Agenda - Council - 01/27/2004 - Laserfiche WebLink

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water level is recommended so that data can be collected to correlate against the long tern trending patterns within the FIG. Permitting: The increase in demand will subsequently require an amended DN-R water appropriations perm_it. At that time, the DN-R is likely to requir~ the collection of the surficial groUndwater data mentioned above, l.n addition, the DN'R may require a pumping test to oorrelate short term temporal relationships between the two aquifers. The monitoring wells needed for this study should also be designed as groundwater sampling wells that can be used to identify potential contain/nation of wellhead protection areas. The design of all additional mun/cipal production wells can then be based on information collected during these studies in an effort to mitigate impacts, assuming any exist. Wellhead Protection: The RTC is located directly within the Wellhead Protection Area (WI~A) and Drinking Water Source Management ,4rea (DWSMA) determined by the preliminary Ramsey wellhead protection plan (Figure 20.1). Additional groundwater modeling information is included in Appendix Fl. Using the MDFI model for weiltxead protection planning purposes and the Maximum ~4amual Capacity shown in Table 13.3 as the pumping rates for wells 3, 4 and 5, the 10-year capture areas for these wells was recalculated. With the inclusion of well 5, the WH2:>A would extend southward from well 5 to the edge of the RTC site. Therefore, th_is area should be considered a WH2~A for' land use'planning purposes. Any contaminating material that is spilled on the permeable sands within the site can potentially migrate imo the groundwater system. City wells were tested for tritium as part of the wellhead protection plan delineation. Tritium is a form of hydrogen and ean act as an indicator ofgrotmdwater age, but does not pose a health risk. Atmospheric tritium levels increased during the 1950's due to testing of atomic bombs, Therefore, tritium levels are used to indicate whether groundwater entered the ground before or after 1950. Public water supply wells wi~ high levels of tritium are classified as '"vuLnerable" to surface processes because of the relatively recent (post-1950) interaction with the surface. Tritium levels in the three city wells around the Town Center are high. A formal well ,rulnerability assessment has not been completed for well 5 but the preliminary wellhead protection plan identifies it as vulnerable in Table 1. A formal assessment could be done in coordination with a plan addendum for additional mtmicipal wells. The results of the formal assessment will most 1/kely confirm that well 5 is also vulnerable to contamination. The vulnerability of these wells may be caused by the rapid rate of infiltration through the higkly permeable sand and gravel materials of the Anoka Sand Plain, by leakage of water around the annular space o£the well, or by the interaction. of the quaternary and bedrock aquifers in the bedrock valle9 to the north of the site (Figure 19.4). To reduce the risk of groundwater contamination, pretrearment of ' srormwater runoff prior to infiltration and community education programs on household ct~emical and fertilizer ase can be implemented. Storm water management practices that encourage the infiltration of treated runoff will be part of the desi~_on and are discussed in detail in Items 17 and 20. 13-8