the cause of the ash spill was described by epa as a limited structural flaw. a storm pipe nearby the deposits of a coal ash slurry containment area broke and allowed for the leakage. coal ash slurry is produced during the process of burning coal. it is the left over impurities that stick around after burning coal for electricity. coal companies have found that the cheapest way to store this waste is to mix it with water and store it in a pond. these ponds have been found to have leaks that can dispose hazardous material into surface water among other things. epa has identified at least 25 coal ash ponds in the southeast that are "high hazard".this material was released into the dan river because of the collapse of a 48 inch drain pipe. the pipe was made of concrete and corrugated metal and reason for the fracture cannot be identified. what resulted was 39 thousand tons of coal ash and 27 million gallons of ash pond water were deposited into the dan river.