Site Characterisation in Support of Monitored Natural Attenuation of Fuel Hydrocarbons and MTBE in a Chalk Aquifer in Southern England
This Case Study Bulletin describes a research project, which was carried out to determine whether monitored natural attenuation was a viable option for managing fuel hydrocarbon contamination in a chalk aquifer in southern England. The research, which was carried out from February 2000 to March 2001, was undertaken by the University of Sheffield on behalf of TotalFinaElf at a petrol filling station site. The study was commissioned following the accidental release of approximately 55,000 L of unleaded petroleum from a ruptured underground storage tank in February 1999. The spilled petroleum fuel contained two ether oxygenates, methyl tertiary-butyl ether (MTBE) and tertiary methyl-amyl ether (TAME), at concentrations of 2.88 % v/v and 1.65 % v/v, respectively. As a result of the spill, the unsaturated zone beneath the site has been contaminated with petrol which belongs to a class of contaminants known as light non-aqueous phase liquids (LNAPL). The petrol has migrated below the water table at 20 m below ground level. Dissolution of the LNAPL has resulted in contamination of the saturated zone with a range of petroleum hydrocarbons that include diesel range hydrocarbons (DRHC), benzene, toluene, ethylbenzene, xylene (BTEX), MTBE, TAME, and other aromatic compounds.