When the first negotiated rulemaking began in 1992, data on existing treatment processes, the impact of modifying treatment processes on treated water quality, and the costs of such treatment were not readily available. The technical support group for the negotiating team gathered available information and used a Water Treatment Plant (WTP) Simulation Model to predict the water quality delivered to customers, both under existing conditions and following treatment plant modifications, to meet more strict regulations. An alternative approach to the process described above is to take advantage of an automated decision making tool which will allow selection of process improvements to satisfy some stated criteria for disinfection and disinfection byproducts (DBP). This paper describes a surface water analytical tool (SWAT) that considers process improvements within a treatment plant in a stepwise manner in order to satisfy some stated criteria. Operating this tool will allow the user to identify the proportions of treatment plants that need various levels of process improvements to satisfy the goal. Includes figures.