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