a longer timeframe is warranted for pipe loop/rig studies. For the subset of systems who must conduct such studies  -  those with lead service lines that exceed the lead action level  -  EPA has removed the requirement for submitting an optimal corrosion control treatment (OCCT) recommendation within six months from the end of the monitoring period in which the exceedance occurred. Instead, these systems must construct pipe loops/rigs and operate them with finished water within one year from the end of the tap sampling period during which the action level was exceeded [§ § 141.81(d)(1)(ii) and (e)(1)(ii)]. Following this period, systems will have 18 months to complete their corrosion control studies [§ § 141.81(d)(3)(i) and (e)(3)]. EPA believes that, by removing the OCCT recommendation requirement, systems will be able to concentrate resources more immediately on the harvesting, building and conditioning of pipe loops/rigs. The one-year `build' period provided under § § 141.81(d)(1)(ii) and (e)(1)(ii) will yield an overall timeframe of 30 months to build conditioned pipe loops/rigs and complete subsequent corrosion control studies. This timeframe is consistent with comments EPA received on the proposed rule, the majority of which anticipated needing an overall timeframe of 30 months, and for which 6 to 12 months would be needed specifically for the construction and conditioning of pipe loops/rigs. EPA does not believe it will be necessary for systems to develop, in coordination with their states, individual timelines for the completion of harvested flow-through pipe loop studies. Under the final rule, systems completing such studies in accordance with either the optimization or re-optimization steps are now provided up to 30 months to harvest lead pipes from the distribution system, construct flow-through pipe loops, and perform the corrosion control study. In the event of any unanticipated delays or problems in performing the study, EPA does not believe the provision of study data, as suggested by commenters, would sufficiently inform state decision-making on water quality conditions, or the corresponding water quality parameter values that would constitute optimized or re-optimized treatment.
In response to comments regarding  the proposed rule's 12-month timeframe for installing re-optimized corrosion control, EPA acknowledges the logistical considerations raised by commenters and agrees the scope of the treatment change would warrant a shorter or longer timeframe. EPA has made modifications to § § 141.81(d) and (e) to reflect these considerations accordingly. Those systems that must complete a corrosion control study would have up to 36 months prior to the 12-month installation period to plan for the upcoming treatment modification. Small and medium systems for which the State determines a study is not required would have 12 to 18 months. For systems that exceed the lead trigger level, but not the lead or copper action level, the State may approve modification of the existing CCT without requiring a study. In these instances, water systems would have 6 months to make the modifications in accordance with § 141.81(d)(1).
With specific regard to the ability for states to designate shorter timeframes for the installation of optimized or re-optimized CCT, EPA encourages systems and states to work together to install optimized or re-optimized CCT on a shorter timeframe, where feasible, than the maximums identified in the final rule. States may, if they choose, adopt timeframes that are more stringent than the revised Lead and Copper Rule.
The proposed step requirements for optimized and re-optimized CCT would require some systems to recommend OCCT to the State 12 months before the corrosion control study would be required to be completed. As discussed above, EPA has included modifications in the final rule that address this consideration. EPA has removed the requirement for initial OCCT recommendations for systems conducting pipe loop studies. This applies to systems installing optimized CCT in accordance with § 141.81(e) as well as to systems that are re-optimizing CCT in accordance with § 141.81(d). Those systems that are not required to conduct corrosion control studies would recommend the optimal treatment based on the results of lead and copper tap sampling and water quality parameter monitoring in accordance with § 141.82(a)(1) within six months after the end of the tap sampling period during which it exceeds either the lead trigger level or copper action level [§ 141.81 (d)(1)(i) and (e)(1)(i)].
EPA disagrees with comments suggesting shorter timeframes for OCCT installation under proposed § 141.81(e)(5), and for follow-up sampling under proposed § § 141.81 (d)(6) and (e)(6). Based on the Agency's experience with implementing the current rule, the vast majority of water systems will need up to 24 months to install the treatment and make any necessary operational adjustments to ensure the treatment is operating as intended. EPA recognizes some systems may be able to install OCCT on a shorter timeframe and notes that these systems would not be precluded from doing so under the final rule. With regard to the follow-up sampling provisions, the purpose of the follow-up monitoring is to demonstrate the newly installed or modified corrosion control treatment has stabilized and is functioning as intended. In the event that it's not, it is in the public's interest for this determination to be made sooner rather than later. Allowing systems to postpone follow-up monitoring would be less protective of public health. For these reasons, EPA  is not revising the existing timeframes for treatment installation and follow-up sampling in the final rule. Finally, it was suggested that "[t]he noncompliance time period that triggers replacement of all lead service lines needs to be lengthened by 12-18 months to allow adjustments to corrosion control to actually be seen in the distribution system." It is not clear which time period the comment is referencing. While reductions from treatment modifications are not immediately observable, EPA does not believe the completion of other complementary actions to reduce lead concentrations should be precluded or delayed by it.
4.3 Process for CCT Steps (Initial Optimization)
EPA received comments on the proposed requirements in § § 141.81 and 82 for initial optimization of corrosion control based on lead 90th percentile and corrosion control treatment status. EPA also received comments on the proposed optimization steps that systems would be required to complete under § § 141.81 and 82.
Initial Optimization Requirements Based on Lead 90th Percentile and Corrosion Control Treatment Status
Summary of Comments
EPA received several comments on the proposal to base corrosion control treatment (CCT) optimization requirements on the lead 90th percentile and CCT status of the system. This section summarizes comments relating to water systems without existing CCT. For systems with CCT, see the separate discussion in section 4.4.1.
Some commenters expressed general support for the proposed approach. One commenter stated "[a]ll water systems should be treating for corrosion control regardless of their sampling results or 90[th] percentile readings." Two commenters expressed specific support for the proposed requirement in § 141.81(a)(1)(ii) for large systems without corrosion control treatment to complete the treatment installation steps after exceeding either the lead trigger level or the copper action level. A third commenter supported "extending the requirements for CCT to systems servicing > 10,000."
One commenter supported the overall approach proposed but suggested using a reduced lead action level as the basis for triggering initial optimization under § 141.81(a)(1)  -  (4). The commenter also made a general suggestion for EPA to "require all water systems to complete a corrosion control study to identify optimal corrosion control treatment" and, as an alternative for small and medium systems, for EPA to "conduct systematic corrosion control studies in typical representative source waters across the country that states could use to extrapolate to treatment requirements."
Some commenters did not support the proposed initial optimization requirements. One of the commenters disagreed with "EPA's proposal to allow states to determine whether a CCT study is warranted for community water systems" and recommended revising the proposal to require "all community water systems, regardless of size and status of CCT, to conduct a study following a Trigger Level or action level exceedance." Another disagreed with the initial optimization requirements "be[ing] solely based on 90[th] percentile values" and recommended EPA "require all water systems to determine if they are optimized, regardless of their 90[th] percentile values" and "require all water systems with [lead service lines] or service lines of unknown material, regardless of their 90[th] percentile, to conduct a CCT evaluation within 12 months of the rule becoming effective." A third commenter stated they "disagree[d] that small or medium systems who exceed the copper AL shouldn't be held to the same standard as for lead." The commenter suggested that "exceedance of either AL trigger the requirement to install CCT or implement applicable small system flexibilities."
A commenter raised concerns over the added burden that the implementation of this re-optimization approach would place on states. The commenter stated that "these additional requirements will have to be reviewed and approved by the state staff;" would result in a "significant increase in the amount of technical assistance;" and that training would be "necessary to prepare state staff, consultants, engineers, and system operators to conduct proper CCT evaluation and recommend appropriate treatment."

In addition to the general comments on the proposed initial optimization requirements summarized above, EPA received several comments specific to the requirements proposed in § 141.81(a). Three commenters suggested adding language to the rule specifically addressing "large water systems without corrosion control treatment that are deemed to have optimized corrosion control." Some generally noted several provisions within § 141.81(a) direct large systems to follow treatment steps and deadlines in § 141.81(e)  -  "Treatment steps and deadlines for small and medium-size systems..."  -  and suggested further clarifying these provisions in the final rule. (See corresponding discussion of § 141.81(e)-related comments further below.) Others provided comment on proposed § 141.81(a)(1)(iv), under which large systems without CCT "that do not exceed the lead trigger level and copper action level but are not deemed to have optimized corrosion control under paragraph (b)(3)" of § 141.81 "may be required by the State to complete the corrosion control treatment steps in [§ 141.81](e)." One commenter supported the proposed approach; others raised a general concern that the proposed approach would "not be as protective as the current rule for large systems" and seemed to create "a new subset of large systems that may not currently be optimized," for which "the revised rule does not appear to explicitly require additional action" and for which "states may not have the authority to require additional action." Instead of the approach proposed in § 141.81(a)(1)(iv), some commenters suggested that "all large systems be required to implement [optimal corrosion control treatment] or be deemed optimized using [§ 141.81](b)(3)." Other commenters noted the proposed language "does not address large water systems without corrosion control treatment that are deemed to have optimized corrosion control" and requested that "large systems without corrosion control treatment be considered optimized and not required to install treatment." Another commenter suggested the final rule explicitly state "[i]f these systems are exempted from corrosion control treatment."
Other commenters expressed a general concern over how the provision  in § 141.81(a)(1)(iv)  -  that a state "may require" large systems without CCT that do not exceed the lead trigger level and copper action level to complete the CCT steps  -  could be implemented by States. One of the commenters believed the proposed approach "sets a third regulatory level" and suggested revising § 141.81(a)(1)(iv) "to remove the possibility of regulators having the authority of arbitrarily requiring large water systems to review their approach to corrosion control based on their 90[th] percentile lead levels not being below the Practical Quantitation Level (currently 5 ppb)." Another commenter similarly stated, "[i]n the situation where a large water system without corrosion control has a 90[th] percentile tap water lead level that is between the practical quantitation and trigger levels of 5 - 10 ppb year after year, a large water system could be ordered by the State to perform corrosion control studies pursuant to § 141.81(e)(2) every year, despite the 90[th] percentile lead level being consistently below the trigger level." The commenter suggested that "the rule should contain a safe harbor that would protect a large system from conducting needless additional corrosion control studies if it has already carried out the required corrosion control studies, except in instances where there has been a significant change to the large water system or in corrosion control technology." Another commenter stated, "the proposed rule could require us to perform lengthy and costly pipe loop corrosion control studies (§ 141.81 (a)(iv)) to prove what we already know and can demonstrate by the scale on our pipes and our water chemistry." The commenter suggested "EPA should revise the rule to allow the flexibility of demonstrating optimized corrosion control in these instances by showing existing distribution system conditions rather than require additional studies by the water system. EPA should also pass that flexibility on to the State regulatory programs."
EPA also received comments on the proposed provisions in § § 141.81(a)(2) & (3) for medium and small systems, respectively. One commenter recommended that "the steps required of a public water system following a lead trigger level exceedance be clarified," stating "the rule language in § 141.81(a)(2)(ii) and (a)(3)(iii) regarding the requirements for small and medium systems to conduct corrosion control treatment steps is confusing and seemingly inconsistent with § 141.81(c)(2)."
