The Southern Nevada Water Authority (SNWA) is installing ozonationfacilities at their existing and new water treatment plants in order to attain an enhanced disinfection barrier of 2-log Cryptosporidium oocysts inactivation credit. Ozone applied to Lake Mead sources forms bromate, which is a regulated disinfection byproduct. Operating strategies must be optimized in order to meet disinfection objectives without excessive bromate formation. One optimization strategy is to operate at the lowest possible ozone dosage. Dose minimization is achieved by good process control and by appropriately computing the Cryptosporidium oocyst inactivation credit. The most complicated and accuratemethod to calculate the disinfection credit is the Integrated Disinfection Design Framework (IDDF). In this study the ozone dose required to achieve a 2-log Cryptosporidium oocyst inactivation credit using the benchmark log-integration CT-value calculation method was assessed using a computer simulation model of the full-scale ozone facilities. Pilot plant and bench-scale ozone demand and decay test results were used to calibrate the model. The model was used to calculatedose increase and decrease at T10/T ratios of 55% and 75%, respectively. These data were then compared to the dosage decrease achieved by using the IDDF methodology. Includes 8 references, table, figures.