v>EPA
United States
Environmental Protection
Agency
Off ice of Water
Washington, D.C.
EPA 832-F-99-009
September 1999
Storm Water
Management Fact Sheet
Coverings
DESCRIPTION
Covering is the partial or total enclosure of raw
materials, byproducts, finished products, containers,
equipment, process operations, and material storage
areas that, when exposed to rain and/or runoff,
could contaminate storm water. Tarpaulins, plastic
sheeting, roofs, buildings, and other enclosures are
examples of temporary or permanent coverings that
are effective in preventing storm water
contamination. The most prominent advantage of
covering is that it is inexpensive in comparison to
other BMPs.
APPLICABILITY
A review of numerous NPDES group applications
indicates that covering is a commonly implemented
BMP. As more facilities identify potential sources
of storm water contamination, the use of coverings
will increase significantly due to their effectiveness
from a performance and cost perspective.
Covering is appropriate for loading/unloading areas,
raw material, byproduct, and final product outdoor
storage areas, fueling and vehicle maintenance
areas, and other high risk areas.
ADVANTAGES AND DISADVANTAGES
Covering is a simple and effective storm water
management BMP. Its advantages relative to other
storm water management BMPs include its
comparative ease of implementation, its potential
low cost, and its widespread applicability.
Disadvantages associated with covering as a BMP
include:
• Temporary covering methods, such as
plastic sheeting, can become torn or ripped,
exposing the contaminant to precipitation
and/or storm water runoff.
Costs may prohibit the building of complete
enclosures.
• Health or safety problems may develop with
enclosures built over certain materials or
activities.
• Coverings require frequent inspection.
• A structure with only a roof may not keep
out all precipitation.
The impact from a covered area depends on the
degree of complexity in the covering design.
Simple plastic sheeting can possibly create a storm
water diversion, and allow for disposal of
uncontaminated water to a storm sewer. An
appropriate structure with a permanent roof may be
less effective, if the material inside is not
sufficiently protected from contact with runoff. An
enclosed structure may need to have internal
drainage. However, if the stored material is
considered hazardous, it must not be connected to
the storm sewer. Depending on the site's NPDES
permit, connection to a sanitary sewer may also be
unsuitable. The internal drains would then need to
be connected to some suitable containment area for
later pretreatment and disposal.
IMPLEMENTATION
When implementing a program to cover materials
to reduce their exposure to runoff, one must first
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choose the proper covering. When deciding on a
covering, it is necessary to evaluate the integrity
and durability of the covering, as well as its
compatibility with the material or activity being
covered.
Covering alone may not protect exposed materials
from storm water contact. Placing material on an
elevated impermeable surface or building curbing
around the outside of the materials may be required
to prevent contact with storm water runoff from
adj acent areas. If the program calls for a material to
be enclosed, the designer should consider materials
access, handling, and transfer during the design of
the enclosure. Materials that pose environmental
and/or safety dangers because they are radioactive,
pathogenic, flammable, explosive, or reactive,
require special ventilation and temperature design
considerations.
In addition to properly designing an enclosure or
cover, practicing proper materials management
within an enclosure or underneath a covered area is
essential. For example, floor drainage within an
enclosure should be properly designed and
connected to a sanitary sewer. The local publicly
owned treatment works should be consulted to
determine if there are any pretreatment
requirements, restrictions, or compatibility
problems prior to discharge of the storm water.
Based on data currently available, it is difficult to
quantify the mitigation of runoff contamination
when covering is used. However, significant runoff
water quality benefits are expected by simply
reducing the contact between potential
contaminants and precipitation or storm water
runoff. One source has estimated that 80 percent of
the environmental damage from de-icing chemicals
is caused by inadequate storage facilities.
Inspecting coverings must be part of an overall
preventive maintenance program. Maintenance
involves frequent inspection of the covering for
rips, holes, and general wear.
COSTS
Covering costs vary in proportion to the degree of
protection desired, and the required life span. The
most inexpensive covering is plastic sheeting, but it
is not suitable where a high degree of protection is
desired for a long period. An enclosed building is
the most expensive type of covering when materials
for the structure, lighting, and ventilation are
considered, but it offers the highest degree of
protection for the longest period.
REFERENCES
1. Minnesota Pollution Control Agency, 1989.
Protecting the Water Quality in Urban
Areas.
2. U.S. EPA, 1992. Summary Guidance:
Storm Water Management for Industrial
Activities: Developing Pollution Prevention
Plans and Best Management Practice. EPA
833-R92-002, U.S. EPA, Washington, DC.
3. Washington State Department of Ecology,
1992. Storm Water Management Manual
for Puget Sound.
ADDITIONAL INFORMATION
Center for Watershed Protection
Tom Schueler
8391 Main Street
Ellicott City, MD21043
Northern Virginia Planning District Commission
David Bulova
7535 Little River Turnpike, Suite 100
Annandale, VA 22003
Oklahoma Department of Environmental Quality
Don Mooney
Water Quality Division, Storm Water Unit
P.O. Box 1677
Oklahoma City, OK 73101-1677
Southeastern Wisconsin Regional Planning
Commission
Bob Biebel
916 N. East Avenue, P.O. Box 1607
Waukesha, WI53187
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United States Postal Service
Charles Vidich
6 Griffin Road North
Windsor, CT 06006-7030
The mention of trade names or commercial
products does not constitute endorsement or
recommendation for the use by the U.S.
Environmental Protection Agency.
For more information contact:
Municipal Technology Branch
U.S. EPA
Mail Code 4204
401 M St., S.W.
Washington, D.C., 20460
1MTB
Excellence In complfance through optimal technical solutions
MUNICIPAL TECHNOLOGY BRANCH
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