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during sporadic, high intensity thunderstorms, it was assumed that 20 percent contributes to alluvial groundwater recharge. The recommended average annual water need for corn and hay crops in the Arkansas River Valley is 32 inches /year (CSU 2009). Irrigation, therefore, must contribute 20 inches /year to make up for the precipitation deficit. Considering the soaking nature of irrigated agriculture, it was assumed that 50 percent of the irrigation water contributes to the aquifer recharge. To estimate the potential dewatering impacts, the radius of influence was assumed to extend to a point where analysis results showed an alluvial groundwater drawdown of approximately 10 percent of the saturated thickness or 2 feet. This assumption is also reasonable considering groundwater elevation and saturated thickness can vary up to several feet seasonally. Within the estimated radius of influence, obstructions will increase and decrease the affects of dewatering. To the south, the Arkansas River borders the site boundary. It is assumed that the river is in direct connection with the alluvial groundwater and, therefore, continuous recharge from the river will significantly influence the affects of dewatering. Impacts from dewatering will not extend south of the river, and the radius of influence will be reduced immediately north of the river due to the increased recharge flux. North of the project site, near U.S. Highway 50, the Pierre Shale bedrock elevation rises sharply and pinches out the Arkansas River alluvium (Nelson et al. 1989). For the steady -state analytical solution results to be accurate, adjacent alluvial groundwater must be available to continually flow towards and into the dewatering radius of influence. This is why the analytical solution assumes that the aquifer extends for a significant distance beyond the dewatering radius of influence. However, north of the property, the alluvial aquifer does not extend for a significant distance beyond the radius of influence and this assumption is no longer valid. Therefore, although the radius of influence does not extend beyond the alluvium boundary, the analytical solution will somewhat under estimate dewatering impacts north of the project site. Immediately west of the Phase I mining pit, mining and reclamation activities have included backfilling in Parcel 1, a compacted clay cutoff wall separating Parcel 1 from Parcel 2, and fresh water settling ponds in Parcel 3 (Figure 1). All of these structures and activities will act to significantly reduce or eliminate the affects of dewatering to the west of Phase I. Additionally, once Phase I is reclaimed with a compacted clay liner, dewatering impacts from Phase II and Phase III will be severely limited west of the Phase I reservoir. Alluvial aquifer saturated thickness and recharge are very important parameters in the analytical solution. In addition to assumptions made estimating the saturated thickness and input from recharge, these two parameters also vary seasonally and from year to year. Values for the parameters, however, are used in the analytical solution based on annual averages. Therefore, variability in these parameters will make observed impacts differ from the analytical solution seasonally and year to year. Additionally, affects from obstructions such as the alluvium boundary, reclamation backfilling, and seasonal recharge from the Arkansas River and irrigation canals such as the Excelsior Ditch (Figure 2) are not considered in the analytical solution. Considering all assumptions and parameter variability, it needs to be noted that results of the analytical solution should only be taken as a rough approximation of potential dewatering impacts and alluvial groundwater elevation monitoring is recommended to evaluate actual groundwater impacts. ('blue eG�tk-, Page 7 of 11 SOLUTIONS