Bioremediation is defined by the U.S. Environmental Protection Agency (EPA) as a managed or spontaneous process in which microbiological processes are used to degrade or transform contaminants to less toxic or nontoxic forms, thereby remedying or eliminating environmental contamination (EPA, 1994). These microbiological processes may reduce hydrocarbon concentrations in various types of soils and sediments to levels that no longer pose an unacceptable risk to the environment or human health (Linz and Nakles, 1997). However, hydrocarbons that remain in treated soils and sediments still might not meet stringent regulatory levels, even if they represent site-specific, environmentally acceptable endpoints (NRC, 1997). This unresolved issue of the availability of residual hydrocarbon contaminants is the focus of this work.