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3.0 Hydrologic Analysis and Design <br />Hydrologic analysis and design were completed for the proposed RPE East refuse pile to establish <br />design requirements for the underdrain and to develop surface water drainage controls. The facility <br />layout with drainage features are shown on the permit drawings provided in Appendix D. A <br />summary of the results of water balance and surface water models are provided below. <br />3.1 Hydrologic Water Balance Analysis <br />The infiltration rates through the cover and refuse layers were modeled using Hydrologic Evaluation <br />of Landfill Performance (HELP), Version 3.07, a computer modeling program designed to perform <br />water balance analyses for design and evaluation of land disposal facilities. The hydrologic inputs to <br />the modeling, modeling parameters, and the modeling results are presented below. HELP model <br />output is provided in Appendix E. <br />3.1.1 Hydrologic Inputs <br />Precipitation and Temperature Data <br />Historical precipitation and temperature data for the mine site were used in the HELP modeling. <br />Daily precipitation and average daily mean temperatures were implemented into the model for each <br />year from 1998 to 2008. <br />Evapotranspiration and Solar Radiation Data <br />Evapotranspiration data was obtained from historical data for Grand Junction, Colorado, that is <br />included in the HELP software. The maximum leaf area index was assumed to be 1.0 for final cover <br />soil areas and 0 for bare refuse areas. The evaporative zone for the final cover and bare refuse layers <br />was assumed to be 12 inches and 6 inches, respectively. <br />The solar radiation data was synthetically generated using coefficients for Grand Junction, Colorado, <br />and station latitude equal to 38.93 degrees. <br />Soils <br />Three soil types were used in the HELP model for the three soil layers: cover soil, refuse, and <br />colluvium. The cover soil layer is assumed to be composed of the upper horizon of native colluvium <br />soil material that will be stripped from the RPE East refuse pile area prior to filling. The refuse <br />Revised July 21, 2011 � 5 <br />2CddV Lc <br />P \Mpls \06 CO \26 \06261003 RPE E. Permit Mod Support \WorkFiles \Permit Application \Text \Exhibit 82 RPEE design 2011 -07 -21 TR 127 doc 12 <br />