Coal storage was designed to alleviate this problem. Two methods of storage were generally used; underwater, or outdoor covered facilities. To the outdoor covered pile, sometimes cooling appurtenances were applied as well; for example, means to allow the circulation of air through the depths of the pile and the carrying off of heat. Amounts of storage varied, often due to local conditions. Works in areas with industrial strife often stored more coal. Other variables included national security; for instance, the gasworks of Tegel in Berlin had some 1 million tons of coal (6 months of supply) in gigantic underwater bunker facilities half a mile long (Meade 2e, p. 379).
