Riddle STP
Riddle, OR · Douglas County · Publicly Owned Treatment Works
- Average flow
- 0.07 MGD
- Design flow
- 1 MGD
- NPDES permit
- OR0020630
- Administratively continued
- Permit expires
- March 2010
- Population served
- 973
- CWNS 2022
Riddle STP is a publicly owned wastewater treatment works in Riddle, Douglas County, Oregon treating an average of 0.07 million gallons per day against a permitted design capacity of 1 MGD, serving about 973 residents. Treatment on site includes clarifiers. It discharges under NPDES permit OR0020630 (administratively continued), which expires in March 2010, with 33 recorded violations in the last three years.
Treatment technology
Treatment structures identified at this facility. Exact unit counts are available in Klarifi.
Clarifiers
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Compliance snapshot (last 3 years)
- Total violations
- 33
- Effluent violations
- 12
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Riddle STP.
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Oakland · 31 mi away
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Grants Pass · 36 mi away
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Powers · 36 mi away
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Shady Cove · 37 mi away
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Riddle STP: frequently asked questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed September 11, 2026; facility record last updated February 27, 2025.