Agency Response
EPA agrees with commenters who support a requirement for water systems to optimize their corrosion control treatment (CCT) based on the lead 90[th] percentile level and CCT status. The strengthened treatment optimization procedures resulting from this approach will promote greater protection of public health by requiring water systems to take more progressive actions to optimize their treatment and, in turn, reduce lead levels at the tap. The final rule includes, in § 141.81(a), a requirement for any system without CCT to conduct the optimization steps in § 141.81(e) upon exceeding the lead trigger or lead and copper action levels. EPA has revised the regulatory text in § 141.81(a) of the final rule to improve its clarity and will work with primacy agencies and water systems to ensure they understand the different actions that must be taken when systems exceed a trigger or action level.
EPA disagrees with the comments suggesting all systems complete a CCT study or determine if they are optimized regardless of their 90th percentile. The Agency believes the use of a trigger-level approach prioritizes optimization actions at systems with higher lead levels and allows states to work proactively with water systems that are a higher priority. Both of the suggested alternatives would substantially increase the number of water systems required to obtain state review. EPA has concluded it is not practicable for such a significant number of water systems to obtain these reviews/approvals from their states. Additionally, such an approach would be overly prescriptive for systems with low lead 90[th] percentiles since they may not be able to achieve further reductions. In such cases, the suggested requirements would not provide meaningful opportunities to protect public health.
EPA also received comment suggesting the Agency conduct corrosion control studies that would be representative of source waters nationally. These studies could, in turn, be used by systems to extrapolate treatment needs for corrosion control. Source water and distribution systems are highly case-specific in their nature and vary over time; EPA does not believe the development of such a tool would be functional. Agency guidance on the implementation of the CCT step requirements was also requested by commenters. See response to comment section 4.1.1 for further discussion of implementation guidance.
Regarding the assertion that the proposal does not hold small and medium systems exceeding the copper action level to the same standard as for lead, and for which it was suggested exceedance of either action level should serve as the trigger for taking action, EPA notes that both the proposed and final rules include provisions that are consistent with the suggested approach. Under the final rule, medium and small systems that exceed either the lead or copper action level are required under § § 141.81(a)(2)(ii) and 141.81(a)(3)(iii) and (iv), respectively, to complete the CCT steps specified in § 141.81(e). For medium systems, EPA believes the suggestion for triggering actions solely on the basis of action level exceedances would hinder these systems' ability to proactively prepare for, and quickly take action if, there is a subsequent action level exceedance. For this reason, the final rule includes a requirement under § 141.81(a)(2)(iii) for medium systems above the trigger level (but below both action levels) to complete the treatment recommendation step specified in § 141.81(e)(1). These systems would then complete the remaining steps in § 141.81(e) if they subsequently exceed either action level. For small systems, as well as non-transient, non-community water systems, EPA instead believes it is important to provide greater flexibility in selecting the treatment action that makes sense for protecting the health of their community. For this reason, the final rule includes a requirement under § 141.93(a) for such systems above the trigger level (but below both action levels) to evaluate the four compliance options prescribed in that section and make a recommendation to the state. The compliance options include CCT installation as well as lead service line replacement, point-of-use devices, and replacement of lead-bearing plumbing.
EPA acknowledges concerns with the added burden the proposed re-optimization approach would place on states and systems. To ease the burden and offer greater flexibility, the Agency has identified `bins' reflecting certain system characteristics that would elevate the potential risk for drinking water lead exposures and thus warrant more rigorous CCT study requirements. These characteristics include CCT status, system size, the presence of lead service lines and lead 90th percentile. The final rule includes modifications that target requirements according to these `bins.' EPA believes this `bin' approach will reduce the overall burden of the rule by more precisely identifying the subset of systems whose conditions would not necessitate a more rigorous CCT study, such as a pipe rig/loop study, to protect public health. See the response in section 4.5.1 for a detailed discussion of these characteristics and how they form the basis for the CCT study requirements and any associated burden reductions.
Per commenters' suggestions, EPA also modified § 141.81(a) to clarify under what circumstances large systems without CCT must complete the CCT optimization requirements. The modification, which is included under § 141.81(a)(1)(ii) of the final rule, requires large systems without CCT to complete the treatment installation steps in § 141.81(e) if they exceed the lead practical quantitation level (PQL), rather than the lead trigger level EPA initially proposed, or the copper action level. EPA believes that requiring such action when the lead PQL is exceeded allows states to work proactively with these systems that are a higher priority by virtue of the larger populations they serve and their lack of existing CCT. EPA also has removed proposed § 141.81(a)(1)(iv) from the final rule since these systems would be required to install CCT in accordance with final rule § 141.81(a)(1)(ii). EPA believes these modifications will make the rule more protective of public health and address concerns by eliminating the potential creation of a subset of large systems for which states may not have the authority to require additional action; eliminating the potential for States to implement the proposed provisions in a manner that sets arbitrary lead 90th concentrations as the basis for requiring the CCT installation; and more directly addressing/clarifying which large systems would be exempted from installing corrosion control treatment (i.e., those whose distribution system conditions demonstrate eligibility for being deemed optimized under § 141.81(b)(3)). This modification also addresses `safe harbor' concerns since final rule § 141.81(a)(1)(ii) contains an explicit CCT installation requirement for the subset of systems whose lead 90ths are between the PQL and trigger level, eliminating the CCT installation `gray area' that was raised as a concern. EPA also has revised § 141.81(b) to provide more clarity on which systems can be deemed optimized and how these systems can continue to be deemed optimized. Language also was added to clarify that all systems optimized under § 141.81(b) must continue to demonstrate that they qualify for the deemed status in all subsequent rounds of monitoring.
Modifications also have been made to the final rule as they relate to the comments seeking clarity on proposed § § 141.81(a)(2) & (3) and suggesting inconsistencies between these provisions and § 141.81(c)(2). EPA believes the following modifications will provide greater clarity and resolve the perceived inconsistency with § 141.81(c). Final rule § 141.81(a)(2)(iii) includes language clarifying that the provision applies to medium systems without CCT that exceed the trigger level, but not the lead or copper action levels. Final rule § § 141.81(a)(3)(iii) and (iv) include language clarifying that small community water systems choosing the corrosion control option pursuant to § 141.93, as well as non-transient, non-community water systems, must complete the CCT steps in § 141.81(e) if they exceed the lead or copper action level; references to the trigger level in the proposal have not been retained in the final rule. Finally, § 141.81(c) has been modified to provide greater clarity on the circumstances under which systems subject to this paragraph may cease completing CCT steps. Systems may cease completing steps if they do not exceed either action level during each of two consecutive six-month monitoring periods prior to the start of Step 3 (§ 141.81(e)(3)) or Step 5 (§ 141.81(e)(5)). The proposal's separate provision in § 141.81(c)(2) that dealt specifically with systems exceeding the trigger level has been removed.
EPA received comments opposing the provisions proposed in § 141.81(c) that would allow small and medium water systems that meet both action levels for two consecutive six-month monitoring periods to cease completing certain initial optimization steps in proposed § 141.81(e). EPA disagrees that any action level exceedance should trigger CCT. The Agency believes it is necessary for the final rule to retain the flexibility provided by § 141.81(c), and the subsequent burden reductions it offers small and medium systems. The Agency also notes, per § 141.81(b)(1) of the previous and proposed/final rules, that small and medium systems who meet both action levels for two consecutive six-month monitoring periods are deemed optimized with regard to their corrosion control. EPA recognizes, however, that there may be circumstances where the increased risk to public health warrants requiring follow-through on a CCT study completion regardless of a system's ability to meet both action levels in subsequent monitoring periods. The Agency believes the presence of LSLs is such a circumstance and has revised the final rule to reflect this consideration.  Under § 141.81(c) of the final rule, medium systems with LSLs and small systems with LSLs that choose the corrosion control option pursuant to § 141.93 must complete a CCT study in accordance with § 141.81(e), Step 3. Systems without LSLs are not required to complete CCT studies or installation of OCCT  -  Steps 3 or 5 of § 141.81(e)  -  if they do not exceed either action level for two consecutive six-month monitoring periods prior to the start of Step 3. The final rule has been revised for added clarity and to specify that systems are not permitted to cease the optimization steps a second time. Any systems initiating Step 5 (installation of OCCT) must also complete the other three remaining steps (i.e. follow-up sampling, State designation of optimal water quality parameters (OWQPs), and operating in compliance with OWQPs).
Proposed Initial Optimization Steps and Requirements
Summary of Comments
EPA received comment on the required treatment steps proposed in § 141.81(e) for systems without corrosion control treatment. Commenters expressed general agreement with the proposal; however, one commenter disagreed with the specific approach for initial sampling requirements proposed in § 141.81(e)(1), claiming it would not "account for water systems that exceed the [trigger or action level] after the initial monitoring periods following promulgation of the rule," and provided specific suggestions on how initial sampling provisions could be revised on the matter.
Other commenters provided suggested revisions to proposed § 141.81(e). One commenter suggested the inclusion of language explicitly stating when "a small/medium supply that exceeded the trigger level can stop the treatment steps in (e) unless/until they subsequently exceed the action level" and "including specific criteria for justifying any requiring optimized corrosion control." Another commenter recommended revising § 141.81(e)(1) to require small and medium systems to base their optimal corrosion control treatment recommendation on "initial water quality parameters within six months of the trigger level exceedance instead of requiring a corrosion control study." A third commenter suggested revising § 141.81(e)(2) to require medium systems to complete corrosion control studies. A fourth commenter stated generally that they could not "imagine a scenario involving waterworks serving 500 or fewer persons where CCT, preceded by corrosion control studies, or lead service line replacement would cost less than point of use treatment and maintenance."
Commenters noted portions of § 141.81(a) as proposed direct large systems to follow treatment steps and deadlines in § 141.81(e)  -  "Treatment steps and deadlines for small and medium-size systems..." Commenters requested clarification on the requirements being proposed for large systems without corrosion control; suggested revising § 141.81(e) to more clearly identify the applicable treatment steps for large systems; and provided several specific suggestions. Other commenters noted the proposed § 141.81(e) does not appear to address medium systems who grow to become large systems due to population increases and suggested adding language to address these types of systems or provide separate guidance on the matter. A final commenter provided specific suggestions on how the proposed language in § 141.81(a) could be clarified further. In addition to comments on § 141.81(e), EPA received comment on the proposed provisions in § 141.82(a)(1)  -  (4) specifying the conditions under which water systems without corrosion control treatment would be required to make an optimal corrosion control treatment recommendation to the state. Under the proposed approach, water systems would make the recommendation in response to a trigger level exceedance and install the treatment if the lead or copper action level were subsequently exceeded. Commenters noted general concerns with the possibility of "an evaluation [prepared after a trigger level exceedance] may be several years old before the subsequent trigger occurs" and that "states will likely require more recent data, which will require the completion of redundant corrosion control activities." One of the commenters recommended providing clarification "for acceptable timelines and system characteristics which would allow the use of a previously completed study or when an entirely new study would be warranted" and on whether "systems are required to repeat corrosion control activities if they continue to exceed the trigger level but not the action level." In relation to the latter, the commenter recommended that "small and medium systems not be required to repeat corrosion control activities unless there is a change in source or treatment."
Commenters suggested "requir[ing] all decisions about and assessments of a water system's corrosion control treatment to be examined and certiﬁed by an independent, certiﬁed professional engineer with expertise in corrosion control" and that "[a]ll documentation involved in this process must be publicly available." A third commenter suggested adding revisions that would "address the impacts of climate change on the water supply and water quality."
