Prosser City WWTP
999 Grande Rd, Prosser, WA 99350 · Benton County · Publicly Owned Treatment Works
- Average flow
- 0.74 MGD
- Design flow
- —
- NPDES permit
- WAR303447
- Terminated
- Permit expires
- December 2020
- Population served
- 6,616
- CWNS 2022
Prosser City WWTP is a publicly owned wastewater treatment works in Prosser, Benton County, Washington treating an average of 0.74 million gallons per day, serving about 6,616 residents. It discharges under NPDES permit WAR303447 (terminated), which expires in December 2020, with 9 recorded violations in the last three years. EPA has recorded 1 formal enforcement action naming the plant, the latest in October 2025.
Treatment technology
4 treatment structures and unit processes identified at Prosser City WWTP.
Available with a free Klarifi account
See the full treatment train at Prosser City WWTP: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 9
- Effluent violations
- 2
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
EPA enforcement history
Federal civil enforcement cases, compliance inspections and informal actions recorded for Prosser City WWTP in EPA's ICIS system.
- Formal actions
- 1
- 1 since FY2020
- Penalties assessed
- $1,500
- all cases
- Compliance actions
- $4,000
- required by EPA orders
- EPA inspections
- 0
- none on record
Latest case · Oct 2025
Prosser POTW Biosolids ESA CWA 309G2E AO For Class I Penalties - Biosolids Expedited Settlement Prog
Administrative order · CWA, NPDES Permit Violations · Final Order With Penalty · Penalty $1,500 · Compliance actions $4,000
EPA's description of the case:
“Land applied Class B biosolids above ceiling concentration limits under 40 CFR 503.13”
Source: EPA ECHO, civil enforcement case 07-2025-0121.
Full case history with a free Klarifi account
Every action against Prosser City WWTP with dates, milestones, violation types and EPA's complete case summaries, plus inspections and informal actions.
Key contacts
Decision-makers at Prosser City WWTP.
No verified contacts on file yet
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Nearby wastewater treatment plants in Washington
Grandview · 7 mi away
0.93 MGD
Mabton · 11 mi away
0.15 MGD
Sunnyside · 13 mi away
1.64 MGD
Sunnyside · 14 mi away
1.34 MGD
Benton City · 14 mi away
0.23 MGD
Granger · 22 mi away
0.17 MGD
Richland · 23 mi away
5.91 MGD
Zillah · 27 mi away
0.2 MGD
Prosser City WWTP: 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 20, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Anaerobic digester · Lift station · all terms