United States Office of Water EPA 916-F-01-022
Environmental Protection (4606) July 2001
Agency
Source Water Protection
Practices Bulletin
Managing Above Ground Storage
Tanks to Prevent Contamination of
Drinking Water
Above ground storage tanks (ASTs) are tanks or other containers that are above ground,
partially buried, bunkered, or in a subterranean vault. These can include floating fuel systems.
This fact sheet focuses on the management of facilities with ASTs to prevent contamination of
drinking water sources (ground water and surface water used as public drinking water supplies).
ABOVE GROUND STORAGE TANK USE
The majority of storage tanks contain petroleum products (e.g., motor fuels, petroleum solvents,
heating oil, lubricants, used oil). Oil storage facilities with ASTs are typically found in
marketing terminals, refineries, and fuel distribution centers. Storage
tanks may also be found in airports, school bus barns, hospitals,
automotive repair shops, military bases, farms, and industrial plants.
Discharges of chemicals, petroleum, or non-petroleum oils from
storage tanks can contaminate source water. Product spilled, leaked,
or lost from storage tanks may accumulate in soils or be carried away
in storm runoff.
Some of the causes for storage tank releases are holes from corrosion,
failure of piping systems, and spills and overfills, as well as
equipment failure and human operational error. The Spill Prevention
Control and Countermeasures (SPCC) regulations require owners or
operators of certain above ground oil storage facilities to prepare and
comply with written, site-specific, spill prevention plans (see 40 CFR
Part 112):
Facilities with a total above ground
oil storage capacity of more than
1,320 gallons;
Single above ground tanks with an
oil storage capacity of more than 660
gallons; and
Facilities with a combined
underground oil storage capacity
greater than 42,000 gallons.
Above ground storage tanks
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Please note, however, that State AST regulations may be more stringent or differ in other ways
from the Federal requirements. You must check with local regulatory authorities to make sure
which ASTs are subject to what requirements. All AST facility owners or operators exempt
from these regulations should still consider implementing the prevention measures described in
this fact sheet to preclude future storage tank problems.
WHY IS IT IMPORTANT TO MANAGE ABOVE GROUND STORAGE TANKS NEAR
THE SOURCES OF YOUR DRINKING WATER?
Storage tank releases can contaminate soil and drinking water supplies. Petroleum products are
composed of volatile organic compounds (VOCs). Any oil spill can pose a serious threat to
human health and the environment, requires remediation that extends beyond your facility's
boundary, and results in substantial cleanup costs. Even a small spill can have a serious impact.
A single pint of oil released into the water can cover one acre of water surface area and can
seriously damage an aquatic habitat. A spill of only one gallon of oil can contaminate a million
gallons of water. It may take years for an ecosystem to recover from the damage caused by an
oil spill. The location of the facility must be considered in relation to drinking water wells,
streams, ponds and ditches (perennial or intermittent), storm or sanitary sewers, wetlands,
mudflats, sandflats, farm drain tiles, or other navigable waters. Factors such as the distance to
drinking water wells and surface water, volume of material stored, worse case weather
conditions, drainage patterns, land contours, and soil conditions must also be taken into
account.
AVAILABLE PREVENTION MEASURES TO ADDRESS ABOVE GROUND
STORAGE TANKS
The following list of prevention measures is not all-encompassing; others can be found in the
references provided at the end of the document. Furthermore, detailed explanations of each
device mentioned below are found in the supporting documents. Please keep in mind that
individual prevention measures may or may not be adequate to prevent contamination of source
waters. Most likely, individual measures should be combined in an overall prevention approach
that considers the nature of the potential source of contamination, the purpose, cost,
operational, and maintenance requirements of the measures, the vulnerability of the source
water, the public's acceptance of the measures, and the community's desired degree of risk
reduction.
Federal AST Requirements under 40 CFR Part 112
Follow standard tank filling practices when filling tanks to prevent spills and overfills.
Furthermore, all ASTs should have a secondary containment area that contains spills and
allows leaks to be more easily detected. The containment area surrounding the tank should hold
110 percent of the contents of the largest tank plus freeboard for precipitation. Secondary
containment for ASTs must be impermeable to the materials being stored. Methods include
berms, dikes, liners, vaults, and double-walled tanks. A manually controlled sump pump should
be used to collect rain water that may accumulate in the secondary containment area. Any
discharge should be inspected for petroleum or chemicals prior to being dispensed.
Routinely monitor ASTs to ensure they are not leaking. An audit of a newly installed tank
system by a professional engineer can identify and correct problems such as loose fittings, poor
welding, and poorly fit gaskets. After installation, inspect the tank system periodically to
ensure it is in good condition. Depending on the permeability of the secondary containment
area, more frequent containment area checks may be necessary. Areas to inspect include tank
foundations, connections, coatings, tank walls, and the piping system. Integrity testing should
be done periodically by a qualified professional and in accordance to applicable standards.
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If an AST has remained out of service for more a year or more, many States require owners to
maintain and monitor the tank, declare the tank inactive, or remove it. If the tank is declared
inactive, remove all substances from the AST system (including pipes) and completely clean
the inside. Secure tanks by bolting and locking all valves, as well as capping all gauge
openings and fill lines. Clearly label tanks with the date and the words "Out of Service."
