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BACKGROUND The City has historically experienced water quality issues associated with nitrification during the summer and fall months within the potable water in the lower zone of the water distribution system. After an intensive sampling program in 2019, it was found that the cause of nitrification was the reduction of chloramines (used to disinfect the water) to unacceptable levels. Chloramines are introduced by Zone 7 at its Del Valle water treatment plant and its groundwater production wells, as well as at City-owned groundwater production wells. However, if water is stored in the distribution system for a long period, the chloramines slowly degrade. The installation of a residual control system (RCS) at the Sycamore and Foothill tank reservoirs was recommended by the project's design consultant, Carollo Engineers, as the mechanism to introduce additional chloramines to reduce nitrification. The Sycamore and Foothill Reservoir Residual Control System Project consisted of the procurement and installation of a pre-manufactured RCS from UGSI Solutions Company, electrical system modification/installation, installation of fencing and general site improvements, and installation of piping at the Sycamore and Foothill tanks reservoir sites. On February 16, 2021 , City Council awarded the contract to the lowest responsible bidder, Cazadoro Construction, Inc., in the amount of $1,471 ,000, and authorized the Director of Engineering to approve change orders up to the project contingency amount of $215,869. DISCUSSION The Sycamore and Foothill Reservoir Residual Control System Project has reduced the nitrification in the system and increased the overall water quality in the lower zone of the City's water distribution system. The project has also improved the operational flexibility and reliability of the water system. The RCS helps generate chloramines that disinfect the water stored in the reservoirs at the Foothill and Sycamore tanks and the water that is conveyed through the distribution system by injecting sodium hypochlorite and liquid ammonium sulfate to promote the formation of chloramines. The system manufactures sodium hypochlorite on-site by using salt, water, and a DC current, requiring only the salt to be replenished by the operators. Liquid ammonium sulfate is delivered monthly and stored within the trailers; the water conditioning tanks are changed out every two weeks during peak operations. Proprietary "control logic" self-monitors the system and automatically doses the water to ensure the proper level of chloramines. Both the advanced design and simplicity of the system allow for ease of operation and maintenance. Mechanical mixers were installed within the tanks that will help with water quality by reducing the stratification of water within the tanks while efficiently mixing the added chemicals. The equipment was connected to the Supervisory Control and Data Acquisition (SCADA) system under the City's existing on-call contract for SCADA integration. Page 2 of 4