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12/12/24 Item 5.13. <br />N -11 -1 -- <br />Conclusions TETRATECH <br />Conclusions <br />• IRCDUS remains compliant with all applicable regulatory standards and consistent <br />with industry practices for corrosion control <br />• Recommendation made to further optimize WTP performance focusing on <br />customer concerns <br />• Recommendations apply solely to water quality and do not account for other . <br />potential contributing factors of corrosion <br />Recommendations <br />• Lower target calcium hardness to 50-60 mg/L as CaCO3 from the 2022 distribution concentrations of 78 to <br />93 mg/L. <br />Goals: <br />Reduce turbidity <br />• Reduce quantity of carbon dioxide <br />Reduce chemical cost and still provide positive LSI <br />• Increase pH to 8.8-9.0 from current range of 8.1-8.3 per recommendation from EPA guidance document <br />Goals: <br />Lower turbidity <br />Require less chemicals to maintain an acceptable LSI at higher pH target <br />• Increase target feed pH to degasifiers to pH of 5.7 from current target range (5.3-5.5) <br />Goals: k <br />• Decrease alkalinity destruction in blend water and reduce sulfates in finished waters <br />r` <br />• Small reduction in sulfuric acid required 91� <br />