Agency Response
EPA has modified the provision in proposed § 141.81(e)(1) in a manner that addresses the concern that it would not account for systems exceeding the trigger or action levels after initial monitoring periods following promulgation of the final rule. The final rule provision omits the references to `initial tap sampling' that were suggested to be problematic.
EPA received a comment suggesting that § 141.81(e) include language explicitly stating when small or medium systems may be allowed to cease optimization steps. The Agency notes the requested criteria are available in § 141.81(c) of the proposed and final rules. This paragraph specifies the specific criteria under which small or medium systems may be eligible to cease completing optimization steps. Final rule § 141.81(c) includes additional modifications to improve the paragraph's overall clarity. EPA has not incorporated these provisions into § 141.81(e) as the Agency does not believe it would meaningfully enhance or improve their clarity.
Commenters suggested requiring in § 141.81(e)(1) the use of initial water quality parameters (WQPs) as a basis for optimal corrosion control treatment (OCCT) and, in § 141.81(e)(2), requiring all medium systems to complete CCT studies, respectively. As discussed in the response to the previous subsection, 4.3.1, EPA has revised the optimization requirements in § 141.81(e) to prioritize actions according to certain system characteristics that would elevate the potential risk for drinking water lead exposures and thus warrant more rigorous requirements. These characteristics include CCT status, system size, the presence of lead service lines and lead 90th percentile. The Agency believes this approach eases the burden and offers greater flexibility to systems and states. In light of these modifications, the suggestion to use WQPs as an OCCT basis is limited to systems that exceed the lead trigger or copper action level [§ 141.82(a)(1)] or to small community water systems or non-transient, non-community water system that exceed the lead trigger or copper action level and choose to pursue a small water system compliance flexibility option and are required to recommend an option in accordance with § 141.81(f) [§ 141.82(a)(1)]. Medium systems are required to conduct pipe rig/loop studies if they exceed the lead action level and lead service lines (LSLs) are present in the distribution system [§141.81(e)(1)(ii)]. Medium systems without LSLs that exceed the lead trigger or either of the action levels may be required by the state to conduct corrosion control studies [§ 141.81(e)(2)].
Although EPA does not believe the majority of very small systems are likely to opt for CCT, the Agency believes it is important to provide water systems greater flexibility in selecting the treatment action that makes sense for protecting the health of their community. For this reason, the provision in § 141.93(a) that requires small systems above the trigger level (but below both action levels) to evaluate their compliance options and make a recommendation to the state includes CCT installation as an option. Those small systems that select CCT installation as their flexibility option are directed in final rule § 141.81(e) to complete each of the treatment optimization steps prescribed in that paragraph.
Several commenters expressed confusion over how proposed § 141.81(a) directs large systems to conduct optimization steps that were labeled in § 141.81(e) as applying to small and medium systems only. Comments also sought clarification on how large systems without corrosion control or medium systems who grow to become large systems are intended to comply with the proposed initial optimization requirements. To address these comments and suggested clarifications, EPA has modified the paragraph title in § 141.81(e) to "Treatment steps and deadlines for systems without corrosion control treatment." EPA believes this modification better reflects the paragraph's intended applicability to the subset of systems that do not have corrosion control treatment in place and alleviates the points of confusion noted in the comments.
Some comments expressed concerns with the possibility of proposed § 141.81(e) and related provisions in § 141.82(a) yielding OCCT recommendations that are several years old by the time the system is triggered into implementing them. EPA recognizes the potential for such circumstances to arise and notes that § 141.81(c) of the proposed and final rules include a provision that directly addresses this concern. Under this provision, water systems are required to repeat treatment steps they have previously completed when the State determines it is necessary to implement the treatment requirements of the rule. The Agency believes this will eliminate the potential for systems to implement the treatment optimization steps using outdated information. EPA disagrees with commenters who suggested the final rule prescribe timelines and system characteristics under which previous optimization activities, including CCT studies, would be acceptable or necessary to repeat. The Agency also disagrees with the suggestion to limit the need for new studies only when source water or treatment changes have occurred. Because of the highly specific nature of such considerations, EPA believes it is important to provide states the flexibility to determine the need for such actions in accordance with § 141.81(c)  on a case-by-case basis.
Commenters suggested requiring treatment decisions to be independently certified by corrosion control experts, promote greater public access to documentation of treatment decisions, and address potential climate impacts. EPA encourages water systems to communicate with their customers and raise awareness of any potential treatment changes the system may be contemplating; however, EPA does not believe such requirements would provide a sufficiently meaningful opportunity to protect public health given the potential for delays it may pose on the optimization process and the added burden to water systems and states. Agency guidance on the implementation of the CCT step requirements was also requested by commenters. See response to comment section 4.1.1 for further discussion of implementation guidance.
4.4 Process for CCT Steps (Re-Optimization)
EPA received comments on the proposed requirements in § § 141.81 and 82 for re-optimization of corrosion control based on lead 90[th] percentile and corrosion control treatment status. EPA also received comments on the proposed re-optimization steps that systems would be required to complete under § § 141.81 and 82, as well as the proposed provisions in § 141.82(b)(3) that relate to a State decision for requiring small or medium sized system corrosion control studies to identify  re-optimized treatment.
Re-Optimization Requirements Based on Lead 90[th] Percentile and Corrosion Control Treatment Status
Summary of Comments
EPA requested comment on the proposed corrosion control treatment (CCT) re-optimization requirements and on "potential actions water systems could take to adjust their corrosion control treatment and how they should work with the state to determine if adjustments to the treatment would better optimize corrosion control." This section summarizes comments relating to water systems with existing CCT.  For systems without CCT, see the separate discussion in section 4.3.1.
In response to the proposed CCT re-optimization requirements, several commenters expressed general support for EPA's proposal "to mandate additional CCT requirements based on the water system's lead 90[th] percentile level and CCT status." One commenter stated "[a]ll water systems should be treating for corrosion control regardless of their sampling results or 90[th] percentile readings;" another was "excited to have a proposed rule that sees corrosion control treatment optimization as a constant process," but suggested EPA "be more transparent of this proposed regulatory change;" and a third supported "extending the requirements for CCT to systems servicing > 10,000." One commenter supported the overall concept, but suggested using a reduced lead action level as the basis for triggering re-optimization under § 141.81(a)(5)  -  (7). Another commenter also supported "evaluating and re-optimizing CCT when sample results show existing CCT is not optimized," but recommended that EPA "clarify in the regulations how this re-evaluation differs from an initial treatment study" and requested "detailed guidance relating to this re-evaluation."
Three commenters supported the proposed requirement for large and medium systems with a trigger or action level exceedance to re-optimize their corrosion control treatment. One of the commenters noted that this approach would be consistent with that of their state drinking water program, which "require[s] both to conduct CCT studies in the event of an ALE." Another  commenter supported "the requirement for PWSs with CCT installed to ensure continued optimization of their CCT, including re-optimization as necessary;" however, they did not believe "implementation of the [lead trigger level] is the most effective way to ensure this." The commenter suggested, "[i]nstead US EPA should take a proactive approach and require PWSs to evaluate CCT when they propose a source or treatment change, in addition to the population (>50,000) and 90[th] percentile triggers (based on an exceedance of the AL or TL)." A fourth commenter agreed "that large and medium systems with an ALE or a TLE should be required to evaluate the effectiveness of their existing CCT" but noted that in their experience "[m]any states see issues not with systems making an incorrect original CCT choice, but with maintaining CCT throughout the system once it's implemented."
Several commenters did not support EPA's proposed re-optimization approach for systems that exceed the lead trigger level of 10 ug/L. One commenter recommended revising the proposal to require "all community water systems, regardless of size and status of CCT, to conduct a study following a Trigger Level or action level exceedance."  Others were concerned the proposed approach would base CCT re-optimization requirements on a "single" or "handful" of lead tap samples. One commenter stated "[s]ingle results can be influenced by a number of site specific factors" and that "[t]here are many other factors to be considered in determining why a particular sample result showed a lead level of concern, especially if past monitoring results showed levels at that locations were not a concern." Another commenter expressed concern over instances where re-optimization requirements are triggered "even if a repeat sample at the same location is a non-detect, the sample result is below the regulated action level of 15 ppb and other water quality parameters in the distribution system are meeting acceptance criteria," and stated their position that such an approach would be "based upon a statistically insignificant and unrepresentative subset of the distribution system." Another commenter claimed the proposed re-optimization approach is "entirely inconsistent with established approaches of data collection and improving corrosion control over time," and that it "discounts the fact that there might be a site specific issue that can be resolved by other means in lieu of expending resources for system-wide evaluations." A  commenter was concerned that "once CCT has been optimized, water systems may not find much room to further mitigate lead risks by CCT alone."
A  commenter claimed "[t]he 90[th] percentile is limited in the useful information it provides" and suggested that "determination of when a water system needs to be re-evaluated for CCT should not only look at the water system's latest 90[th] percentile, but at the historical trends in the system's data and should conduct a more detailed data analysis." The commenter also suggested EPA develop "data analysis tools" to help states "evaluate WQPs and lead data to determine whether CCT is performing well and whether it should be re-evaluated" and for "use during a Sanitary Survey to help States evaluate CCT performance."
 Some commenters raised concerns over how the proposed CCT requirements on lead 90[th] percentile level and CCT status would be implemented. One commenter was concerned with the potential for large water systems and states to "have deemed corrosion control treatment `optimized' simply when 90[th] percentile values have met the LCR lead action level, irrespective of the system's ability to achieve further systemwide lead-in-water reductions." In light of this concern, the commenter suggested requiring any large water systems that exceed the trigger level to "[c]onduct a comprehensive study of all the factors that contributed to the exceedance" and achieve "the lowest possible 90[th] percentile value, even if other water treatments must be adjusted." Another commenter was concerned that § 141.82(h) "would allow a primacy agency to... modify its determination of optimal CCT without bounding this to provide a level of certainty to the [water system]." The commenter, and others, suggested that the rule prescribe a threshold 90[th] percentile, such as 5 μg/L, where system optimization "can be considered equivalent or acceptable."
A commenter raised concerns over the added burden that the implementation of this approach would place on states. The commenter stated that "these additional requirements will have to be reviewed and approved by the state staff;" would result in a "significant increase in the amount of technical assistance;" and that training would be "necessary to prepare state staff, consultants, engineers, and system operators to conduct proper CCT evaluation and recommend appropriate treatment."
 In addition to the general comments on the proposed re-optimization requirements summarized above, EPA received several comments on specific provisions within § 141.81(a). Commenters suggested clarifying under what circumstances large systems without lead trigger level exceedances or copper action level exceedances should be required to complete re-optimization" and claimed the proposal "leaves a gray area of a 90[th] percentile between 5 and 10 ppb where a system is no longer optimized but is not required to re-optimize." A commenter also provided specific suggestions on how the proposed language in § 141.81(a) could be clarified further.
Other  commenters expressed a general concern over how the authority provided in § 141.81(a)(1)(iii)  -  that a state "may require" large systems with CCT that do not exceed the lead trigger level and copper action level to complete the CCT steps  -  could be implemented by States. Commenters raised a general concern that the proposed approach would "not be as protective as the current rule for large systems" and seemed to create "a new subset of large systems that may not currently be optimized" for which "the revised rule does not appear to explicitly require additional action" and for which "states may not have the authority to require additional action." Instead of the approach proposed in § 141.81(a)(1)(iii), some commenters suggested that "all large systems be required to implement [optimal corrosion control treatment] or be deemed optimized using [§ 141.81](b)(3).One of the commenters believed the proposed approach "sets a third regulatory level" and suggested revising § 141.81(a)(1)(iii) "to remove the possibility of regulators having the authority of arbitrarily requiring large water systems to review their approach to corrosion control based on their 90[th] percentile lead levels not being below the Practical Quantitation Level (currently 5 ppb)." Another commenter expressed a similar concern but suggested removing proposed § 141.81(a)(1)(iii) altogether.
