Why are aircraft and ground vehicle maintenance a stormwater issue?


Automotive maintenance facilities are considered to be stormwater “hot spots.” Aircraft and ground vehicle maintenance has the potential to contaminate stormwater if performed in an area that drains to the storm system or if spills or leaks are not cleaned up immediately. Common activities at maintenance shops that generate this waste include the cleaning of parts, changing of vehicle fluids, and replacement and repair of equipment. Additionally, fluid spills and improper disposal of materials result in pollutants, heavy metals, and toxic materials that could enter ground and surface water supplies, creating public health and environmental risks. Potential pollutants may include:

  • Solvents (paints and paint thinners)
  • Antifreeze
  • Brake fluid and brake lining
  • Batteries
  • Motor oils
  • Fuels (gasoline, diesel, kerosene)
  • Lubricating grease

The MAA has a number of measures in place to help tenants minimize environmental impacts when performing aircraft and ground vehicle maintenance. A multi-use building is available for vehicle maintenance at BWI Marshall Airport that provides tenants a covered location for vehicle maintenance and infrastructure (oil/water separators) to limit environmental impacts.

The MAA also has infrastructure in place to prevent discharges of oil and grease to the storm and sanitary sewer systems. Where tenants lease space and conduct maintenance, building floor drains lead to oil/water separators and to the sanitary sewer system. Areas outside of buildings lead to oil/water separators and to the stormwater system. The MAA cleans common use oil/water separators. Keep in mind that where tenants own individual shops, these tenants are responsible for cleaning the oil/water separators.

Tenants are required to prevent or reduce pollutants exposed to or discharged to stormwater from aircraft and vehicle maintenance and repair. However, there is flexibility in what measures tenants can implement to accomplish this. The MAA has developed Stormwater Pollution Prevention Plans (SWPPPs) for BWI Marshall and Martin State Airports. These plans identify a number of best management practices for both MAA staff and tenants related to activities such as ground vehicle and aircraft maintenance.

BWI Tenant Directive 212.1 (Parking Fueling Vehicles), BWI Tenant Directive 212.2 (Aircraft Self-Fueling Operations at Baltimore/Washington International Airport), and MTN Tenant Directive 212.1 (Self-Fueling Operational Requirements) provide specific details on tenant responsibilities.

Tenant staff should be aware of what has been included in the SWPPP and follow the best management practices identified in the document. Alteration of practices involving the cleanup and storage of automotive fluids and cleaning of vehicle parts can help reduce the influence of automotive maintenance practices on storm water runoff and local water supplies.

Some examples of best management practices tenants can adopt include:

