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Request ti3: 3.4.2 Water Table(continued) <br /> Please provide a cross-section oriented roughly perpendicular to the northern portion of the <br /> ECOSA, displaying the features shown on Plate 9 (Rev. 1) and Plate 17(Rev. 1), including the <br /> ECOSA, the ECOSA underdrains, the Grassy Valley perched aquifer, Grassy Valley Creek, the <br /> contact between the diatreme and Precambrian rocks, and the portion of the area identified on <br /> Plate 9 (Rev. 1) as the "area where drainage tunnels do not cause significant head change in <br /> diatreme"which underlies the ECOSA. <br /> Please ensure all cross-sections show shallow bedrock groundwater, groundwater flow direction, <br /> and indicate the saturated zone (either visually or in notes provided on the cross-section). These <br /> cross-sections should provide a unifying picture of the hydrogeology of the area specified, <br /> showing the relationships between the ECOSA, the ECOSA underdrains, Grassy Valley Creek, <br /> the contact between the diatreme and Precambrian rocks, and the additional features shown on <br /> Plate 9 (Rev. 1) and Plate 17(Rev. 1), with the local groundwater regime. <br /> Response: <br /> The location of the cross section is presented in Plate 28. The section selected passes through <br /> the northern edge of the ECOSA, approximately normal to the axis of the overburden storage <br /> facility. It was selected to run approximately at the edge of the diatreme in this area, so as to <br /> indicate the location and purpose of the seepage collection underdrains. <br /> The resulting cross section is Section A-A', presented in Plate 29. <br /> The section has been prepared by the following process: <br /> 1. Assembling all groundwater data for the colluvial ("soil") surface aquifer in the vicinity of the <br /> section and plotting the resulting "water table" which represents the top of the zone of <br /> saturation (where present) in the colluvium on the section. <br /> 2. Assembling all groundwater head/water pressure data for the underlying bedrock in the <br /> vicinity of the section, selecting the elevation at each monitored location that best <br /> represents the top of the zone of saturation in the bedrock, and plotting these values on <br /> the section. <br /> 3. Drawing direction arrows on the section to indicate groundwater flow direction, as <br /> requested. It should be noted that the section cuts through a three-dimensional flow <br /> regime, and the flow arrows indicate the component of flow in the plane of the section. In <br /> this section flow is predominantly vertically downward in the colluvial aquifer, and <br /> predominantly downward with a significant out-of-plane horizontal component to the south <br /> in the bedrock. <br /> Page 5 of 16 <br />