United States Office of Water EPA 816-F-02-018

Environmental Protection (4606) August 2002

Agency

Source Water Protection

Practices Bulletin

Managing Aircraft and Airfield

Deicing Operations to Prevent

Contamination of Drinking Water

The Federal Aviation Administration (FAA) requires that aircraft surfaces be deiced and antiiced to ensure the safety of passengers. However, when performed without prevention

measures in place, airport deicing operations can contribute to contamination of ground water

and surface water supplies. This bulletin addresses two basic types of deicing/anti-icing

operations that take place at airports: the deicing/anti-icing of aircraft, and the deicing/anti-icing

of paved areas including runways, taxiways and gate areas. It also discusses some source

water contamination prevention measures available for use at smaller airports. Additional

information on deicing of roadways is presented in the bulletin on highway deicing.

AIRCRAFT DEICING/ANTI-ICING CHEMICAL USE

The most common technique for deicing/anti-icing of aircraft is the application of chemical

deicing/anti-icing fluids (ADF), which are composed primarily of ethylene or propylene glycol. 

Frequently this is achieved using fixed booms or trucks with an operator bucket mounted on a

boom. Temperature and weather conditions dictate the required concentration of glycol in ADF,

but most operators use fluid with fifty percent glycol concentration by volume. Deicing/antiicing fluids also contain additives, including corrosion inhibitors, flame retardants, wetting agents,

and thickeners that protect aircraft surfaces and allow ADF to cling to the aircraft, resulting in

longer holdover times (the time between application and takeoff during which ice or snow is

prevented from adhering to aircraft surfaces). Limited information is available on the actual

chemical compositions of ADF because their formulations are considered trade secrets.

Four types of deicing/anti-icing fluid are used on aircraft, and vary by composition and holdover

time. Type I fluids, which contain glycol and less than one percent additives, are most

commonly used for deicing and have relatively short holdover times. Types II, III, and IV fluids

are used for anti-icing protection because

they contain higher concentrations of

additives (two percent or less) in addition

to glycol. Larger airlines use both Type I

and Type IV fluids for deicing and antiicing. Because longer holdover times are

not as important a consideration at smaller

airports, smaller airlines typically use Type

I and II fluids, which contain smaller

amounts of additives, or no anti-icing fluids

at all.
AIRFIELD PAVEMENT DEICING/ANTI-ICING CHEMICAL USE

Ice and snow is cleared from runways, taxiways, roadways, and gate areas using a combination

of mechanical methods (e.g., plows and brushes) and chemical deicing agents. Pavement is

typically cleared with mechanical equipment, then chemically treated to prevent further snow

and ice accumulation. Chemicals commonly used for deicing/anti-icing include ethylene or

propylene glycol, urea, potassium acetate, sodium acetate, sodium formate, calcium magnesium

acetate (CMA), or an ethylene glycol-based fluid known as UCAR (containing ethylene glycol,

urea, and water). Sand and salt (sodium or potassium chloride) may also be used, but they can

cause damage to aircraft surfaces and mechanical parts.

WHY IS IT IMPORTANT TO MANAGE RUNOFF OF DEICING FLUID NEAR

THE SOURCES OF YOUR DRINKING WATER?

EPA estimates that 21 million gallons of ADF (50 percent glycol concentration) are discharged

to surface waters annually from airport deicing operations across the country, and an additional

2 million gallons are discharged

to publicly owned treatment

works (POTWs). Unless

captured for recycling, recovery,

or treatment, deicing agents will

run off onto bare or vegetated

ground where they may travel

through the soil and enter ground

water, or run off into streams. 

Unprotected storm water drains

that discharge to surface water

or directly to the subsurface

(i.e., through a dry well) are also

of concern.

Ethylene and propylene glycol

can have harmful effects on aquatic life due to their high biological oxygen demand (BOD). 

Depletion of oxygen, fish kills, and undesirable bacterial growth in receiving waters may result. 

Although pure ethylene and propylene glycols have low aquatic toxicity, ethylene glycol exhibits

toxicity in mammals, including humans (with the potential to cause health problems such as

neurological, cardiovascular, and gastrointestinal problems, serious birth defects, and even death

when ingested in large doses). Additionally, ethylene glycol is considered a hazardous air

pollutant (HAP), and is subject to reporting requirements under the Comprehensive

Environmental Response, Compensation and Liability Act (CERCLA).

Additives in deicing/anti-icing fluids can be significantly more toxic to the aquatic environment

than glycols alone. Corrosion inhibitors are highly reactive with each other and with glycols;

reactions can produce highly toxic byproducts. Other additives such as wetting agents, flame

retardants, pH buffers, and dispersing agents also exhibit high aquatic and mammalian toxicities. 

