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BACKGROUND The goal of the Project is to implement PFAS treatment at the City's groundwater wells and rehabilitate the existing facilities to extend their useful life so that they remain a reliable,locally controlled source of water for the City.On September 1,2020,City Council approved an agreement with Carollo Engineers in the amount of$437,374 to prepare a basis of design report for the Project. The scope of work for the basis of design report includes the following tasks: • Determine the preferred location(s)to install PFAS treatment equipment. • Perform laboratory testing of groundwater from City wells to refine annual operation and maintenance cost estimates for PFAS treatment. • Identify necessary rehabilitation and upgrades to Well 5,6,and 8 facilities in order to extend their useful lives 20 to 30 years(i.e.to align with the life of new PFAS treatment equipment). • Define the scope of improvements for the Project including ten percent level design drawings. • Develop a project schedule to implement the Project and prepare construction cost estimates and life cycle cost estimates. The current estimated completion schedule for the basis of design report is March 2021. DISCUSSION While preparing the basis of design report,staff has identified two additional items that are recommended for evaluation and incorporation into the report. CrVI Treatment In 2014,California's Division of Drinking Water(DDW)issued a maximum containment level(MCL)of 10 parts per billion(ppb)as part of its regulation of the contaminant. In 2017,the Superior Court of Sacramento County issued a judgment invalidating the MCL on the basis that the economic feasibility of the MCL was not properly considered. DDW is currently in the process of reissuing an MCL that includes an economic feasibility evaluation.An MCL may be reissued as early as 2022. In review of previous sampling data at Wells 5,6,and 8, CrVI was detected in the range of 3 to 8 ppb. Due to these values being in the ballpark of potential new MCL values being considered by DDW,staff recommends that an evaluation be performed to select the preferred treatment technology so that it can be implemented if required to meet future regulations. Well 5 and Well 6 Casings A well casing is a tube-shaped shell that is inserted belowground to seal and support the sides of the well. It contains screens that allow groundwater in and houses the well pump that delivers water to the distribution system.A structurally sound well casing is necessary for proper operation. As part of the basis of design report,Carollo Engineers was tasked with doing a desktop review of record information and historical video inspections of the casings at Well 5 and 6 to assess their condition.The desktop review determined that Well 5 and Well 6 Page 2 of 4