United States                  Office of Water                 EPA 816-F-01 -024
                 Environmental Protection           (4606)                      July 2001

oEPA    Source Water  Protection

                 Practices Bulletin

                 Managing Vehicle  Washing to

                 Prevent Contamination  of

                 Drinking  Water

                 Vehicle washing is the cleaning of privately owned vehicles (cars
                 and trucks), public vehicles (school buses, vans, municipal buses,
                 fire trucks, and utility vehicles), and industrial vehicles (moving
                 vans  or trucks and tractors). The vehicle wash water can carry
                 sediment and contaminants to surface waters, and can
                 contaminate groundwater by infiltration or by drainage to
                 subsurface wells and/or septic systems. This fact sheet focuses
                 on management of vehicle washing to prevent contamination of
                 drinking water sources.


                 Vehicle washing occurs at commercial car wash facilities (for both interior and exterior
                 cleaning), public works garages, car dealerships, truck stops, and any other facility that washes
                 vehicles.  When vehicles are washed, contaminants in the wash water and the overspray can
                 enter source water untreated through surface runoff (e.g., through storm drains) and
                 underground discharge (e.g., through carwash wells or septic systems).  Vehicle wash water
                 contains oil, grease, metal (paint chips), phosphates, detergents, soaps, cleaners, road salts, and
                 other chemicals that can contaminate source water.

                 EPA  estimates that there are 7,200 carwash wells in the United States. These carwash wells,
                 which inject wash water into the subsurface, are categorized by EPA as Class V underground
                 injection wells. In a 1999 EPA study on Class V wells,  concerns were raised about the use of
                 carwash wells to dispose of wash water from "wand washes" such as coin-operated, manual
                 facilities where people use hand-held hoses to wash vehicles.  Because an attendant is not
                 usually on site, individuals may wash their engines or undercarriages using degreasers, wash the
                 exterior of their vehicles with chemicals other than common soap solutions, or may pour used oil,
                 antifreeze, or other hazardous materials down these drains.


                 Managing vehicle washing near drinking water sources is important because the wash water
                 can flow  into storm water drains  and enter surface water sources untreated. The wash water
                 can also percolate through the soil or enter the subsurface through carwash wells, and
                 contaminate ground water.  The contaminants in vehicle wash water can cause a variety of
                 health effects, including kidney damage, circulatory system problems, increased cancer risk, and
                 delays in  physical or mental development.

Once a water supply becomes contaminated, it is very difficult and costly to treat.  Treating the
water supply is a lengthy process and is not always successful. Using an alternative water
source may also be costly and impractical.


A variety of prevention measures, including nonstructural and structural activities, are available
to address vehicle washing. 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 waters, the public's acceptance of the measures,
and the community's desired degree of risk reduction. Some of the more conventional
prevention measures are described below.

Local governments can use a variety of land use controls to protect  source water from
potential contamination.  For example, zoning can restrict certain activities to specific geographic
areas that are distant from drinking water sources. Localities can also prohibit certain uses
within certain areas.  For example, prohibition of vehicle washing activities in source water
protection areas can reduce the risk that harmful contaminants may enter source water.  Local
governments may also require permits that impose additional requirements such as setbacks,
open spaces, buffers, walls and fences; street paving and control of site access points; and
regulation of hours and methods of operation. Local municipal treatment plants may have a
storm water treatment program; coordinate with your local municipal treatment plant to
eliminate illicit discharges.  States may require vehicle washing facilities to apply for ground
water discharge permits.  Many of these facilities discharge wastewater containing regulated
contaminants above the State's ambient ground water standards.

Design and Operation of Washing  Facilities

Warning signs should be posted for customers and employees instructing them not to dump
vehicle fluids, pesticides, solvents,  fertilizers, organic chemicals, or toxic chemicals into catch
basins.  Catch basins are chambers or sumps which collect runoff and channel it to the storm
water drain or to the sanitary sewer. Vehicle wash facilities should stencil warnings on the
pavement next to the grit trap or catch basin. All signs should be in a visible location and
maintained for readability.
                                                 Wash areas should be located on well-
                                                 constructed and  maintained, impervious
                                                 surfaces (i.e.,  concrete or plastic) with drains
                                                 piped to the sanitary sewer or other disposal
                                                 devices.  The  wash area should extend for at
                                                 least four feet on all sides of the vehicle to
                                                 trap all overspray. Enclosing wash areas
                                                 with walls and properly  grading wash areas
                                                 prevent dirty overspray from leaving the
                                                 wash area, allowing the  overspray to be
                                                 collected from the impermeable surface.
                  Enclosed carwash
The  impervious  surfaces should be marked to indicate the boundaries of the  washing area and
the area draining to the designated collection point.  Washing areas should not be located near
uncovered vehicle repair areas or chemical storage facilities; chemicals could be transported in
wash water  runoff.

Regular cleaning of wash areas and grit traps or catch basins can minimize or prevent debris
such as paint chips, dirt, cleaning agents, chemicals, and oil and grease from being discharged
into storm drains or injection wells.

