In situations where there is insufficient space to retrofit conventional oil water separators into existing stormwater drains at an aircraft refueling ramp, the use of permanent booms can be used to perform the function of removing sheen from stormwater and containing any fuel spills that migrate through the storm drain system to surface waters.
The associated photograph shows a conventional spill containment boom in place at an outfall from an aircraft refueling ramp at Newark Liberty International Airport. The purpose of this boom is to capture sheen and spills from the aircraft fueling ramp that travel down the storm sewer system. Most containment booms have been developed for emergency response use, which involves short-term deployment rather than long-term use.
At Newark Liberty International Airport, a study is underway to update the boom system and add absorption filter media behind the booms to prevent fuel passing under the booms due to current conditions or over the booms due to wind conditions. The photograph below indicates a newly developed permanent boom system being considered in the study.
Where the stormwater outfall discharges via a headwall into surface water body, the use of spill containment booms at the outfall can prevent the flow of spilled fuel from spreading on the surface water body.
Such booms typically can retain a layer of fuel up to four inches thick within the boomed area. By sizing the boomed area, adequate spill retention can be achieved for spills of a few hundred gallons. The disadvantage of booms is that they will start to leak fuel when the current reaches a velocity of approximately .85 mph. This is caused by the flow of water under the boom skirt entraining fuel drops and causing fuel to be carried past the boom.
Under high-wind conditions (above 15 mph) wave action can also cause fuel to be pushed over a normal boom.
Stormwater outfalls at large airports typically have very high flow rates during storm events. A four-foot diameter stormwater pipe (which is not large for airport stormwater systems) can convey up to 54,000 gpm (120 cfs) and the use of in-line adsorption media filters is not practicable at such high flow rates.
For such stormwater outfalls, it is normally more cost-effective to capture the fuel beyond the end of the outfall pipe by using a spill containment boom where conventional oil water separators cannot be installed. Such outfalls require approximately one linear foot of boom for every cubic foot per second of flow from the outfall. The upstream side of the boom must have absorbent filter booms installed to capture fuel and prevent boom leakage under high current or wind conditions. The presence of this absorbent boom ensures that hydrocarbons in the first flush of stormwater are removed cost effectively.
N.D. ‘Dennis’ Eryou, Ph.D., P.E. is an engineer in private practice with 25 years experience in aviation fueling systems and environmental issues. He can be reached at firstname.lastname@example.org