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.1 KEI-P91-0202 .R7 March 18 , 1993 Page 4 and assumed zero volatilization, which was again extremely conservative. No surface parameters or volatilization to the atmosphere were considered since the source was assumed to be at a depth of 25 feet below the surface. Input parameters used in Simulation #1 are included in Appendix A. 2 . Simulation #2 The second simulation was conducted using assumptions which were more realistic and representative of the actual parame- ters encountered in the field. The input data were again divided into four general categories, which included climate, soil, pollutant characteristics , and application data. The climate and soil input data used were the same as for Simulation #1, since the characteristics of these categories are unique to the site and not to the simulation. The pollutant characteristics were again created to simulate the migration of benzene The properties of benzene used were the same as in Simulation #1, except that a conservative but more realistic biodegradation rate was introduced in this simulation. The application parameters used were more realistic than those used in Simulation #1 . The source of contamination was again assumed to be at a depth of 26 feet below the surface, corre- sponding to the area of highest contaminant concentration left in place. The horizontal area was assumed to be five feet by five feet, corresponding to the width of the largest excava- tion bucket typically used to remove soil . The five by five foot area is considered to be a more realistic dimension for an area of contaminated soil left in place beneath a former underground tank. SESOIL conservatively assumes that the entire five by five foot area is contaminated with the maximum concentration of benzene detected at that depth. The area of the SESOIL model for Simulation #2 is shown on Figure 2 . The introduction of pollutants to the subsurface system was again created by entering an instantaneous spall corresponding to the time of the tank excavation (which was in March of 1991) . This source was again assumed to occur only in the first month of the simulation. The simulation was run for a period of ten years as before, and assumed partial volatiliza- tion, which is more realistic than zero volatilization as in Simulation #1. As before, no surface parameters or volatil- ization to the atmosphere were considered since the source was Is assumed to be at a depth of 26 feet below the surface. Input parameters used in Simulation #2 are included in Appendix A.