MassGIS Data: MassDEP Tier Classified Oil and/or Hazardous Material Sites (MGL c. 21E) (2023)


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MassGIS Data: MassDEP Tier Classified Oil and/or Hazardous Material Sites (MGL c. 21E) (1)

Location types featured in this datalayer include the approximate center of a site, the center of a building on the property where the release occurred, the source of contamination, or the location of an on-site monitoring well. For the purposes of this document, the terms “MassDEP Tier Classified oil and/or hazardous material disposal sites” and “Tier Classified Chapter 21E sites” are synonymous and are often referred to simply as “sites”. The layer is namedC21E_PT.

Releases of oil and/or hazardous materials are reported to the MassachusettsDepartment of Environmental Protection’s (MassDEP)Bureau of Waste Site Cleanup(BWSC), according to procedures established in the MCP (310 CMR 40.0000). The sites mapped in this datalayer represent only a subset of the total reported Chapter 21E sites tracked by MassDEP BWSC. Chapter 21E sites that have not yet been Tier Classified are not contained in this datalayer.

Under Massachusetts’ Waste Site Cleanup Program, which is a largely privatized program, data maintained by the MassDEP regarding site location are provided to MassDEP BWSC by Responsible Parties (RP), Potentially Responsible Parties (PRPs) and by Licensed Site Professionals (LSP), hired by the RP or PRP to conduct cleanup at a site. Location data is provided in a paper format (e.g., map and textual information) and maintained by MassDEP BWSC in individual site files. These site files are available to the public through the MassDEP’sRegional Offices.

Anyone wishing to view Chapter 21E site files can make arrangements with the regional offices though a Freedom of Information request. MassDEP encourages persons to review these site files when they make decisions that consider a specific site. Most of the site locations included in the MassDEP Tier Classified Oil and/or Hazardous Material Sites datalayer are interpretations of data provided by PRPs and LSPS converted to a digital format by MassDEP staff. These data have not been field-verified. In some cases where file information was inadequate or unavailable, locations were provided by MassDEP technical staff through knowledge gained in the course of their professional activities.

The State Superfund Law and the Massachusetts Contingency Plan (MCP)

The rules requiring notification, assessment and remediation of releases of oil and hazardous materials are codified in the Massachusetts Contingency Plan (MCP) 310 CMR 40.0000. Under the MCP and M.G.L. Chapter 21E, the PRPs are responsible for the timely assessment and cleanup of disposal sites in Massachusetts. The MassDEP BWSC is required to audit PRP response actions performed on 20% of the sites and when necessary provides direct agency oversight of cleanup efforts.

If permanent cleanup is not achieved for a disposal site within a year of being reported to MassDEP, the site must be classified as Tier I or II based on a variety of factors, including the site’s complexity, the type of contamination, and the potential for human or environmental exposure to the contamination. In addition, some sites are automatically given a Tier I classification if they pose an imminent hazard or affect public water supplies. A site’s Tier Classification determines the level of MassDEP oversight. Tier I sites require a permit and sites, and the most complicated sites, require direct MassDEP BWSC oversight.

Data Limitations

Many of the locations in this datalayer are based on information provided by the RP, PRP or their LSP. Locations in this datalayer should ONLY be considered as an ”approximation” or “best estimate” based on the information submitted to the MassDEP BWSC.The accuracy and completeness of the information submitted has not been verified by MassDEP.

There are other Chapter 21E sites in Massachusetts that are not contained in this datalayer. For example, this datalayer does not include (1) contaminated sites that have not been reported to MassDEP or (2) sites for which a Response Action Outcome (RAO) has been submitted to MassDEP. Furthermore, not all Tier Classified Chapter 21E sites may have been located. Please refer to the associated Unlocated Sites List (C21E_PT_USL)for a current list of unmapped Tier Classified Chapter 21E sites.

Tier Classified Chapter 21E site data are extremely temporal. Although the datalayer is updated on a regular basis, it will never be complete or up-to-date. Users should check MassDEP BWSC site files (at the appropriate MassDEPRegional Office) for the most current information.