Manufacturers and formulators have attempted to reduce the toxicity of additives present in

their ADF formulations and, when possible, use environmentally benign chemicals. The Society

for Automotive Engineers (SAE) is currently working to set an ADF toxicity standard in the

near future.

Sodium chloride, or salt, is applied to paved surfaces to prevent icing. (See the bulletin on

highway deicing for more information on deicing paved surfaces.) Sodium can contribute to

cardiovascular, kidney, and liver diseases, and has a direct link to high blood pressure. There is

no MCL or health advisory level for sodium; however, there is a Drinking Water Equivalent

Level of 20 mg/L, a non-enforceable guidance level considered protective against
Infra-red radiant heating unit. 

non-carcinogenic adverse health effects. Sodium is one of the contaminants EPA is considering

for a regulatory determination. Chloride, which has a national secondary drinking water

standard of 250 mg/L, adds a salty taste to water and corrodes pipes.

AVAILABLE PREVENTION MEASURES TO ADDRESS AIRCRAFT AND

AIRFIELD DEICING

An overview of several management measures are described in this section, though they are not

exhaustive. The reference materials below can provide additional resources and information. 

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.

Alternative Deicing/Anti-Icing Materials

Use alternative airfield deicing products such as potassium acetate, sodium acetate, sodium

formate, potassium formate, or CMA instead of urea or glycol deicers. These products have

lower toxicities, are readily biodegradable, and have a lower BOD in the environment. Many of

these products can be applied using the same mechanical spreaders used for urea or spray

booms used for glycol-based fluids. (See the bulletin on highway deicing for more information

on some of these alternative deicers.)

Reducing Deicing/Anti-Icing Fluid Usage

On Aircraft: 

Mechanical deicing technologies eliminate

the need for deicing fluids and reduce the

need for anti-icing fluid. Below are some

examples of newer technology.

• Boot deicing works by inflating a

rubber boot located on the leading

edge of an aircraft wing. When

inflated, the boot causes ice to

crack and become dislodged from

the surface. Passing air blows the

ice away. This method is used

primarily on propeller-driven

aircraft.

• For small aircraft, infra-red deicing systems use natural-gas-fired radiant heaters

inside a drive-through hanger. Follow-up chemical deicing or anti-icing is usually

required to prevent re-freezing. 

• Electrical resistive heating can remove ice from the surface of small to medium sized

aircraft. By applying resistive heating to heating mats located near the skin of an

aircraft, ice is melted and is easily dislodged from aircraft surfaces.

• Hot air blast deicing systems use heated compressed air to blow snow and ice off of

aircraft wings. This may be followed by conventional deicing/anti-icing.

The installation of a computerized spraying system to apply deicing chemicals may reduce the

use of deicing/anti-icing fluids. These systems can reduce both the volume of deicing fluid used

and the time needed for deicing, and increase the collection efficiency of runoff. These “carwash” style systems can be operated by personnel with a minimum of training. This option may
be cost-prohibitive for smaller airports, and in some cases, planes may need additional deicing

using traditional means (trucks or fixed booms) to deice engine inlets, undercarriages, or the

underside of aircraft wings. Deicing fluid sprayed from truck-mounted booms allows more

effective and efficient deicing. The deicer can be sprayed closer to the aircraft surface,

reducing over-spray and wastage.

Using ice detection systems or sensors,

especially on larger aircraft, can reduce and,

in some cases, eliminate application of

deicing fluid. Because operators and flight

crews often have difficulty detecting ice on

aircraft wings, aircraft are deiced whenever

ice is suspected to be present.

Magnetostrictive, electromagnetic, and

ultrasonic devices can detect ice on aircraft

surfaces, including areas that are difficult to

inspect visually and in cases where ice buildup is not apparent. This allows operators to

more accurately determine when deicing is unnecessary and can decrease the amount of ADF

used at an airport.

Increase storage for multi-strength glycol solutions. Using a technique called “blending to

temperature,” operators can vary the concentration of glycol in deicing fluid. Operators,

particularly at small airports, commonly use a fluid with 50 percent glycol, a concentration that is

formulated for worst-case cold weather conditions. However, concentrations of 30 to 70

percent glycol may be used in different conditions. Reducing the glycol concentration in deicing

fluid decreases the amount of glycol in surface runoff and storm water collection systems.

On Pavement Surfaces:

Prevent strong bonding of ice to pavement surfaces by pre-treating and/or promptly treating

pavement using either mechanical methods or chemicals. Pre-treating pavement with chemicals

such as aqueous potassium acetate prior to the onset of freezing conditions or a storm event can

allow easy removal of snow and ice using sweepers and plows. The FAA estimates that the

correct application of pavement anti-icing chemicals can reduce the overall quantity of

pavement deicing/anti-icing agents used by 30 to 75 percent.

