0

Regulation 85 - Nutrients Management Control Regulation

An image of the Fort Collins municipal wastewater treatment plant in northern Colorado.

What is the Reg. 85?

Regulation 85, Nutrients Management Control Regulation, was adopted in 2012 to improve water quality by reducing nutrient concentrations in state waters. The current Regulation 85 technology-based effluent limits are set to expire in December 2027. If Regulation 85 were to expire, more stringent nutrient standards for lakes and reservoirs would take effect. The resulting more rigorous permit limits could result in ambiguous regulation for some dischargers.
The division and stakeholders agreed that we need more time to evaluate the results from the feasibility and implementation subgroup work to develop a longer-term regulatory approach to reduce nutrients statewide.

At the 2025 Water Quality Forum annual retreat, stakeholders agreed to a two-phase approach to extending and updating Regulation 85: 

  • Phase 1 (2026-2027) will include stakeholder working group discussions focused on extending the existing Regulation 85 beyond 2027. We plan to propose changes by late 2026 and hold a rulemaking hearing in the fall of 2027.
  • Phase 2 (2028-2029) will include stakeholder working group discussions focused on developing a longer-term statewide nutrient control regulation (e.g., updated Regulation 85). Our goal is to incorporate lessons learned from the feasibility & implementation efforts and to have a fully developed redline of proposed changes by late 2029 in order to conduct a rulemaking hearing in the Fall of 2030.

The division is hosting informal topical discussion groups to contribute to this effort. The division will update and inform stakeholders about discussion group progress during routine Water Quality Roadmap meetings.

Sign up for Regulation 85 topical task group discussion meetings

  • Voluntary Incentive Program discussion
  • Nonpoint source
  • Monitoring
  • MS4 (existing quarterly meetings with Stormwater Council, ongoing updates to MS4 permits)

How to get involved