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Overview
The GIS dataset represents approximate service areas for sewer systems operated by publicly owned treatment works (POTWs), sewer districts and non-POTW systems. Some of these discharge to surface water (requiring a National Pollutant Discharge Elimination System (NPDES) permit), while others have a groundwater discharge (GWD) permit (required for systems discharging over 10,000 gallons per day (GPD) in Massachusetts). In 2017, as part of its "Enhancing Resilience and Emergency Preparedness of Water Utilities through Improved Mapping" (Critical Infrastructure Mapping Project), the MassDEP Water Utility Resilience Program (WURP) began to uniformly map NPDES-permitted POTW service areas throughout Massachusetts using information collected from various sources. WURP began mapping GWD-permit facilities in 2022. Along with confirming this service area information, the MassDEP Water Utility Resilience Program Mapping Project collected and verified estimated service area delineations for NPDES and GWD permitted systems not previously delineated and will continue to update the information contained in the datalayers. As of the date of publication, WURP has delineated POTWs and non-POTWs with NPDES and GWD permits (for systems discharging over 10,000 GPD).
The polygon data are stored and distributed as the following feature classes:
- SEWER_SERVICE_AREA_POTW_POLY (publicly owned treatment works)
- SEWER_SERVICE_AREA_NONPOTW_POLY (non-publicly owned treatment works)
In addition, there is a table of Unlocated Sites which contains a list of known, unmapped active POTW and NON-POTW services areas at the time of publication:
- SEWER_SERVICE_AREA_USL
Attributes
The polygon attribute table for the POTW Sewer Service Area dataset (SEWER_SERVICE_AREA_POTW_POLY) contains the following fields:
| Field Name | Alias | Data Type | Description |
|---|---|---|---|
| OBJECTID | OBJECTID | Object ID | (ESRI generated) |
| Shape | SHAPE | Geometry | meters (ESRI generated) |
| Shape_Length | Shape_Length | Double | meters (ESRI generated) |
| Shape_Area | Shape_Area | Double | meters (ESRI generated) |
| SYSTNAME | System Name | Text | Name of system |
| PERMIT_ID | Permit ID | Text | Current Permit ID |
| ORIG_PERMIT_ID | Original Permit ID | TEXT | Original Permit ID (from historic records) |
| SEWER_ID | Sewer Area ID | Text | Combination ID (Town Name & Permit ID) |
| PERMIT_DATE | Permit Date | DATE | NPDES Permit: effective date (source: EPA ICIS) GWD Permit: start date (source: MassDEP Groundwater Database) |
| DISCHG_TYP | Discharge Type | Text | Ground, Surface, or Both. Note: data for the primary permit is associated with the polygon if the system has both discharge types |
| TRTMTPLANT | Treatment Plant | Text | Name of treatment plant |
| TOWNNAME | Town Name | Text | MassGIS City/Town name |
| TOWN_ID | Town ID | Short | MassGIS City/Town ID number |
| OWNER_TYPE | Ownership Type | Text | Municipal, Regional/District, State, Federal, or Private |
| FAC_TYPE | Facility Type | Text | POTW or Non-POTW |
| SECTOR | Sector | Text |
|
| REGION | DEP Region | Text | MassDEP Region: WE, CE, NE, SE |
| REGION_ID | DEP Region ID | Short | MassDEP Region ID |
| ADDRESS | Address | Text | Permittee Address |
| BASIN | Major Basin | Text | Basin (watershed) discharge is located |
| SA_SQMI | Service Area Square Miles | Double | Area of POTW service area, calculated from GIS Shape Area (ESRI generated) |
| SA_ACRES | Service Area Acres | Double | Area of POTW service area, calculated from GIS Shape Area (ESRI generated) |
| MUNI_SQMI | Municipal Area Square Miles | Double | Area of town boundary (field: SUM_SQUARE_MILES) |
| PERCNTAREA | Percent AREA Served by System | Double | Percent of town area served by POTW (POTW_AREA_SQMI/ TOWN_AREA_SQMI) |
| SERVCECONF | Service Area Confirmed | Text | Indicates whether service area was confirmed by system |
| SERVCEYEAR | Service Area Year | Short | Year service area is valid for |
| MULTIPOTW | Multiple POTW | Double | Number if sewer systems serving municipality |
| MULTIPOTW_D | Multiple POTW description | Text | List of POTWs serving municipality |
