Denver Water proposes innovative plan to remove an estimated 75,000 lead service lines in 15 years

Lindsay McCormick, is a Program Manager. Tom Neltner, J.D., is the Chemicals Policy Director.

Update (12/18/19): EPA approved Denver Water’s Lead Reduction Program on December 16, 2019. The utility will start implementing the program in 2020. 

Yesterday, Denver Water’s board approved its proposed “Lead Reduction Program Plan” to fully replace the estimated 75,000 lead service lines (LSLs) in their system within 15 years.  The plan is an innovative solution that will remove the primary source of lead within Denver Water’s system, while avoiding the use of orthophosphate that can further exacerbate nutrient pollution problems in rivers, streams and oceans, an issue EDF’s Ecosystems team is working hard to solve.

As proposed, Denver Water would fund full replacement of LSLs through water rates, bonds and sales of new connections to the system, hydropower production and other sources rather than have individual property owners contribute.  In addition, the utility’s proposal to provide filters to residents until their LSLs are replaced represents a model other communities should consider based on the effectiveness of their ongoing pilot.  Before implementing the plan, Denver Water will need to receive approval from the Environmental Protection Agency (EPA).

The Backstory

In 2012, Denver Water exceed the Lead and Copper Rule (LCR) lead action level of 15 ppb, initiating a series of studies to identify the optimal corrosion control treatment to reduce the lead levels in homes with lead plumbing.  In such situations, utilities may be required by regulators to “optimize their corrosion control” by treating the water with chemicals, like orthophosphates, to reduce lead that leaches from the service line into drinking water. Chemical treatment works by building up a protective layer or “scale” inside the pipes, limiting the amount of lead that can be released into the water.  In March 2018, the Colorado Department of Public Health and Environment (CDPHE) directed Denver Water to implement orthophosphate treatment by March 2020.

However, orthophosphate treatment is not a magic bullet. As with all corrosion control, it can manage the lead risk but may still allow lead to unpredictably release into the water.  Further, when orthophosphate is added to the water supply, some of the chemical passes from the drinking water to the sewage, through the treatment system and, ultimately, increases the amount of phosphorous discharged to rivers and lakes.  Because phosphorus is a nutrient, it can lead to algae growth including harmful algal blooms, seen in places like Salem, Toledo, and Lake Erie.  As described by Clean Water Action, algae blooms are a concern in the South Platte River, south of Denver.  And, once started, orthophosphate treatment cannot easily be stopped without increasing corrosion of lead pipes.

The Proposed Plan

To avoid introducing an additional source of phosphorous into wastewater, Denver Water is proposing a multi-pronged strategy to address lead in water without orthophosphate treatment.  Its plan involves ramping up their existing program to replace LSLs – the largest source of lead in water – and protecting residents in the meantime by increasing pH corrosion control treatment and providing them with filters to remove the lead until their LSL is replaced.  Denver Water explains that compared to orthophosphate treatment, LSL replacement will provide “a multi-generational benefit of significantly reduced lead exposure” for its customers as the source of lead will be permanently removed within 15 years.

Specifically, the utility plans to:

  1. Pursue an accelerated LSL replacement program fully funded by the utility, accomplishing replacement of approximately 75,000 LSLs within 15 years (annual average of 7% LSLs replaced per year) instead of the current pace that would take more than 50 years.
  2. Undergo a rigorous investigative effort to build a more accurate inventory of where LSLs are in their system and develop an online map to make the inventory publicly available.
  3. Provide residents that have known, suspected, or possible LSLs with filters certified to remove lead until six months after the LSL servicing their home is replaced.
  4. Enhance existing corrosion control treatment by adjusting the current pH of 7.8 to 8.8 and maintaining alkalinity above 30 mg/L to reduce corrosion of LSLs as well as household plumbing like fixtures.
  5. Conduct outreach and communications with residents, public health agencies, government, and other stakeholders.

The next step for the utility, now that it has received approval from its board, is to receive approval from the EPA.

