April 2011

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The Department of Environmental Protection (DEP) Division of Watershed Management (DWM) Water Permitting Program (WPP) is responsible for regulating the discharge of pollutants to the ground waters of The Commonwealth (314 CMR 5.00). See http://www.mass.gov/dep/water/resources/groundwa.htm for details.

The Ground Water Discharge Permits datalayer (formerly known as Groundwater Discharge Points) is a statewide point dataset containing approximate locations of permitted discharges to groundwater. The permitted discharges in this datalayer may have one or more of the following criteria:

  • Sanitary sewage in excess of 10,000 gallons per day (gpd)
  • Discharges of non-contact cooling water
  • Discharges from coin operated laundromats
  • Discharges from car washes
  • Discharges from treatment systems designed to remediate contaminated groundwater
In ArcSDE the layer is named GWP_PT.

Data Development

Source Materials
Locations contained in this datalayer are based on DEP WPP staff interpretation of information provided by the DEP WPP Permit Application Files in the Boston Office. The DEP WPP is responsible for providing the DEP GIS Program with a comprehensive with locations as well as a listing of Ground Water Discharge Permits for the purposes of maintaining this datalayer.

Automation Methodology 
Collection of point locations began in 1989 and is ongoing. Originally discharge point locations were marked on USGS quadrangle sheets for use by DEP technical staff. These locations were digitized to create the original DEP Groundwater Discharge Permit datalayer.

Currently The DEP GIS Program has two standard techniques for automating groundwater discharge permit locations. These include using digital base imagery to digitize locations on screen and the use of global positioning systems (GPS) technology.

On Screen Digitizing Technique
The DEP GIS Program’s primary method of point data automation is on screen digitizing using digital base imagery. To facilitate conversion of paper data to a digital format, the DEP GIS Program created the Point Development Tool  (PDT).   The PDT provides a standardized platform that guides users through the automation and documentation of geographically referenced point data.

Using development level data, the PDT navigates data developers to the general vicinity of the target feature. The PDT then displays the best digital base imagery available for that vicinity. The PDT uses MassGIS 1 meter (1:5,000) black and white digital orthophoto images (DOQ) as the default base image. Digital USGS topographic imagery can also be utilized.

After interpreting the source manuscripts, data developers use the PDT to generate a new point location or select and/or refine an existing development location on the base image that best represents the site location. The PDT then guides 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. The PDT also records the developer’s name, program and date of automation, as well as providing for developer’s comments.

Global Positioning Systems 
The DEP also uses GPS technology to develop high quality locational data. The DEP standard for GPS data collection is the Trimble Navigation GeoExplorer GPS receiver and differential correction. Please refer to the DEP GIS Program’s Global Positioning Systems (GPS) Standard Operating Reference for standards and guidance relating to GPS field data collection with the GeoExplorer and GeoExplorerII receivers. Depending on the application and requirements for locational data quality, non-differential GPS receivers (ex. Garmin) may also be suitable for data capture.


The point attribute table for the DEP Ground Water Discharge Permits datalayer contains the following items:
PER BRP Permit Number, Unique site ID
PERR BRP Permit Number plus Renewal Number, Unique site ID
NAME GWP Name according to WPP
ADDRESS GWP Address according to WPP
TOWN Standard (1-351) MassGIS town name in which the GWP is located
Standard (1-4) DEP Region ID in which the GWP is located:
 1 = Western
 2 = Central
 3 = Northeast
 4 = Southeast
BASIN Basin (watershed) in which the GWP is located
TYPE Status / type of discharge according to WPP:
 S = Sanitary Discharge
 C = Car Wash
 L = Laundromat
 O = Other
Note: a small number of features are coded with the combined TYPEs of L/C and S/C.
FLOW Metered flow of discharge; gallons per day (GPD) according to WPP

Related Database Table

DEP Location Documentation Table (GWP_PT_LDT) - See DEP Standards for Point GIS Data .

The table GWP_PT_USL contains a list of unlocated DEP Ground Water Permits. With the April 2011 update, all current, active permits have been located so the table is empty and not distributed.


The DEP GIS Program in cooperation with the DEP WPP maintains this datalayer. Updates to this datalayer will be provided to MassGIS on a quarterly quarterly (Dec., Mar., June, and Sept.) basis. As a standard component of the update, The DEP GIS Program will remove from the datalayer sites that are no longer groundwater discharge points according to the latest WPP data. The addition of new (GWP) sites to the datalayer will be dependent on the availability of staffing resources and source information. Datalayer updates may also include refinements to existing site locations.

If you have questions regarding this datalayer, please contact the DEP GIS Program at (617) 574-6856. General and technical questions regarding DEP discharge to groundwater permitting should be directed to the DEP Water Permitting Program (617) 556-1150.

In the September 2002 update the item PER was added to the polygon attribute table to reflect DEP point data documentation standards and changes in the programmatic database on which the data is based. In November 2002 seven new sites were added. In April 2003 one Permit location was deleted and 4 Permit IDs (PERRs) were updated. In July 2003 four permit sites were added and six sites had attribute updates. In February 2004 one site was added and three sites had permit classification changes. In May 2009 all discharge locations in MassDEP Northeast Region were revised.

Last Updated 9/1/2011