Put it down your trousers, making sure your socks are on the outside. Up the road shake a leg and the soil disappears. Saw this in a film once
Might take a while though.
Seriously though talk to the council who might accept the soil as waste at your local tip. It cannot be considered 'clean' unless tested. Probably easier to dispose of to a farmer or similar who needs it. What volume are you looking at? Should go to a licensed site or big fines. All you will save is the transport cost so doubt it is a worthwhile exercise to dispose of the soil yourself.