Waste Reduction
  • The number of solvents used should be kept to a minimum to make recycling easier and to reduce hazardous waste management cost.
  • Perform all liquid cleaning at a centralized station to ensure that solvents and residues stay in one area.
  • Locate drip pans and draining boards to direct solvents back into solvent sink or holding tank for reuse.
Using Safer Alternatives
  • Use non-hazardous cleaners when possible.
  • Replace chlorinated organic solvents with non-chlorinated ones like kerosene or mineral spirits.
  • Recycled products such as engine oil, transmission fluid, antifreeze, and hydraulic fluid can be purchased to support the market of recycled products.
Spill Clean Up
  • Obtain and use drain mats to cover drains in the event of a spill.
  • Use as little water as possible to clean spills, leaks, and drips.
  • Rags should be used to clean small spills, dry absorbent material for larger spills, and a mop for general cleanup. Mop water can be disposed of via the sink or toilet to the sanitary sewer.
Good Housekeeping
  • Use drip pans to collect fluid leaks.
  • Use absorbent materials at potential problem areas.
  • Adequately collect/remove absorbent materials from area after use and dispose of them in an appropriate manner.
  • Drain and crush oil filters (and oil containers) before recycling or disposal. Store crushed oil filters and empty lubricant containers in a leak-proof container; cover if outdoors.
  • Abide by any labels on storm drain inlets that indicate they are to receive no wastes. Do not hose down work areas to the storm drainage system or use concrete cleaning products, unless the storm drain inlet is blocked and wash water is collected and properly disposed of through a permitted sewer connection. As an alternative, use mops, dry sweeping compound, or contract professional cleaning services.
  • Confirm the use of appropriate disposal practices by contract cleaning services.
  • Do not pour liquid waste down floor drains, sinks, or outdoor storm drain inlets.
  • Store cracked batteries in leakproof secondary containers.
  • Drain and properly dispose of all fluids and remove batteries from salvage aircraft, vehicles, and equipment.
  • Drain parts and equipment of all fluids. Store on secondary containment under cover.
  • Recycle or properly dispose of the following: grease, oil, antifreeze, brake fluid, cleaning solutions, hydraulic fluid, batteries, transmission fluid, and filters.
  • Promptly transfer used fluids to recycling drums or hazardous waste containers; do not leave full drip pans or other open containers around the shop. Empty and clean drip pans and containers.
  • Use biodegradable products and substitute materials with less hazardous properties where feasible.
  • Maintain an organized inventory of materials used in maintenance areas.
  • Label and track the recycling of waste material (e.g., used oil, spent solvents, batteries).
  • Use drip plans, drain boards, and drying racks to direct drips back into a sink or fluid holding tank for reuse.
Parts Cleaning
  • Use detergent-based or water-based cleaning systems instead of organic solvent degreasers.
  • Steam cleaning and pressure washing may be used instead of solvent parts cleaning. The wastewater generated from steam cleaning can be discharged to the on-site oil/water separator.
  • Perform all cleaning at a centralized station so the solvents stay in one area.
  • If parts are dipped in liquid, remove them slowly to avoid spills.
Minimizing Exposure
  • Perform all cleaning operations indoors or under covering when possible. Conduct the cleaning operations in an area with a concrete floor with no floor drainage other than to sanitary sewers or treatment facilities.
  • If operations are uncovered, perform them on concrete pad that is impervious and contained.
  • Park vehicles and equipment indoors or under a roof whenever possible where proper control of oil leaks/spills is maintained and exposure to stormwater is prevented.
  • Watch vehicles closely for leaks and use pans to collect fluid when leaks occur.
  • Store used fluids indoors or under covering when possible. Provide secondary containment when appropriate.
Management of Runoff
  • Use berms, curbs, or similar means to ensure that stormwater runoff from other parts of the facility does not flow over the maintenance area.
  • Collect the stormwater runoff from the cleaning area and providing treatment or recycling. Discharge vehicle wash or rinse water to the sanitary sewer (if allowed by sewer authority). DO NOT discharge washwater to a storm drain or to surface water.
Inspections and Testing
  • Inspect the maintenance area regularly for proper implementation of control measures.
  • Develop regular maintenance and inspection programs for oil/water separators.
  • Characterize wastes collected from oil/water separators. Provide appropriate employee training.
Physical Site Usage
  • Where feasible, move maintenance activities indoors or provide cover over work area.
  • Use designated washing, steam cleaning, and degreasing areas to clean equipment.
  • Store mechanical parts and equipment that may yield even small amounts of contaminants (e.g., oil or grease) under cover and away from drains.
  • Store aircraft, vehicles, and equipment awaiting maintenance in designated areas only.
  • Storage should be indoors or under cover if practicable.
  • Conduct maintenance work such as fluid changes indoors.
  • Update facility schematics to accurately reflect all plumbing connections.
Structural Controls
  • Equip maintenance and cleaning areas with runoff controls that prevent discharge to storm sewers.
  • Install and maintain catch basin filter inserts that assist in the removal of oil and grease, sediments and floatables.
  • Plug floor drains that are connected to the storm or sanitary sewer; if necessary, install a sump that is pumped regularly.
  • Maintain clean equipment by eliminating excessive amounts of external oil and grease buildup. Use water-based cleaning agents or non-chlorinated solvents to clean equipment.
  • Regularly clean any catch basins that receive runoff from a maintenance area, especially after larger storms.
  • Inspect, clean and maintain sump and oil/water separators, if necessary.
Contingency Response
  • Maintain adequate supplies of spill response equipment and materials in accessible locations near areas where spills may be likely to occur.
  • Furnish all maintenance vehicles with adequate supplies of spill response materials and appropriate spill response procedures.
  • Provide the appropriate level of employee training in the following areas: spill response and prevention, stormwater pollution prevention, right-to-know awareness training, and hazardous materials management.
  • Provide employee stormwater quality awareness training.
  • Train employees on proper waste control and disposal procedures.

Successful implementation depends on effective training of employees on applicable BMPs and general pollution prevention strategies.

One of the requirements of tenant leases is that tenants must adhere to the requirements of the applicable tenant directives and associated regulations. Not adhering to these requirements can impact the standing of the tenant lease.

Additionally, many of the best management practices identified above are those included in the SWPPP, which is applicable to both the MAA and tenants at the airport. Not implementing best management practices in association with tenant activities may result in the contamination of stormwater at the airport. The MAA is legally obligated to report any illegal discharges to MDE who may issue fines or penalties for non-compliance with the Clean Water Act and the NPDES Permit. This may result in civil or criminal penalties (see Part II.C.15 and 16 of the NPDES Permit available on the Resource Documents page for more details).