Background
On February 18, 2015, while ExxonMobil was conducting maintenance on its Fluid Catalytic Cracking Unit (“FCCU”), an explosion occurred in its Electrostatic Precipitators (“ESPs”). The ESPs control air pollution, and the explosion rendered the ESPs totally inoperable. The FCCU has remained completely shut down since the explosion.
ExxonMobil repaired the ESPs and proposed to re-start the FCCU and associated equipment, including the air pollution control system, altering its start-up sequence by operating for approximately six (6) hours without the ESPs being fully energized. The alteration of the start-up process was anticipated to result in higher opacity and particulate matter emissions during that six-hour period compared to prior start-ups at the Torrance Refinery. ExxonMobil stated that the new start-up sequence was necessary to improve the safety of their operations.
During a public hearing on April 2, 2016, following testimony from South Coast AQMD staff, Exxon Mobil representatives, and members of the public, the South Coast Air Quality Management District (South Coast AQMD) Hearing Board issued an Order for Abatement (OA) (PDF) to ExxonMobil, designed to minimize emissions and protect the health and safety of nearby residents while the refinery restarted its major gasoline producing unit and effectively resumed full operations.
Air Monitoring
South Coast AQMD conducted an air monitoring assessment during the startup of the ExxonMobil FCCU using a combination of monitoring methods to assess pollutants of primary concern (PM10 and PM2.5) in the adjacent areas of the facility. Monitoring efforts focused on real-time continuous monitors and employed other portable PM monitoring device and sensors for gradient measurements during the startup event. More details including the results are published here. (NOTE: select the ExxonMobil monitoring sites from the Monitoring Sites drop-down in the upper right corner of the screen to view the results). Information regarding the mobile platform measurements can be found here.
NOTE #1: On June 17, 2016, repaving activity conducted nearby the Site #1 monitors may have resulted in elevated readings not related to the FCCU startup.
NOTE #2: On May 6, 2016 from 6am to 11am, the monitor labelled “ExxonMobil Site 1 – PM2.5” had technical issues and reported high values (65530 ug/m3) as error flags that were inadvertently passed to the real-time monitor webpage. As indicated in the FAQ, data published to the website is preliminary and therefore subject to change upon final review. Data QC and review for the continuous hourly measurement are performed later to confirm the validity of the measurements, and this process follows the EPA guidelines for data handling. Preliminary data is subject to automatic QC routines, which filter out bad data caused by power failure and instrument malfunction. The automatic QC routine did not appropriately filter out the bad data caused by the instrument issue on May 6, 2016, causing incorrect high hourly and 24 hour averages of PM2.5 for this monitor. The instrument has been checked and the automatic QC routines are being assessed to prevent future occurrences.