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1. EXECUTIVE SUMMARY The St. Anthony Village City Council authorized WSB & Associates, Inc. to study the available options to address 1,4-Dioxane (Dioxane) that has been detected in the City’s water supply and provide a long term, reliable source of potable water that meets all the recommended State and Federal health guidelines. This Feasibility Report summarizes these options. There may be sources of third-party funding to pay for some or all of the costs associated with remedial action to address the Dioxane contamination. This Feasibility Report does not attempt to assess the likelihood or scale of such funding, and does not evaluate remedial options based on funding source or amount. Dioxane has been detected in the City’s three drinking water wells since March 2015, likely emanating from the Twin Cities Army Ammunition Plant in Arden Hills (TCAAP). Dioxane is used to stabilize chlorinated solvents and can be found in personal care products, laundry detergents, and food in small amounts. TCAAP used Dioxane as an additive in the solvents used at the facility. Other contaminants from TCAAP have been detected since the early 1980s in the aquifers supplying groundwater for the City. In contrast, Dioxane was recently classified as an emerging contaminant by the Environmental Protection Agency (EPA), and testing for Dioxane in the aquifers below the City first occurred in March 2015. This report summarizes five options that were selected for analysis as possible means to address Dioxane in the City’s drinking water: • Option 1 – Blend the existing wells; • Option 2 – Construct deeper Mount -Simon Hinckley wells; • Option 3 – Purchase water from Minneapolis Water; • Option 4 – Purchase water from St. Paul Regional Water; and • Option 5 – Implement treatment to remove Dioxane. During initial screening, Options 1 and 4 were determined to be either ineffective and/or clearly inferior to other measures, and were therefore not analyzed in detail. Costs were evaluated for Options 2, 3, and 5 as these were the options that were determined to be most feasible. A 3.5% inflation rate was assumed for the O&M costs to match other programs within the City. The total estimated 20-year capital cost s and operation and maintenance costs for each of these options is as follows: Option Estimated Capital Cost Finance Cost (4% Interest) Estimated 20- Year O&M Cost (3.5% inflation rate) 20-Year Cost of Purchasing/ Producing Water Estimated Total 20- Year Cost 2 $7,115,600 $3,356,000 $2,812,300 $4,954,000 $18,237,900 3 $9,480,300 $4,471,200 $4,487,800 $17,472,000 $35,911,300 5 $7,177,600 $3,385,200 $1,080,200 $4,954,000 $16,597,000 1,4-DIOXANE PROJECT FEASIBILITY REPORT CITY OF ST. ANTHONY VILLAGE WSB PROJECT NO. 3183-00 PAGE 1