Arsenic Water Quality Standards

 

Right now - arsenic is regulated in wastewaters statewide due to water quality standards that were conceived of over 20 years ago. Because arsenic can be quite detrimental to human health and for surface waters that are a source of drinking water, it is important to protect the drinking water supply by adopting protective standards.

Colorado has surface water standards to protect both drinking water (water supply) and fish ingestion. The surface water standard for water supply is 20 nanograms per liter (ng/L). This is quite low, and comparable to the PFAS maximum contaminant levels proposed by EPA (4 nanograms per liter).

The Safe Drinking Water Act regulates arsenic at 10 micrograms per liter (ug/L), or 10,000 nanograms per liter as a maximum contaminant level (or MCL). Also, the practical quantitation limit, or PQL for arsenic currently stands at about 1 micrograms per liter. Having such large discrepancies between the water quality standard, the drinking water MCL, and the PQL creates challenges in implementation of standards within the permitting framework.

The division worked with stakeholders and the commission throughout the 2010s and the early part of this decade to implement statewide temporary modifications because of uncertainty in what the standard should be, and the challenges presented by these discrepancies. While being an interim solution that is unique to Colorado, this solution is only temporary. Each time we extend it, we have to get it approved by our partners at EPA Region 8. Colorado has utilized the temporary modification tool since 2011 (Reg. No. 38.79) to recognize the underlying, use-based standard as a goal while using the level generally deemed to be technologically feasible to set permit limits (i.e., 0.02-3 ug/L). Currently, the arsenic temporary modification is scheduled to expire in 2029. 

As part of the Water Quality Roadmap, the division is currently scoping out what implementation of the protective arsenic standards will look like in the permitting framework. Keep informed of our progress through our quarterly roadmap meetings, which will also offer regular stakeholder input opportunities. The next Roadmap meeting will be held on March 5, 2026.

➽ Tyson Ingels, Watershed & Engineering Program Manager

Coaches' Classroom: Public Notices: Division Tools and Templates to Cover All Your Bases

The public notification rule establishes requirements for public water systems to communicate any problems about the water to anyone using the water they produce. Specifically, problems related to meeting drinking water standards, failing to test the water, or other situations related to protecting the health of consumers all require public notice and must meet the requirements in the Colorado Primary Drinking Water Regulations (Regulation 11).  

Resources
Public Notice Templates are a great tool for efficiently meeting the regulatory requirements. The templates can be generated using our online public notice generator tool. Using the generator tool ensures that your public notice contains the 10 required elements of a public notice, as well as any specific required language.  

Choosing the correct violation category
There are three tiers of public notice:  

• Tier 1 is required for the most immediate potential public health impacts.
• Tier 2 is for situations with potential to have serious effects, such as exceeding a maximum contaminant level.
• Tier 3 is for violations and situations that may not directly impact public health. 

In addition to the tier levels for public notification, public notices may have different language requirements depending on the specific violation. Field-based violations are those that are identified during sanitary survey inspections. When creating a public notice for a field-based violation, you will select the violation category that lists “sanitary survey identified violations - Tier 2 or 3” (see image below). The template will contain instructions and a link to the Public Notice Health Effects Language for Sanitary Survey Tier 2 Violations chart, which provides the language required to be entered for each violation found on your Sanitary Survey findings letter. You will also need to add the description of each violation, the date the violations need to be corrected, and the steps you are taking to correct them in the table provided in the template you generate. Once completed, you are ready to deliver the notices to your customers per the tier requirements. After you distribute the public notice(s), please submit a final copy, along with a certificate of delivery to the drinking water portal.   

Consumer Confidence Reports to Meet Public Notification Requirements
Community public water systems are required to complete a Consumer Confidence Report (CCR) each year.  Under some circumstances, a Tier 3 public notice requirement can be met using the CCR. 

1. The CCR must fall within 1 year of learning of the violation.
2. The CCR must be delivered using a direct delivery method.
3. All 10 public notice elements must be included.

While Tier 2 violations can’t be satisfied with the CCR, all unresolved violations and significant deficiencies are required to be reported on the CCR, this includes those listed on a corrective action plan for a Sanitary Survey deficiency. 

Want to learn more?
If you are interested in learning more about field violations during a sanitary survey and how to complete your public notice requirements, sign up for one of our upcoming free Sanitary Survey Preparation Trainings. If you have more specific questions about health-based violations and PN requirements, join us for our Monitoring and Operating for Regulatory Compliance (MORC) training. All of our training is free and offered in virtual or face-to-face formats.

➽ Angela Green Garcia, Drinking Water Training Specialist