Sites" Definition in the UK Similarly to the US, the UK defines an underground tank as having 10% of its combined potential volume below the ground. Decommissioning an underground tank in the UK The requirements set by The Environment Agency for Decommissioning an underground tank apply to all underground storage tanks and not just those used for the storage of fuels. They give extensive guidance in The Blue Book and PETEL 65/34. The Environment Agency states that any tank no longer in use should be immediately decommissioned. This process includes both the closing and removal of a UST system (the tank and any ancillaries connected to it) as a whole and the replacing of individual tanks or lengths of pipe. Regardless of whether the decommissioning of the tank is permanent or temporary; it must be ensured that the tank and all components don't cause pollution. This is true of the removal and of any filling of the tank with inert material. The Decommissioning of a tank can be via removal from the ground after any volatile gas or liquid has been removed. This is called bottoming and degassing the tank. The other option involved filling the tank with either: A Sand and Cement Slurry Hydrophobic Foam Foamed Concrete If any plan is made to leave the tank on site, the owner will be responsible for keeping record of: The Tank's Capacity The Product it Contained The Method used to Decommission the tank, if any The Date of the Decommissioning If any tanks and their pipework have been deemed unsuitable for petroleum spirits then they shouldn't be used for the storage of any hydrocarbon based products without first checking their integrity. See also Environmental impact of the petroleum industry References External links EPA UST Program EPA summary of 2015 rule and compliance information State UST programs: California New Mexico Oklahoma Pennsylvania Texas Wisconsin Oil storage Containers Fuels Filling stations Petroleum infrastructure Storage tanks