In the course of their work along the East Coast, over boards have used any material which proved suitable in rebuilding the sea walls and which could be transported at reasonable cost. Slag from the steel works at Scunthorpe was used on the Lincolnshire coast; and ashes mixed with chalk were used along the North Kent coast. Experiments in the use of colliery waste proved unsuccessful. The use of this waste material is in any case severely restricted by the high cost of haulage from the source of supply to the coast.