The algorithm estimates ground-level concentrations resulting from up to 19 colocated elevated stack emissions for an entire year and prints out the highest and second highest 1-, 3-, and 24-hour concentrations as well as the annual mean concentrations at a set of 180 receptors (5 distances by 36 azimuths). The algorithm is based on a modified form of the steady-state Gaussian plume equation which uses either Pasquill-Gifford or Briggs urban dispersion coefficients and includes adjustments for plume rise and limited mixing. Terrain adjustments are made as long as the surrounding terrain is physically lower than the lowest stack height input. Pollutant concentrations for each averaging time are computed for discrete, non-overlapping time periods (no running averages are computed) using measured hourly values of wind speed and direction, and estimated hourly values of atmospheric stability and mixing height. Software Description: The model is written in the FORTRAN programming language for implementation on an IBM 3090 computer. The software is distributed on a 5 1/4-inch IBM/PC-compatible diskette. Data is in compressed format but a dearchive utility is included.