Ilwaco Wastewater Treatment Plant
336 Elizabeth Ave SE, Ilwaco, WA 98624 · Pacific County · Publicly Owned Treatment Works
- Average flow
- 0.22 MGD
- Design flow
- 3.03 MGD
- NPDES permit
- WA0023159
- Effective
- Permit expires
- August 2030
- Population served
- 9,303
- CWNS 2022
Ilwaco Wastewater Treatment Plant is a publicly owned wastewater treatment works in Ilwaco, Pacific County, Washington treating an average of 0.22 million gallons per day against a permitted design capacity of 3.03 MGD, serving about 9,303 residents. It discharges under NPDES permit WA0023159 (effective), which expires in August 2030, with 4 recorded violations in the last three years.
Treatment technology
Treatment structures and unit processes at Ilwaco Wastewater Treatment Plant.
Treatment structure data not yet analyzed for this facility.
Compliance snapshot (last 3 years)
- Total violations
- 4
- Effluent violations
- 0
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Ilwaco Wastewater Treatment Plant.
No verified contacts on file yet
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Cathlamet · 27 mi away
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Ryderwood · 43 mi away
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Hoquiam · 48 mi away
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Castle Rock · 49 mi away
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Winlock · 50 mi away
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Longview · 51 mi away
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Ilwaco Wastewater Treatment Plant: 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 December 22, 2024.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Tertiary treatment · Significant industrial user · all terms