Use mechanical methods for dry snow removal rather than applying chemicals.

Use the proper amount of pavement deicing/anti-icing chemicals by following

recommendations from the manufacturer, and properly maintaining spreading equipment. This

will reduce unnecessary or over-application of chemicals. Avoid applying glycol-based deicers

near storm drains, particularly those that are not routed to a publicly-owned sewage treatment

plant.

Collection and Disposal of Spent Fluid to Reduce Runoff

Centralized deicing pads restrict aircraft deicing to a small area, minimizing the volume and

allowing for the capture of deicing waste. A deicing pad is specially graded to capture and route

contaminated runoff to tanks. If the pads are located near gate areas or at the head of runways,

deicing may be completed just prior to takeoff; as a result, less Type IV anti-icing fluid may be

necessary for shorter holdover times, reducing the amount of glycols released onto the runway

or into the air. In addition, fluids recovered from deicing pads may be suitable for reuse.
Vacuum sweeper trucks collect spent aircraft and airfield deicing fluids as well as any slush or

snow from gate areas, ramps, aircraft parking areas, taxiways, and aircraft holding pads. 

Vacuum vehicles are a cost-effective alternative to installing traditional drainage collection

systems or deicing pads, typically ranging in cost from $200,000 to $400,000 each. In addition,

the recovered fluid may be suitable for recycling. 

Detention basins or constructed wetlands are open-water ponds that collect ADF runoff from

runways and airport grounds. Basins allow solids to settle, and reduce oxygen demand before

the runoff is discharged to receiving waters. A pump station can discharge metered runoff by

way of an airport storm sewer. Airports operating these may be required to install liners to

protect ground water and monitoring wells to detect leakage from breached liners. An aeration

system may be required to treat glycol contaminated runoff. See the storm water bulletin for

more information on runoff controls.

Anaerobic bioremediation systems, in conjunction with sewage treatment plants or detention

basins, can be an effective means to dispose of glycol-contaminated runoff. Bioremediation

systems generally consist of a runoff collection and storage system, an anaerobic bioreactor

treatment system (one that requires little or no oxygen), and a gas/heat recovery system. These

systems can reduce oxygen demand levels sufficiently to permit unrestricted disposal to a

sewage treatment plant. Additionally, these systems can remove additives from runoff. An

economic benefit to the anaerobic process is that it converts glycol in runoff to methane gas that

can be used for heating.

Transport of spent fluid to a sewage treatment plant by way of a sanitary sewer is almost

always the most economical method of treating deicing fluid, provided that sufficient biological

loading capacity is available at the treatment plant. However, many sewage treatment plants

will only accept limited quantities of glycol-contaminated runoff; check with the appropriate local

agency to verify applicable regulations. Airport maintenance crews should not assume that

storm drains are routed to a sanitary sewer. They should be knowledgeable about which drains

or collection systems discharge directly to surface waters or to the subsurface, e.g., through a

dry well.

Recycling and Recovery of Spent Fluid

Recycling of glycol from spent deicing/anti-icing fluid decreases the amount that reaches and

potentially impairs surface and ground waters. The recycling process consists of several steps

including filtration, reverse osmosis, and distillation to recover glycol from spent deicing fluid. 

Technology is available to recycle fluids containing at least 5 percent glycol. Glycol recycling

reduces the amount and strength of wastewater, reducing wastewater disposal costs. In addition,

the recovered glycol may be sold; the value of recovered glycol depends on the type of glycol

and its concentration and purity. Recent developments have made on-site recycling successful at

smaller airports; however, the volume of fluid used at very small airports may still be insufficient

to make recycling economically viable at these facilities.

Additional Prevention Measures

Under the National Pollutant Discharge Elimination System (NPDES) Permitting Program,

airports are required to obtain permit coverage for storm water discharges from vehicle

maintenance, equipment cleaning operations, and airport deicing operations. While specific

permit conditions vary from state-to-state, in general, NPDES storm water permits require

airports to develop and implement Storm Water Pollution Prevention Plans (SWPPPs) that

include the following elements:
• Description of potential pollutant sources and a site map indicating the locations of

aircraft and runway deicing/anti-icing operations and identification of any pollutant or

pollutant parameter of concern.

• Description of storm water discharge management controls appropriate for each area of

operation.

• Consideration of alternatives to glycol- and urea- based deicing/anti-icing chemicals to

reduce the aggregate amount of deicing chemicals used and/or lessen the environmental

impact. 

• Evaluation of whether deicing/anti-icing over-application is occurring and adjustment as

necessary.

