A malfunctioning flare from the Marathon Petroleum Corporation’s refinery ended up being the cause of a foul odor wafting over Detroit this past weekend.
The odor is from mercaptan, which is a chemical used to make natural gas smell like rotten eggs. That makes is easily detectable. Marathon said it will take days to get the flare shut down and properly repaired.
The company said the air is not harmful.
“Our ongoing air monitoring has not detected dangerous levels of any substances,” said a statement from Marathon.
Marathon released a statement Sunday:
“Marathon Petroleum has implemented processes at its Detroit refinery to stop a release from a flare that is not functioning properly. These processes have significantly reduced the amount of material flowing to the flare since this morning.
“In order to conduct repairs to the flare, we are also removing the contents of various vessels connected to the flare. We are conducting this work as safely and as quickly as possible, and we anticipate completion by the end of the day tomorrow, Feb. 4. Although there has been an odor from the release, our ongoing air monitoring has not detected dangerous levels of any substances. We believe the odor is largely from mercaptan, a substance added to natural gas to give it a detectable smell. We will continue to conduct air monitoring on a constant basis in nearby communities as a precaution, and are making our air-monitoring data available to regulatory and emergency response agencies.
“We apologize for the inconvenience to the community, and we are conducting a thorough investigation to determine what caused this release. Once determined, will implement the necessary corrective actions so that this does not happen again.”
The Michigan Department of Environmental Quality (MDEQ) released this statement:
“The MDEQ continues to coordinate with EPA and the City of Detroit on air monitoring and response activities related to the malfunction of the coker flare gas system and resulting odors from the Marathon refinery in Detroit.
“MDEQ, City of Detroit, and EPA staff met with Marathon personnel at the refinery today and were briefed on steps taken to reduce and reroute gas normally combusted by the flare system in an effort to reduce the rotten egg odors being emitted from the refinery. Marathon also briefed MDEQ on plans to safely shut-down the refinery in the coming days to make repairs to the coker flare gas system.
“The source of the odors created by the flare gas system are suspected to be hydrogen sulfide and mercaptan compounds. Both of these compounds have extremely low odor thresholds meaning they can be smelled even at very low levels.
“Apart from the odor, neither EPA’s or Marathon’s air quality sampling have detected any exceedances of health thresholds. MDEQ’s Air Quality Division is reviewing monitoring data from DEQ’s own ambient air monitoring stations in the area in addition to reviewing the Marathon data.
“A follow-up meeting is scheduled with the company and government officials tomorrow afternoon.”