Grand Mound STP
20248 Grand Mound Way SW, Rochester, WA 98579 · Thurston County · Publicly Owned Treatment Works
- Average flow
- 0.17 MGD
- 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 treating an average of 0.17 million gallons per day against a permitted design capacity of 1.52 MGD, serving about 2,555 residents. It discharges under NPDES permit WA0042099 (effective), which expires in February 2029, with 3 recorded violations in the last three years.
Treatment technology
2 treatment structures and unit processes identified at Grand Mound STP.
Available with a free Klarifi account
See the full treatment train at Grand Mound STP: structures, unit processes and planned upgrades, with exact unit counts.
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
0.05 MGD
Olympia · 19 mi away
12.08 MGD
Pe Ell · 20 mi away
0.31 MGD
Chehalis · 21 mi away
0.07 MGD
Winlock · 22 mi away
0.54 MGD
Yelm · 23 mi away
—
Olympia · 23 mi away
0.03 MGD
Toledo · 24 mi away
0.002 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 October 26, 2026; facility record last updated May 29, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Anaerobic digester · Lift station · all terms