May 1996

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(ESRI Shapefile with ArcGIS .lyr and ArcView 3x .avl)

Overview

The Sole Source Aquifer datalayer was compiled by the Department of Environmental Protection (DEP) Division of Water Supply (DWS). Seven Sole Source Aquifers have been designated by the US Environmental Protection Agency (EPA) for Massachusetts.  A Sole Source Aquifer (SSA) is an aquifer designated by US EPA as the 'sole or principal source' of drinking water for a given aquifer service area; that is, an aquifer which is needed to supply 50% or more of the drinking water for that area and for which there are no reasonably available alternative sources should that aquifer become contaminated. The Sole Source Aquifers layer is named AQSOLE_POLY in ArcSDE.

Methodology

The aquifers were defined by a EPA hydrogeologist. Aquifer boundaries were then drafted by EPA onto 1:25,000 USGS quadrangles. For the coastal sole source aquifers the shoreline as it appeared on the quadrangle was used as a boundary. Delineated boundaries were then digitized into ARC/INFO. However, to ensure that aquifer boundaries coincide with MassGIS coast data, the ARC RESELECT command was used to select the aquifer boundaries for Martha’s Vineyard, Nantucket and Cape Cod SSAs. The coastal SSA boundaries are fluid and change with the change of shore line. Checkplots of the aquifers were submitted to US EPA Region 1 for verification.

Attributes

This datalayer's attribute table has the following attributes associated with each polygon:
  SSA_NUM a unique id for each SSA
  SSA_NAME the name of the SSA
  SOURCE_CODE the source of SSA linework
Several small waterbodies also are found within this coverage. These have been coded with a SSA_NAME of 'WATERBODY'.

Maintenance

The DEP Division of Water Supply and MassGIS are maintaining this datalayer.

Last Updated 6/7/2004