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mounding. Additionally, no structures are known to exist within these properties that could be <br /> affected by potential groundwater mounding. Similarly, southwest of Lamb B and Lamb C, the <br /> land surface elevation, and depth to groundwater increases quickly from the lakes and alluvial <br /> floodplain. <br /> The Fort Collins Irrigation Canal Ditch runs along the west and south property boundaries. The <br /> ditch is typically about 4 feet deep and does not appear to be lined. It is reasonable to assume <br /> that, while the ditch is carrying water, seepage increases groundwater elevations and gradients <br /> flowing to the south and southeast. Construction of slurry walls immediately downgradient from <br /> the ditch would likely slow a major portion of the seepage and maximize flows through the ditch. <br /> However, if the ditch flows are maintained at the same rate/elevation as operated historically, <br /> slurry wall effects to groundwater would not be anticipated west or south of the ditch. <br /> Shadowing impacts downgradient of Lamb Lakes are not likely. It is assumed that the Cache la <br /> Poudre River is in direct hydraulic connection with adjacent alluvial groundwater. Immediately <br /> northeast and east of the site, the river would be expected to minimize most shadowing effects <br /> from the slurry walls. Similarly, impacts from shadowing are not anticipated east of the river. <br /> Since it is difficult to anticipate and quantify exact mounding and shadowing groundwater <br /> elevation changes, alluvial groundwater elevation monitoring is recommended. Since mounding <br /> and shadowing would occur following site reclamation, it is important that any monitoring <br /> program include wells that are not destroyed by mining or reclamation activities. <br /> 5.0 GROUNDWATER MONITORING <br /> Routine groundwater elevation measurements and evaluation of potential dewatering and slurry <br /> wall impacts is recommended as part of a comprehensive groundwater monitoring plan <br /> Recommendations provided here define monitoring procedures and methods to be used during <br /> mine operations and reclamation activities at the Lamb Lakes Site to ensure monitoring data is <br /> accurate and representative of actual field conditions. <br /> Based upon preliminary assessment of the site hydrogeologic characteristics, the monitoring plan <br /> should include the installation of new alluvial wells or, if constructed appropriately, existing <br /> alluvial wells. The monitoring wells shall penetrate the entire alluvial aquifer. The screened <br /> interval and surrounding filter pack shall allow for seasonal groundwater fluctuations and enable <br /> accurate depth to water data collection. The surface seal around the well shall be made of <br /> bentonite or other impermeable material that prevents surface water from directly draining to the <br /> well or filter pack. Wells to be included in the monitoring plan shall be surveyed to provide well <br /> coordinates and top of casing elevations (measuring point elevations) so that groundwater <br /> elevations can be used for potential groundwater impact evaluations. <br /> Approximate locations for alluvial wells to be included in the monitoring plan are illustrated <br /> on Figure 4. Locations identified in the figure are approximate, and actual monitoring well <br /> locations may vary depending upon the potential inclusion of existing wells and property use <br /> restrictions. If necessary, it is assumed that permission can be obtained from landowners to <br /> locate wells outside the permit boundary. Eight wells should be placed outside of the anticipated <br /> mining and reclamation activities, but within the estimated dewatering radius of influence <br /> Dewatering and slurry wall impacts are not anticipated north and east of the Cache la Poudre <br /> River and, therefore, wells are not proposed across the river from the property. <br /> (blue earth Page 11 of 12 <br /> SOLUTIONS <br />