Pierce Island Wastewater Treatment Plant
200 Pierce Island Rd, Portsmouth, NH 03801 · Rockingham County · Publicly Owned Treatment Works
- Average flow
- 3.28 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 3.28 million gallons per day against a permitted design capacity of 4.8 MGD, serving about 22,900 residents. It discharges under NPDES permit NH0100234 (effective), which expires in November 2028, with 47 recorded violations in the last three years. EPA has recorded 4 formal enforcement actions naming the plant, the latest in February 2013.
Treatment technology
2 treatment structures and unit processes identified at Pierce Island Wastewater Treatment Plant.
Available with a free Klarifi account
See the full treatment train at Pierce Island Wastewater Treatment Plant: structures, unit processes and planned upgrades, with exact unit counts.
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.
EPA enforcement history
Federal civil enforcement cases, compliance inspections and informal actions recorded for Pierce Island Wastewater Treatment Plant in EPA's ICIS system.
- Formal actions
- 4
- 0 since FY2020
- Penalties assessed
- $100,000
- all cases
- Compliance actions
- $140M
- required by EPA orders
- EPA inspections
- 0
- none on record
Latest case · Feb 2013
PORTSMOUTH WWTP
Judicial case · CWA, NPDES Permit Violations · Final Order No Penalty · Compliance actions $140M
EPA's description of the case:
“Modification of Consent Decree to impose secondary treatment schedule and adjust CSO schedule. Consent Decree Modification lodged on 7/25/2012. THE CITY OF PORTSMOUTH HAS VIOLATED THE CLEAN WATER ACT…”
Unlock EPA's full description by creating a free account on Klarifi. Create a free account →
Source: EPA ECHO, civil enforcement case 01-2007-2027.
Full case history with a free Klarifi account
Every action against Pierce Island Wastewater Treatment Plant with dates, milestones, violation types and EPA's complete case summaries, plus inspections and informal actions.
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
0.11 MGD
Rye · 3 mi away
0.0005 MGD
Dover · 8 mi away
2.18 MGD
Durham · 9 mi away
0.72 MGD
Newmarket · 10 mi away
0.44 MGD
Hampton · 11 mi away
2.24 MGD
Exeter · 11 mi away
1.45 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 October 26, 2026; facility record last updated April 5, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Lift station · Sludge dewatering · all terms