Colton STP
54 Depot St, Colton, WA 99113 · Whitman County · Publicly Owned Treatment Works
- Average flow
- 0.08 MGD
- Design flow
- 0.38 MGD
- NPDES permit
- WA0023175
- Administratively continued
- Permit expires
- May 2020
- Population served
- 452
- CWNS 2022
Colton STP is a publicly owned wastewater treatment works in Colton, Whitman County, Washington treating an average of 0.08 million gallons per day against a permitted design capacity of 0.38 MGD, serving about 452 residents. It discharges under NPDES permit WA0023175 (administratively continued), which expires in May 2020, with 69 recorded violations in the last three years.
Treatment technology
2 treatment structures and unit processes identified at Colton STP.
Available with a free Klarifi account
See the full treatment train at Colton STP: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 69
- Effluent violations
- 69
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Colton STP.
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Nearby wastewater treatment plants in Washington
Pullman · 10 mi away
2.46 MGD
Clarkston · 11 mi away
0.69 MGD
Clarkston · 16 mi away
0.06 MGD
Palouse · 23 mi away
0.07 MGD
Pomeroy · 24 mi away
0.12 MGD
Colfax · 25 mi away
0.33 MGD
Endicott · 36 mi away
0.08 MGD
Oakesdale · 38 mi away
0.09 MGD
Colton 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 October 26, 2026; facility record last updated November 8, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Sludge dewatering · Biological nutrient removal · all terms