During formulation of emergency response plans for a proposed new chemical plant, it is predicted that ammonia would be released continuously at 100 lb/s if a particular pipeline in the plant were to rupture. The pipeline would be located near ground level. It is decided that anyone exposed to potential concentrations exceeding 500 ppm must be evacuated. What will be your recommendations as to the evacuation distance in the downwind direction? Assume a wind speed of 6 mph and that the sun is shining brightly. Consider both rural and urban siting options for the plant.