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Overview
The datalayer contained an identical number of records as the ODS database at the time it was created. New records may have subsequently been added to the ODS database that are not reflected in this GIS datalayer. There are many additional fields and information maintained by the ODS in its database that are not included in the GIS data. These data have been excluded for privacy, security, accuracy and administrative reasons.
The ODS database includes detailed information about each dam for operational purposes. Most of the location information was derived from historic data and has been ground-truthed against inspection and ownership reports that are maintained by the ODS.
Dams regulated by the ODS in accordance with regulation CMR 302 10.00 are listed as "Office of Dam Safety" in the Regulatory_Authority field.
Please report any data errors or inconsistencies to the Office of Dam Safety (dam.safety@mass.gov) or DCR-GIS (chandreyee.lahiri@mass.gov).
MassGIS stores the GIS datalayer as DAMS_PT.
Production
Original Source Manuscripts and Production
The Massachusetts Office of Dam Safety has historically maintained records of dams through maps, deeds, site visit documentation and correspondence. A unique identifier ('NATID') for each dam links all documents. The original GIS dataset was created from historical documents of varying accuracy in 2001. An organized digital data logging system in recent years has enabled better ground-truthing and location verifications through annual site inspections.
Current Source Manuscripts and Production Methodology
An interactive database is currently used by ODS staff to continually update information about dams.
All of the dams regulated by Office of Dam Safety, FERC, ACOE and FWS have had their locations verified. The ODS continues to verify the locations of dams classified as Non-Jurisdictional.
Attributes
The DAMS_PT attribute table has the following items:
| Field Name | Type | Description /Codes |
|---|---|---|
| NATID | String | Unique ID for the dam in the Office of Dam Safety database |
| DAM_NAME | String | Currently recognized and official name of the dam |
| CITY_TOWN | String | City or town in which the dam is located |
| MASSGIS_TOWN_ID_CODE | Number | MassGIS city/town identifier (1-351) |
| LATITUDE | Double | Dam location – Latitude in decimal degrees |
| LONGITUDE | Double | Dam location – Longitude in decimal degrees |
| REGULATORY_AUTHORITY | String | The authority responsible for regulating the dam: FERC Jurisdiction - FERC (Federal Energy Regulation Commission) Jurisdiction applies to facilities that generate hydro-electric power and are subject to FERC regulation. May be privately or publicly owned. Army Corps of Engineers Jurisdiction - Dams regulated by the Army Corps of Engineers (ACOE) Fish & Wildlife Service Jurisdiction - Dams regulated by the Fish & Wildlife Service (FWS) Office of Dam Safety - Dams which may be privately or publicly owned but are regulated by and under the jurisdiction of the Massachusetts Office of Dam Safety (ODS) in accordance with regulation CMR 302 10.00. Non-Jurisdictional - NOT regulated by the ODS or under their jurisdiction. Typically under 6 ft in height and/or under 15 acre-feet in storage and do not have an assigned 'Hazard Code'. Dams owned and regulated by the Federal Government are also typically Non-jurisdictional but DO have assigned Hazard Codes. Under review - The Regulatory Authority has yet to be determined. |
| FERC_PROJECT_NO_ | String | Project number used by the Federal Energy Regulatory Commission (FERC) |
| HAZARD_POTENTIAL_CLASSIFICATION | String | Codes that indicate severity of hazards presented to communities in case of dam failure: High - Located where failure will likely cause loss of life and serious damage to home(s), industrial, commercial facilities, important public utilities, main highway(s) or Railroad(s). Significant - Located where failure may cause loss of life and damage home(s), industrial or commercial facilities, secondary highway(s) or railroad(s) or cause interruption of use or service of relatively important facilities. Low - Located where failure may cause minimal property damage to others. Loss of life is not expected. N/A - No hazard classification: Non-jurisdictional dams do not have hazard classifications except when owned and regulated by the Federal Government. Under review - The Hazard Classification has yet to be officially determined. Removed/Breached - The dam has been removed or breached. Removed dams are included in the data to aid in the documentation and tracking of efforts to restore river habitats for anadromous fish and other wildlife. |
| RIVER | String | Name of the river, stream or brook where the dam is impounding water or is intended to impound water. |
| WATERSHED | String | Name of the major watershed basin that contains the dam. |
| OWNERSHIP_TYPE | String | Owner types with details where available: Federal - The owner of the dam is a federal agency. The specific agency is also included after a hyphen. State - The owner of the dam is a state agency. The specific agency is also included after a hyphen. Most of the information tends to be repeated in the OWNER_S_ field. Municipal - The owner of the dam is a municipal government. May include co-owner (Private, FERC, or Political Subdivision (a specific municipal agency)). Private - Ownership is held by a private entity. These are either listed as "Private" or "Private-FERC Regulated" for those dams that are regulated by the Federal Emergency Regulatory Commission. Under Review - The ownership of the dam is being confirmed. Unknown - The ownership of the dam is currently unknown. |
| OWNER_S_ | String | Name of the owner or owners of the dam. |
Maintenance
ODS and DCR-GIS will send updates to MassGIS periodically as new information becomes available in the ODS database. Future data enhancements include verifying all dam locations. Please report any data errors or inconsistencies to the Office of Dam Safety (dam.safety@mass.gov).
The February 2026 update includes a revised attribute table schema and an extensive review of the data.
| Last updated: | February 23, 2026 |
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