Westerly Wastewater Treatment Facility
303 Boundary St, Marlborough, MA 01752 · Middlesex County · Publicly Owned Treatment Works
- Average flow
- 1.58 MGD
- Design flow
- 2.89 MGD
- NPDES permit
- MA0100480
- Effective
- Permit expires
- December 2026
- Population served
- 40,085
- CWNS 2022
Westerly Wastewater Treatment Facility is a publicly owned wastewater treatment works in Marlborough, Middlesex County, Massachusetts treating an average of 1.58 million gallons per day against a permitted design capacity of 2.89 MGD, serving about 40,085 residents. It discharges under NPDES permit MA0100480 (effective), which expires in December 2026, with 26 recorded violations in the last three years. EPA has recorded 2 formal enforcement actions naming the plant, the latest in December 2009.
Treatment technology
10 treatment structures and unit processes identified at Westerly Wastewater Treatment Facility.
Available with a free Klarifi account
See the full treatment train at Westerly Wastewater Treatment Facility: structures, unit processes and planned upgrades, with exact unit counts.
Compliance snapshot (last 3 years)
- Total violations
- 26
- Effluent violations
- 19
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 Westerly Wastewater Treatment Facility in EPA's ICIS system.
- Formal actions
- 2
- 0 since FY2020
- Compliance actions
- $25M
- required by EPA orders
- EPA inspections
- 1
- latest Sep 2023
Latest case · Dec 2009
MARLBORO WEST WWTF
Administrative order · CWA, NPDES Permit Violations · Final Order No Penalty · Compliance actions $25M
EPA's description of the case:
“On 12/11/09, EPA issued a CWA administrative order to the City of Marlboro that puts the city on a schedule to upgrade its westerly wastewater treatment plant in order to come into compliance with…”
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Source: EPA ECHO, civil enforcement case 01-2010-2001.
Full case history with a free Klarifi account
Every action against Westerly Wastewater Treatment Facility with dates, milestones, violation types and EPA's complete case summaries, plus inspections and informal actions.
Key contacts
17 verified contacts for Westerly Wastewater Treatment Facility, with validated emails and direct phone numbers.
Unlock 17 verified contacts (14 more than shown)
Names, validated emails and direct phone numbers for decision-makers at Westerly Wastewater Treatment Facility, plus the full compliance history and discharge data.
Nearby wastewater treatment plants in Massachusetts
Westborough · 4 mi away
4.86 MGD
Hudson · 6 mi away
1.33 MGD
Marlborough · 6 mi away
2.77 MGD
Millbury · 13 mi away
30.02 MGD
Wayland · 13 mi away
0.03 MGD
Concord · 17 mi away
0.83 MGD
Leicester · 17 mi away
0.13 MGD
Medfield · 18 mi away
0.77 MGD
Westerly Wastewater Treatment Facility: 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 19, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Ozonation · Activated sludge · all terms