Along with the rest of the UK electricity generation, distribution and supply industry the client has a large number of transformer sub-station sites which must be brought up to compliance standards.  Even modest sized electricity transformers contain large quantities of oil for cooling and insulating. For many years there has been gradual leakage and occasional spills from routine re-filling and emptying so at most sites, without satsifactory containment, there has been a history of possible localised ground contamination and the risk of wider pollution in the event of major failure. All electricity companies have been aware of the problems of inadequate oil containment and have been making good, steady progress in upgrading their sites over the last ten years or so but this is a very costly exercise.