A study will be performed on the use of a monotone implicit Large Eddy Simulation for the determination of time averaged velocity fields as well as eddy diffusivities for transport phenomenon. The ADVEDS code (Atmospheric Dispersion of Vapor and Evaporating Drops and Solids), which decouples the determination of a steady or time-averaged velocity field from the transport phase, will be employed in the study. Results of simulations using various grids and turbulence models will be compared to measured concentration profiles for a release of vapor in the vicinity of an L-shaped building. A treatment for making the LES consistent with atmospheric boundary layer profiles is also discussed.