The aim, when decommissioning a refuelling site - whether commercial, military, industrial or retail - is to return the land to a state where a builder can move in and start construction with no more problems than on any other site. There is around a 50/50 chance of having pollution on refuelling sites in the first place. In our experience, where there is pollution, it will be extensive, as it is likely to have come from a leak that no one has noticed for some time and fuel tends to spread fairly easily through the ground. Generally, the older the site the worse the pollution. Very old sites would have been constructed with the tanks just bedded into sand. These would often have rotted and leak extensively. Constructers of later sites would embed the tanks in concrete, which helped confine the problem, but it was not a complete answer. The latest double-skinned tanks and lines, equipped with leak detection technology, have improved things enormously. The geology of the site also has a bearing on how far pollution will spread. For example, clay soil will confine it to a limited area, while sandy soil will spread it throughout the site, and even into adjoining land.
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