Using alternative cleaning agents such as phosphate-free, biodegradable detergents for
vehicle washing will reduce the amount of contaminants entering storm drains. Cleaning agents
containing solvents and emulsifiers should be discouraged because they allow oil and grease to
flow through the oil/water separator (see below) instead of being separated from the effluent.
In addition, these cleaning agents will remain in the wastewater and can pollute drinking water

Proper Management of Wastewater

There are several approaches for managing wastewater, depending on the size of the site and
the resources available.  These are described below.

Oil/water separators are tanks that collect oily vehicle wash water that flows along corrugated
plates to encourage separation of solids and oil droplets.  The oily solids or sludge can then be
pumped out of the  system through a different pipe. The sludge can be hauled off site, and the
wash water can be discharged to vegetated areas or to a treatment plant.  There are two types
of oil/water separators, one that removes free oil that floats on top of water, and one that
removes emulsified oil, a mixture of oil, water, chemicals, and dirt.  Choose the separator that
fits the needs of the vehicle wash facility.
Collection sumps are deep pits or reservoirs that hold liquid waste.  Vehicle wash water
accumulates in the collection sumps, and is pumped or siphoned to  a vegetated area (such as a
grassed swale or constructed wetland).  Sediment traps can also be used to strain and collect
the vehicle wash water, prior to pumping or siphoning the wash water to a vegetated area.

Recycling systems reduce or eliminate contaminated discharges to storm water drains and
injection wells by reusing the wash water until the water reaches a certain contaminant level.
The wastewater is then discharged to a collection sump or to a treatment facility.
Where wastewater is not to be
disposed to a sanitary sewer, grassed
swales (shallow, vegetated ditches)
or constructed wetlands (retention
ponds with emergent aquatic
vegetation) can be used to hold
wastewater and allow contaminant
removal through infiltration and
filtration.  These devices are
described in greater detail in the fact
sheet on managing storm water
Education and Training
                                                       Carwash with vegetated area
Employee training is an important tool to prevent vehicle wash water from entering storm
water drains and injection wells and contaminating source waters.  Employees should be aware
of operation and maintenance procedures, proper disposal practices, and general housekeeping
activities. They should be aware of toxic chemicals, if any, with which they may come in
contact, and have access to a chemical management plan, if applicable, and an emergency
contact list.

At all designated washing areas, spill prevention, control, and management should be planned
and designed to prevent any spills of pollutants from entering surface water, ground water, or a
publicly or privately owned treatment works.  A chemical management plan should be
implemented for vehicle washes that use metal brighteners, caustics or acids, halogenated
hydrocarbons, or solvents. The plan should include a list of the chemicals used, the method of
disposal such as reclamation or contract hauling, and procedures for assuring that toxic
chemicals are not discharged into source water.


These sources contain information on vehicle wash facilities and provide prevention measures to
avoid source water contamination. All of the  documents listed are available for free on the
Internet.  EPA's Office of Science and Technology provides effluent guidelines, pretreatment
standards and new source performance standards for transportation equipment cleaning

California Department of Transportation, Storm Water Compliance Review Task Force.
Maintenance Storm Water Pollution Prevention Bulletin. Retrieved February 24, 2001, from
the World Wide Web: http://www.dot.ca.gov/env/storm water/_pdfs/maintain/m6_98.pdf.

Natural Resources Defense  Council. Storm Water Strategies. The Consequences of Urban
Storm Water Pollution.  Retrieved March 9, 2001, from the World Wide Web:

New Hampshire Department of Environmental Services. Environmental Fact Sheet.
Retrieved June 22, 2001, from the World Wide Web:

Oregon Department of Environmental Quality. Best Management Practices for Storm Water
Discharges Associated with Industrial Activities. Retrieved February 24, 2001, from the
World Wide Web: http://www.deq.state.or.us/nwr/Industrial%20BMPs.pdf.

United States Environmental Protection Agency, Office of Ground Water and Drinking Water.
Class V UIC Study Fact Sheet:  Carwash Wells Without Undercarriage Washing or Engine
Cleaning.  Retrieved March 08, 2001, from the World Wide Web:

U.S. EPA, Office of Ground and Drinking Water. The Class  V Underground Injection Control
Study, Volume 4.  Wells that Inject Fluids from Carwashes Without Engine or
Undercarriage Cleaning. Retrieved March 9, 2001, from the World Wide Web:

U.S. EPA, Office of Science and Technology. Final Development Document for Effluent
Limitations Guidelines and Standards for the  Transportation  Equipment Cleaning
Category.  Retrieved March 9, 2001, from the World Wide Web:

U.S. EPA, Office of Wastewater Management.  Storm Water Management Fact Sheet: Non-
Storm Water Discharges to Storm Sewers.  Retrieved March 9, 2001, from the Wold Wide
Web: http ://www. epa.gov/owm/mtb/nonstorm.pdf.

University of Wisconsin-Extension Water Resources Programs.  Cleaning up Storm Water
Runoff, A Series of Fact Sheets about Storm  Water Runoff.  Retrieved January 23, 2001,
from the World Wide Web: http://clean-water.uwex.edu/pubs/stormie/index.html.