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:
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.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.
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.
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.On Dec. 16, 2019, USEPA granted Denver Water's variance request.
➽ Tyson Ingels, lead drinking water engineer
