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wells (MW -1, MW -2, and MW -3) were installed in June 1998. The fourth monitoring well, MW -4, was <br />installed in April 1999. These wells are shown on Figure 1 relative to CKD disposal area A2. Table 1 <br />provides a summary of the known well construction details of these four existing monitoring wells. <br />Groundwater was sampled from the four monitoring wells for water quality analysis beginning in April <br />1999 through July 2000. During this period, a total of eight groundwater samples were collected from <br />each well. Subsequently, one sampling event was conducted in September 2010, which has been <br />followed by quarterly sampling of the monitoring wells beginning in March 2011. These water quality data <br />for wells MW -1 though MW -4 are summarized in Tables 2A through 2D, respectively. <br />1.3.3 Geology and Hydrogeology <br />Geology <br />The Boettcher Quarry was mined for limestone in the Niobrara Formation, which is Cretaceous aged and <br />of marine origin. The Niobrara Formation consists of alternating bands of limestone, argillaceous (i.e., <br />clayey) limestone, and calcareous shale (Ideal 1977). The argillaceous limestone bands are typically <br />fossiliferous and contain trace amounts of pyrite. The Niobrara Formation is bounded by the older CodeII <br />sandstone (of the Carlile Formation) and the younger Pierre shale, as shown on the geologic stratigraphic <br />column of the Boettcher Quarry area (Ideal 1962) in Figure 2. The Niobrara Formation limestone is <br />subdivided into members (bands), identified as A through G from older to younger aged rock, and for <br />which E -band is further subdivided into El through E3 based on calcium oxide (CaO) content (Figure 2). <br />The boundaries within the E -band are gradational, rather than physically or chemically distinct (Ideal <br />1977). The A through G bands names and approximate thicknesses are also provided on Figure 2. <br />Geologic Structure <br />The Niobrara Formation strikes north -south and dips approximately 16 degrees east (Ideal 1977). The <br />A -band forms a prominent north -south trending hogback along the west side of the quarry and each of the <br />overlying limestone bands form less prominent north -south ridges or hogbacks paralleling the A -band <br />outcrop. These ridges are removed where the high lime content bands have been quarried. Changes in <br />strike represent zones of flexure and are seen as a bend or curve in the hogback. There are some minor <br />changes in dip and minor faulting (small displacement) within these flexure areas (Ideal 1977). Such a <br />curve /band is located in the area of interest (the CKD disposal areas A2 and A2 -A). Figure 3 provides a <br />generalized cross section through the area of proposed investigation. <br />Hydrogeology <br />October 2012 <br />Attorney Work Product, <br />Confidential and Privileged <br />3 <br />103- 81640A <br />The groundwater flow direction has been observed to generally flow easterly to southeasterly using data <br />from monitoring wells MW -1 through MW -4 (Golder 2011). Previous hydraulic testing of monitoring wells <br />MW -1 through MW -3, by pumping out water and measuring recoveries, (Secor 1998) have yielded <br />\10 \81640\ 0400\ charactenzationpin_ fnl- 23oct12 \charactenzationpin_fnl- 23octl2 docx <br />e rip , --4 Golder <br />Associates <br />