Preozonation facilities were installed at the Los Angeles Aqueduct Filtration Plant originally to enhance coagulation assistance (microflocculation). The Surface Water Treatment Rule will amend this primary purpose to meeting disinfection standards. Additional ozone generation equipment and a revised ozone system operating strategy will be required to accomplish these changed objectives. The topics discussed in this paper are the considerations surrounding the development of a successful, cost-effective operating strategy. The strategy proposed herein was based on data collected between January and July 1991. On-line process monitoring plans and automated system control logic are described.