Regulation 85 Monitoring Information
Overview
Colorado’s Regulations 31 and 85 (Nutrient Management Control Regulation) were adopted in 2012 to address nutrient pollution in the state’s surface waters.
Under the Clean Water Act, states and authorized tribes are responsible for establishing water quality standards that protect designated uses and aquatic ecosystems. Regulation 85 helps Colorado better understand and manage nutrient impacts by requiring certain permitted dischargers to collect and report nutrient monitoring data.
The information gathered through these monitoring efforts supports the evaluation of nutrient sources and conditions across Colorado and helps inform future water quality management decisions.
Regulation 31
Reg. 31 is the Water Quality Control Commission document that establishes statewide water quality regulations for surface waters.
Regulation 85
Reg. 85 establishes requirements for organizations holding a NPDES permit and with the potential to discharge either nitrogen or phosphorus to begin planning for nutrient treatment based on treatment technology and monitoring both effluents and streams for nitrogen and phosphorus.
Why Nutrient Monitoring Matters
Nitrogen and phosphorus are naturally occurring nutrients that play an essential role in healthy aquatic ecosystems. However, excessive concentrations can lead to water quality issues, including:
Excess N and P in aquatic systems can stimulate production of plant and microbial biomass, which leads to depletion of dissolved oxygen, reduced transparency and changes in biotic community composition. This effect is called eutrophication. In estuaries and coastal waters, nitrogen and phosphorus loading can cause hypoxic zones which are areas of extremely low dissolved oxygen. Hypoxic zones can have severe impacts on fisheries in areas such as the Gulf of Mexico.
Common sources of nutrients include:
Regulation 85 Requirements
Regulation 85 establishes monitoring requirements for certain facilities operating under Colorado Discharge System (CDPS) permits with the potential to discharge nitrogen and phosphorus. The monitoring data collected under Regulation 85 helps improve understanding of nutrient conditions across Colorado and supports science-based decision making.
Required monitoring activities may include:
CMF’s Role
CMF, in collaboration with the Colorado Water Quality Monitoring Council (CWQMC) and the Colorado Water Quality Control Division (WQCD), supports the implementation of Regulation 85 by providing technical resources, guidance, and opportunities for collaboration among regulated entities. CMF works to promote consistent monitoring practices, data sharing, and scientific analysis that support effective nutrient management throughout Colorado.
Sampling and Analysis Plan (SAP)
To assist regulated entities with meeting Regulation 85 requirements, CMF and the CWQMC developed a Sampling and Analysis Plan (SAP). This serves as a guidance document that organizations may adapt to support nutrient monitoring programs and develop monitoring approaches that meet regulatory requirements.
Monitoring Recommendations
While monitoring is only required at a few locations a few times throughout the year, both the CWQMC and CMF recommend establishing a comprehensive sampling plan that includes a variety of compounds. Parameters such as dissolved oxygen (DO), pH, and chlorophyll-A, temperature, and turbidity can provide valuable context for understanding water quality conditions and nutrient impact. Having a comprehensive picture of water quality that is both spatially and temporally diverse may allow for comprehensive models to be developed to expertly discuss and solve water quality problems on a site-specific basis.