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Design and Operations Plan <br />Western Gravel E & P Waste Disposal Facility <br />Based upon a 70 year period, average annual precipitation at Meeker is 16.63 inches. Based upon a 105 year <br />period, the annual pan evaporation rate obtained for Grand Junction Walker is 92.34 inches from March <br />through November. The highest evaporation rates were reported from May through September at 12.18 <br />inches, 15.96 inches, 16.53 inches, 14.02 inches, and 10.98 inches, respectively. Low humidity, intermittent <br />winds, low precipitation, and high pan evaporation rates at the site result in a net pan evaporation excess that <br />significantly decreases available water for aquifer recharge. Climatic data is provided in Appendix C. <br />2.3.3.6 Site Surface Hydrology <br />The only natural surface water body present at the site is the White River. The river meanders through a <br />flood plain and along the north and east sides of the site and approximately 45 feet below the landfill terrace. <br />The closest that a constructed landfill cell will be to the river and/or associated wetland is approximately 200 <br />feet. Including the terrace slope, the net distance from a landfill cell to the river and/or wetland is <br />approximately 205 feet. An irrigation ditch located between the terrace toe and the river flows to the west <br />and is used for irrigating hay meadow and pasture land to the west. Several drainages are located along the <br />terrace face and drain towards the irrigation ditch and river flood plain. Drainage flow is only intermittent <br />during spring runoff and/or during heavy rain events resulting from storms. Based upon landfill designs <br />presented herein, the irrigation ditch that is located outside the COD and along the terrace slope toe will not <br />be impacted from landfill activities. <br />2.3.3.7 Site Groundwater <br />Groundwater does not appear to be present within overburden or shallow bedrock at the proposed facility. <br />Shallow groundwater is likely to be present in alluvial deposits located in the lower portion of the property <br />along the White River. The site lies in the vicinity of the Wasatch and Green River Formation contact. <br />However, based upon the geotechnical evaluation discussed in Section 2.4.2, Wasatch underlies the proposed <br />facility. It is estimated that the Lower Piceance Basin Aquifer is stratigrahpically located approximately 800 <br />feet above the Wasatch in the facility area. <br />Bedrock groundwater reportedly occurs in sandstone intervals within the Wasatch . Because the Wasatch is <br />composed of sedimentary rocks of fluvial and lacustrine origin including claystone, mudstone, shale, and <br />lenticular sandstones, the formation is not known as a significant groundwater source. Sandstone units in the <br />Wasatch are laterally discontinuous; therefore, any water bearing zones are likely to contain confined <br />formation water where recharge or discharge is limited. The Wasatch is considered a confming unit <br />exhibiting permeabilities ranging from 1 x 10 -6 cm/sec to 1 x 10 -9 cm/sec. It is estimated that over 1,000 feet <br />of Wasatch underlies the site. <br />As discussed below, three approximately 50 foot deep bedrock boreholes were advanced beneath the <br />proposed landfill area and below the river elevation. Groundwater was not measured in any of the boreholes <br />during advancement. Moreover, the boreholes remained dry for approximately three months until abandoned <br />during groundwater assessment activities. <br />Part of the White River alluvial aquifer is located along the north and east sides of the facility. The COD is <br />located approximately 45 feet above and 205 feet from the White River floodplain. The only considered <br />activity to be conducted along the toe of the terrace and an existing irrigation ditch located along the <br />floodplain was a groundwater monitoring well installation and long -term groundwater monitoring. However, <br />it is unlikely that residual petroleum constituents contained in landfill waste would be detected in the <br />groundwater monitoring well because the bedrock bedding plane dips t o the south and away from the White <br />River and because of significant dilution in the White River aquifer where the groundwater well would be <br />located. Therefore, in accordance with discussions with Rio Blanco County, surface water monitoring of the <br />White river will be conducted as discussed in Section 3.10.2. <br />NWCC, Inc. <br />October 24, 2011 <br />Page 13 of 51 <br />