31 Mar 97
disposing of AFFF solution would be a hot, dry climate with high
wind velocities. To facilitate the evaporation process, the
holding area would need a relatively large surface area in order
to make this a viable option. Ponds should be designed with a
shallow depth and large surface area. For example, a pond
designed to contain 20,000 gallons of foam solution should have
an area of approximately 12,000 square feet and be filled to a
depth of approximately three inches. Such a pond of circular
configuration would require a diameter of about 120 feet.
Assuming the absence of rain, complete evaporation would take
about 64 days under calm, damp conditions. But under windy, dry
conditions, the 3-inch depth would evaporate in less than one
day. It is important to keep in mind that this example is based
upon there being no rainfall during the evaporation period.
Rainfall must be considered in sizing the pond in the same manner
as done for earthen ponds.
Under certain conditions, on site treatment may be the most cost
effective disposal method for AFFF wastes. This may involve
aerobic digestion, anaerobic digestion, air stripping or other
treatment method. Several different methods of on-site AFFF
treatment are being developed and may be available in the near
future. Permits may be required if the effluent from such
treatment systems are discharged to surface waters.
In certain circumstances, it may be necessary to truck AFFF waste
to an off-site treatment facility. This method of disposal is
very costly and should only be considered as a last resort.
Aqueous film-forming foam (AFFF) is frequently used in fixed fire
suppression systems for combating flammable and combustible
liquid fires. Discharges from these systems can produce
thousands of gallons of foam-water solution. Unplanned
discharges usually occur due to system malfunction or human
error. Planned discharges are associated with acceptance and
routine testing of these systems. "Open" systems such as deluge
sprinkler and nozzle systems are more susceptible to inadvertent
AFFF discharges than are closed-head sprinkler systems.
Accordingly, foam solution containment requirements for closed
system are less than for open systems. Designers need to