Respondent owns and operates a chemical plant to produce many grades of high density polyethylene (HDPE). On August 2, 2015, Respondent identified a release of hexane into the adjacent facility to Respondent cooling water system and released to atmosphere. The cause was due to two of 658 “U” tubes from the LHC Tails Cooler failed due to fretting (wearing away) at the baffle hole contact point. Respondent estimated that 154,000 pounds of hexane was released to the cooling water system and released to the atmosphere over an 11 day period, from July 22 to August 2 when the leak was identified and the cooler was isolated. The time of the leak was determined by an investigation after the leak was isolated. The fretting was caused by water flow induced vibration which compromised the support of the tubes at the baffle holes due to corrosion of the carbon steel baffles.