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1. The Mount -Simon Hinckle y Aquifer is likely to contain concentrations of radium that exceed the EPA MCL for combined Radium 226+228. o Radium is required to be removed from drinking water to below the MCL. The City’s existing treatment system, specifically the greensand filters, would remove most of the radium. o Once the radium is removed, it will accumulate on the filter media, making the media radioactive. o Radium cannot be effectively backwashed from greensand media, so the media would need to be replaced on a more frequent basis to reduce the plant operators’ exposure to the radioactive media. o Disposal of radioactive media is expensive and very few landfills across the country will accept the material. o The water treatment plant HVAC systems would likely need to be increased in size and modified to provide more air changes throughout the day as the radium will decay to radon gas. o The air quality within the treatment facility could be become hazardous when radon is emitted into the air. This has been found to occur during filter backwashing when the radioactive filter media is cleaned. 2. The average static water levels in the Mount-Simon Hinckley Aquifer are approximately 125-feet deeper than the static water levels in the Jordan Aquifer in the area of St. Anthony Village. As a result, larger well pumps would be required inside the Mount-Simon Hinckley Wells to pump water from its deeper water levels. This would increase the City’s electrical utility costs. 3. Constructing and pumping deeper Mount-Simon Hinckley Aquifer wells could produce groundwater well interference with the City of New Brighton’s water supply wells. Currently, the City of New Br ighton is utilizing Mount -Simon Hinckley wells that were constructed before the state moratorium went into effect for the Mount-Simon Hinckley Aquifer in the Twin Cities. The groundwater interaction at this aquifer depth was unknown at the time of this study, and extensive groundwater modeling would be required to predict the potential interference effects between these wells. 4. It would likely take the DNR at least two years to evaluate and approve the use of the Mount -Simon Hinckley Aquifer and another one to two years to design and construct new Mount -Simon Hinckley wells. The City would continue drinking Dioxane from existing wells during this time. Estimated Capital and Long Term O&M Costs Estimated capital and long term O&M costs were based on present worth analysis on the assumption that the capacity of the Mount-Simon Hinckley Aquifer is less than the existing capacity of the Jordan Aquifer wells within the City. Therefore, four Mount- Simon Hinckley wells were assumed to be needed to meet the City’s water demand s. 1,4-DIOXANE PROJECT FEASIBILITY REPORT CITY OF ST. ANTHONY VILLAGE WSB PROJECT NO. 3183-00 PAGE 8