| PERCSERV | Percent Served by System | Text | Percent of Town served by system |
| PERSERDET | Percent Served Details | Text | Percent served source detailed |
| PERSOURCE | Percent Source | Text | Percent source |
| PERYEAR | Percent Year | Text | Percent year |
| PERCALL | Percent Served by All Systems | Text | Percent of Town served by All systems |
| MUNI_POP | Population of Municipality | Long | Population of municipality |
| POP_SRC | Population Source | Text | Population source |
| POP_SRC_DATE | Population Source Date | Long | Population source date (year) |
| PARINSA | Parcels in Service Area | Long | Parcels in service area |
| DEVPARINSA | Developed Parcels in Service Area | Long | Developed parcels in service area |
| PCTDEVPARINSA | Pct. Dev. Parcels in Service Area | Double | Percent developed parcels in service area |
| PCTDEVPARINMUNI | Pct. Dev. Parcels in Municipality | Double | Percent developed parcels in municipality |
The polygon attribute table for the Non-POTW Sewer Service Area dataset (SEWER_SERVICE_AREA_NONPOTW_POLY) contains the following fields:
| Field Name | Alias | Data Type | Description |
|---|---|---|---|
| OBJECTID | OBJECTID | Object ID | (ESRI generated) |
| Shape | SHAPE | Geometry | meters (ESRI generated) |
| Shape_Length | Shape_Length | Double | meters (ESRI generated) |
| Shape_Area | Shape_Area | Double | meters (ESRI generated) |
| SYSTNAME | System Name | Text | Name of system |
| PERMIT_ID | Permit ID | Text | Current Permit ID |
| ORIG_PERMIT_ID | Original Permit ID | TEXT | Original Permit ID (from historic records) |
| SEWER_ID | Sewer Area ID | Text | Combination ID (Town Name & Permit ID) |
| PERMIT_DATE | Permit Date | DATE | NPDES Permit: effective date (source: EPA ICIS) GWD Permit: start date (source: MassDEP Groundwater Database) |
| DISCHG_TYP | Discharge Type | Text | Ground, Surface, or Both. Note: data for the primary permit is associated with the polygon if the system has both discharge types |
| TRTMTPLANT | Treatment Plant | Text | Name of treatment plant |
| TOWNNAME | Town Name | Text | MassGIS City/Town name |
| TOWN_ID | Town ID | Short | MassGIS City/Town ID number |
| ACTORNAME | Owner Information | Text | Owner/operator name |
| OWNER_TYPE | Ownership Type | Text | Municipal, Regional/District, State, Federal, or Private |
| FAC_TYPE | Facility Type | Text | POTW or Non-POTW |
| SECTOR | Sector | Text |
|
| REGION | DEP Region | Text | MassDEP Region: WE, CE, NE, SE |
| REGION_ID | DEP Region ID | Short | MassDEP Region ID |
| ADDRESS | Address | Text | Permittee Address |
| BASIN | Major Basin | Text | Basin (watershed) discharge is located |
| SA_SQMI | Service Area Square Miles | Double | Area of POTW service area, calculated from GIS Shape Area (ESRI generated) |
| SA_ACRES | Service Area Acres | Double | Area of POTW service area, calculated from GIS Shape Area (ESRI generated) |
| SERVCECONF | Service Area Confirmed | Text | Indicates whether service area was confirmed by system |
| SERVCEYEAR | Service Area Year | Short | Year service area is valid for |
Related Table
Unmapped Sewer Service Areas: A related table SEWER_SERVICE_AREA_USL contains a list of known, unmapped active POTW and Non-POTW sewer service areas at the time of publication.
| Field Name | Alias | Data Type | Description |
|---|---|---|---|
| SYSTNAME | System Name | Text | Name of system |
| PERMIT_ID | Permit ID | Text | Current Permit ID |
| SEWER_ID | Sewer Area ID | Text | Combination ID (Town Name & Permit ID) |
| TOWNNAME | Town Name | Text | MassGIS City/Town name |
| ADDRESS | Address | Text | Permittee Address |
| ACTORNAME | Owner Information | Text | Owner/operator name |
Production
Data Universe
Effluent wastewater treatment plants in Massachusetts are permitted either through the Environmental Protection Agency’s (EPA) National Pollutant Discharge Elimination System (NPDES) surface water discharge permit program or the MassDEP Groundwater Discharge Permit Program. The WURP has delineated active service areas served by publicly and privately-owned effluent treatment works with a NPDES permit or a groundwater discharge permit.
