ENV-16-42 EPA Modeling Guideline Changes: Important Updates for the Petroleum Industry

Description:

In 2015, EPA proposed substantial changes to its modeling guidance (“Appendix W”) for the first time in over 10 years. The changes to the modeling approaches, expected to be finalized before the end of 2016, will have important implications for the petroleum industry. Proposed changes to EPA’s preferred short-range model, AERMOD, involve more accurate predictions in low-wind conditions. However, a battle between industry and environmental groups has ensued on the accuracy of these changes, which often result in lower predictions. Other important issues for AERMOD involve source characterization advancements that EPA is considering for modeling applications, and important updates to the tiered NO2 modeling options. For long-range transport modeling, EPA has proposed an important change by determining that long-range transport modeling is rarely needed, and can be taken care of with AERMOD used as a screening tool at a distance of 50 km. In addition, EPA has decided to withdraw its support of the currently-preferred long-range transport model, CALPUFF. In response to the Sierra Club petition that new sources need to model their impacts for ozone and secondary PM2.5 concentrations (for which there are currently no preferred models), EPA has proposed a tiered approach for accomplishing this objective. The approach is “flexible”, but currently lacks specifics. As of August 1, 2016, EPA proposed a new Significant Impact Level (SIL) for ozone and has re-proposed SILs for PM2.5. The SILs are important because of the ability to waive modeling requirements if new source emissions are below a threshold (the Model Emission Rate for Precursors, or “MERPs”) that EPA may propose by the time of the AFPM conference.