PM10 dispersion modeling for Treasure Valley, Idaho

The recorded exceedances of the 24-hr PM10 National Ambient Air Quality Sta ndard (NAAQS) in Treasure Valley, Idaho, have been associated with prolonge d stagnation periods during the winter. A comprehensive modeling study of P M10 impact in Treasure Valley was performed to support the State Implementa tion Plan (SIP). The study included base-year and short-term episodic condi tions. The ISCST3 (Industrial Source Complex Short Term 3) model, using the base-year meteorology and gridded emissions of mobile sources, point sourc es, and wood burning as input, generally agreed well with measurements in b oth temporal patterns and annual averages. The WYNDvalley model was evaluat ed using monitoring data and was used to simulate the PM10 impact for episo dic exceedances during stagnant winter conditions. An emission inventory wa s prepared for a base year (1995) and then extrapolated to the years 2000, 2005, 2010, and 2015 in order to determine air quality planning requirement s. According to the simulations using base-year emissions and meteorology, exceedances are not expected. However, exceedances at some stations could b e expected using projected emissions and episodic meteorology. Results from emission control strategies we developed indicate that mobile-source emiss ions have the most significant impact; reduction of 25% would be needed to eliminate the simulated exceedances in all projected years.