National Pollutant Discharge Elimination System (NPDES) Permits
In the Commonwealth of Massachusetts, the EPA is the permitting authority for regulating point sources that discharge pollutants to surface waters. NPDES permits regulate wastewater discharge by limiting the quantities of pollutants to be discharged and imposing monitoring requirements and other conditions. NPDES permits are typically co-issued by EPA and the MassDEP. The limits and/or requirements in the permit ensure compliance with the Massachusetts Surface Water Quality Standards and Federal Regulations to protect public health and the aquatic environment. Areas served by effluent treatment plants with an active NPDES permit are included in this datalayer based on a master list developed by MassDEP based on information sourced from the EPA’s Integrated Compliance Information System (ICIS).
Groundwater Discharge (GWD) Permits
In addition to surface water permittees, the WURP has delineated all active systems served by publicly and privately owned effluent treatment works with groundwater discharge (GWD) permits, and some inactive service areas. Groundwater discharge permits are required for systems discharging over 10,000 GPD sanitary wastewater – these include effluent treatment systems for public, district, or privately owned effluent treatment systems. Areas served by an effluent treatment plant with an active GWD permit are included in this datalayer based on lists received from MassDEP Wastewater staff.
Creation of Unique IDs for Each Service Area
The Sewer Service Area datalayer contains polygons that represent the service area of a particular wastewater system within a particular municipality. Every discharge permittee is assigned a unique NPDES permit number by EPA or a unique GWD permit identifier by MassDEP. MassDEP WURP creates a unique Sewer_ID for each service area by combining the municipal name of the municipality served with the permit number (NPDES or GWD) ascribed to the sewer that is serving that area. Some municipalities contain more than one sewer system, but each sewer system has a unique Sewer_ID. Occasionally the area served by a sewer system will overlap another town by a small amount – these small areas are generally not given a unique ID. The Estimated sewer Service Area datalayer, therefore, contains polygons with a unique Sewer_ID for each sewer service area. In addition, some municipalities will have multiple service areas being served by the same treatment plant – the Sewer_ID for these will contain additional identification, such as the name of the system, to uniquely identify each system.
Classifying System Service Areas
WURP staff reviewed the service areas for each system and, based on OWNER_TYPE, classified as either a publicly-owned treatment work (POTW) or a non-POTW (see FAC_TYPE field). Each service area is further classified based on the population type served (see SECTOR field).
Methodologies and Data Sources
Several methodologies were used to create service area boundaries using various sources, including data received from the systems in response to requests for information from the MassDEP WURP project, information on file at MassDEP, and service area maps found online at municipal and sewer system websites. When MassDEP received sewer line data rather than generalized areas, 300-foot buffers were created around the sewer lines to denote service areas and then edited to incorporate generalizations. Some municipalities submitted parcel data or address information to be used in delineating service areas. Many of the smaller GWD permitted sewer service areas were delineated using parcel boundaries related to the address on file.
Verification Process
Small-scale pdf file maps with roads and other infrastructure were sent to systems for corrections or verifications. If the system were small, such as a condominium complex or residential school, the relevant parcels were often used as the basis for the delineated service area. In towns where 97% or more of their population is served by the wastewater system and no other service area delineation was available, the town boundary was used as the service area boundary. Some towns responded to the request for information or verification of service areas by stating that the town boundary should be used since all, or nearly all, of the municipality is served by one wastewater system.
To ensure active systems are mapped, WURP staff developed two work flows. For NPDES-permitted systems, WURP staff reviewed available information on EPA’s ICIS database and created a master list of these systems. Staff will work to routinely update this master list by reviewing the ICIS database for new NPDES permits. The master list will serve as a method for identifying active systems, inactive systems, and unmapped systems.
For GWD permittees, GIS staff established a direct linkage to the groundwater database, which allows for populating information into data fields and identifying active systems, inactive systems, and unmapped systems.
