Optimize corrosion control treatment NOW! Get it done now to put yourself in the best position for LCRI

In late 2023, EPA released the proposed Lead and Copper Rule Improvements (LCRI). See this article for more information on the proposed LCRI.The LCRI is intended to improve upon the requirements promulgated in early 2021 in the Lead and Copper Rule Revisions (LCRR). The LCRR/LCRI will affect more than 1,050 community and non-transient, non-community public water systems in Colorado, serving nearly 6.5 million people. The LCRI public comment period is closed and EPA is planning to finalize the rule in October 2024. The LCRI compliance date is estimated to be late 2027. This gives water systems time to prepare and optimize their corrosion control treatment (CCT) before the LCRI requirements take effect. 

What is corrosion control treatment (CCT)? CCT is chemical treatment at the water treatment plant that makes the potable water less corrosive to water lines and premise plumbing. CCT is typically achieved by adding a phosphate-based corrosion inhibitor or with pH/alkalinity adjustment. The Lead and Copper Rule (Section 11.26 of Regulation 11) requires installation of CCT for systems with action level exceedances (ALE) and requires optimal corrosion control treatment (OCCT) for all systems serving more than 50,000 people. Approximately 65 systems in Colorado are operating OCCT with Department set optimal water quality parameters (OWQP) to comply with the current Lead and Copper Rule. 

Several changes in the proposed LCRI may impact systems that either have corrosion control treatment (CCT) installed currently or that may need to install CCT as a result of elevated lead or copper levels. Proposed LCRI changes that may impact CCT include:

• Setting a lower lead action level at 10 parts per billion (ppb).
• 1st and 5th liter lead sampling at lead service lines may result in higher lead levels than seen under the current rule. 
• Corrosion control study required for large systems without OCCT that exceed the practical quantitation limit (PQL) of 5 ppb based on 90th percentile lead levels.
• Medium and large systems with lead service lines that are required to conduct a corrosion control study must use harvested lead pipe in a pipe loop rig.
• Deferred OCCT installation or re-optimization for systems that replace 100 percent of lead service lines within five years of the date they trigger CCT steps.
• Removal of hardness as a corrosion control treatment option and specifies any phosphate inhibitor must be orthophosphate.
• Small system compliance options (e.g., point of use devices, replacement of all lead-bearing plumbing materials) for community water systems with 3,300 people or less and all non-transient, non-community systems.
• Review of CCT during sanitary surveys.

While these changes were part of the proposed LCRI, we will need to wait for the final rule to see if all of these items are included and if new items are added. Also, under the proposed LCRI, water systems will also have to provide Tier 1 public notice to consumers within 24 hours after a lead action level exceedance.

Possible actions to take:

• Review your 90th percentile lead results: One of the key changes in the draft LCRI is setting the lead action level at 10 ppb; the current lead action level is 15 ppb. Since 2010, approximately 115 systems had 90th percentile lead levels that were between 10 ppb and 15 ppb. Investing in operational controls, treatment, and/or treatment optimization now may allow you to lower your lead levels below the 10 ppb action level before the LCRI takes effect.  
• Evaluate treatment at large systems that are deemed optimal: Systems that have a population of more than 50,000 people “large systems” are required to have optimal corrosion control treatment (OCCT). The majority of Colorado’s systems that serve over 50,000 people have been “deemed” to have OCCT based on low source water lead and 90th percentile lead concentrations less than 5 ppb. The proposed LCRI requires large systems with a 90th percentile lead value greater than 5 ppb to complete a corrosion control study (CCS). For systems with lead service lines, the proposed LCRI requires the CCS be completed using harvested lead lines in a pipe loop. Many large systems have treatment processes that may impact corrosion. If possible, you should work on optimizing any existing treatment to lower lead levels as much as possible. 
• For systems with CCT,  determine if you can optimize your treatment process: Analyze your treatment process and determine if your corrosion control treatment could be optimized. A great tool for this is a bench scale immersion coupon study.  
• pH/alkalinity CCT systems: Systems using pH/alkalinity adjustment may want to more tightly control pH and/or find the optimal target pH. The EPA guidance document recommends a pH range at the entry point of 0.4 s.u. (for example: 7.8 to 8.2 s.u.) and a 0.6 s.u. range within the distribution system. Maintaining a tighter pH range may also improve other water quality contaminants such as disinfection byproducts. Conducting an immersion study to determine the optimal pH target may also be beneficial.
• Phosphate-based inhibitor systems: Phosphate-based inhibitor systems may want to optimize their dosing. Orthophosphate is the chemical that is effective at corrosion control and the EPA generally recommends a minimum orthophosphate concentration of 1.0 mg/L as PO4 in the distribution system. Blended phosphate inhibitors are a blend of orthophosphate and polyphosphates, which are typically used to sequester iron and manganese. These systems may want to review the percentage of orthophosphate in their chemical to better control corrosion. A bench scale immersion coupon study may be advantageous to determine the more effective dose and/or chemical.  
• Systems with CCT and OWQPs should review their OWQPs: Systems with OWQPs should review their monitoring schedule to verify the required OWQPs at the entry point(s) and in the distribution system. You may want to request an OWQP modification if you have additional water quality data or immersion coupon study results. 

Making changes to your CCT now can help you meet the LCRI requirements that are coming down the pipe. If you have any questions, please contact Melanie Criswell at melanie.criswell@state.co.us.

Resources:

• LCRR guidance, FAQs, and forms are available on the department’s Lead and Copper Rule & Revisions Webpage.
• Review the department’s initial service line inventory development policy.
• Visit the department's drinking water training and assistance website to register for upcoming Lead and Copper Rule courses (online and in-person options available) and other free training opportunities.

➽ Melanie Criswell Lead Service Line, Corrosion, and Emerging Contaminants Engineer

➽ Haley Orahood Regulatory Development and Implementation Specialist

Optimal Corrosion Control Treatment

Inter agency stakeholder collaboration for the win!

In 2012, Denver Water exceeded the lead and copper rule’s action level of 15 ppb for lead in drinking water. For each set of tap water samples collected by a water system during a given monitoring period, the 90th percentile concentration of lead is calculated and compared with the action level. If the action level is exceeded, then a public water system must take action. 

The lead and copper rule is unique in several ways:

• It requires “first-draw” sampling at kitchen sinks
• There is no maximum contaminant level (MCL), but rather action levels for both lead and copper
• Public education on lead exposure is part of the treatment technique
• There is a requirement to reduce the overall corrosivity of the water

EPA did not set a drinking water maximum contaminant level for lead because the Centers for Disease Control has deemed there to be no safe level of lead in drinking water. Therefore, when a system exceeds the action level for lead, it is required to take steps to reduce lead and ensure its treatment processes are optimal for minimizing lead exposure at customer’s taps. 

In such cases, the Safe Drinking Water Act and the Colorado Primary Drinking Water Regulations (Regulation 11) require the water provider to install and operate optimal corrosion control treatment (OCCT). A treatment is called “optimal” when it is identified as the best option to reduce lead at the customer's taps while not causing the water system to violate any other part of the Colorado Primary Drinking Water Regulations. If the division determines that a provider’s current treatment is not optimal and a different treatment is designated as OCCT, then the system must install the new OCCT to reduce lead at a customer's drinking water taps within 24 months. 

OCCT Study

After 2012, Denver Water undertook multi-year studies to determine what the best treatment is for lead control in their system. After an initial desk-top study proved inconclusive,  a pipe-loop study was conducted that involved harvesting lead service lines from their system and testing them with different treatment regimes. The study took multiple years to complete because harvesting lead service lines is time consuming and difficult, and running a pipe loop study takes large investments of staff time and expertise. 

