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Kimley»>Horn Page 7 The clearwell turbidity data at Hobart suggest operations has challenges maintaining target pH values and maximum turbidity than at Oslo. This was confirmed during operational testing. Elevated alkalinity in the distribution system has resulted in fewer pH excursions and o The elevated alkalinity has resulted in fewer pH excursions, but an overall reduction in system pH. o Increase in alkalinity and mitigating turbidity excursions through supplementing lime slurry pH adjustment with caustic will assist IRCU in maintaining target pH of —8.3. In 2013, Indian River County Utilities Department (IRCU) implemented a finished water stabilization system to replace the zinc orthophosphate (ZO) feed system in order to improve finished water quality, enhance control of potential corrosion, and provide water with more buffering capacity within the distribution system. This project consisted of discontinuation of zinc orthophosphate corrosion inhibitor feed and implementation of carbonic acid solution with lime slurry feed at both water treatment plants in order to improve buffering capacity and stability of finished water. In 2016, Kimley-Horn provided a distribution system water quality and corrosion investigation report which included gravimetric and linear polarization resistance (LPR) testing results, water quality data review, and operational adjustments at the WTPs in an effort to yield more favorable finished water quality conditions. In summary, several key observations from the previous evaluation include: • Inconsistent water quality influences corrosion rates negatively. Variations in water quality may have been more tolerable in the past with the use of corrosion inhibitor (ZO), allowing wider fluctuations in these parameters without mattering. • Lead corrosion rates were less than copper corrosion rates with the change in corrosion control treatment from ZO to CO2/lime. o Supports the concept that copper corrosion is more susceptible to fluctuations in water quality. • The quality and purity of lime slurry (Cal—Flo) directly affects the turbidity of the product water, and subsequent effectiveness at increasing pH and alkalinity. Suspected impurities in the Cal—Flo product may contribute to this issue. • The Hobart water plant produced more inconsistent water quality from the post-treatment system, mostly during the SCADA system improvements. Operating the West/South and East/North clearwells separately may contribute to this inconsistency. • Lack of consistent chlorine feed to the Hobart West/South clearwell was observed, which may interfere with lime dissolution in the mixing chamber. • Flushing of areas within the water distribution system helped expedite flushing and removal of zinc and other turbidity formed during the transition from ZO discontinuation and CO2/lime feed system implementation. • Raw water blend was reduced at both facilities to reduce the disinfection byproduct formation, and the CO2/lime feed system was implemented to restore alkalinity and hardness. Although the system was designed to operate at higher feed rates, operating costs will be higher with this change in operation. Approximately five years have lapsed since this evaluation was prepared for IRCU. Accordingly, IRCU desires to continue to monitor and evaluate the water quality of its distribution system to confirm regulatory 67