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C. Quality and Quantity of Water Supplying the Public Water Supply Well - Water in the Centerville water distribution system is regularly sampled and analyzed for contaminants regulated under the federal Safe Drinking Water Act. No contaminants have been detected recently in the water samples from the Centerville system. The city disinfects the water with chlorine to safeguard water users from disease organisms. D. The Land and Groundwater Uses in the Drinking Water Supply Management Area - Land use is not believed to have any significant impact on the Jordan Aquifer used by city Well No.1 because the aquifer exhibits confined hydraulic conditions and is not vulnerable to contamination from land use. On the other hand, land use in the DWSMA around Well No.2 may affect the Prairie du Chien Aquifer even though the aquifer exhibits confined conditions because water quality data indicate the well and aquifer are vulnerable. These conclusions will be developed in more detail in the vulnerability assessment (Chapter 3). CHAPTER TWO WELLHEAD PROTECTION AREA AND DRINKING WATER SUPPLY MANAGEMENT AREA DELINEATION (4720.5205) Hydrogeologic setting - The City of Centerville is located in southern Anoka County, at the intersection of Anoka County Highways 14 and 54. The city maintains two wells in the same general part of town (Figure 1). Subsurface hydrogeology - Few detailed geologic studies are available that describe subsurface geologic conditions in the area around the City of Centerville. However, the Anoka County area benefits from a number of regional-scale geologic and hydrogeologic studies. Well construction records were used as necessary to supplement the regional information. The area around Centerville is generally characterized by unconsolidated deposits above bedrock. These unconsolidated deposits consist mostly of glacial drift that is less than one hundred feet thick (e.g., 512748). The coarse-grained nature of many of the surficial materials serves to involve surficial processes such as precipitation, snow melt, surface water interactions, and land use in the shallow aquifer dynamics near the City of Centerville. Deeper bedrock aquifers used by the city for a water supply are more protected, as described below. The Anoka County area is on the northern part of the Twin Cities structural basin, which is itself located at the northern end of the Hollandale Embayment. The embayment formed during the Paleozoic Era and is a syncline between the Wisconsin Arch to the east and the Transcontinental Arch to the west (MossIer, 1972). The Twin Cities basin is centered approximately where the Minnesota and Mississippi Rivers meet, and is bounded on the east by the St. Croix River and on the north and west by the sub crop of Precambrian rocks in Wright, Sherburne, and Isanti Counties. Beneath the Hollandale Embayment are a series of Proterozoic rocks, some of which are offset locally by faults. There is no evidence these faults extend into the overlying Paleozoic rocks, but they may cause local structural anomalies. 3