How To Manual: Update and Enhance Your Local Source Water Protection Assessments

This manual describes opportunities for improving local delineations, potential contaminant source inventories, and susceptibility determinations based on assessments performed under Safe Drinking Water Act 1453.
EPA 816-K-05-004

What is a source water assessment?
An assessment is a study and report, unique to each water system, that provides basic information about:

  • Where the drinking water comes from: an assessment provides a map and information about the area that most directly provides the raw water used by a public water system to supply potable water.

What could pose a threat to drinking water quality?

An assessment identifies the major potential sources of contamination to the drinking water supply. This information is used to determine how susceptible the water system is to contamination.

Today more than 140,000 public water systems have a source water assessment. In 1996 section 1453 of the Safe Drinking Water Act amendments required all states to get EPA approval for a source water assessment program (SWAP) and use that plan to conduct assessment for all public water system supplies within 3 years. Pennsylvania has completed these Section 1453 assessments.

Is more assessment work needed?
Assessments should be reviewed for update on an annual basis.  The Section 1453 assessments were a snapshot in time, and water supply sources and risk factors change over time.  For example, systems are continually adding new sources; a water system that had relied on surface water may develop a new ground water source. In addition, land uses and development in source water protection areas may change over time, introducing new risks that should be managed.  At the local level, assessments can be used to prioritize needed protection measures, but they may or may not be adequate. The assessments need to be updated, enhanced, and refined at the local level. A Source Water Protection Plan will help by updating the original assessment that was completed by PA DEP.

Does my state have a source water assessment program?
All states, including Pennsylvania, have EPA-approved SWAPs.  Each assessment report contains the following information for a water system:

  • a delineated protection area;
  • an inventory of potential sources of contamination; and
  • an evaluation of the likelihood of the water system being contaminated.

For example, a small public rest area might have a very simple assessment, whereas a large residential community would have a more detailed one. Generally, PA DEP chose to do more detailed assessment work in areas that were already known to be vulnerable to contamination.


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