In September 2017, Denver Water submitted their report showing that orthophosphate reduced lead by approximately 70% while pH reduced lead by approximately 45%. Despite this difference, Denver Water suggested that the department designate pH as OCCT largely because phosphorus could have negative impacts on waterways. In accordance with Regulation 11 and consultation with EPA, the department designated orthophosphate as Denver Water’s OCCT in March 2018.  

Community concerns

The water and wastewater communities had notable concerns about the long-term implications of adding phosphorus including watershed impacts (e.g. large treatment costs at wastewater plants to remove phosphorus, algal blooms in receiving waters, etc.) and downstream drinking water impacts. Because there were many shared concerns, the department signed a memorandum of understanding (MOU) with several parties agreeing to work together to avoid litigation, discuss additional studies, and investigate potential opportunities to implement OCCT and reduce environmental impacts. The MOU included the following success statement:

MOU Stakeholders will collaboratively seek long-range regional solutions that maintain public trust and protect public health and the environment per the Safe Drinking Water Act and the Clean Water Act, while additionally minimizing impacts to water supplies, wastewater treatment plants and watersheds.

The department organized a stakeholder process to investigate whether the OCCT designation could be modified to protect both public health and the environment. During this effort, stakeholders reviewed findings and recommendations from technical working groups regarding drinking water, wastewater and watershed interests. This stakeholder process concluded in September 2019. The final Watershed and Wastewater Stakeholder Summary Report provides the results of this effort. 

During the stakeholder work, Denver Water, CDPHE, and EPA explored whether pH adjustment alone could achieve similar public health protection. Based on study results for lead service lines, pH adjustment is not equivalent to orthophosphate. However, at homes served by copper with lead solder (pre-1988 homes) that don’t have a lead service line, both orthophosphate and pH adjustment (adjusting pH to 8.8) will result in lead levels below 5 ppb for copper with lead solder homes. Below 5 ppb, the difference between the performance of orthophosphate and pH adjustment was very low in terms of risk to public health. Therefore, the department concluded that if customers with lead service lines could be provided filters and the lead service lines eventually removed, Denver Water could use pH adjustment as OCCT. 

Concurrent to this stakeholder work, Denver Water, CDPHE, and EPA cooperatively negotiated a possible alternative to OCCT where Denver Water would undertake large-scale public health interventions in lieu of implementing orthophosphate. For an alternative like this to be allowable, both CDPHE and EPA would have to take regulatory action. CDPHE would have to modify our 2018 OCCT designation and USEPA would have to grant a variance from the requirement to install and operate OCCT. Denver Water submitted a request to EPA for a variance from the Safe Drinking Water Act in September 2019. Also in October 2019, Denver Water requested that the department modify their original designation acknowledging the new data that had been generated over the two year period. 

Denver Water's Variance Request - Key Elements

• Comprehensive outreach and education about lead in drinking water, and the steps taken to reduce exposure, to the 1.4 million customers served.
• At-home pitcher filters, replacement cartridges, and follow-up surveying for all users who drink water from a lead service line.
• Refinement of Denver Water’s existing inventory of homes that have lead service lines to ensure accuracy.
• Replacement of all lead service lines within 15 years, including cities served by Denver Water (e.g. Wheat Ridge).
• Implementation of pH control at a high level (near 8.8 vs. currently 7.8) to further reduce lead.
• Focus on health equity and environmental justice in rolling the program out, for example, prioritizing neighborhoods where cultural factors may inhibit filter use.

In November 2019, the department submitted two documents to EPA and Denver Water in response to Denver Water's request for variance. The department sent EPA a letter of support for the variance and a modification letter to Denver Water with regards to the March 2018 department decision. 

On Dec. 16, 2019, USEPA granted Denver Water's variance request.

The department views the outcome of this process to be best for public health and the environment while also being more cost effective and addressing an inherent environmental justice issue (lead in drinking water). The department is looking forward to working with the agencies to oversee Denver Water’s implementation of this variance and to partner with Denver Water to remove a major source of lead from the region’s drinking water.

➽ Tyson Ingels, lead drinking water engineer