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PART 2. ASSESSMENT OF DATA ELEMENTS USED TO DELINEATE THE WELLHEAD PROTECTION AREA A. Use of the Wells – The wells shown in Table 1 serve as the primary drinking water source for residents of the City of Centerville who are connected to the City’s water supply system. Well 2 is the primary well and Well 1 serves as an emergency backup. The City also maintains an interconnection with the City of Lino Lakes that is capable of supplying 2000gpm. This interconnection is only used during emergencies or periods when the City’s wells are unavailable for pumping. Table 2 shows a comparison of the usage of the City of Centerville wells for the past five years versus a projected pumping rate 5 years into the future. The greatest amount of pumping from any of these years is used to represent the pumping rate for that well in the groundwater model. This is done for the purpose of developing a delineation that is conservative and takes into account the potential volume each well may be pumped in the near future. Other high capacity wells being included within the model, but not being delineated in the plan, are modeled using an average pumping rate taken from a 5-year period. This is explained in greater detail in the Metropolitan Council’s 2014 technical report for the Metropolitan Model. High capacity wells within two miles of the Centerville wells are shown in Table 3. These wells were modeled based on an average rate from the years 2012-2016. These pumping volumes modify the volumes originally modeled by the Metropolitan Council. B. Wellhead Protection Area Delineation Criteria 1.Time of travel – The minimum time-of-travel for porous-flow aquifer delineations is 10- years, which is what was used for the Prairie du Chien aquifer. For the fracture-flow delineation, a 5-year fixed radius with a 5-year upgradient extension is used to represent an approximate 10-year capture zone for flow within the fractured Prairie du Chien aquifer. A 1-year-year time-of-travel zone was also delineated for both porous-flow and fracture-flow systems and represents the Emergency Response Area. 2.Hydrologic flow boundaries – The St. Croix River and Mississippi River represents the major flow boundaries for the Prairie du Chien aquifer in the northeast metropolitan area. Hydrologic flow boundaries included in the groundwater model are documented in greater detail in the technical report for the Metropolitan Model (Metropolitan Council, 2014). 3.Daily volume – Projected annual pumping volumes for the Centerville wells are shown in Table 2. The maximum projected annual pumping volumes were converted to cubic meters per day in order to be applied to the groundwater model. 4.Groundwater flow field – The groundwater flow field was calculated by the groundwater flow model. Original model calibration and ambient flow-field simulation results are described in the technical report for the Metropolitan Model (Metropolitan Council, 2009). Model calibration remains relatively unchanged, since the only significant updates to the model are updates to the wells and their pumping rates, and small-scale changes to hydraulic conductivity and aquifer thickness near the Centerville well field. These changes were not enough to significantly impact calibration results. 5.Aquifer transmissivity – Aquifer transmissivity for regional model was established by the Metropolitan Council’s calculations for the 2014 update to the Metropolitan Model. To refine transmissivity for the Centerville area, the aquifer pumping test from Centerville Well 2 was utilized. This test was conducted by the MDH in March 1998 for the purposes of wellhead protection planning. Transmissivity for the Prairie du Chien aquifer was calculated based on a 24-hour aquifer pumping and recovery test. The results of the test 7