In this study, we evaluated the heterotrophic microbial communities colonising stone ballasts at diesel depots. The number of bacteria (both total culturable heterotrophic bacteria and hydrocarbon-degrading bacteria) was proportional to the level of hydrocarbon contamination. However, there was no significant difference in the level of total culturable heterotrophs (TCHs) and the hydrocarbon degrading bacteria. Addition of nutrients to the ballast stimulated the biological activity and possibly the removal of hydrocarbons. However, this was only evident in the highly contaminated stone ballasts samples. The biological activity was evaluated using CO2 production. The production of CO2 was higher in nutrient amended treatments in which high numbers of TCHs were present. Characterisation of heterotrophic communities using Biolog revealed differences in the microbial metabolic profiles for the different sites. The results suggest that the heterotrophic microbial communities at different diesel depots are different.