Agency Response
EPA agrees with commenters who support a requirement for water systems to re-optimize their corrosion control treatment (CCT) based on the lead 90[th] percentile level and CCT status. The strengthened treatment optimization procedures for systems with existing CCT will promote greater protection of public health by requiring water systems to take more progressive actions to re-optimize their treatment and, in turn, reduce lead levels at the tap. The final rule includes, in § 141.81(a), a requirement for any system with CCT to conduct the re-optimization steps in § 141.81(d) upon exceeding the lead trigger or lead and copper action levels. EPA has revised the regulatory text in § 141.81(a) of the final rule to improve its clarity and will work with primacy agencies and water systems to ensure they understand the different re-optimization actions that must be taken when systems exceed a trigger or action level.
EPA disagrees with the comments suggesting all systems complete a CCT study or determine if they are optimized regardless of their 90th percentile. The Agency similarly disagrees with the suggested requirement for all systems to evaluate CCT when they propose a source or treatment change. The use of a trigger-level approach prioritizes re-optimization actions at systems with higher lead levels and allows states to work proactively with water systems that are a higher priority. Each of the suggested alternatives would substantially increase the number of water systems required to obtain state review. EPA has concluded it is not practicable for such a significant number of water systems to obtain these reviews/approvals from their states. Additionally, such an approach would be overly prescriptive for systems with low lead 90ths since they may not be able to achieve further reductions. In such cases, the suggested requirements would not provide meaningful opportunities to protect public health. EPA has instead revised the re-optimization requirements to account for certain system characteristics that may elevate the potential risk for drinking water lead exposures and thus would warrant more rigorous CCT study/evaluation requirements. These characteristics include CCT status, system size, the presence of lead service lines and lead 90th percentile. To ease the burden and offer greater flexibility, the final rule includes modifications that target requirements according to these characteristics (i.e., `bins'). EPA believes this `bin' approach will reduce the overall burden of the rule by more precisely identifying the subset of systems whose conditions necessitate a more rigorous CCT study, such as a pipe rig/loop study, to protect public health. See the response in section 4.5.1 for a detailed discussion of these characteristics and how they form the basis for the CCT study requirements and any associated burden reductions.
Other commenters were concerned the proposal would base CCT re-optimization requirements on a "single" or "handful" of tap samples that are not statistically significant or representative of the distribution system. EPA disagrees with comments suggesting the proposal failed to account for alternatives that could be used to address such site-specific issues in lieu of CCT re-optimization. Under the proposal as well as the final rule, a water system would be required to determine if problems with the CCT itself are contributing to elevated lead levels at individual sites, then implement a mitigation strategy if necessary. In addition to follow-up sampling, the water system could review distribution system operations or other factors to determine the cause of the elevated lead level. CCT re-optimization may not always be necessary to address an exceedance.
With regard to the concern that systems may not find room to further mitigate lead risks by CCT alone once the system has been optimized, the Agency notes that, in addition to LSLs, lead may leach into drinking water from household sources such as leaded brass fixtures and lead solder. A study published by American Water Works Association (AWWA) Water Research Foundation (2008) "Contributions of Service Line and Plumbing Fixtures to Lead and Copper Rule Compliance Issues" (Sandvig et al., 2008) estimates that 50 to 75 percent of lead in drinking water comes from LSLs, while the remainder comes from leaded solder, brass/bronze fittings, galvanized piping, faucets, and water meters. Therefore, EPA believes use of CCT over the long-term would continue to provide public health protection from these sources. While there may be instances where systems are fully optimized, EPA notes that the final rule includes a suite of actions, in addition to CCT, that taken together will further reduce lead exposure in drinking water.
The Agency encourages systems to be proactive in identifying opportunities to improve CCT effectiveness and recognizes that evaluating historical trends/detailed data analyses can be helpful in achieving such improvements. However, the Agency believes the development and subsequent review of such analyses for re-optimization purposes would add considerable burden to systems and states, and that a regulatory requirement for such analyses would be overly prescriptive given the extent to which such analyses and interpretation of results would be highly case-specific. As discussed earlier in this sub-section's response, EPA believes the process to re-optimize CCT should be determined based on system characteristics such as system size, the presence of LSLs and 90th percentile value. Re-optimization requirements in the final rule have been modified to reflect this approach. With regard to EPA development of analytical tools that states could use to evaluate CCT performance, the Agency similarly believes the factors that must be considered during such evaluations  -  e.g., water quality conditions, distribution system patterns, historical data trends  -  are highly case-specific in nature; therefore, the development of such analytical tools at the national level by EPA would not be functional for system-specific evaluations.
EPA disagrees with the suggestion to require all large systems to conduct a CCT study if they exceed the trigger level. The Agency believes it is important for the final rule to provide states the flexibility to determine whether slight modifications of the existing CCT would more quickly address the underlying cause of the exceedance. In the final rule, states are allowed to approve existing corrosion control modifications without a corrosion control study for systems that exceed the lead trigger level, but not the lead or copper action levels [§ 141.81(d)(1)(i)].
With regard to the suggestion to modify proposed § 141.82(h)  -  modification of State treatment decisions for optimal corrosion control and re-optimized corrosion control  -  to reference a threshold 90[th] percentile upon which such modifications could be considered acceptable. EPA notes that such threshold exists in § 141.81(b)(3). In accordance with the provision, any water system demonstrating that the lead 90[th] percentile is less than or equal to the practical quantitation level for lead would be deemed to have optimized or re-optimized corrosion control. Therefore, EPA does not believe the suggested modification to §141.82(h) is necessary.
EPA acknowledges concerns with the added burden the proposed re-optimization approach would place on states and systems and has identified a `bin' approach that will reduce the burden and add greater flexibility under the final rule. See above, 2nd paragraph of this response section, for more complete information about the `bin' approach and how it will reduce the overall burden on states and systems.
Per commenters' suggestions, EPA has modified § 141.81(a)(1)(iii) to clarify that large systems with CCT that do not exceed the lead trigger or action levels, but do exceed the lead PQL, may be required by the state to complete the corrosion control treatment steps in § 141.81(d).
With regard to the implementation concerns with proposed § 141.81(a)(1)(iii), EPA disagrees with the assertions that the proposal would be less protective than the previous rule for large systems with existing CCT, or that it would create a new subset of large systems that may not currently be optimized. The Agency notes the suggested approach of requiring all large systems to implement optimized corrosion control treatment or to be deemed optimized in accordance with § 141.81(b)(3) is consistent with provisions in the previous rule as well as the proposal (see proposed § 141.81(a)(1)(i)). The Agency believes the use of a trigger level of 10 ug/L, as proposed in § 141.81(a)(1)(i), provides a reasonable concentration that is below the action level and above the practical quantitation level of 5 ug/L at which to require water systems to take a progressive set of actions to reduce lead levels prior to an action level exceedance and to have a plan in place to rapidly respond if there is an action level exceedance. Requiring such actions of systems when a trigger level 10 ug/L is exceeded prioritizes actions at systems with higher lead levels and allows states to work proactively with water systems that are a higher priority. EPA has retained this provision in the final rule. For the proposed provision in § 141.81(a)(1)(iii), the Agency believes it is necessary to provide states the flexibility to assess the need for re-optimization on a case-by-case basis for the subset of systems whose 90ths are above the PQL but below the lead trigger and copper action levels. Universally requiring large systems to re-optimize regardless of whether they are below the lead trigger or copper action level would substantially increase the number of water systems required to obtain state review. EPA has concluded it is not practicable for such a significant number of water systems to obtain these reviews/approvals from their states and has thus retained the provision in the final rule. As discussed in the previous paragraph, the final rule provision includes modified language clarifying how it applies to systems with CCT whose 90[th] percentiles are above the lead PQL but below the lead trigger or copper action level. EPA disagrees with the suggested elimination of proposed § 141.81(a)(1)(iii) or revision to preclude states from having the authority to require these systems to re-optimize. Because of the general magnitude of the population served by large water systems, EPA believes it is important for states to have the flexibility to require system re-optimization where it determines further lead reductions are achievable by these systems.
 Proposed Re-Optimization Steps and Requirements
Summary of Comments
EPA requested comment on the proposed corrosion control treatment (CCT) re-optimization requirements and on "potential actions water systems could take to adjust their corrosion control treatment and how they should work with the state to determine if adjustments to the treatment would better optimize corrosion control." The steps by which a water system exceeding the lead trigger level or copper action level would be required to re-optimize their corrosion control treatment are prescribed in § 141.81(d). Additional requirements associated with these steps are further described throughout § 141.82.
One commenter generally stated they "support[ed] the addition of re-optimization steps which provide a clear path for improving treatment at supplies with existing treatment in place" and "support[ed] progressive action for supplies with higher lead action levels or exposure risk."
One commenter stated generally that "[t]he proposed rule does not present a clear distinction between `optimization' and `re-optimization' and claimed, "most readers view the proposal as (1) requiring the same level of analysis as initial optimization (subject to modification by the state), (2) requiring an evaluation of potential treatment efficacy using a single determinative test, pipe loop studies, and (3) constraining the required evaluation to treatment practice." The commenter suggested a "more appropriate description of re-optimization would reflect: evaluation of the existing corrosion control process control; evaluation of whether current operations are achieving targeted conditions in the distribution system; identifying actions to correct shortcomings found in process control and achieving target conditions in distributed water; and, if current practice is operating as intended and the trigger level or action level is being exceeded then, the system should initiate a review of corrosion control." Another commenter suggested that "information is necessary to define what re-optimization under the Revised LCR requires" and stated that "[i]t is unclear as to whether water systems are required to engage in a new CCT Study following a second (or more) trigger or action level exceedance, or whether the re-optimization steps are permitted to be situation specific and are able to be adjusted accordingly." Another  commenter believed "EPA is proposing essentially the same steps for re-optimization of CCT as the steps for originally designating CCT" and stated their disagreement with such an approach. This commenter, and many others, instead suggested requiring that water systems first evaluate their existing treatment before `restarting' the OCCT steps. (See discussion under section 4.9  -  Comments on CCT Study vs. Re-Optimization.) Several comments expressed concerns over the proposed procedures potentially triggering a `restart' of OCCT designation and subsequent installation of a new OCCT. In response to these concerns, the commenters suggested separate analysis or evaluation under which systems would first review how effectively they are implementing their existing CCT and identify potential modifications prior to considering, evaluating, or conducting CCT studies for an alternate OCCT that is not already installed. One of the commenters suggested revising § 141.82(a) to include the requirement for such an approach. (See discussion under section 4.9  -  Comments on CCT Study vs. Re-Optimization.) Another commenter provided detailed suggestions on how the proposed language for each of the re-optimization steps in § 141.81(d) could be clarified. The commenter expressed a concern over potential confusion with the terms `initial' vs. `standard' monitoring in § 141.81(d)(1); found references to other sections in § 141.81(d)(2) to be confusing and inconsistent; suggested combining § § 141.81(d)(3), (4) and (5); and suggested § 141.81(d)(6) require follow-up monitoring on `January 1 or July 1, whichever is sooner,' rather than 'within 12 months from completion of Step 5.' Another commenter suggested clarifying the proposed language in § 141.81(d)(1) and (d)(3)(i) on the basis that they "seem similar but stipulate different timeframes," and suggested that "changes to corrosion control treatment be implemented on a reasonable timeframe following discussions with the state primacy agency." EPA also received comments more specifically related to the proposed re-optimization step proposed under § 141.81(d)(1), where water systems exceeding the lead trigger level or copper action level would be required to make an optimal corrosion control treatment (OCCT) recommendation to the state; this recommendation would be made in accordance with the procedures prescribed in proposed § § 141.82(a)(5)  -  (7). (See discussion under section 4.9  -  Comments on CCT Study vs. Re-Optimization.)
