Not directly relevant, but useful comparative info.
Before every flight, fuel samples are taken from sump drains in the bottom of the tanks of light aircraft. The purpose is to verify the type of fuel (via smell and dye color) and to look for any evidence of water (water will bubble to the bottom of the sample jar.)
This takes about 3-4 ounces of fuel out of each check point. Pilots usually don't want to put this potentially contaminated fuel back in the tank, so back in "the old days" we'd just hurl it out onto the tarmac; it would evaporate virtually immediately.
However, these days the EPA and most states' DEPs prohibit such activity. All
require that the fuel either be recycled back into the tank (through a filter) or disposed of properly into a waste/reclaim tank/drum. There have actually been reports of EPA (or was it state DEP?) officials witnessing folks throwing these few ounces of fuel onto the tarmac, and the small airports were shut down for decontamination as a result. Many airports, especially older ones and those that evolved from military bases, have grounds that are are highly contaminated.
If one were to be working on, let's say, approvals for a new race track and there were concerns about ground water contamination of hydrocarbons (and lead!), I'd suggest that refueling - and maybe even other activities involving the possibility of spills, such as oil changes - be limited areas specifically designed to handle any such spills. I'm no waste containment expert, but these precautions could include concrete-lined areas with proper drainage towards vessels specifically designed to collect and filter any hydrocarbon wastes that may spill.
Some interesting reads on the subject:
http://www.nj.gov/dep/airworkgroups/docs/wps/NA005_fin.pdf
http://www.aopa.org/asf/hotspot/fuel_check.html
http://www.nifc.gov/ihog/chapters/2006chapter13.pdf
...and many more... [/b]