The report includes an evaluation of candidate meteorological models and acid deposition models. The hybrid acid deposition/air quality modeling system for the Rocky Mountains makes use of a mesoscale meteorological model, which includes a new diagnostic wind model, as a driver for a Lagrangian puff model that treats transport, dispersion, chemical transformation, and dry and wet deposition. Transport will be defined from the diagnostic wind model based on the wind at the puff center. The treatment of dispersion will be based on the parameterization in the PNL/MELSAR-POLUT, while retraining the MESOPUFF-II dispersion algorithms as an option. Based on the evaluation of the chemical mechanisms, the RIVAD chemistry appears to be the most scientifically sound, as well as consistent, with the Lagrangian puff model formulation. Dry deposition will use the CCADM dry deposition module with some minor adjustments. Wet deposition will be based on the scavenging coefficient approach as used in the ERT/MESOPUFF-II.