Cain and Associates Engineers and Constructors, Inc. of Mobile, Alabama, were engaged by a Law Firm from Knoxville, Tennessee, to investigate the cause and origin of the collapse of a large Wastewater Treatment Plant Equalization Basin in Gatlinburg, TN. On April 5, 2011, following a period of very heavy rains, the equalization basin at the wastewater treatment plant experienced a catastrophic failure when the east wall of the structure collapsed (Figures 1 and 2). As a result, over one million gallons of wastewater were released. In addition, two employees working in a flow control building located approximately 8 feet in front of the east wall were killed in the incident.