On April 11, 2003, DDW experienced an explosion of a feeding tank used in a caramel coloring process. This tank was subjected to pressures of up to 35 pounds per square inch on a daily basis, but it was not equipped with a pressure safety relief valve. The explosion caused the death of an employee, the release of 8000 pounds of ammonia into the surrounding community, and resulted in debris from the tank explosion being ejected over a wide area. A five hundred piece of the tank lid landed on a commercial rail road track. People within a two block radius were evacuated and people within a one-half mile radius were required to shelter-in-place. DDW violated the General Duty Clause by failing to: (1) identify hazards associated with its caramel coloring process and to perform a hazard analysis on the feeding tank; (2) design a safe facility by not incorporating pressure relief safety valves or other pressure relief devices on the feeding tank and by failing to design the feeding tank with sufficient engineering design and layers of protection to prevent the explosion and subsequent release of nearby toxic chemicals; and (3) minimize the consequences of the release by failing to train its operators as to how to respond to process upset or emergency conditions. Following the explosion, DDW did not conduct its own internal investigation of the accident. The requirement to conduct this investigation is contained in 40 CFR � 68.60. The Louisville Metro Air Pollution Control