MassDEP recognizes that point features are not the ideal spatial model for representing contaminated areas, especially in the case of large sites or if considerable contaminant migration has occurred. Due to the limitations of the information that PRPs and LSPs are currently required to submit to MassDEP, the spatial representation of sites as point features is currently the only realistic method for generating Tier Classified Chapter 21E site data on a statewide scale.

Due to the limitations of this datalayer, the following disclaimer language will apply to any MassDEP map product containing Tier Classified 21E site data:

Data Disclaimer:
Point locations representing Tier Classified Chapter 21E sites in this datalayer have not been field-verified and should be considered approximate. Locations were derived through review and interpretation of paper maps and textual information contained in MassDEP BWSC site files, which are maintained in MassDEP’s Regional Offices. Generally, such information was submitted to MassDEP by potentially responsible parties (PRPs) and the PRPs’ licensed site professionals (LSPs).

Please be advised that this datalayer is incomplete. MassDEP has been unable to locate some sites due to inadequate source material. Sites that are not yet reported or tier-classified are not mapped, nor are sites for which a Response Action Outcome (RAO) has been submitted to MassDEP.

Site contamination may extend well away from the point representing a site on this map. The MassDEP BWSC site files should be reviewed for the most accurate and up-to-date information about a particular site. While the Tier Classified Chapter 21E site data shown on this map provides some useful information, the user should be aware of the data’s limitations. For further information, please consult the datalayer description documentation of MassDEP Tier Classified Oil and/or Hazardous Material Sites, available on the MassGIS Web Site:

Questions regarding Tier Classified Chapter 21E site data on this map may be referred to the MassDEP GIS Program (617) 574-6856.

Data Development

1. Source Materials

a. Data Universe
MassDEP BWSC is responsible for providing the MassDEP GIS Program with a comprehensive listing of Tier Classified Chapter 21E sites, including street address information and unverified coordinate data. A “development coverage” was created from this data using address matched and coordinate-generated data.

b. Source Manuscripts
Chapter 21E site files maintained by MassDEP contain a variety of types and qualities of maps, including surveys, site plans and locus maps. MassDEP GIS Program staff reviewed this file information and identified the best manuscript maps and supplemental text information for locating sites. In limited cases, textual manuscripts, contained in the site files, provided sufficient descriptive information for estimating site locations.

2. Automation Methodology

Point Development Tool
To facilitate conversion of paper data to a digital format, the MassDEP GIS Program created the Point Development Tool (PDT), a customized application using ESRI’s ArcView software (the PDT application is available as an extension to the MassGIS DataViewer). The PDT provides a standardized platform that guides users through the automation and documentation of geographically-referenced point data.

On-screen digitizing using the PDT and the best available manuscript map information was the primary method of automation. In situations where manuscript maps and other source information from the file record were inadequate or unavailable, MassDEP technical staff were asked to help locate the site based on knowledge gained in the course of their professional activities involving that site.

Using data in the “development coverage,” the PDT navigates data developers to the general vicinity of a site. The PDT then displays the best digital base imagery available for that vicinity. The PDT usesMassGIS 1990's Aerial Imageryas the default basemap. Where 1 meter B&W 1:5,000 DOQs were not available, the PDT defaulted to 1 meter USGS (1:12,000) black and white digital orthophoto images orUSGS (1:25,000) topographic quadrangle images, respectively. When data development began, the only available digital basemap imagery for much of Massachusetts was the MassGIS scanned USGS (1:25,000) topographic images. Therefore, the base scale of this datalayer is considered to be 1:25,000. The PDT currently uses MassGIScolor digital orthophotography imagesas the default statewide basemap.

After interpreting the source manuscripts, developers used the PDT to select a point on the base image that best represents the site location. The PDT guided the developer through the data documentation process, recording information about the type of source material, type of feature located, and an assessment of the locational accuracy of the mapped point.


1. Data Structure
The point attribute table for the MassDEP Tier Classified Oil and/or Hazardous Material Sites datalayer contains the following fields:

RTNRelease Tracking Number (RTN), unique site ID
NAMESite name assigned by MassDEP BWSC describes the site in terms of its location use or type.
ADDRESSSite address assigned by MassDEP BWSC
TOWNStandard (1-351) municipality name
REGIONMassDEP Region code
STATUSChapter 21E compliance status according to MassDEP BWSC
SITE_INFOLink to site's description web page

2. Description of General Site Information Items
General site information attributes are populated using the most current MassDEP BWSC database information available at the time of update.

