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The Source Water Assessment & Protection (SWAP) Program

Overview of the Program

Protecting Source Water

Massachusetts has over 1,700 public water systems that provide drinking water to homes, schools, businesses, and industries. Over 90 percent of the state's population depends on public water supply sources, which are often vulnerable to contamination. More than 70 communities have shut down at least one source because it was contaminated. The Massachusetts Department of Environmental Protection (MassDEP) has had a strong water supply protection program since 1980. Federal requirements helped MassDEP focus its resources on improving protection statewide. As a result, local water suppliers and municipal officials received more hydrogeological and planning assistance from MassDEP for improved protection of local drinking water sources.

Incorporating New Requirements

The Federal Safe Drinking Water Act Amendments of 1996 emphasize the importance of protecting public drinking water from contamination. The law required every state to examine existing and potential threats to the quality of all its public water supply sources and to develop a Source Water Assessment and Protection (SWAP) Program.  The assessments in Massachusetts were completed in 2004.

MassDEP's SWAP process:

  1. delineated protection areas for all public ground and surface water sources;
  2. inventoried land uses in these areas that may present potential threats to water quality;
  3. determined the susceptibility of water supplies to contamination from these sources; and
  4. publicized the results.

Source Water Assessment reports help local and state officials target inspections and focus technical assistance where they are needed the most, encourage cooperative emergency response, and contribute to comprehensive protection of all public water sources.


The top five potential threats to public water sources that were identified through the SWAP Program include:  1) residential lawn care/gardening; 2) residential septic systems and cesspools; 3) residential fuel oil storage; 4) stormwater discharge; and 5) state-regulated underground storage tanks.  MassDEP is using this information to target technical assistance and outreach work.

Building On Existing Programs

Local Protection

State and local officials use the SWAP results to enhance their drinking water protection programs. Approximately 20% of Massachusetts community public water systems meet MassDEP's most stringent requirements for groundwater protection. Many communities still lack adequate protection controls. With the SWAP process, local officials received assessment results accompanied by prioritized recommendations for improving water supply protection. SWAP information helps educate the public and build support for program implementation.

Involving the Public

SWAP Reports can help local citizen's groups, including watershed groups, with their efforts to protect and improve water quality for a variety of uses including drinking water.

MassDEP encourages cooperation between local citizen's groups, local officials, water suppliers and state agencies to use the SWAP reports as resources and help guide future water supply protection efforts.

Where can I find a SWAP Report?

Electronic versions of Community and Non-Transient Non-Community SWAP reports are posted on the MassDEP website (see link below). The reports have been organized by region and within region, by town. The Source Water Assessment and Protection (SWAP) Program was conducted several years ago.  The potential sources of contamination identified in the reports and the recommendations provided by MassDEP to public water systems to address them are still useful as a basis for local water supply protection planning and for developing a surface water or wellhead protection plan.  To request an updated SWAP GIS map, contact MassDEP’s Drinking Water Program at or 617-292-5770.

Printed versions of all SWAP reports and maps were provided to the public water supplier, the local Board of Health, and local planning officials (usually the town selectmen) as part of the assessment process. To review a printed-paper version with map, either contact one of the local entities mentioned above or contact the appropriate MassDEP regional office and make arrangements to review the SWAP report.

To see SWAP reports and other documents click here


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