One commenter did not support the proposed re-optimization requirements and claimed, without providing any additional information or supporting rationale, that "[p]roof of optimization of CCT should not be required of water utilities by the EPA, it is unconstitutional and unnecessary."
Some commenters provided other general suggestions on potential revisions that could be made to the proposed re-optimization requirements. One commenter recommended adding flexibility "to deal with systems that have more complicated configurations" and for states to "require additional information such as water quality parameters, a follow-up corrosion control study and report, changing treatment, additional monitoring, and any other applicable requirements, to be determined by the state." The commenter believed that "[s]ince many states do not have the flexibility to be more stringent than the federal rule it is important for those states that the rule is clear on what the states are allowed to require." Additionally, the commenter recommended a proactive water management planning approach to "help water systems manage distribution water quality issues that may affect corrosion (such as nitrification, iron, manganese, distribution flushing programs, and managing biological activity within the distribution system)." Another commenter suggested adding "flexibility in what constitutes `re-optimization' and stated "[s]ometimes it is simply a treatment process issue that causes a system to exceed when they have CCT." The commenter suggested that "[s]ubmitting plans on how to prevent these process issues from happening in the future should be adequate  -  a system shouldn't have to go through a study or re-evaluation of various treatment options to be considered `re-optimized.'" Another commenter made a similar suggestion for flexibility, suggesting that "allow[ing] flexibility in determining what, if any, changes should be made to [a system's] corrosion control approach."
Two commenters suggested revising the re-optimization requirements to include three levels of corrosion control evaluations that would be triggered based on sample results collected from individual locations as well as systemwide. Under this approach, elevated results at a given location would "trigger action at the individual location" while system-wide levels exceeding the trigger or action level would respectively "require planning and preparation for changes to corrosion control treatment" or "trigger the requirement for implementing changes to treatment if determined to be necessary." Other commenters provided more specific suggestions on potential provisions that could be added to the final rule. Four commenters suggested clarifying "whether partial corrosion control treatment (ie  - corrosion control of some but not all sources of treated water) is viewed as no corrosion control, or should be treated in some other manner not currently specified." Another commenter suggested requiring "more oversight and transparency for CCT" and stated their position that "[t]he lack of CCT or WQP review results in systems with no baseline knowledge of why an TL or AL exceedance might occur and with no plan to address it," and that it "puts residents at risk of long-term exposure to lead... as systems determine the problem and develop a plan to address the problem." Another commenter suggested that "corrosion control should be considered a short-term solution while [lead service line] replacement activities are occurring" and that, "[b]ecause of competing priorities, the corrosion control should not be required to be `optimized' but `improved' if the 90[th] percentile level is above 10 ug/L." Another commenter claimed "[t]he regulation does not consider the source of elevated lead, which can be from a localized source due to household plumbing... that the rule's prescribed treatment techniques are not designed to control or reduce." In light of these concerns, the commenter suggested "[t]he option for a corrosion control study at these lower levels should be determined by the water system as they have many other competing treatment and infrastructure needs to balance" and recommended "including data review and source assessment prior to initiating a re-optimization study." One commenter noted that water systems "routinely add several new wells to their water systems in any given year" and was concerned that systems may be required to "perform re-optimization evaluations at such regular frequencies" that "would be infeasible and unwarranted." The commenter, and one other, requested including language that would exempt "new groundwater wells drawing from the same aquifer as existing approved ground water wells, demonstrated to have comparable pH and alkalinity as existing wells" from triggering re-optimization requirements. One commenter suggested "require[ing] all decisions about and assessments of a water system's corrosion control treatment to be examined and certiﬁed by an independent, certiﬁed professional engineer with expertise in corrosion control" and that "[a]ll documentation involved in this process must be publicly available." Another suggested adding revisions that would "address the impacts of climate change on the water supply and water quality."
EPA also received comments more specifically related to the proposed re-optimization step proposed under § 141.81(d)(1), where water systems exceeding the lead trigger level or copper action level would be required to make an optimal corrosion control treatment (OCCT) recommendation to the state; this recommendation would be made in accordance with the procedures prescribed in proposed § § 141.82(a)(5)  -  (7). EPA received several comments expressing concern over the proposed procedures potentially triggering a `restart' of OCCT designation and subsequent installation of a new OCCT. In response to these concerns, the commenters suggested separate analysis or evaluation under which systems would first review how effectively they are implementing their existing CCT and identify potential modifications prior to considering, evaluating, or conducting CCT studies for an alternate OCCT that is not already installed. One of the commenters suggested revising § 141.82(a) to include the requirement for such an approach. (See discussion under section 4.9  -  Comments on CCT Study vs. Re-Optimization.)
Another commenter suggested clarifying the proposed language in § 141.81(d)(1) and (d)(3)(i) on the basis that they "seem similar but stipulate different timeframes," and suggested that "changes to corrosion control treatment be implemented on a reasonable timeframe following discussions with the state primacy agency."
EPA also received comments related to the proposed requirement in § 141.82(a)(5) for systems with CCT to "conduct a re-optimization evaluation of the existing corrosion control treatment," after a lead trigger level exceedance, and to "make a recommendation to the State for modification (if any) of the designation of optimal corrosion control treatment." One of the commenters indicated they did not support the § 141.82(a)(5) re-optimization proposal. The commenter believed "systems should approach changes in corrosion control practice as a long-term and continuous improvement process rather than rapid responses to exceeding regulatory triggers," and that "[r]e-optimization should focus on whether corrosion control is being effectively implemented rather than re-evaluating the state-approved optimization strategy." The commenter believed the "proposal over-emphasizes changing corrosion control over maintaining effective process control for existing corrosion control practice;" "discourage[s] water systems from collecting additional water quality and treatment performance data for actively managing and improving corrosion control treatment;" and that "[t]he proposal does not address the considerations relevant to best professional judgement that go into determining if a corrosion control change should actually be made." The commenter stated "[t]he final rule should recognize that any decision to make a change is complex and must consider an array of factors. For example, if a corrosion control study shows that a new corrosion control treatment approach slightly lowers lead compared to the existing approach -- they must determine whether the reduction justifies the change." The commenter noted that under certain circumstances, changes can entail complexities "where the transition period result[s] in elevated lead release, significant turbidity, and red water" and that "[t]he potential for unintended impacts and undesirable elevation in lead release." In light of these concerns, the commenter suggested incorporating into the final rule a "find-and-fix" evaluation  -  distinct from the find-and-fix EPA proposed in § 141.82(j)  -  that would be initiated "when the 90th percentile of samples exceeds a threshold" and could include consideration of distribution system conditions, treatment operations, and any other factors that may have contributed to the exceedance; "temporal and spatial trend analyses;" and desktop corrosion control evaluations. The evaluation would also assess "current water quality conditions and trends as well as current treatment regardless of system size or type." According to the commenter, the purpose of such an evaluation would be to "focus on better implementation of the current corrosion control strategy or initiation of an optimization study to potentially change the current corrosion control strategy." The commenter also stated their position that "[t]his distinction is significant. It is possible to take immediate steps to correct implementation of an appropriate corrosion control strategy. Changing that underlying strategy is a much more significant undertaking."
One commenter indicated they were very concerned "about systems adjusting their CCT without State discussion and/or agreement" and believed "all OCCT adjustments should be done in coordination with the States." Another commenter raised a similar concern with regard to potential "risks associated with the transition from one form of corrosion control to another" and the perceived potential for "systems to be forced into making changes of marginal longer-term benefit and uncertain intermediate risk." The commenter recommended that EPA "provide explicit flexibility within regulatory language, and develop guidance to assist states in appropriately reviewing system data to avoid this potential public health risk."§ 141.82(a)(5), noting that "re-optimization under proposed § 141.82(a)(5) can be applicable only to [a system with] CCT that has been designated as optimal." The re-optimization requirements therefore would not apply to other types of systems that "may have CCT installed but are deemed optimized because they haven't exceeded an [action level]." One of the commenters noted that "small systems currently using CCT should not discontinue their techniques without state approval." One commenter suggested revising § § 141.82(a)(5)  -  (7) to reference applicable requirements in § 141.82(c)(3) for systems with an inhibitor-based corrosion control treatment process.
Agency Response
EPA recognizes the suggested need for greater clarity on whether the re-optimization steps require evaluating treatment practices under the existing, state-designated optimal corrosion control treatment (OCCT) or `restarting' the steps for a new OCCT designation. EPA also agrees that some systems may be able to achieve lead reductions more quickly by modifying the existing CCT. Final rule § 141.81(d) includes modifications that provide greater clarity on the matter. Under § 141.81(d)(1), for systems without lead service lines (LSLs) that exceed the lead trigger level, but do not exceed the lead or copper action level, states may approve modifications to the existing corrosion control treatment (CCT) without requiring a CCT study. These systems must then complete the treatment modifications within 6 months of state approval. For systems with LSLs, the Agency believes the elevated risk posed by their presence warrants more rigorous CCT study/evaluation requirements to be triggered by a lead action level exceedance. These systems are required under § 141.81(d)(1)(ii) to commence the initial steps for a pipe rig/loop study for subsequent submission and review by the state. These modifications also eliminate the potential confusion surrounding the terms `initial' vs. `standard' monitoring that was raised as concern in proposed § 141.81(d)(1) and add consistency to the references in § 141.81(d)(2). EPA has not incorporated the suggested revisions for § § 141.81(d)(3)  -  (6). The Agency believes these suggested language revisions do not add clarity to an extent that is significant or meaningfully different.
EPA received several suggestions on how the proposed rule could be revised to address other considerations that related to CCT re-optimization. One commenter noted many states do not have the flexibility to be more stringent than the federal rule and suggested including provisions that would allow states to require additional information related to water quality parameters, corrosion control studies, treatment changes and additional monitoring. The final rule includes an additional provision under § 141.80(d)(4) giving states the authority to require additional monitoring or other actions the State deems appropriate prior to a system's implementation of any upcoming long-term change in treatment or addition of a new source, to ensure the water system maintains minimal levels of corrosion in its distribution system. The final rule also modifies an existing provision in § 141.82(d) to address systems that are installing initial CCT vs. re-optimized CCT. Under this provision in the final rule, both types of systems must provide any additional information the state requests to aid its review during the designation of OCCT or re-optimized OCCT. EPA also notes a provision in the previous rule, which has been retained in the final, gives states the authority to require any additional information the state requests to aid its review of source water treatment recommendations. The Agency believes the added provisions, together with the existing provision, sufficiently address the matter.
