Pierce Island Wastewater Treatment Plant
Portsmouth, NH · Rockingham County · Publicly Owned Treatment Works
- Average flow
- 2.38 MGD
- Design flow
- 4.8 MGD
- NPDES permit
- NH0100234
- Effective
- Permit expires
- November 2028
- Population served
- 22,900
- CWNS 2022
Pierce Island Wastewater Treatment Plant is a publicly owned wastewater treatment works in Portsmouth, Rockingham County, New Hampshire treating an average of 2.38 million gallons per day against a permitted design capacity of 4.8 MGD, serving about 22,900 residents. Treatment on site includes clarifiers, biogas balloons. It discharges under NPDES permit NH0100234 (effective), which expires in November 2028, with 47 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
- 47
- Effluent violations
- 20
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Capital improvement projects in Portsmouth
Portsmouth's capital improvement plan lists 11 water, sewer and wastewater line items worth $74M starting 2025–2027. The largest budgeted items are shown here.
All water and sewer capital projects in Portsmouth →
| Project | Budget | Years |
|---|---|---|
| Mechanic Street Pumping Station Upgrade | $25,550,000 | 2025–2031 |
| Annual Water Line Replacement | $10,000,000 | 2026–2031 |
| Annual Sewer Line Replacement | $9,000,000 | 2026–2031 |
| Wastewater Reuse at Pease Wastewater Treatment Facility | $8,400,000 | 2027–2031 |
| Peirce Island Wastewater Treatment Facility | $4,900,000 | 2025–2027 |
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
38 verified contacts for Pierce Island Wastewater Treatment Plant, with validated emails and direct phone numbers.
Unlock 38 verified contacts (35 more than shown)
Names, validated emails and direct phone numbers for decision-makers at Pierce Island Wastewater Treatment Plant, plus the full compliance history and discharge data.
Nearby wastewater treatment plants in New Hampshire
Portsmouth · 3 mi away
—
Portsmouth (newington) · 3 mi away
0.1 MGD
Rye · 3 mi away
0.0021 MGD
Dover · 8 mi away
1.91 MGD
Durham · 9 mi away
0.83 MGD
Newmarket · 10 mi away
0.35 MGD
Hampton · 11 mi away
2.08 MGD
Exeter · 11 mi away
1.1 MGD
Pierce Island 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 September 11, 2026; facility record last updated April 5, 2025.