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6 <br />In summary, it is SEH's opinion that there is a 95% to 99% certainty that the source water <br />aquifer for the City of Ramsey will continue to produce potable water to meet present and <br />foreseeable future demands; however, the City of Ramsey should plan additional well <br />sites to ensure static water levels remain sufficiently above top of aquifers to meet MnDNR <br />thresholds. <br />Single well pumping for the City of Ramsey, as depicted by Well 5 in May, 2019 saw <br />approximately 90 to 100 feet of temporary drawdown. This observed drawdown nears the <br />MnDNR 50-percent threshold; however, the pumping extended multiple days and recharged <br />within the same time period back to static levels. This supports the ability of the wells to supply <br />continued water and ability to stay within prescribed State Statute. <br />A single well also creates a radius of influence drawing down adjacent water levels. The zone of <br />influence for a single well was observed and modeled to be approximately two to three thousand <br />feet, meaning that a single well pumping at approximately 800 feet will not cause a significant <br />drawdown in another well. When multiple wells are being utilized such as under heavy day <br />demand or under 2040 conditions the modeled and observed drawdown in nearby wells sees a <br />substantial drop in static water levels from that of a single well pumping. Modeled drawdown <br />during present heavy day conditions depict 30-40 feet of drawdown approximately 1,500 feet <br />around the wellfield. After pumping stops, the aquifer will recharge to static levels within one or <br />two days. In general, it appears new well sites should be spaced at least 1,500 to 2,000 feet <br />away from existing wells to ensure a pumping scheme that gives the aquifer sufficient time to <br />recharge. <br />Future well sites should attempt to balance the City's current economics, well spacing, and take <br />into account the underlying geology. The City of Ramsey should continue to utilize the current <br />source water aquifer for both a water quantity and a water quality standpoint. The source water <br />aquifer is underneath protective "confining" units that appear to inhibit the influence of new water <br />from brining contaminants to the City's wells and will likely produce consistent water quality <br />unlikely unconfined sources such as surface water that may have a highly variable water quality. <br />Additional considerations for well Sites should take into account the thickness of the two <br />hydrogeologic units that make up the source water aquifer. The Tunnel City aquifer is not as <br />prolific an aquifer as the Wonewoc aquifer, meaning that the Wonewoc aquifer is a more <br />economical source of water. Figure 15 in Appendix D depicts three potential well sites taking into <br />account these issues. Well Site Area A has Tunnel City aquifer thickness ranging from 100 to 150 <br />feet and Wonewoc thickness ranging from 45 to 60 feet. Well Site Area B has Tunnel City aquifer <br />thickness ranging from 0 to 80 feet and Wonewoc thickness ranging from 35 to 100 feet. Well <br />Site Area C has Tunnel City aquifer thickness ranging from 90 to 100 feet and Wonewoc <br />thickness ranging from 15 to 35 feet. All of these sites have potential for potable water sources, <br />but a test well will need to be installed to confirm their viability. As opportunities to investigate <br />these well sites present themselves the City should consider these as potential well sites. <br />Regional Water Supply Study <br />Metropolitan Council Environmental Services in conjunction with the Cities of Ramsey, Dayton, <br />Rogers, and Corcoran prepared a study in 2020 that looked at various options for a regional <br />water system. SEH was the consulting engineer on the project. The Northwest Metro Area <br />Regional Water Supply System Study (Study) evaluated four approaches to water supply: <br />FEASIBILITY STUDY RAMSY 154354 <br />Page 25 <br />