The Omohundro (OMO) Water Treatment Plant (WTP), built in 1889, is on the National Register of Historic places. This aging plant is placed under the continuous stress of meeting service area demands. As such, Metro Water Services (MWS) has begun the effort to significantly rehabilitate, expand, and modernize the OMO WTP. This upgrade effort will see the design and construction of new facilities for all WTP processes. These comprehensive modifications will be logically sequenced and coordinated so the plant may continue producing safe, high-quality water with minimal operational interruptions. The existing hardware and software for the distributed control system (DCS) at the OMO WTP is obsolete. Additional parts to integrate the new facilities with the existing DCS are not available and would not provide a practical long-term solution. Utilizing separate SCADA systems for new and old facilities is not desirable for operational effectiveness. The best solution for this imperfect situation was the design and implementation of a new control system throughout the existing WTP. The planning stage included defining communication, programming, and visualization standards. Carollo Engineers worked with MWS management, operations, and maintenance staff to develop standards and a customized SCADA interface. The design phase included the development of as-built P&IDs, control strategies, I/O lists, and new network topologies. These documents were prepared through detailed site investigations and a series of workshops with MWS staff. The implementation of the plans and designs will require detailed cutover plans to ensure quick delivery and avoid operational interruptions. Critical to the success of the project and its goals for enhanced process oversight and optimization were the following elements: •Inclusion of the programmers and integrators during the planning and design phases. •Involvement of operations and maintenance staff in development of standard code blocks, alarm management, data utilization, visualization, and optimized reporting. •Leveraging the limited existing I/O to optimize the functionality of the current process facilities. This included the introduction of various control strategy upgrades such as implementation of overall plant flow control and automatic filter backwashes to boost process performance within the existing facility. •Performing detailed I/O checks in the field during the design phase to expedite cutover to the new DCS. •Detailed plans and schedules for the cutover of each network and control cabinet to prevent treatment upsets. The new SCADA system at OMO WTP will provide operation staff with enhanced process control, functionality, and tools for process optimization within the existing facility. With the overall plant flow control being managed through the new SCADA platform, staff manpower can be shifted from manual tasks to the optimization and oversite of the treatment process.