The most serious violations that EPA found involve the facility burning hazardous waste in the kiln under conditions which do not meet required standards. The kiln is subject to the HWC MACT standards at all times that hazardous waste is in the combustion chamber. The HWC MACT requires Lone Star to continuously monitor and record operational data and keep the values under the Operation Parameter Limits (OPLs) set during a required performance test. There were several instances in which the Carbon Monoxide (CO) concentrations in the kiln combustion chamber suddenly spiked to values above the monitors measurement capabilities and instantly brought the hourly rolling average CO concentration above the 100 parts per million (ppm) limit required under the HWC MACT at 40 C.F.R. ? 63.1220(a)(5)(i)(A). A high CO concentration is indicative of incomplete combustion in the combustion chamber. Ring build up collapse in the rotary kiln makes up a large contribution of CO OPL exceedances. An Automatic Waste Feed Cut-Off (AWFCO) will initiate any time that there is an exceedance of an OPL; a valve will close to shut off hazardous waste feed. There is a relay time between when the monitors detect the CO concentration, the values are averaged, and, when the limit is exceeded, relay to back to the AWFCO system. During that relay time, hazardous waste is still being fed to the combustion chamber and conditions are not conducive to complete combustion due to decreased oxygen levels. EPA has es