November 2021

The 2021 Combined Sewer Overflow (CSO) spatial data layer shows the point locations of National Pollutant Discharge Elimination System (NPDES) permitted combined sewer overflow discharges. These outfalls occur in older cities in Massachusetts that still have areas of combined sewer and stormwater systems which overflow during heavy storm events. MassDEP has responsibility for ensuring that these systems, along with other sanitary sewer systems, are in compliance with the Clean Waters Act https://www.epa.gov/laws-regulations/summary-clean-water-act and the regulations adopted under 314 CMR 1.00 through 9.00 – please see https://www.mass.gov/regulations/314-CMR-9-401-water-quality-certification for more detail. Please refer to the Sanitary Sewer Systems and Combined Sewer Overflows guide for additional information.A list of active CSO locations was created and checked against lists contained in the NPDES permit for each CSO system along with lists contained in reports available from the systems online or on town websites. In some cases, when needed, CSO systems were contacted to verify active status of outfalls.Outfall locations are estimates based on the best available maps or coordinates and may contain errors and should only be used as a guide. For additional locational information please contact the CSO systems involved.Source Materials and Data AutomationMassDEP staff used information including maps and general descriptions of CSO locations found online and in NPDES permits to assist in mapping. This information was supplemented by maps and coordinates received from municipal staff responsible for CSO management in each of the systems involved, staff knowledge of outfall locations, maps found in system reports, and maps found on town web sites. MassDEP staff viewed the material and then mapped or verified the location of the CSO using the 2019 orthophoto as a basemap. Some systems were able to provide GIS data directly to MassDEP staff – in these cases, CSO locations were placed directly onto the provided points s or the systems provided point locations were used to verify MassDEP locations. When available, coordinates were entered directly and then checked against the orthophoto and other available maps for general accuracy. Last updated July, 2021.

FIELD

TYPE/WDTH

DEFINITION

NPDES_ID

C/50

Permit Number for the National Pollutant Discharge Elimination System (NPDES)

SYSTEMNAME

C/50

CSO System Name

OUTFALL_ID

C/15

Outfall number according to the Town or System

DEP_OUTFL_ID

C/15

Unique ID for the CSO which combines the Town or System abbreviation with the CSO Outfall No

RECVING_WATER

C/100

The body of water the CSO drains into

ADDRESS

C/120

General locational description of the CSO

TOWN

C/40

Standard (1-351) municipality name where the CSO is actually located

DEP_REGION

C/4

MassDEP Regional Office Code

L_TYPE

C/10

Type of location, i.e., estimated location, center of site, etc.

POINT_X

D

X Coordinate Decimal Degrees

POINT_Y

D

Y Coordinate Decimal Degrees

MAJOR_BASIN

C/100

Major Basin the outfall is located within

PERMIT_URL

C/200

URL to permit online

Data Universe

A list of active CSO locations was created and checked against lists contained in the NPDES permit for each CSO system along with lists contained in reports available from the systems online or on town websites. In some cases, when needed, CSO systems were contacted to verify active status of outfalls.CONTACTS AND TERMS OF USE

The CSOs contained in the CSO spatial data layer are based on a list provided by the MassDEP Bureau of Water Resources Wastewater program – for general questions please contact Lealdon Langley at (617) 574-6882. Locations are estimates and should only be used as a guide. For additional locational information please contact the CSO systems involved. For GIS related questions please contact the MassDEP GIS Program at (617) 292-5500.

Updated Continually

This service identifies the locations of more than 29,000 potential, unverified, vernal pool habitats. Vernal pools are small, shallow ponds characterized by a lack of fish and annual or semi-annual periods of dryness. Vernal pool habitats are extremely important to a variety of wildlife species, including some amphibians that breed exclusively in vernal pools, and other organisms such as fairy shrimp which spend their entire life cycles confined to such locales.Potential vernal pools visible on aerial photographs were interpreted and included in this layer. However, this datalayer does not include every vernal pool in Massachusetts. Many vernal pools have not been identified due to unfavorable conditions in the landscape topography, pool physiography and/or photograph quality. Furthermore, vernal pool habitats occur in a wide variety of landscape settings, including forested swamps, bogs, and other wetlands. Vernal pools within these settings were not typically interpreted, but are nonetheless legitimate and valuable vernal pools. Also, field verification of all potential vernal pools in this study will identify errors such as the inclusion of features that are not actually vernal pools.Potential vernal pools identified in this survey are not to be confused with Certified Vernal Pools. Data pursuant to the official “Guidelines for the Certification of Vernal Pool Habitat” must be collected in the field and presented to the Massachusetts Natural Heritage & Endangered Species Program to obtain official certification for a vernal pool. Potential vernal pools identified in this survey do not receive protection under the Massachusetts Wetlands Protection Act Regulations (310 CMR 10.00), or under any other state or federal wetlands protection laws.More details...Map service also available.