All unmapped systems are added to the Sewer Service Area Unlocated List (SEWER_SERVICE_AREA_USL) for future mapping. A secondary method for quality control is comparing mapped discharge points to the NPDES master list of active systems and the active list of GWD permitholders. Some service areas have not been mapped but their general location is represented by a small circle which serves as a placeholder - the locations of these circles are estimated based on the general location of the treatment plant or the general estimated location of the service area - these do not represent the actual service area.
Percent Served Statistics
The attribute table for the POTW sewer service areas (SEWER_SERVICE_AREA_POTW_POLY) has several fields relating to the percent of the town served by the particular system and one field describing the percent of town served by all systems in the town. The field ‘Percent AREA Served by System’ is strictly a calculation done dividing the area of the system by the total area of the town and multiplying by 100. In contrast, the field ‘Percent Served by System’, is not based on a particular calculation or source – it is an estimate based on various sources – these estimates are for planning purposes only. Data includes information from municipal websites and associated plans, the 1990 Municipal Priority list from CMR 310 14.17, the 2004 Pioneer Institute for Public Policy Research “percent on sewer” document, information contained on NPDES Permits and MassDEP Wastewater program staff input. Not all POTW systems have percent served statistics. Percentage may reflect the percentage of parcels served, the percent of area within a community served or the population served and should not be used for legal boundary definition or regulatory interpretation.
Sources of information for estimated wastewater service areas
Maps of service areas for these systems were collected from various sources to create service areas digitally in GIS, including data received from the system in response to requests for information from the MassDEP WURP project, information on file at MassDEP, and service area maps found online at municipal and wastewater system websites. The following information was used to develop estimated drinking water service areas:
- EEOA Water Assets Project (2005) sewer lines (these were buffered to create service areas)
- Horsely Witten Report (2008)
- Municipal Master Plans, Open Space Plans, Facilities Plans, Wastewater and Sewer System Webpages, reports and online interactive maps
- GIS data received from POTWs and NON-POTWs
- Detailed infrastructure mapping completed through the MassDEP WURP Critical Infrastructure Initiative
In the absence of other service area information, for municipalities served by a town-wide sewer system serving at least 97% of the population, the municipality’s boundary was used. Percent served information and determinations of which municipalities are 97% or more served by the wastewater system were made based on the Percent Sewer Service Map created in 2018 by MassDEP based on various sources of information including but not limited to:
- The number of services as a percent of developed parcels
- Taken directly from a Master Plan, Sewer Department Website, Open Space Plan, etc. found online
- Calculated using information from the town on population served
- MassDEP staff estimate
- Horsely Witten Report 2008 or Pioneer Institute 2004
- Calculated from Sewer System Areas Mapped through MassDEP WURP Critical Infrastructure Initiative, 2017-2022
Information found in publicly available POTW planning documents submitted to MassDEP or as part of infrastructure planning. Additionally, information for towns usually does not include permitted privately owned groundwater discharge systems. See attribute information for more details on percent served sources.
Terms of Use
The MassDEP Estimated Sewer System Service Area Boundaries datalayer may not be complete, may contain errors, omissions, and other inaccuracies, and the data are subject to change. The user’s use of and/or reliance on the information contained in the draft Document (e.g. data) shall be at the user’s own risk and expense. MassDEP disclaims any responsibility for any loss or harm that may result to the user of this data or to any other person due to the user’s use of the Document.
All sewer service area delineations are estimates for broad planning purposes and should only be used as a guide. The data is not appropriate for site-specific or parcel-specific analysis. Not all properties within a sewer service area are necessarily served by the system, and some properties outside the mapped service areas could be served by the wastewater utility – please contact the relevant wastewater system. Not all service areas have been confirmed by the systems.
Please use the following citation to reference these data:
MassDEP. Water Utility Resilience Program. 2025. Publicly-Owned Treatment Work and Non-Publicly-Owned Sewer Service Areas (PubV2024_12).
We want to learn about the data uses. If you use this dataset, please notify WURP staff via email.
Maintenance
The MassDEP Estimated Sewer Service Area Boundaries datalayer will be updated based on information submitted by municipalities and sewer systems to the WURP and the wastewater programs. If you have questions, please email the WURP.
| Date published: | February 27, 2025 |
|---|---|
| Last updated: | March 26, 2025 |