&EPA
Office of
United States	Ground Water and
Environmental Protection Agency	Drinking Water
CLASS V UIC STUDY FACT SHEET
SUBSIDENCE CONTROL WELLS
What is a subsidence
Subsidence control wells are Class V underground injection control (UIC) wells whose
control well?
primary objective is to control land sinking, or subsidence, caused by ground water

withdrawal and other activities (but not oil and gas production).
What types of fluids are
Untreated surface water, untreated ground water, saline water, and/or surface water treated to
injected into subsidence
drinking water standards.
control wells?

Do injectate constituents
No data on injectate constituents or concentrations associated with subsidence control wells
exceed drinking water
are available.
standards at the point of

injection?

What are the
None of the known, active subsidence control wells inject into underground sources of
characteristics of the
drinking water. Some wells are being used to inject beneath construction zones to minimize
injection zone of a
damage from settlement caused by construction, and other wells inject into a salt dome cavity
subsidence control well?
that is used for the storage of oil at the Strategic Petroleum Reserve Weeks Island site in LA.
Are there any
No contamination incidents associated with the operation of subsidence control wells have
contamination incidents
been reported.
associated with subsidence

control wells?

Are subsidence control
Details on the design, construction, and operation of subsidence control wells are not
wells vulnerable to spills or
available. Thus, it is not possible to determine if subsidence control wells are vulnerable to
illicit discharges?
receiving spills or illicit discharges.
How many subsidence
There are 28 subsidence control wells documented in the United States. The estimated
control wells exist in the
number of subsidence control wells in the nation is approximately 158.
United States?

Where are subsidence
All documented subsidence control wells are located in LA (8), OR (14), and WI (6). Of the
control wells located within
estimated subsidence control wells in the nation, as many as 50 wells may be located in NY.
the United States?
The documented and estimated numbers of subsidence control wells do not include any wells

in AK; however, officials responsible for the UIC Program in that state did not rule out the

possibility that some exist.
How are subsidence
Permit bv rule: LA, OR
control wells regulated in

states with the largest
Individual permit. NY
number of this type of

well?
Ban new wells: WI
Where can I obtain
For general information, contact the Safe Drinking Water Hotline, toll-free 800-426-4791.
additional information on
The Safe Drinking Water Hotline is open Monday through Friday, excluding federal
subsidence control wells?
holidays, from 9:00 a.m. to 5:30 p.m. Eastern Standard Time. For technical inquiries.

contact Amber Moreen, Underground Injection Control Program, Office of Ground Water

and Drinking Water (mail code 4606), EPA, 401 M Street, SW, Washington, D.C., 20460.

Phone: 202-260-4891. E-mail: mo re e n. a mb e r Vv c pa. go v. The complete Class VUIC Study
(EPA/816-R-99-014, September 1999), which includes a volume addressing subsidence
control wells (Volume 23), can be found at http://www.epa.gov/OGWDW/uic/cl5study.html.

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