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<br />3. EVALUATION OF OPTIONS <br /> <br />The City’s ability to operate its municipal drinking water supply system has been <br />impacted by the presence of Dioxane at levels over 1ppb in Well No. 4. The uncertainty <br />of future impacts to the remaining two wells by Dioxane has initiated the need for the <br />City to evaluate alternatives to provide dependable safe supplies of water to the public at <br />levels less than 1 ppb. <br /> <br />This report summarizes five options that were selected for analysis as possible means to <br />address Dioxane in the City’s drinking water: <br /> <br />• Option 1 – Blend the existing wells; <br />• Option 2 – Construct deeper Mount-Simon Hinckley wells; <br />• Option 3 – Purchase water from Minneapolis Water; <br />• Option 4 – Purchase water from St. Paul Regional Water; and <br />• Option 5 – Implement treatment to remove Dioxane. <br /> <br />Descriptions for each option, the benefits and costs are provided below: <br /> <br />3.1 Option 1: Blend City Wells <br /> <br />The first option is to blend the City’s three existing groundwater wells prior to <br />distribution in an effort to dilute the higher concentrations of Dioxane to acceptable <br />health levels. <br /> <br />Description <br />St. Anthony draws its drinking water from three wells, labeled Well Nos. 3, 4, and 5 <br />(Well Nos. 1 and 2 were taken out of service and abandoned). Well Nos. 4 and 5 draw <br />water exclusively from the Jordan Aquifer, while Well No. 3 is screened to draw water <br />from both the Jordan and Prairie du Chien Aquifers. To meet the City’s water needs, the <br />City must have two wells operating at any given time, and sound management also <br />requires having the third well available as a backup during maintenance of other wells, or <br />in the event of an emergency. <br /> <br />Historically, the City would rotate usage of the wells. Since the installation of the <br />Carbon plant , the City has primarily depended on the operation of Well Nos. 4 and 5, as <br />the operation of Well No. 3 appears to deplete the carbon in the filters at a more rapid <br />rate than the use of the other two wells <br /> <br />The current wells are not equipped with Variable Frequency Drives (“VFD s”), meaning <br />that water is drawn at equal flow rates from the two wells that are operating. This limits <br />the ability of the current operation to blend water from the wells in a controlled and <br />efficient manner. <br /> <br /> <br />1,4-DIOXANE PROJECT <br />FEASIBILITY REPORT <br />CITY OF ST. ANTHONY VILLAGE <br />WSB PROJECT NO. 3183-00 PAGE 4