SEPA
United States	Office of Ground Water and Drinking Water
Agencym6nta' Pr0teCt'°n	September 2009
CLASS V FACT SHEET
AQUIFER RECHARGE AND AQUIFER STORAGE AND RECOVERY WELLS
What are aquifer recharge
(AR) and aquifer storage and
recovery (ASR) wells?
What types of fluid are
injected into AR and ASR
wells?
Do injectate constituents
exceed drinking water
standards at the point of
injection?	
What are the characteristics of
the injection zone of AR and
ASR wells?
Are there any contamination
incidents associated with AR
and ASR wells?
Are AR and ASR wells
vulnerable to spills or illicit
discharges?
How many AR and ASR wells
exist in the United States?
Where are AR and ASR wells
located within the United
States?
Where can I obtain additional
information on AR and ASR
wells?
AR and ASR wells are used to replenish the water in an aquifer. AR wells have been
utilized to deter salt water intrusion into freshwater aquifers and to control land subsidence.
While an aquifer recharge well is used only to increase the water supply in an aquifer, ASR
wells are used to achieve two objectives: (1) storing water in the ground; and (2) recovering
the stored water either using the same well or by pairing injection wells with recovery wells
located on the same wellfield. ASR wells have been used to store and recover water for
drinking supplies, irrigation, and ecosystem restoration projects. Although the process of
ASR includes production of the injected water, the UIC program regulates the
injection of fluids, not separate production or recovery activities.
Water injected into AR and ASR wells ranges from potable drinking water and recycled
water treated at a public water system to meet primary drinking water standards to untreated
ground water and surface water.
Water injected into AR and ASR wells is typically treated to meet primary and secondary
water standards. However, it should be noted that, in some instances, constituents have been
measured at concentrations above drinking water standards at the point of injection.
AR and ASR wells are drilled to various depths depending on the depth of the receiving
aquifer. Aquifers used for AR and ASR activities may be confined, semi-confined or
unconfined.
Exceedances of primary drinking water standards for arsenic and disinfection by-products in
recovered water and within the injection zone of the aquifer have occurred. Secondary
drinking water standard exceedances for iron and manganese have also been reported to
EPA. Radionuclides continue to be a concern for AR and ASR operations although
contamination incidents have not been reported.
Spills and discharges that would risk human health and the enviromnent are unlikely to
occur with operation of AR and ASR wells. Water used in AR and ASR injection activities
is typically high quality and potable.
EPA is aware of 1203 AR and ASR wells operating or capable of operation in the U.S. Of
the 1203 known wells, 661 are used for AR and 542 are dedicated to ASR. The number of
ASR wells has quadrupled since the Class V Study was published in 1999.
The Southeast, Southwest, and Pacific Northwest have the greatest numbers of AR and ASR
wells. Only one EPA region - including Maine, Vermont, New Hampshire, Massachusetts,
Rhode Island, and Connecticut ~ does not have AR or ASR wells.
For general information, contact the Safe Drinking Water Hotline toll-free at 1-800-426-
4791. The Hotline accepts calls Monday through Friday, 9:00 am to 5:30 pm Eastern
Standard Time, excluding Federal holidays. For technical inquiries, contact Jill Dean,
Office of Ground Water and Drinking Water, EPA East, 1200 Pennsylvania Ave. NW,
Mailcode 4606M, Washington, DC 20460; phone 202-564-8241; email dean.jill@epa.gov.
The UIC website includes AR and ASR information at 
 and Volume 21 of the
Class V UIC Study (EPA/816-R-99-014, Sept 1999) addressing AR and ASR wells may be
found at http://www.epa.gov/safewater/uic/class5/classv_study.html.
* This fact sheet revises the information on Aquifer Recharge and Aquifer Storage and Recovery wells published in the Class V Study (1999).
Information in this fact sheet was updated based on EPA Regional Office data.

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