A proactive water management planning approach intended to help systems manage water quality in the distribution system was also suggested. EPA recognizes the importance of managing other water quality issues that may impede a water system's ability to deliver drinking water safely and effectively. EPA notes that under § 141.82(f) of the final rule, the State may designate values for additional water quality parameters, beyond those specified in the rule, as determined necessary by the State to reflect optimal corrosion control for the water system.
The modifications to final rule § 141.81(d)(1), described in the first paragraph above, offer the suggested flexibility in what constitutes re-optimization, and whether any changes should be made to a system's corrosion control approach. As discussed above, systems without LSLs that exceed the lead trigger level, but not the lead or copper action levels, may, with state approval, modify their existing CCT without requiring a CCT study. As suggested, this will allow systems to address treatment process issues if it is found to be the root cause of elevated 90th percentiles. For systems with LSLs, the Agency believes the elevated risk posed by their presence warrants more rigorous CCT study/evaluation requirements to be triggered by a lead action level exceedance. These systems are required under § 141.81(d)(1)(ii) to commence the initial steps for a pipe rig/loop study for subsequent submission and review by the state.
Commenters also suggested revising the re-optimization requirements that would compel water systems to conduct corrosion control evaluations system-wide and at individual sites. EPA believes the proposal's trigger/action level approach and find-and-fix assessment, which have been incorporated under the final rule, are consistent with these suggestions. For elevated levels system-wide, the comments suggested requiring planning and preparation for CCT changes or implementing those changes. Under the proposal, systems whose 90th percentiles exceed the trigger level are required to conduct the planning and preparatory steps in a manner that is consistent with what the comments suggested. Similarly, systems whose 90[th] percentiles exceed an action level are required to implement those treatment changes. Finally, the comments suggest corrosion control evaluations that would be triggered based on sample results collected from individual locations. EPA notes the find-and-fix provisions are based on individual locations and are triggered when those samples exceed the lead action level. Systems are then compelled to evaluate whether localized or system-wide corrosion control adjustment is necessary based on the system's review of monitoring results collected at individual sites.
With regard to comments suggesting a need for clarity on what constitutes CCT (or a lack thereof), the final rule revisions add a definition for "systems without corrosion control treatment." This term is defined in § 141.2 as being a public water system that does not have or purchases all of its water from a system that does not have: 1) an optimal corrosion control treatment approved by the State; or 2) any pH adjustment, alkalinity adjustment, and or corrosion inhibitor addition resulting from other water quality adjustments as part of its treatment train infrastructure. The Agency believes this definition will address the suggested need for greater clarity on the matter and will ensure consistent implementation for LCRR requirements for conducting CCT studies.
Regarding the suggestion for greater oversight and transparency of CCT and a periodic review of CCT and water quality parameters (WQPs) the final rule includes a provision under § 141.401(c)(2) that requires the review of CCT and WQP data against most recent CCT guidance issued by EPA during sanitary surveys. The Agency believes this provision achieves the aims sought by the suggestion for greater oversight and transparency of CCT, as well as the periodic review of that CCT and the monitored WQPs. This provision will provide a recurring opportunity annually or every three years, for surface and ground water systems, respectively to engage with states on the matter, and to assess the need for improving the effectiveness of the system's corrosion control.
Regarding the suggestion that CCT should be considered a short-term solution while lead service line (LSL) replacement activities are occurring, or that it does not consider localized sources of lead, EPA notes that a study published by American Water Works Association (AWWA) Water Research Foundation (2008) "Contributions of Service Line and Plumbing Fixtures to Lead and Copper Rule Compliance Issues" (Sandvig et al., 2008) estimates that 50 to 75 percent of lead in drinking water comes from LSLs, while the remainder comes from leaded solder, brass/bronze fittings, galvanized piping, faucets, and water meters. Therefore, EPA believes use of CCT over the long-term would continue to protect the public from these sources. EPA also believes that merely requiring CCT improvements when a system exceeds the lead trigger level, rather than requiring re-optimization, would be insufficiently protective of public health given the known risks associated with drinking water lead exposures. Finally, regarding the suggestion for flexibility in determining when a re-optimization study is needed, final rule § 141.81(d) includes modifications that provide the requested flexibility. See the first response paragraph above for additional information about these modifications.
With regard to the suggestion that the rule include language exempting certain groundwater wells from triggering re-optimization requirements. EPA has not included such a modification in the final rule as the Agency believes site-specific considerations warrant State decision-making on a case-by-case basis to ensure water systems maintain optimal levels of corrosion control in their distribution system .
Commenters suggested requiring treatment decisions to be independently certified by corrosion control experts, promote greater public access to documentation of treatment decisions, and address potential climate impacts. EPA encourages water systems to communicate with their customers and raise awareness of any potential treatment changes the system may be contemplating; however, EPA does not believe such requirements would provide a sufficiently meaningful opportunity to protect public health given the potential for delays it may pose on the optimization process and the added burden to water systems and states. Agency guidance on the implementation of the CCT step requirements was also requested by commenters. See response to comment section 4.1.1 for further discussion of implementation guidance.
It was suggested that systems should approach changes in CCT as a long-term and continuous improvement process and that re-optimization should focus on whether the CCT is being implemented effectively. To achieve these aims, a "find-and-fix" treatment evaluation approach was suggested that would be triggered after exceeding an unspecified 90th percentile. This additional approach would be distinct from the find-and-fix assessment requirement EPA proposed in § 141.82(j) and would direct systems to conduct a robust analysis using a variety of tools to fully assess the underlying cause of an exceedance and inform the subsequent actions needed to re-optimize the existing treatment. EPA has not incorporated the suggested approach because it would add complexity to the rule such that it would not be feasible in conjunction with the other re-optimization requirements.
Concerns were raised over how the re-optimization requirements in § 141.82(a) could affect systems that have installed an OCCT that has not been designated as such by the State. Health risks were also raised as a concern if a state OCCT designation would require the system to switch OCCTs because of the possibility for unintended consequences resulting from potentially drastic changes that could occur under such a scenario. As noted earlier above, EPA has added a definition for "systems without corrosion control treatment." Under the definition, systems with any pH adjustment, alkalinity adjustment, and or corrosion inhibitor addition resulting from other water quality adjustments as part of its treatment train infrastructure would be considered to have CCT. Systems operating a non-state-designated OCCT would meet this definition and thus would be subject to the re-optimization steps of § 141.81(d). EPA also notes that each of the final rule provisions in § 141.81(a) direct systems with CCT to complete the corrosion control steps specified in § 141.81 (d). The initial step systems would take under § 141.81(d) requires coordination with the state since these systems would be required to either make a re-optimized optimal corrosion control treatment recommendation to the state [§ 141.81(d)(1)(i)] or commence the initial steps for a pipe rig/loop study for subsequent submission and review by the state [§ 141.81(d)(1)(ii)]. Additionally, large systems with CCT that exceed the lead PQL, but not the lead trigger or copper action levels, would be directed to complete the corrosion control treatment steps in § 141.81(d) at the state's direction and thus in coordination with the state. The Agency believes this approach addresses the concerns noted above by eliminating the potential for OCCT switches to occur without first evaluating the technical merits of such a change.
 Proposed State Decision Provisions for Requiring Studies to Identify Re-Optimized Corrosion Control Treatment
Summary of Comments
EPA received comment on the proposed provision in § 141.82(b)(3), under which states may require "any small or medium-size water systems with corrosion control treatment exceeding either the lead trigger level or copper action level to perform corrosion control treatment studies" in accordance with § 141.82(c)(3). Three commenters suggested EPA "clarify in § 141.82(b)(3) that the study required under this proposed provision for re-optimization applies only to systems with designated OCCT, not all systems with CCT." Additionally, to ensure systems would not discontinue, without state approval, the treatment in place at the time of the lead trigger or copper action level exceedance, commenters suggested EPA clarify that "the state may require small and medium systems with CCT to perform CCT studies under § 141.82" and explicitly state in the rule that "systems with CCT, when treatment has not been designated cannot turn off the treatment process without state approval."
Commenters also noted that language in § 141.82(b)(3) did not appear to include reference to § 141.82(c)(2), applicable to systems with a pH and alkalinity corrosion control treatment process that are conducting re-optimization corrosion control studies.
Agency Response
In consideration of the comments above, EPA has added a definition to § 141.2 for "systems without corrosion control treatment." Under the definition, systems with any pH adjustment, alkalinity adjustment, and or corrosion inhibitor addition resulting from other water quality adjustments as part of its treatment train infrastructure would be considered to have CCT. Because these systems are considered to have CCT, they would be subject to § 141.82(b)(3). Additionally, they would be required under §141.82(g) to continue operating and maintaining their OCCT. The provision in § 141.82(g) has been modified in the final rule to more clearly reflect its applicability to these types of systems. The provision specifies that any water system with CCT, OCCT or re-optimized OCCT that is not required to monitor water quality parameters under § 141.87 are required to continue operating and maintaining their OCCT. The Agency believes this modification is sufficient to address the concerns noted above and therefore has not added an explicit `cannot turn off' provision to the final rule.
EPA has also modified language in the final rule to specify the corrosion control study-related requirements in § 141.82(c) that would be applicable to systems with corrosion-inhibitor based treatment.
4.5 Corrosion Control Treatment Studies
EPA received general comments on the corrosion control study requirements proposed in §141.82(c). EPA also received comments on specific requirements proposed in §141.82(c) that relate to evaluating orthophosphate addition at residual concentrations of 1 and 3 mg/L and performing pipe rig/loop testing and coupon studies.
Proposed Corrosion Control Study Requirements
Summary of Comments
EPA received numerous comments on the proposed treatment recommendation requirement in § 141.82(a), corrosion control study requirements in § 141.82(c), and other related provisions throughout § 141.82. By and large, the majority of commenters expressed concerns with these requirements in general and believed them to be overly prescriptive; may not provide sufficient flexibility for water systems or primacy agencies to consider case-specific needs, factors, constraints or lead sources; may be impractical or impose a significant burden to water systems and states; may delay system efforts to implement treatment modifications that would reduce lead levels; may provide limited lead concentration reduction benefits; and may prevent approval of other, "more rapid, less expensive studies that can be tailored to system-specific issues" or other treatment options, "such as when a water system can provide established optimum control treatment strategies with effective supporting data."
With regard to the proposed methods by which systems would be required to perform the corrosion control studies prescribed in § 141.82(c), two commenters suggested that, for any pH adjustment alternative, the revised rule "specifically state that removal of [disinfection byproduct] precursors should be considered in conjunction with increased pH in the distribution system so that utilities are less likely to disregard increased pH as a realistic alternative for corrosion control." Several commenters suggested that the rule incorporate a "toolbox" or "bin" approach for corrosion control studies. This approach would establish study requirements for a given "bin;" clarify pertinent criteria for water systems to consider when balancing objectives and constraints during the selection of appropriate corrosion control strategies; and identify which types of studies (e.g., desktop solubility studies, coupon testing, pipe rig/loop testing, scale analyses) and points of consideration would most appropriately tailor corrosion control studies to the specific circumstances of individual systems.