Samples may be required when removing tanks to determine if any contamination has occurred.
Most States require out-of-service tanks to be inspected and meet leak detection requirements
before they are put back into service.
Additional AST Prevention Measures
The following prevention measures go beyond the Federal regulations under 40 CFR Part 112,
but are highly recommended:
The location of the facility must be considered in relation to drinking water wells, streams,
ponds and ditches (perennial or intermittent), storm or sanitary sewers, wetlands, mudflats,
sandflats, farm drain tiles, or other navigable waters. The distance to drinking water wells and
surface water, volume of material stored, worse case weather conditions, drainage patterns, land
contours, and soil conditions must also be taken into account.
ASTs should have corrosion protection for the tank. Options include elevating tanks, resting
tanks on continuous concrete slabs, installing double-walled tanks, cathodically protecting the
tanks, internally lining tanks, inspecting tanks according to American Petroleum Institute
standard, or a combination of the options listed above. All underground piping to the tank
should be double-walled or located above ground or cathodically protected so you can inspect it
when it fails.
To maximize system safety, seal the floors, containment area, and sump pump pit with an
appropriate coating (e.g., petroleum resistant coating). Any accumulated water should be
inspected for petroleum or chemicals prior to discharge
Accumulated minor spillage, over time, may result in a film or sheen on collected rain water,
making it unsuitable for discharge to the soil or drains. Periodic cleanup of the containment
areas (e.g., sweeping with a broom and using limited absorbent) can prevent unnecessary dirt
and contaminant buildup.
•
While not a preventative measure for source water protection,
preventing evaporation has economic and air quality
benefits. To keep out rain and reduce evaporation losses and
moisture condensation, paint tanks a reflective color, install
them in an east-west direction, install a low-pressure valve on
top of the tank, and cover the structure. A roof structure
covering a 10,000 gallon tank will conserve 600 to 1,000
gallons of gasoline per year, which would
have escaped by evaporation without the
shade cover.
Local jurisdictions may want to implement
registration programs for exempt tanks, in
order to exercise some oversight of their
construction and operation. Furthermore,
most States also require inspections for
ASTs by fire marshals. Inspection programs
can be expanded to cover water
contamination issues.
Covered AST with secondary containment
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FOR ADDITIONAL INFORMATION
The following documents contain more detailed information on ASTs and are available for free
on the Internet. You can contact your EPA Regional SPCC or Oil Coordinator for more
information, as well. There are also State and local authorities that are often located in Oil,
Environmental, or Pollution Control Divisions who can provide you with local regulations for
ASTs.
Contact local government authorities in your area to see if there are ordinances in place to
manage ASTs. Numerous examples of local source water protection-related ordinances for
various potential contaminant sources can be found at:
http://www.epa.gov/r5water/ordcom/
http://www.epa.gov/owow/nps/ordinance/
http://www.epa.gov/owow/nps/ordinance/links.htm
The following documents provide additional information on AST prevention measures and
regulations:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University
of Florida.. Above-Ground Fuel Storage Systems (EES-61). (1992, October). Retrieved
February 9, 2001 from the World Wide Web:
http://www.cdc.gov/niosh/nasd/docs2/as04300.html
Minnesota Pollution Control Agency. Above-Ground Storage Tank Systems. (2000, October
18). Retrieved February 9, 2001 from the World Wide Web:
http://www.pca.state.mn.us/cleanup/ast.html
Minnesota Pollution Control Agency. Out-of-Service Tank Systems. (1998, November).
Retrieved February 9, 2001 from the World Wide Web:
http://www.pca.state.mn.us/cleanup/ast.html
Purdue University Extension Service. Petroleum Product Storage Practices on the Farm.
(1991). Retrieved February 12, 2001 from the World Wide Web:
http://pasture.ecn.purdue.edu/~epados/farmstead/fuel/src/title.htm
South Dakota Department of Environment and Natural Resources, Ground Water Quality
Program.. Frequently Asked Questions about UST and AST Systems. (n.d.). Retrieved
February 19, 2001 from the World Wide Web:
http://www.state.sd.us/denr/DES/Ground/tanks/FAQTANK.htm
U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response.
SPCC Requirements and Pollution Prevention Practices for Bulk Storage Facilities, (n.d.).
Retrieved February 9, 2001 from the World Wide Web:
http://www.epa.gov/oilspill/spcc/index.htm
U.S. Environmental Protection Agency, Office of Water. Storm Water Management for
Industrial Activities - Developing Pollution Prevention Plans and Best Management Practices.
Section 3.6 - Liquid Storage in Above-Ground Storage Tanks (EPA 832/R-92-006). (1992,
September). Retrieved February 9, 2001 from the World Wide Web:
http://www.epa.gov/owm/sw/indguide/index.htm
U.S. Environmental Protection Agency, Oil Spill Program. Introduction and Background to the
Oil Pollution Prevention Regulation, (n.d.). Retrieved May 1, 2001 from the World Wide
Web: http://www.epa.gov/oilspill/spcc/index.html
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