In 2020 EPA began stakeholder engagement as part of its review of Microbial/Disinfection Byproducts (M/DBP) Rules. The M/DBP rules are an important suite of drinking water rules designed to protect the public from the acute risks associated with waterborne disease outbreaks by requiring strong treatment and disinfection. However, the rules also try to balance the chronic health risk associated with cancer from certain disinfection byproducts. The Safe Drinking Water Program engaged in this process and shared some of our thoughts and experiences with these rule.
Regarding microbial risks, the department shared experiences in evaluating sources of drinking water that could be Groundwater Under the Direct Influence (GWUDI) of surface water and disinfection treatment evaluations. We also recommended that EPA synchronize its timing of promulgating any new or updated M/DBP rules with final regulatory determinations regarding cyanotoxins and brominated disinfection byproducts.
We shared our belief that sources of drinking water initially identified as groundwater, but that are actually under the direct influence of surface water represent a significant public health risk from waterborne disease. This is because filtration treatment to remove pathogens like giardia and cryptosporidium is not required for groundwater sources. The Safe Drinking Water Program has long recognized this risk and developed a policy to determine whether groundwater sources were being directly influenced by surface water. This policy was developed in 2012 after extensive engagement with academic researchers and stakeholders across Colorado. Unfortunately, it takes well-specific evaluations to determine whether the source is indeed GWUDI. This is an impactful determination for the water system if their source is re-classified to GWUDI. We work with water systems to both gather data in support of these determinations and after determinations are made to see if a source can be improved to be able to be reclassified to groundwater and, if not, help move along the process to install surface water treatment. Over the last ten years of implementing the policy, we have evaluated about 456 wells, and 87 of them were determined to be GWUDI. Thus, addressing this source water risk is a significant public health protection advance. We also recommend that federal requirements or guidance specifically address hand-pumped wells often seen at campgrounds.
We further shared that as part of our evaluations of surface water treatment disinfection, we launched the Disinfection Outreach and Verification Effort (DOVE) around 2016. We are evaluating filtration and disinfection at each surface water treatment system in Colorado to ensure that log removal requirements in the surface water treatment rule are met. University research showed serious issues with EPA baffle factor guidance and that it was not sufficiently protective. As part of the DOVE process, about 70 percent of Colorado’s surface water treatment systems had some type of treatment or sampling location issue to address.
We also called to attention that distribution system problems can be a concern for all water systems, and not just surface water systems. The 2008 Salmonella outbreak at Alamosa, Colorado was at a groundwater system with deep wells and most likely caused by a storage tank deficiency. Issues with cross connections, tanks, etc. occur at all systems. Applying any proposed storage tank or cross connection rules only to surface water systems is not justified. Instead of only promulgating new rules, we also encouraged EPA to consider guidance and how they institute primacy requirements for states as part of their routine processes.
One topic of interest to EPA is considering requiring a numeric disinfectant residual concentration beyond a “trace” for all water systems. We shared Colorado’s experience involving studies that showed colorimetric “trace” readings were not reliable. The detection limit for chlorine was 0.09 mg/L. We also highlighted our data showing 300% fewer E. coli positive samples when chlorine residual was above 0.2 mg/L, and that we have had very few E. coli violations in Colorado since 2014. Finally, we shared our understanding of concerns about transition for historically non-disinfecting systems and that we think EPA should consider disinfection waivers for water systems with adequate source and other protections in place.
We also shared our our view DBP concerns are likely to be exacerbated going forward by a variety of source water quality issues. These issues include:
- Drought
- Wildfires
- Nutrients
- DBP Precursors
- Wastewater treatment “Effluent dominated” or impacted sources
It will be the mid-2020s before EPA fully updates the M/DBP rules, but these are highly impactful rules and we encourage water systems to be aware of and engaged in the process. Thank you.
➽ Ron Falco, P.E. Safe Drinking Water Program Manager
