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Sole Source Aquifer Protection Program 

EPA defines a sole or principal source aquifer as an aquifer that supplies at least 50 

percent of the drinking water consumed in the area overlying the aquifer. These areas 

may have no alternative drinking water source(s) that could physically, legally and

economically supply all those who depend on the aquifer for drinking water. For 

convenience, all designated sole or principal source aquifers are referred to as "sole 

source aquifers" (SSAs). 

SSA designation is one tool to protect drinking water supplies in areas where there are 

few or no alternative sources to the ground water resource and where, if contamination 

occurred, using an alternative source would be extremely expensive. The designation 

protects an area's ground water resource by requiring EPA to review certain proposed 

projects within the designated area. All proposed projects receiving federal funds are 

subject to review to ensure that they do not endanger the water source. 

The SSA protection program is authorized by section 1424(e) of the Safe Drinking 

Water Act of 1974 (Public Law 93-523, 42 U.S.C. 300 et seq.). It states the following: 

"If the Administrator determines, on his own initiative or upon petition, that an area has 

an aquifer which is the sole or principal drinking water source for the area and which, if 

contaminated, would create a significant hazard to public health, he shall publish notice 

of that determination in the Federal Register. After the publication of any such notice, no 

commitment for federal financial assistance (through a grant, contract, loan guarantee, 

or otherwise) may be entered into for any project which the Administrator determines 

may contaminate such aquifer through a recharge zone so as to create a significant 

hazard to public health, but a commitment for federal assistance may, if authorized 

under another provision of law, be entered into to plan or design the project to assure 

that it will not so contaminate the aquifer." 

Petition for Designation

EPA published the Sole Source Aquifer Designation Petitioner Guidance in 1987 to 

assist those interested in preparing and submitting SSA designation petitions to EPA 

regional offices. The document provides procedures and criteria for proposing aquifer 

boundaries, determining whether an aquifer is the sole or principal source of drinking 

water, and evaluating alternative sources of drinking water. 
 Sole source aquifer designation petitioner guidance

Any person may apply for SSA designation. A "person" is any individual, corporation, 

company, association, partnership, state, municipality or federal agency. Most 

petitioners work closely with their EPA regional office in developing an SSA petition. A 

petitioner is responsible for providing EPA with hydrogeologic and drinking water usage 

data, as well as technical and administrative information required for assessing 

designation criteria, as detailed in the Guidance. Following EPA's technical review of a 

petition, the Agency summarizes the information in a technical support document that is 

made available for public review. A Federal Register notice is published at the end of 

the review process to announce EPA's decision to designate the area as a sole source 

aquifer and explain the basis for the decision. 

Post-Designation Review Authority and Coordination

Proposed federal financially assisted projects that have the potential to contaminate a 

designated sole source aquifer are subject to EPA review. Proposed projects funded 

entirely by state, local or private concerns are not subject to EPA review. Examples of 

federally funded projects that EPA has reviewed under the SSA protection program are 

 Highway improvements and new road construction

 Public water supply wells and transmission lines

 Wastewater treatment facilities

 Construction projects that involve management of stormwater

 Agricultural projects that involve management of animal waste

 Projects funded through Community Development Block Grants

EPA has developed Memorandums of Understanding (MOUs) with federal funding 

agencies to establish review responsibilities under the SSA protection program and to 

list categories of projects that should or should not be referred to EPA for review. MOUs 

help to ensure that projects that pose serious threats to ground water quality are 

referred to EPA. Examples of MOUs are: 

 US Department of Agriculture, Rural Development Mississippi Office and EPA 

Region 4 (PDF 2 pp, 25 K)

 Federal Highway Administration of Florida and EPA Region 4 (PDF 2 pp, 26 K)

As a result of EPA review of a proposed federally financed project in the designated 

SSA, concerns regarding ground water quality protection lead to specific 

recommendations or additional pollution prevention requirements as a condition of 

funding. Most projects referred to EPA for review are approved without any additional 

conditions being imposed because they meet all federal, state and local ground water 

protection standards. Federal funding has been denied, however, when an applicant 

has been unwilling or unable to modify a project. 

Whenever feasible, EPA coordinates the review of proposed projects with other EPA 
offices and with other federal, state or local agencies that have a responsibility for 

ground water quality protection. This coordination helps EPA to understand local 

hydrogeologic conditions and specific project design concerns, and it ensures that the 

SSA protection measures enhance and support existing ground water protection efforts. 

Public Awareness and Participation

SSA designations help to increase public awareness of the nature and value of local 

ground water resources by demonstrating the link between an aquifer and a 

community's drinking water supply. The realization that an area's drinking water 

originates from a vulnerable underground supply can lead to increased interest in 

protection measures. The public has an opportunity to participate in the SSA 

designation process by providing written comments to EPA or by participating in an 

EPA-sponsored public hearing before a designation decision is made. 

Sole Source Aquifer Designation Regional Program Web sites

To learn more about the 73 existing designated SSAs, see the list of links below for 

regional contacts and more information:

 Region 1

 Region 2

 Region 3

 Region 4

 Region 5

 Region 6

 Region 7

 Region 8

 Region 9

 Region 10

 Source water protection case studies for systems using SSAs are also available.



Limitations of the Program

The designation of an SSA provides limited federal protection of ground water 

resources and by no means constitutes a complete protection strategy. Effective 

protection of sources of drinking water requires the integration of federal, state and local 

efforts, as called for under the Comprehensive State Ground Water Protection Program 

approach. For example, local wellhead protection programs designed to protect the 

recharge areas of public water supply wells should work in concert with contaminant 

source control and pollution prevention efforts at all levels of government. This 

coordination ensures that source water activities meet the same protection goal without 

duplication of time, effort and resources. 

Many valuable and sensitive aquifers have not been designated because nobody has 

petitioned EPA for such status or because they did not qualify for designation because 
of drinking water consumption patterns. Ground water's value as drinking water and its 

vulnerability to contamination can vary considerably between and within designated 

aquifers. As a result, EPA does not endorse using SSA status as the sole or 

determining factor in making land use decisions that might affect ground water quality. 

Rather, site-specific hydrogeological assessments should be considered along with 

other factors such as project design, construction practices and long-term management 

of the site. 

http://cfpub.epa.gov/safewater/sourcewater/sourcewater.cfm?action=SSA

Last updated on Friday, July 30, 2010