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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />C. Current Water Supply, Quality, and Treatment <br />As previously explained, the City currently obtains all of its municipal water <br />supply from five shallow wells (Wells No, 1, No.3, No.4, No, 5, and No. 13) which <br />withdraw water from the South Platte alluvium. The following discussion summarizes <br />the general hydrogeology and groundwater quality of the of the Fort Lupton area, <br />along with the present level of treatment the City provides. <br /> <br />1. General Hydrogeology <br />The Fort Lupton area is underlain by unconsolidated sediments of Quaternary <br />age on top of a great thickness of consolidated sedimentary rocks of Tertiary and <br />Cretaceous age that lie on crystalline rocks of Precambrian age. The consolidated <br />sedimentary rock formations include Fox Hills Sandstone and the Laramie <br />Formation. The formations that do not crop out in the area lie at depths that are <br />considered excessive for present economic development of groundwater. In addition, <br />oil-well tests have been reported to indicate that the water in many of them is of <br />unsuitable quality for general use (United States Geological Survey [USGS] Water <br />Supply Paper 1658, pg. 19). <br />The USGS reports the Laramie Formation is located just below the topsoil of the <br />eastern edge of Fort Lupton, Though this formation yields water to many small- <br />capacity wells in Weld County, it is generally incapable of yielding sufficient quantities <br />of water for large-scale uses (USGS Water Supply Paper 1658, pg, 19; Plate 1), The <br />USGS has developed a comprehensive geologic history of these formations, and the <br />reader is referred to reports and books prepared by the USGS and others for further <br />information. Because of generally small quantities of water they contain, limited <br />aquifer thicknesses, and poor water quality, the Precambrian crystalline formations, <br />the Fox Hills Sandstone Formation, and the Laramie Formation are not considered <br />acceptable for wells to serve Fort Lupton. <br />The primary, unconsolidated, valley-fill sedimentary deposits underlying <br />Fort Lupton consist of alluvium, deposits of the Kersey Terrace, and slope-wash <br />deposits. The slope-wash deposits exist generally on the eastern boundaries of <br />developed portions of Fort Lupton and are reported to consist of poorly sorted clay, <br />silt, sand, and gravel. In Weld County, the slope-wash deposits yield small to <br />moderate quantities of water to domestic and stock wells and to a few irrigation wells. <br /> <br />25325,100; 12/09194 <br /> <br />3-2 <br />