Monroe STP
806 W Main St, Monroe, WA 98272 · Snohomish County · Publicly Owned Treatment Works
- Average flow
- 1.79 MGD
- Design flow
- —
- NPDES permit
- WA0020486
- Administratively continued
- Permit expires
- November 2023
- Population served
- 19,838
- CWNS 2022
Monroe STP is a publicly owned wastewater treatment works in Monroe, Snohomish County, Washington treating an average of 1.79 million gallons per day, serving about 19,838 residents. It discharges under NPDES permit WA0020486 (administratively continued), which expires in November 2023, with 0 recorded violations in the last three years.
Treatment technology
One treatment structure or unit process identified at Monroe STP.
Available with a free Klarifi account
See the full treatment train at Monroe STP: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 0
- Effluent violations
- 0
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Capital improvement projects in Monroe
Monroe's capital improvement plan lists 51 water, sewer and wastewater line items worth $101M starting 2025–2030. The largest budgeted items are shown here.
All water and sewer capital projects in Monroe →
| Project | Budget | Years |
|---|---|---|
| Biosolids Treatment Project (CIP 5) | $29,241,700 | 2025–2026 |
| CIP 3 Membrane Enhanced Trtmnt | $17,966,882 | 2029–2030 |
| Valley View Pump Station Upgrades | $6,427,480 | 2026–2027 |
| Fryelands PS and FM Upgrades | $5,469,269 | 2029–2030 |
| Trombley Hill from Reservoir to Airport/179th SE | $4,052,933 | 2025–2026 |
Full project details — scope, funding source, engineering consultant and the decision-makers behind each project — are available in Klarifi, along with similar wastewater capital projects in other cities.
Key contacts
Decision-makers at Monroe STP.
No verified contacts on file yet
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Nearby wastewater treatment plants in Washington
Sultan · 7 mi away
0.59 MGD
Granite Falls · 16 mi away
0.41 MGD
Edmonds · 16 mi away
2.45 MGD
Edmonds · 17 mi away
3.96 MGD
Marysville · 20 mi away
0.2 MGD
Seattle · 25 mi away
106.93 MGD
Kingston · 25 mi away
0.16 MGD
Renton · 29 mi away
74.4 MGD
Monroe 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 19, 2026; facility record last updated November 29, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Equalization tank · Centrate · all terms