Highlights:

The PRF ponds continue to function well as designed to reduce suspended solids and phosphorus.

During 2025:

• PRF effectiveness was evaluated for significant changes over time and geospatially using the PRF statistical analysis tool available on the data portal.
• The Cottonwood Creek “treatment train” and both PRF ponds have effectively reduced phosphorus (TP) and total suspended solids (TSS) in storm flow conditions as designed for the last 10 years or more. 
• Although the Peoria Pond did not demonstrate the same benefit in WY 2025, the Perimeter Pond also demonstrated lower median TP and TSS concentrations downstream during  base flows.
• All monitored nutrients were reduced upstream to downstream of the stream reclamation projects completed on McMurdo Gulch.

The Cherry Creek basin has multiple pollutant reduction facilities (PRFs) in various locations throughout the watershed, most notably in Cottonwood Creek. Together, stream reclamation and wetland detention systems comprise a passive treatment train approach to reduce nutrients and sediments, especially during storm events.

These PRFs are monitored on an ongoing basis to assess water quality benefits upstream to downstream annually and over time.

While results from a single water year are often insufficient to support robust statistical analysis, annual calculations are included for reference. The analysis uses the PRF Statistics Tool available through the data portal to evaluate the statistical significance of upstream and downstream changes at PRFs during WY 2025. No statistically significant trends were observed across the Cottonwood Treatment Train as a whole during WY 2025 but some of the nitrogen fractions were lower downstream of both ponds during base flows. Additionally, limited stormflow sampling during the year likely reduced the ability to detect patterns that are typically observed under higher-flow conditions.

Cottonwood Treatment Train as a whole (Peoria Pond, Phases 1 and 2 of stream reclamation completed on Cottonwood Creek downstream, and the Perimeter Pond), Peoria Pond and Perimeter Pond all show statistically significant reductions of TP and TSS during stormflow conditions over the last 10 years. 

The McMurdo Gulch upstream to downstream concentration analysis continues to demonstrate statistically significant reductions of most nutrients since monitoring began at those sites.