Commenters also offered numerous additional suggestions and perspectives on how the proposed requirements could be revised in the final rule. Commenters generally suggested EPA consider including additional evaluation options (e.g., desktop studies, bench-scale testing, coupon studies, jar testing). One commenter believed "[a]ll study options should remain acceptable." Another stated that "[e]valuating options for improving treatment in a system that is already doing CCT is a substantially different technical challenge" and that the "tools available, including pipe loops, are often not sensitive enough to provide a clear distinction between [corrosion control treatment] options." This commenter recommended "that EPA's regulatory and guidance language reflect this concern." Commenters also generally suggested adding flexibility on the contents and methods that would constitute an acceptable study and "allowing states to limit the scope of the study and/or allow alternate study techniques." Other commenters suggested a "separate option for evaluation of CCT to include `other, as approved by the State'" and requiring all corrosion studies to be designed by consulting engineers, or under the supervision of a registered professional engineer, and subsequently reviewed by a third party prior to primacy agency approval. One commenter recommended including corrosion control study requirements for "systems with LSLs or service lines of unknown material to conduct pipe scale analysis and sequential monitoring as part of the proposed CCT study requirements." A final commenter recommended "allowing water systems with similar source and treated water to share and use the results from the corrosion control study."
Another commenter raised a concern that "[i]f the final rule includes a requirement to remove all the lead pipes and provide POU treatment at the highest risk homes, water systems can optimize corrosion control treatment to address household plumbing sources of lead and provide more health protection to all consumers because water systems will no longer have to design corrosion control treatment for lead service lines. In this way, the existence of lead service lines may have the unintended consequence of increasing the risk of lead exposure in homes that have other sources of lead in solder and brass fittings and fixtures but no lead service lines."
Commenters also provided additional, more specific suggestions on how the proposed evaluation requirements and procedures could be revised in the final rule. One commenter suggested that "minor treatment changes might require a simple desktop evaluation be done, but in no way should require pipe loops and a re-evaluation of the OCCT or OWQCP designations." Another believed "[s]mall and NTNC systems may have an easier time conducting CCT studies which are less time consuming and costly compared to options such as pipe loop or coupon studies." A third commenter claimed they "[did] not anticipate many [small] systems will be required to evaluate the 1 mg/L or 3 mg/L orthophosphate requirement, as they will likely not be required to conduct CCT studies." A fourth commenter suggested requiring large systems to "[c]onduct a comprehensive study of all the factors that contributed to the exceedance," in addition to the "list of water quality parameters in the current LCR" and provided peer-reviewed literature for other potential water quality parameters for consideration towards the final rule. A fifth commenter suggested requiring "mak[ing] the corrosion control study available to the public and hold at least one public meeting during the study process." A commenter similarly suggested "includ[ing] a requirement to hold a public meeting to discuss treatment changes and make corrosion control studies and recommendations available for public review." A seventh commenter suggested "evaluat[ing] a scenario that drops the polyphosphate dose to 10% or less (i.e., 90% orthophosphate)." A  commenter suggested water systems "rely on historical data for technologies that have been used and proven to be effective" to inform corrosion control treatment modifications.
Commenters also questioned the need to evaluate all of the treatment options prescribed in proposed § 141.82(c), even if chemical or physical constraints have been identified that would limit or prohibit the use of a particular treatment. Two commenters suggested "a system should only be required to evaluate all options by demonstration if they are unable to implement the best option from the [EPA] Optimal Corrosion Control Treatment Guidance due to simultaneous compliance issues or other similar impacts." Another commenter suggested "if a system adds orthophosphate for corrosion control, a re-optimization study should not concentrate on pH/alkalinity adjustment in lieu of orthophosphate treatment. The re-optimization study should focus on finding the optimal orthophosphate dosage." Another  commenter believed the evaluation of the four treatment options as proposed in § 141.82(c) may lead to systems "missing [other] causes of increased lead solubility in their system" that may arise from switching from free chlorine to chloramine disinfection or from sulfate-based to chloride-based coagulants.
With regard to the revision proposed in § 141.82(c), to clarify that water systems must evaluate "the addition of an orthophosphate-based [emphasis added] corrosion inhibitor," one commenter expressed their general support for the clarification, stating they "agree[d] with the proposed requirement" "since orthophosphate products are more effective at inhibiting corrosion than blended phosphate products." Another commenter claimed the specification of an orthophosphate-based corrosion inhibitor "severely limits CCT options. Phosphate inhibitor options other than orthophosphate have a record of successful corrosion control to maintain compliance with the LCR" and suggested that non-orthophosphate options "should be permitted if they allow a system to meet Pb and Cu compliance levels." One commenter suggested adding requirements "for systems that currently use a polyphosphate or a polyphosphate blend to conduct a re-optimization study" and "[e]valuate a scenario that drops the polyphosphate dose to 10% or less (i.e., 90% orthophosphate)." The commenter also suggested adding a requirement for chlorinating systems to "evaluate effectiveness of chlorination to maintain [a tetravalent lead] scale before switching to orthophosphate."
Another commenter suggested clarifying, whether in the final rule or subsequent implementation guidance, "how to handle polyphosphate/orthophosphate changes or blends and how the rule expects to address simultaneous compliance and efficacy of other treatment methods." The commenter claimed that "[t]he proposed rule handles polyphosphate and orthophosphate differently which could mean systems transitioning" and stated needing "consistent ways to deal w/ Fe & Mn sequestration moving to oxidation & filtration." In light of the proposed specification of orthophosphate-based corrosion inhibitors, one commenter sought to "confirm that a blended polyorthophosphate, which many systems use, will still be acceptable" and questioned whether "a system that has a history of complying with the action level, while optimized at a lower orthophosphate target, [would] be required to raise targets to 1 mg/L." Another sought clarity on whether a "ortho-/poly-phosphate blend [would] be considered an orthophosphate-based inhibitor" and whether orthophosphate "residual concentrations need to be evaluated if the PWS has a copper ALE and is required to complete a study." Finally, one commenter provided specific language suggestions relating to blend phosphates for consideration towards the final rule.
EPA also received comments on the requirements specifically proposed in § § 141.82(c)(1)(ii), (c)(2)(ii), and (c)(3)(ii), where water systems would be required to "evaluate each of the corrosion control treatments using either pipe rig/loop tests, partial-system tests, or analyses based on documented analogous treatments with other systems of similar size, water chemistry, and distribution system configurations," and under which "[c]oupon tests can be used as a screen to reduce the number of options that are evaluated." Numerous commenters provided specific suggestions on the use of pipe rig/loop and coupon studies; these are summarized and discussed separately in their own respective section. One commenter suggested revising the provisions to allow the use of coupon studies when systems evaluate modifications to existing corrosion control treatments. Two commenters also suggested revising these provisions to allow the use of desktop studies. One of the commenters further suggested that a "water system may conclude from the desktop study that a coupon or full pipe loop study is needed to evaluate changes in treatment and specify the time period for the plan, design, construction, operation, and analyses of the coupons or pipe loops." With regard to partial-system testing, one commenter supported the proposal to evaluate treatments using partial-system tests. Another did not oppose the proposed use of this evaluation approach, but suggested requiring systems with lead service lines to "evaluate corrosion control effectiveness using sequential samples that measure water collected from lead service lines," and that the final rule "prevent water systems from making new decisions based on old studies that do not meet the revised requirements" and clarify that if a system "rel[ies] upon a previous analysis, it must include evaluation of the currently mandated study options and cannot rely solely on coupon studies." With regard to analyses based on documented analogous treatments with other systems of similar size, water chemistry, and distribution system configurations, one commenter supported the proposal and another did not. Finally, one commenter claimed "[i]t may be very difficult for a system to perform a partial system study or leverage data from an analogous system."
Commenters also provided comment on the proposed requirements in § § 141.82(c)(1)(iii), (c)(2)(iii), and (c)(3)(iii) for systems to measure certain "water quality parameters in any tests conducted under [§ § 141.82(c)(1), (2) or (3)] before and after evaluating the corrosion control treatments listed above]." One commenter suggested that the final rule "should not remove any of the required parameters from the list of required sampling to justify OCCT selection and perhaps should expand the list to ensure that a sufficient water quality panel is obtained for accurate modeling." The commenter also suggested expanding the list to include "chloride, sulfate, total phosphorus, iron, and manganese, at a minimum." Another commenter suggested adding calcium as "an important parameter to consider when completing a corrosion control study or recommendation report" so that systems may "determine the upper limit pH that would cause calcium carbonate to precipitate in the distribution system." A third commenter stated their position that "the chloride to sulfate mass ratio (CSMR) is a valuable tool in evaluating potential corrosivity." The commenter provided anecdotal information about an analysis they conducted on 11 water systems that exceed the lead action level. Of these, the commenter stated "10 had a CSMR value over 0.57," thus "saturation indices can be used for risk categorization" and "CSMR can be an important indicator of corrosion in certain public water systems." A fourth commenter suggested including "the water quality factors that affect release of lead and copper as listed in the EPA Optimal Corrosion Control Guidance Manual."
One commenter disagreed with the data and documentation sources proposed in § § 141.82(c)(1)(iv), (c)(2)(iv), and (c)(3)(iv) when identifying chemical or physical constraints that would limit or prohibit the use of a particular corrosion control treatment. The commenter suggested replacing proposed subparagraphs A and B in each of these sections with the following language: "with applicable references to the peer reviewed literature, EPA guidance, recognized standards of practice, or site-specific studies."
For systems without corrosion control treatment, one commenter raised technical, managerial, and financial capacity concerns and suggested addressing them by revising § 141.82(c)(1) to require primacy agencies to determine the optimal corrosion control treatment on the behalf of small and medium water systems. Another commenter suggested revising § 141.82(c)(1)(iv)(B) to allow the use of "previous coupon study data that found a specific treatment to be ineffective or detrimental to other processes" when demonstrating a previous attempt to evaluate a particular corrosion control treatment.
For systems with existing corrosion control treatment in place, commenters suggested requiring an initial assessment of whether the treatment is already optimized and being implemented effectively, prior to conducting a subsequent assessment of each of the treatments identified in § § 141.82(c)(2) & (3) (i.e., alkalinity and pH adjustment, addition of orthophosphate- or silicate-based corrosion inhibitors, or addition of orthophosphate-based corrosion inhibitors at residual concentrations of 1 and 3 mg/L).
EPA also received numerous comments requesting clarification in the final rule on various aspects of the corrosion control study and evaluation procedures proposed in § 141.82(c), including when corrosion control treatment recommendations or studies would be required; what evaluation procedures specifically would be required as part of corrosion control studies; and whether a single study would suffice for systems triggered into the requirement but that are "expect[ing] one or more source changes in 5-10 years." One commenter sought clarity on what constituted alkalinity adjustment and under what circumstances a water system would be required to monitor alkalinity, noting that "[a]ny adjustment in pH has an effect on the alkalinity." Additional commenters requested clarification on whether orthophosphate residual concentrations prescribed in § § 141.82(c) are to be measured as mg/L of phosphate or as mg/L of phosphorus; what specific circumstances under § 141.82(c) would permit the use of desktop studies or require corrosion control studies, pipe rig/loop tests, or orthophosphate residual treatment option evaluations; what specific types of source water or treatment changes would trigger the requirement for such a study; whether specific study requirements would vary based upon system size, initial optimization versus re-optimization, or other circumstances; and how the required corrosion treatment evaluation requirements would apply to water suppliers and their consecutive systems. Where such system-specific differences in study requirements may exist, one commenter requested EPA "discuss the degree of analysis and why this level of analysis is protective for these systems." Commenters also requested clarification on "definitions regarding corrosion testing techniques" and whether "bench-scale methods would be considered `metal coupon tests' or `pipe rig/loop tests';" the intended regulatory approach for scenarios "when a public water system adds an additional new source or changes in source while in the process of doing a corrosion control study or after completing the corrosion control study;" and whether the rule would permit systems to substitute other treatment options by evaluating the same or similar treatments at different concentration doses instead of the four prescribed in § 141.82(c) (i.e., alkalinity and pH adjustment, addition of orthophosphate- or silicate-based corrosion inhibitors, or addition of orthophosphate-based corrosion inhibitors at residual concentrations of 1 and 3 mg/L). Other commenters also provided suggested language and typographical revisions for the final rule.
