Evaluation of AERMOD at a Rural Petroleum Refinery in Simple and Complex Terrain

AERMOD’s performance was evaluated against both observed and ISC3 model-predicted SO2 concentrations for impacts emitted from BP-Amoco’s Mandan, North Dakota refinery and surrounding sources. Observed concentrations were obtained from monitoring stations located in both simple and complex terrain. Evaluation of the results showed that AERMOD predicted significantly lower concentrations than ISC3 in the complex terrain, with predicted to observed concentrations of approximately 2:1, versus ratios for ISC3 of nearly 10:1. Aermod-predicted impacts in the simple terrain were approximately the same as ISC3, and the predicted to observed ratios were approximately, 1:1 for both models.

Since this is one of the first efforts to use Aermod for regulatory compliance and permitting purposes, several interesting lessons were learned. Meteorological data processing can be an extensive process if the surface and upper air data are not in one of the expected formats. Terrain processing is limited to areas in which USGS DEMs data is available. Sensitivity analysis of AERMET input parameters revealed the importance of these in determining model-predicted maximum concentrations. These comments, and others, are provided to the AERMIC committee with the intention of suggested improvements for the future.