Characterisation and modelling of a fractured crystalline aquifer contaminated with hydrocarbons

Abstract

A-1 Jet fuel leaked into the environment through a pipeline near Movements 2 in Louis Trichardt Air Force Base. The duration of fuel spillage continued for approximately 15 years resulting in a free phase pollution plume of approximately 750m in length and 250m in width. The free phase plume attained a maximum apparent thickness of 10.2m. This is currently the largest hydrocarbon pollution event in South African history. An investigation commenced during December 2000, which had the following broad objectives: determine the lateral extent of free phase and dissolved contaminants, prevent the spreading of contaminants and determine the most efficient method to rehabilitate the environment. A total of 67 boreholes were drilled in a phased approach following various geophysical surveys. A numerical model was developed to evaluate the extent and migration of dissolved contaminants. Monitoring of the plume though water quality samples indicate that low levels of pollution are present adjacent to the free phase plume. The available data and numerical model indicate that pollution is restricted to the air force base. Current remedial measures include the bailing of fuel from selected boreholes, which will be replaced by a pump-and-treat system.