Clean Water Services Thermal Trading — Riparian Shade Planting Credited Against Wastewater Heat Discharge on Oregon's Tualatin River (USA)

Clean Water Services, the wastewater and stormwater utility of Washington County, Oregon, meets temperature limits on its discharges to the Tualatin River by buying thermal credits rather than building chillers: it plants and maintains streamside trees with farmers and public agencies and releases stored water from Hagg Lake and Barney Reservoir.
Its 2025 annual trading report records 221 active planting projects generating about 660 million kcal/day of thermal credit, 10 new projects in 2025 covering over 7 stream miles (~17 million kcal/day), and stored-water releases and an instream lease worth 1,535 and 1,895 million kcal/day in July and August. The credits are reported to fully offset the thermal load of its Rock Creek, Durham and Forest Grove plants.
Caution: credits are modelled, not measured. The programme manager told reporters that stream temperature is naturally variable and the benefit of shading is hard to separate from other factors, and critics call Oregon's thermal-trading rules expensive and unproven. Projects are selected for broader ecological uplift (habitat, cold-water refugia), which is the main verifiable co-benefit.

Read the full analysis: https://cleanwaterservices.org/wp-content/uploads/2026/03/2025-Water-Quality-Credit-Trading-Annual-Report.pdf