CC WORKSESSION 12142015 - Laserfiche WebLink

Home Browse Search

there is a reasonable likelihood that the contaminant plume will eventually move towards Well Nos. 3 and 5 and produce higher concentrations of Dioxane as these wells are used to pump more water from the aquifer. This condition could also prohibit blending depending on the concentrations of Dioxane detected over time. 4. Blend ing the well water would not remove Dioxane from the environment like other treatment options. Blending the well water reduces the concentration at the point of consumption but the overall concentration within the environment would remain untreated. 5. The manganese levels in Well No. 3 are the greatest of the three wells. Therefore, pumping this well at a higher rate to blend and reduce the Dioxane concentrations in the blended water would increase the manganese levels that are treated by the water treatment plant. Shorter filter runs would be experienced because of the higher manganese concentrations. This would require the filters to be backwashed more frequently and higher chemical dosages would be required to oxidize and treat the higher levels of manganese at the water treatment plant. 6. Blending the City’s wells could become more complicated in the future when Well No. 3 requires major rehabilitation. Well No. 3 has been grandfathered-in as a multi-aquifer well and the DNR no longer allows multi-aquifer wells to be constructed. The DNR may not allow major rehabilitation or redesign to be done to this well. T herefore, a new well may need to be constructed that could produce higher concentrations of Dioxane. 7. Because of aquifer limitations, at least three wells must always be operable to provide firm capacity and supply adequate volumes of water for the City’s demands. If one well goes down, with only two wells in service blending could be prohibited. Estimated Capital and Long Term O&M Costs The City well pumps are not equipped with VFDs that would allow the pumping rates to be varied as needed to optimize blending. The wells can be manually throttled to adjust the pumping rates, resulting in reduced capacity and consumption of additional energy. This option does not appear to be feasible as concentrations of Dioxane in the City's wells are likely to exceed 1ppb at which point blending will no longer provide drinking water below 1 ppb. Ultimately, this option does not have the ability to reduce Dioxane concentrations should they increase in the City’s wells in the future. Therefore, estimated capital and O&M costs to implement Option 1 were not further studied. 3.2 Option 2: Construct Deeper Mount-Simon Hinckley Wells The second option analyzed was to construct and utilize deeper Mount -Simon H inckley wells instead of the Jordan Aquifer wells that are currently being used by the City. The 1,4-DIOXANE PROJECT FEASIBILITY REPORT CITY OF ST. ANTHONY VILLAGE WSB PROJECT NO. 3183-00 PAGE 6