Several commenters also requested EPA guidance, training and tools that would provide technical assistance to water systems and states in completing corrosion control studies. One commenter also recommended "EPA substantially simplify the regulatory language and develop (and plan to regularly update) guidance with effective and flexible recommendations for study designs" in accordance with the recommendations of the National Drinking Water Advisory Council. Commenters also requested additional guidance that would address the following, more specific topics: "choos[ing] the correct tool for commonly occurring treatment considerations;" "how to perform corrosion studies;" determining the appropriate [study] options and when to use other types of stud[ies];" and on "geochemical modeling tools" to "reduce the burden on water systems and promote expedient installation." Once commenter additionally requested EPA "provide a corrosion testing design standard."
In addition to the guidance requests summarized above, one commenter suggested "a minimum funding of $10 million of corrosion control research" that would "support PWS decision making."
Agency Response
EPA agrees that more clarity is needed on which systems proceed down the optimization or re-optimization pathways. EPA agrees that optimization and re-optimization processes should provide more flexibility. EPA added a definition of systems without corrosion control treatment to define `bins' for optimization or re-optimization. System without corrosion control treatment means a public water system that does not have, or purchases all of its water from a system that does not have: 1) an optimal corrosion control treatment approved by the State; or 2) any pH adjustment, alkalinity adjustment, and/ or corrosion inhibitor addition resulting from other water quality adjustments as part of its treatment train infrastructure. One of the key `bin' factors is the presence or absence of corrosion control treatment and whether the system will proceed down the optimization or re-optimization pathway. In the final rule, systems that do not meet these criteria will utilize the re-optimization pathway. EPA agrees that for some systems, lead reductions can be achieved quickly with slight modifications of the existing CCT and should not be delayed potentially by two years for the results of the corrosion control study. EPA agrees it is appropriate for states to approve modifications of the system's existing corrosion control treatment for systems that are between the trigger level and action level without a corrosion control treatment study. In the final rule, states are allowed to approve existing corrosion control treatment modifications without a corrosion control study for systems with lead levels between the trigger level and the action level.
EPA agrees that a `bin' approach based on system characteristics such as system size, the presence of lead service lines and 90[th] percentile value can provide more flexibility for some systems doing corrosion control studies. EPA agrees that requirements for harvested pipe loops and coupon studies are best delineated through such a `bin' approach. Harvested pipe loops are only required for systems with lead service lines that exceed the lead action level. To the extent that there are any large systems without corrosion control treatment that have lead service lines and exceed the lead practical quantitation level of 5 ug/L, those systems would also need to conduct a harvested pipe loop study. EPA believes that the corrosion control treatment changes needed for systems above the action level merit a thorough investigation of the impacts of the options on the existing pipe scale. Another cost implication of the pipe loop study for small systems is that the study costs will be front-loaded with nearly $300,000 that would have to be paid within a few years of the action level exceedance. However, if a small system with lead service lines selects the corrosion control treatment option, a harvested pipe loop study would have to be conducted to ensure optimized corrosion control treatment is implemented. For large and medium systems, coupon studies can serve as a screen to reduce the number of options for the harvested pipe loop study. Commenters noted that the construction of harvested flow-through pipe loops and the stabilization of those loops can take six months to one year before options can be evaluated. EPA agrees that more time is needed to construct pipe loops from harvested pipes; therefore the Agency is removing the requirement for initial treatment recommendations in the final rule for these systems. For these systems, the final rule directs them to start constructing and operating the flow-through pipe loops after the action level exceedance in place of the initial treatment recommendation step, since the pipe loop study will be the basis for their treatment recommendation. For these systems, Step 1 of the optimization or re-optimization process is the construction and operation of the flow-through pipe loops after the action level exceedance, which must be completed within one year of the exceedance. EPA retained the requirement that coupon studies can only be used as a screening tool for these systems. Commenters indicated that for some systems, coupon studies rather than pipe loop studies may be an appropriate treatment recommendation tool. EPA agrees that coupon studies can be used for systems that do not have lead service lines because existing scale impacts are not as significant and it would be very difficult to harvest internal plumbing fixtures and soldered copper pipes and re-install them in a pipe loop/rig. The final rule includes requirements to allow coupon studies to be the basis for treatment recommendation for other systems that do not have a lead action level exceedance and lead service lines. The following table lists the `bins' for the final rule based on systems size, presence/absence of lead service lines, corrosion control treatment status, and lead 90[th] percentile:
`Bins' based on status of corrosion control treatment, lead service lines, and 90[th] percentiles

                                      Bin
                           Large System (>50,000)
                       Medium System (10,001  -  50,000)
          Small System (<=10,000), if select CCT compliance option
No CCT w/ LSLs > Pb AL
Mandatory pipe loop
Mandatory pipe loop
Mandatory pipe loop[1]
No CCT w/ LSLs
Mandatory pipe loop unless <= PQL[2]
CCT recommendation if ALE in future, State decision on CCT study[3]
CCT recommendation if ALE in future, State decision on CCT study[3]
No CCT w/o LSLs > Pb or Cu AL
CCT study  -  coupons
CCT recommendation, State decision on CCT study[4]
CCT recommendation, State decision on CCT study[4]
No CCT w/o LSLs > TL, < ALs
CCT study  -  coupons
CCT recommendation if ALE in future, State decision on CCT study[3]
CCT recommendation if ALE in future, State decision on CCT study[3]
CCT w/ LSLs > Pb AL
Mandatory pipe loop
Mandatory pipe loop
Mandatory pipe loop[1]
CCT w/ LSLs > TL, <ALs
Can modify existing CCT w/o study  -  State[5]
Can modify existing CCT w/o study  -  State[5]
Can modify existing CCT w/o study  -  State[5]
CCT w/o LSLs > Pb or Cu AL
CCT study  -  coupons
CCT Rec., State decision on CCT study[4]
CCT Rec., State decision on CCT study[4]
CCT w/o LSLs > TL, < ALs
Can modify existing CCT w/o study  -  State[5]
Can modify existing CCT w/o study  -  State[5]
Can modify existing CCT w/o study  -  State[5]
Notes:
[1] Small lead service line systems are recommended to select lead service line replacement if they exceed lead action level due to cost and complexity of studies  -  pipe loop study cost ≈ replacement of 55 lead service lines
[2] It is unlikely that there are large lead service line systems without corrosion control treatment that meet the new definition for systems without corrosion control treatment, but this scenario will be covered in rule. One possibility might be medium system that grew to become a large system. Since a large system must have optimized corrosion control, these systems would have to conduct a pipe loop study.
[3] The intent for systems without corrosion control between the trigger level and action level is to proactively determine what they will do if they ever exceed the action level, so they can react quickly. This can be based on treatment recommendation or after a State required corrosion control treatment study.
[4] Desk-top studies are an option if States require a study.
[5] Systems with existing corrosion control treatment between the trigger level and action level can have existing treatment modifications approved by the State without a study  -  tweaks of the existing corrosion control treatment, which will save time and money as systems will likely try to enhance the performance of their current treatment process to lower lead levels. These modifications have a faster approval and implementation time frame, since the treatment is already installed.

EPA disagrees with comments about polyphosphate inhibitors being an effective treatment for lead corrosion control and believes that an orthophosphate-based inhibitor is the appropriate approach as it covers both orthophosphate and blends of ortho- and polyphosphate while emphasizing that the orthophosphate is the key control parameter. The Science Advisory Board report (EPA-SAB-20-007) supported the requirement that the phosphate inhibitor be orthophosphate-based. The report noted that research by Hozalski et al. (2005) and others (e.g., Holm and Schock, 1991) has shown that polyphosphate, as a metal chelator, can result in much higher lead levels than when using orthophosphate alone. EPA has finalized the revision to note that the key parameter is orthophosphate measured as PO4 as the residual from orthophosphate-based inhibitors, which can include blends of ortho- and polyphosphate or just inhibitors containing orthophosphate.
EPA disagrees with the comment about requiring chlorinating systems to evaluate the effectiveness of chlorination to maintain a tetravalent lead scale before switching to orthophosphate. EPA does not have a record basis for concluding that many chlorinating systems have the conditions to produce a consistent tetravalent lead scale throughout the distribution system. Two of the best examples for a tetravalent lead scale are the Washington, DC system in the early 2000s with very high chlorine doses that created problems with disinfection by-products and Cincinnati, OH where the system uses granular activated carbon to remove disinfection by-product precursors. Systems that are triggered into a study will be using their existing treatment as a control and can compare the results with the orthophosphate results to compare the two approaches.
Several commenters did not think it was necessary to evaluate all of the options and some, in particular, thought it was unnecessary to evaluate the pH/alkalinity option if they were adding orthophosphate. The final rule allows states to approve treatment modifications without a study for systems between the trigger level and action level. Systems with lead service lines with an action level exceedance are required to do a study and medium and small systems without lead service lines may be required to conduct a study, since more extensive revisions to the corrosion control treatment may be necessary and that these systems need to investigate all options. . There were also several comments that deal with the impact of long-term treatment changes, which were addressed by the upfront notification and State approval that was added to the lead and copper rule in 2007. Systems conducting a study to evaluate the impact of a long-term treatment change prior to making it would want to include parameters that can affect the corrosivity of the water to see if corrosion control treatment adjustments would be necessary in conjunction with the approved long-term treatment change.
EPA received several comments about water quality parameters that should be monitored as part of the corrosion control treatment study. The water quality parameters that must be monitored in the corrosion control treatment study are the critical parameters associated with that treatment strategy. EPA agrees that systems may want to add other parameters based on their system-specific water quality considerations. However, EPA disagrees with mandating that all systems conducting studies add all of these parameters as it would significantly increase the cost of the study and many of the parameters may be unnecessary for defining the optimal corrosion control treatment. Parameters such as chloride and sulfate may be useful in evaluating if a long-term treatment change of coagulants could affect the chloride to sulfate mass ratio, which can affect the corrosivity of the water. These parameters are not critical to a corrosion control treatment strategy. As noted above, systems that have been required to conduct a corrosion control study prior to making such a long-term treatment change should include chloride and sulfate along with the critical corrosion control parameters. EPA has provided costs for harvested pipe loops in the Economic Analysis with a default set that includes some of the additional parameters. The following is intended to show the impact of additional parameters on the cost of the study. EPA used the default for costing purposes. The baseline cost for a pipe loop for systems serving greater than 50,000 people is $304,617 that includes monitoring for lead, pH, alkalinity and orthophosphate. The default cost for a pipe loop study is $342,476 and includes monitoring for calcium, iron, free and total chlorine, ammonia, heterotrophic plate count, total coliform, and total dissolved solids. The addition of chloride and sulfate to the default would result in a pipe loop study cost of $367,643.