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F FUM • ue.[I.IY94~4:J! Y. V <br />Mrs. Margaret Winter <br />July 2, 1982 <br />Page 3 <br />' HydrogeoloRY <br />The surficlel geology in the area to the west of Greeley is <br />complex. The surface is comprised of alluvial deposits and <br />the Cretaceous Laramie Formation (Figure 1). The surface in <br />Sections 35 and 36, T6N, R66W is comprised entirely of <br />flood-plain deposits. These deposits consist primarily of <br />sand and gravel with minor amounts of clays. Geologic lags <br />from wells 7$370 and 78858-A, located in the southeast corner <br />of Section 35; TbN, R66W indicate that the flood plain <br />deposits are approximately 50 feeC thick. One mile to the <br />east, in the SouCheaee corner of Section 36, the Flood-plain <br />deposit is approximately 25 feet Chick, as indicated by Che <br />geologic log of well 19932. The North ~, of Section t TSN, <br />R66W is covered by flood-plain deposits and the SouCh ~ with <br />terrace deposits. Terrace deposits consist mainly of arkosic <br />gravel and sand wiCh frec)uent lenses of sandy clay. Terrace <br />deposits between Fort Collins and Greeley rarely exceed 35 <br />feet in thickness (Hershey, 1964). To the southwest in <br />Sections 2 and li, TSN, R66W the Laramie Formation forms the <br />surface. <br />This formation consists of ai1Cy lenticular sands, <br />carbonaceous and gypslferous shales and coals. T1te Laramie is <br />non-resisCant to erosion and, as such, is poorly exposed. The <br />soils that develop on the Laramie are very sandy. This <br />formation underlies Che alluvial deposiCa throughouC the area <br />west of Greeley. IC ranges from 60 to 400 feet in thickness. <br />The top of the Laramie Formation is about 25 feet below the <br />surface in the immediate vicinity o£ the Ketler well. 'this is <br />indicated by the geology log of well 15830 which is located a <br />few hundred feet to the southeast of the Ketler well.. Here <br />Che Laramie consists mainly of interbedded sandstones and <br />shales. The sandstone beds and the shale beds average about 3 <br />Co 6 feet in thickness. <br />1C is dif icult to determine which aquifer the Ketler well <br />and the R dy well are developed in because no geologic log <br />exists For either well. However, based on the depths of both <br />wells and the log of well 15830, they are prohahiy developed <br />in the Laramie Formation. The Laramie yields small to <br />moderate quantities of soft alkaline water to stock and <br />domestic wells. Yields are primarily from the sandstone beds. <br />Ground water in the alluvium and Che Laramie FormaC]~bn flows <br />northeastward towards the Cache La Poudre River. This is <br />shown by arrow on Figure 1. This flow direction was found <br />from plots of depth Co water data contained in well permiC <br />records (Table 1). Flow direction is also confirmed by the <br />fact that the Cwo shallow Ketler walla are affected by the <br />applicaCion of irrigation watex to the alfalfa field to the <br />west. Both of the shallow wells are probably developed in Che <br />flood-plain deposits. Due to the liChology of Che Laramie <br />le0md (tlce CaneuAYp Ylefer Enplreere, Inu <br />