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EXISTING HYDROGEOLOGIC CONDITIONS <br />Historically the groundwater table in the vicinity of the site has ranged from an elevation of <br />4871 feet above sea level on the southern boundary of the site to 4863 feet on the nonhem <br />boundary of the site (United States Geologic Survey, 2000). A copy of a map showing the <br />historic groundwater elevations in the immediate area developed by the USGS in 2000 is <br />included in Appendix A. <br />The existing groundwater flow in the vicinity of the Duckworth Pit is strongly influenced by <br />Boulder Creek to the west of the site and Idaho Creek to the east. In the summer, <br />groundwater levels are highly influenced by irrigation in the area and groundwater is <br />encountered at depths as high as two feet below the surface. Grotmdwater levels generally <br />decline in the winter as recharge from Boulder Creek, Idaho Creek, seepage from irrigation <br />ditches, and irrigation in the area decreases. <br />The Smith & Emmons Ditch is an unlined irrigation ditch that currently runs through a <br />portion the site. The Smith & Emmons Ditch generally tames water in the irrigation season <br />from April through October. During periods when the ditch is carrying water, the ditch acts <br />as a significant recharge source to the alluvium in the area. <br />Bedrock is encountered at depths ranging from 20 to 30 feet below the surface in the vicinity <br />of the site. The bedrock effectively creates an impermeable boundary to groundwater flow <br />in the alluvium. Appendix B contains a map showing the bedrock elevation contours in the <br />area developed by the USGS in 2000. <br />Lafarge West. Inc. -2- Applegate Group, Inc. <br />Duckworth Pit Groundwater Study March, 2004 <br />