• Employee training on topics such as spill response, good housekeeping, and material

management practices for all personnel that work in the deicing/anti-icing area.

Many NPDES storm water permits issued to airports also require a variety of monitoring

activities to evaluate the effectiveness of storm water controls in preventing deicing/anti-icing

activities from impacting receiving water quality. For example, monitoring requirements for

airport deicing/anti-icing activities in EPA’s Multi-Sector General Permit include monthly

inspections of existing storm water controls during the deicing season (weekly if large quantities

of deicing chemicals are being spilled or discharged), quarterly visual monitoring of storm water

discharges, and periodic effluent monitoring for BOD, chemical oxygen demand (COD),

ammonia, and pH (for larger users of deicing/anti-icing chemicals) during storm events.

Storm water that discharges directly to the subsurface by way of dry wells, drain fields, or any

other type of distribution system is subject to Underground Injection Control (UIC) Program

requirements. These types of drainage systems are regulated as Class V injection wells and

operators should contact their state or federal UIC Program authority for information on

applicable regulations.

Employee training is an important tool in reducing contaminated runoff. Deicing personnel

receive eight hours of FAA-mandated training, but industry sources state that three years of

experience is required to become adept at aircraft deicing. Personnel should be trained on

proper application techniques and best management practices, and be informed of the presence

of any sensitive water areas nearby. Properly trained personnel will also use less deicing/antiicing fluid, saving money and reducing contamination.

Monitor ground water quality and identify the direction of ground water movement on-site

through the creation of a water table map. Once the direction of ground water flow is known,

annual monitoring up gradient and down gradient of deicing areas should provide early detection

of deicing fluid contamination and other harmful impacts.

FOR ADDITIONAL INFORMATION

These sources contain information on airport deicing practices and facilities and provide

prevention measures to avoid source water contamination. All of the documents listed are

available for free on the Internet. 

Bremer, Karl. The Double Deicing Dilemma. Airport Magazine.

http://www.airportnet.org/depts/publicat/airmags/am91093/deicing.htm

Bremer, Karl. The Three Rs, Reduce, Recover and Recycle. Airport Magazine. 

http://www.airportnet.org/depts/publicat/AIRMAGS/Am3498/deicing.htm

FAA (2001) Northwest Mountain Regional Airport Plan 2001. 

http://www.nw.faa.gov/airports/Plans/RAP/
FAA (2001) Electronic Aircraft Icing Handbook. Chapter III. 

http://www.fire.tc.faa.gov/aar421/eaihbpg.html

FAA Management of Airport Industrial Waste. Change 1 (1997) and Change 2 (2000) 

http://www.faa.gov/arp/pdf/5320-151.pdf

http://www.faa.gov/arp/pdf/5300-142.pdf

Minnesota Pollution Control Agency. (2000) Protecting Water Quality in Urban Areas: Best

Management Practices for Dealing with Storm Water Runoff from Urban, Suburban and

Developing Areas of Minnesota. http://www.pca.state.mn.us/water/pubs/swm-ch7.pdf

Switzenbaum, Michael S., Shawn Veltman, Theodore Schoenberg, Carmen Durand, Dean

Mericas, and Bryan Wagoner. (1999) Best Management Practices for Airport Deicing

Stormwater. University of Massachusetts Water Resources Research Center. 

http://www.umass.edu/tei/wrrc/pdf/Switz173.pdf

USEPA. (1999) Storm Water Technology Fact Sheet: Airplane Deicing Fluid Recovery

Systems. EPA-832-F-99-043, United States Environmental Protection Agency Office of Water,

Washington DC. http://www.epa.gov/owm/mtb/airplnde.pdf

USEPA. (1998) EPA Office of Compliance Sector Notebook Project: Air Transportation

Industry, Sector Notebook Project, EPA/310-R-97-001. http://es.epa.gov/oeca/sector/#air

USEPA. (2000) Preliminary Data Summary: Airport Deicing Operations (Revised). EPA-821-

R-00-016, United States Environmental Protection Agency Office of Water, Washington, DC. 

http://www.epa.gov/ost/guide/airport/airport.pdf

USEPA. (2001) Contaminant Candidate List Preliminary Regulatory Determination Support

Document for Sodium, EPA 815-R-01-014, United States Environmental Protection Agency,

Office of Water. http://www.epa.gov/safewater/ccl/pdf/sodium_final_rsd.pdf

USEPA. (No Date) EPA Office of Federal Activities: Pollution Prevention / Environmental

Impact Reduction Checklist for Airports. http://es.epa.gov/oeca/ofa/pollprev/airport.html

USEPA. (No Date) Shallow Injection Wells (Class V ). Available at

http://www.epa.gov/safewater/uic/classv.html