Know Your EPA Water Rules: Sole Source Aquifers

Posted on March 13,2017 by Anthony Cardno

The Safe Drinking Water Act Amendments of 1986 (SDWA) required the Environmental Protection Agency (EPA) to establish criteria through which an aquifer may be declared a critical aquifer protection area. These aquifers are colloquially referred to as “sole source aquifers.” These are, essentially, aquifers that are the only drinking water supply for the population of a region.

What Is A Sole Source Aquifer?

EPA Safe Drinking Water ActAn aquifer is defined at 40 CFR 144.3 as “a geologic formation, group of formations, or part of a formation that is capable of yielding a significant amount of water to a well or spring.” Most regions of the country have multiple aquifers from which groundwater can be drawn to be provided to the local population.

The EPA has never defined the words “sole” or “principal” in regard to this statutory mandate. The EPA’s website defines sole source aquifers as “supplying at least 50 percent of the drinking water for the service area and having no reasonably available alternative drinking water sources should the aquifer become contaminated.” However, at 40 CFR 149.3(b), the Agency more clearly defines four criteria to be used to designate an aquifer as a sole or principal source aquifer:
  1. Vulnerability of the aquifer to contamination due to the hydrogeologic characteristics of the aquifer
  2. The number of persons or proportion of the population using groundwater as a drinking water source
  3. The likelihood of the aquifer to become contaminated without a program to reduce or prevent contamination
  4. Reasonably foreseeable contamination resulting in significant cost, taking into account the cost of replacing the drinking water supply and other social, economic and environmental costs resulting from contamination.
There are two ways for an aquifer to be designated as a sole source aquifer:
  1. It is part of an area-wide groundwater protection plan under the Clean Water Act, or
  2. An application for designation as “sole source” has been approved by the EPA.
 Check out EPA's interactive map of sole source aquifers in the US here. 

State Management Plans for Sole Source Aquifers

The safe management and protection of sole source aquifers is largely the responsibility of the state in which the aquifer exists. The state is required to prepare and implement an area-wide waste treatment management plan aimed at preventing contamination of the aquifer in question. These State plans require facilities in the sole source aquifer area to incorporate additional controls to protect the aquifer.

Here are some examples these State programs at work:

Edwards Underground Reservoir in San Antonio, Texas

The Edwards Underground Reservoir is designated as a sole source aquifer for the San Antonio, Texas area and is the only sole source aquifer administered in the Federal regulations. 40 CFR 149, Subpart B prohibits any project in the area that might create a significant health hazard and sets rules for the review of any such project.

New York’s Three Sole Source Aquifers

The state of New York has petitioned for and received approval for the designation of three sole source aquifers within the state: the Clinton Street-Ballpark Valley Aquifer System around Binghamton, the Long Island Aquifer System, and the Schenectady/Niskayuna Aquifer System in the State capitol area.

The New York Department of Environmental  Conservation (NYSDEC) places requirements on hazardous waste generators regarding additional secondary containment for hazardous waste containers and tanks, found at 6 NYCRR 373-1.1(d)(iv).

Understanding New York’s unique hazardous waste requirements with respect to sole source aquifers is crucial to effective waste management in the state. 
You can find more details about the sole source aquifer program at

New Clean Water Act & Safe Drinking Water Act Online Training

New for 2017! The Clean Water Act and Safe Drinking Water Act Regulations Online Course will help you build a full understanding of the EPA’s major water regulations and how they affect your operations.

Major topics covered in the new online course include:

  • NPDES permit and control requirements  
  • SPCC plan basics and EPA reporting obligations
  • US EPA pretreatment standards
  • EPA’s Underground Injection Control (UIC) program
  • Water quality standards for public systems and MCLs


More courses for EHS Managers:

Clean Air Act Regulations Online
TSCA Regulations Online
Clean Water Act & SDWA Regulations Online
New! Superfund and Right-to-Know Act Regulations Online 


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