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5,1.5.3 <br />5.1.6 <br />Table 11 - Drawdown in Ramsey Wells <br />Well <br />No., <br />nig" ''''' <br />Well No. <br />Tota <br />Depth <br />(ft) <br />Casi <br />Dept <br />(ft) <br />Static Wa - <br />evel De <br />(ft) <br />Approximate <br />•rawdown to <br />Top of <br />Aquifer (ft) <br />Approximate <br />Drawdown to <br />50% <br />threshold (ft <br />Approximate <br />Drawdown to <br />25% <br />hreshold (ft) <br />161441 <br />323 <br />243 <br />9.5 <br />233.5 <br />116.75 <br />175.1 <br />2 <br />416183 <br />, <br />320 <br />240 <br />9.5 <br />230,5 <br />115,25 <br />172.8 1 <br />3 <br />580306 <br />345 <br />222 <br />26 <br />196 <br />98 <br />147 <br />4 <br />580313 <br />321 <br />191 <br />18 <br />173 <br />86.5 <br />129.7 <br />5 <br />593672 <br />316 <br />215 <br />25 <br />190 <br />95 <br />142.5 <br />6 <br />706840 <br />390 <br />282 <br />37 <br />245 <br />122.5 <br />183,7 <br />7 <br />743832 <br />332 <br />216 <br />25 <br />191 <br />_ <br />95.5 <br />1432 <br />8 <br />743833 <br />354 . <br />245 <br />15 <br />230 <br />115 <br />, <br />1725 <br />These MnDNR threshold values are approximate as an observation well has to be established by <br />the MnDNR for baseline water elevations; however, the table above provides an estimate for <br />which the city should manage water levels. <br />Well Specific Capacity <br />Well specific capacity is the rate of pumping per unit of drawdown expected. This is generally <br />expressed as gallons per minute (GPM) per toot of drawdown, All of the City of Rarnsey wills <br />experience a sharp initial displacement of water as the wells are turned on (as seen in Well 5 <br />drawdown example above). For the purpose of this report, this initial displacement was not <br />considered in the calculations for Well Specific Capacity in order to give a more accurate <br />depiction of how the aquifer will respond once stabilized to various pumping rates. <br />Well Specific Capacity for the City of Ramsey was determined to be approximately 30 - 40 GPM / <br />ft after initial displacement. This indicts a 30 - 40 GPM increase in pumping rate will increase <br />total drawdown by a 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 potentionnelric 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 tow' to 'High'. <br />FEASIBILITY STUDY -DRAFT RAMSY 154354 <br />Page 19 <br />