Grand Mound STP
Rochester, WA · Thurston County · Publicly Owned Treatment Works
- Average flow
- —
- Design flow
- 1.52 MGD
- NPDES permit
- WA0042099
- Effective
- Permit expires
- February 2029
- Population served
- 2,555
- CWNS 2022
Grand Mound STP is a publicly owned wastewater treatment works in Rochester, Thurston County, Washington, serving about 2,555 residents. Treatment on site includes clarifiers, carrousels / oxidation ditches. It discharges under NPDES permit WA0042099 (effective), which expires in February 2029, with 3 recorded violations in the last three years.
Treatment technology
Treatment structures identified at this facility. Exact unit counts are available in Klarifi.
Compliance snapshot (last 3 years)
- Total violations
- 3
- Effluent violations
- 2
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Grand Mound STP.
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Nearby wastewater treatment plants in Washington
Littlerock · 8 mi away
0.04 MGD
Olympia · 19 mi away
—
Chehalis · 21 mi away
0.03 MGD
Winlock · 22 mi away
0.15 MGD
Ryderwood · 29 mi away
—
Montesano · 30 mi away
0.24 MGD
Shelton · 34 mi away
0.000000013 MGD
University Place · 35 mi away
17.07 MGD
Grand Mound 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 May 29, 2025.