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5.1.6 <br />5.1.7 <br />Well Specific Capacity for the City of Ramsey was determined to be approximately 30 to 40 GPM <br />/ ft after initial displacement. This indicates a 30 to 40 GPM increase in pumping rate will increase <br />total drawdown by 1 foot. The Specific Capacity was established analyzing the following recent <br />results from pumping. <br />Bedrock Hydrogeologic Sensitivity to Pollution <br />Water quality for bedrock aquifers are generally a function of recharge rates for water originating <br />from surficial waters, or percolation from direct precipitation, that may carry contaminants. <br />Aquifers generally flow from areas of high potentiometric conditions to areas of low potentiometric <br />conditions which can be influenced by surface topography, bedrock topography, Well Influence, <br />and the hydraulic properties of the geologic units. <br />The areas of higher potentiometric conditions often correspond to recharge areas or where water <br />enters the aquifer and, as a result, are the most susceptible to distributing such contamination to <br />the bedrock aquifer. Recharge areas may have variable recharge rates and may even decrease <br />because of the properties of the material in which it flows. Confining units, formations primarily <br />made up of fine-grained material, reduce groundwater flow rates and provide more geologic <br />protection. Geologic protection can be described in categories as to how quickly water can <br />percolate from the surface to the bedrock from `Low' to `High'. <br />Figure 4 in Appendix D depict bedrock protection `Geologic Sensitivity' for Anoka County. While <br />the majority of the bedrock aquifers exhibit a low geologic sensitivity, some areas are depicted <br />with a high sensitivity. The areas of high sensitivity do not appear to correspond to specific <br />bedrock geologic conditions. Instead, high sensitivity is more likely related to where confining <br />units have been removed and where coarse -grained Quaternary sediment overlies the bedrock <br />surface. <br />Figure 5 in Appendix D depicts tritium samples taken within the City of Ramsey. Tritium is a <br />radioactive isotope of hydrogen that can be used to indicate water age. MDH classifies young <br />(post-1953) water, as indicated by the presence of 1 TU or greater in the well water. Tritium <br />results for these samples depict a mixed result. This mixed result reflects uncertainty about the <br />pathway for young water (containing tritium) to reach the deeper bedrock aquifers. Although the <br />presence of tritium may be the result of a compromised well casing allowing surface water <br />seepage, conservatively, it is assumed that some pathways may exist. <br />Well Spacing <br />Determining the proper spacing of wells in Artesian Aquifers is a balance of well drawdown, the <br />ability of the surrounding formation to recharge, and further economic considerations (USGS <br />1961). In general, the farther apart high -capacity wells are from one another, the less mutual <br />interference will occur on the wells. Additionally, the economics of well spacing needs to be <br />weighed against the potential drawdown of the wells. <br />The USGS in 1961 developed a method utilizing the Theis equation for hydraulics to determine <br />expected well drawdown and the surrounding cone of depression. Calculations using this <br />equation were completed to understand the hydrogeology of this aquifer system. <br />The following example depicts drawdown in well 8 over the course of 12-hour period while well 7 <br />was pumping at an Average of 800 GPM. <br />FEASIBILITY STUDY RAMSY 154354 <br />Page 21 <br />