The Release Tracking Number (RTN), is a unique 7-digit site identifier assigned to reportable releases by MassDEP BWSC. This number is preceded by either 1,2,3 or 4 (e.g. 3-0001234) according to the MassDEP region in which the site is located (see:description of MassDEP Region ID below).

The name assigned by MassDEP BWSC that best describes the site location. The site name does NOT necessarily reflect the identity of any PRPs.

The number and street that most accurately describes the site location; mile markers or similar highway designations may also be used.

STATUS (Chapter 21E Tier Classification)
Current status of the site. Chapter 21E Tier Classification is based on the requirements, standards and procedures set forth in 310 CMR 40.0500 or 40.0600.

MCP/Chapter 21E Tier Classification Definitions

-TIER I:Any disposal site which meets the following criteria at the time of Tier Classification shall be classified as Tier I:

(a) there is evidence of groundwater contamination with oil and/or hazardous material at concentrations equal to or exceeding the applicable RCGW-1 Reportable Concentration set forth in 310 CMR 40.0360, and such groundwater is located within an Interim Wellhead Protection Area, Zone II, or within 500 feet of a Private Water Supply Well;

(b) an Imminent Hazard is present;

(c) one or more remedial actions are required as part of an Immediate Response Action pursuant to 310 CMR 40.0414(2); or

(d) one or more response actions are required as part of an Immediate Response Action to eliminate or mitigate a Critical Exposure Pathway pursuant to 310 CMR 40.0414(3).

- TIER ID:(1) A disposal site shall be deemed a Tier ID ("default") disposal site if any of the following apply:

(a) an Responsible Party (RP), Potentially Responsible Party (PRP) or Other Person for such disposal site fails to submit to MassDEP one of the following by the applicable deadline in 310 CMR 40.0501:

1. a Permanent Solution Statement; or

2. a Tier Classification Submittal; or

(b) the person undertaking response actions is in noncompliance with M.G.L. c. 21E, 310 CMR 40.0000 or any other applicable requirement, and MassDEP reclassifies the disposal site as a Tier ID disposal site pursuant to 310 CMR 40.0583.

- TIER II:Any disposal site that is not Tier ID pursuant to 310 CMR 40.0502 or 40.0520(5) and does not meet the Tier I Criteria described at 310 CMR 40.0520(2).

3. Geographic Information Fields
Geographic Information Fields are populated using GIS overlay/identity functionality.

MassGIS standard town name

The REGION field lists the MassDEP Region in which the feature is physically located. This field must be populated with one of the following numeric MassDEP Region codes:

DEP Region Code

DEP Region – Office LocationAcronym
1Western Region - SpringfieldWERO
2Central Region - WorcesterCERO
3Northeast Region - WilmingtonNERO
4Southeast Region – LakevilleSERO

Related Tables

1. MassDEP BWSCDownloadable Sites List - This compressed file (RELEASE.ZIP) includes a database file (RELEASE.DBF) containing a record for all reportable releases tracked by the MassDEP BWSC, as well as accompanying documentation (README.DOC). MassDEP BWSC updates this file on a regular schedule. Tablular datasets in RELEASE.ZIP can be related to the AUL datalayer by the RTN. Please note that Oil and/or Hazardous Material Sites with AULs are only a subset of the total reportable releases contained in the MassDEP BWSC Downloadable Sites List.

2. DEP Location Documentation Table (C21E_PT_LDT) - SeeMassDEP Standards for Point GIS Data.

3. Unlocated Sites Table (C21E_PT_USL)– Contains a list of known, unlocated Tier Classified Oil and Hazardous Materials Sites at the time of publication.


The MassDEP GIS Program maintains this datalayer in cooperation with MassDEP BWSC. If you have questions regarding this datalayer, please contact the MassDEP GIS Program at (617) 574-6802 or (617) 574-6856.

The current data are up-to-date through December 23, 2021.

Also see theMassDEP Oil and/or Hazardous Material Sites with Activity and Use Limitations (AUL) Datalayer, which often is updated in conjunction with the 21E sites.

Last updated: December 29, 2021
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