The Challenges

There are many challenges involved in implementing LSL replacement programs. Below are some key issues Denver Water is grappling with:

Identifying LSL Locations

A major challenge for Denver Water is that it – like many utilities – does not currently have a robust inventory of where LSLs are located.  Denver Water plans to undertake a rigorous investigative effort, particularly in the initial years of the program, to build up its inventory.  To do so, the utility will rely on information like historical records and knowledge of materials used in certain time periods as well as field investigations, using methods such as visual inspections in the home or through potholing, water testing, and feedback from its outreach to customers that includes an interactive online map.

Because there is always some level of uncertainty in developing an inventory, Denver Water has developed five categories based on the probability of a residence having an LSL: known LSL, suspected LSL, possible LSL, unlikely LSL, and non-lead.  In addition to pinpointing geographic locations to investigate for LSLs, these categories are designed to help inform participation in the filter program and the LSL replacement program.

Under its program evaluation plan, Denver Water will investigate at least 1.4% of the total estimated number of suspected and possible LSLs each year.  To start, that would be roughly 1,400 properties a year and decline to zero as they make process.  This is in addition to the roughly 5,250 replacements the utility must complete a year through the accelerated LSL replacement program as well as routine processes such as water main replacement, road improvement programs, and leak fixes. Overall, such a strategy pragmatically recognizes uncertainty, while setting benchmarks to improve the LSL inventory overtime.

Ensuring an Effective Filter Program

Part of the success of Denver Water’s plan hinges on an effective program to protect people with LSLs until the lines are replaced and lead levels reduced.  While the utility estimates 65,000-85,000 known, suspected, and possible LSLs, Denver Water plans to distribute roughly 150,000 NSF-53 certified-filter kits by March 2020. 

However, a filter is ineffective if it is not used.  And, unlike other measures to reduce lead in water, relying on the use of filters requires ongoing and active cooperation by the customer.  Thus, the “filter adoption rate” (the percentage of residents actually using and regularly replacing the filter cartridge) is key to success.  As part of its program evaluation, Denver Water plans to conduct an annual survey to identify the filter adoption rate, and if rates fall below a to-be-determined benchmark over the course of three years, Denver Water will default to orthophosphate treatment – a complex, multiyear endeavor (see p. 13 and p. 78-79). Further, Denver Water is currently conducting a pilot of 300 customers to set initial benchmarks for its filter adoption rate and will refine their approach based on the outcome.  EDF is interested to see what a realistic adoption rate will be under this voluntary program.

Sequencing LSL Replacement

Unfortunately, all of the LSLs cannot be removed overnight.  This may create challenges as some customers will likely want to jump to the front of the “LSL replacement line” as they become more educated about the risks of lead in water as well as benefits of LSL replacement (e.g., protecting health, increasing value of home at sale).

Denver Water’s approach to sequencing and prioritizing LSL replacement, which relies on predictive modeling, may help manage this challenge.  In addition to factors such as logistics and incorporation into existing infrastructure projects, Denver Water plans to schedule LSL replacements based on a number of risk-based factors to address health equity. Such factors include:

  • Public health considerations (e.g., odds ratio for childhood lead poisoning);
  • Areas where filter adoption is low;
  • Critical customers (e.g., child care, primary schools, nursing facilities);
  • Age-related considerations (e.g., probability of children under 5 years, adults over 70 years, or women of childbearing age); and
  • Social economic factors (e.g., under federal poverty level).

We anticipate that clear communication of the risk factors considered while sequencing replacement will be critical to manage customer expectations.

Ongoing Guidance

These are complicated issues. Fortunately, Denver Water is proposing to convene a Leadership Committee to provide guidance during the design and implementation of the plan, which will meet at least every six months.  The Committee is to be made up of representatives appointed by the EPA, CDPHE, Denver Water as well as other invited stakeholders such as from watershed groups, wastewater dischargers, and public health agencies.  Notably missing from the Committee’s membership are community members affected by the Lead Reduction Program Plan.  That omission may undermine its credibility and effectiveness.


EDF supports Denver Water’s plan as an innovative solution to a challenging problem. We’re hopeful that this type of resilient solution can be adopted and replicated to both protect public health and prevent degradation of our natural systems.

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