Laserfiche WebLink
3.0 Hydrologic Analysis and Design <br />Hydrologic analysis and design were completed for the RPEE waste rock pile to establish design <br />requirements for the underdrain and to develop surface water drainage controls. The facility layout <br />with drainage features is shown on the permit drawings provided in Appendix D. A summary of the <br />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 collected in a mine site monitoring station were used in <br />the HELP modeling. Daily precipitation and average daily mean temperatures obtained from the site <br />data for the period of 1998 to 2008 were used in the model. <br />Evapotranspiration and Solar Radiation Data <br />Historical evapotranspiration data was obtained from a data set included in the HELP model software <br />for Grand Junction, Colorado. The maximum leaf area index was assumed to be 1.0 for final cover <br />soil areas and 0 for unreclaimed refuse areas. The evaporative zone for the final cover and <br />unreclaimed refuse layers was assumed to be 12 inches and 6 inches, respectively. <br />The solar radiation data was synthetically generated by the model using coefficients for Grand <br />Junction, Colorado, and station latitude equal to 38.93 degrees. <br />Soils <br />Three soil types were used in the HELP model for the three modeled soil layers: cover soil, refuse, <br />and colluvium. The cover soil layer is assumed to be composed of the upper horizon of native <br />colluvium soil material that will be stripped from the RPEE waste rock pile area prior to filling. The <br />refuse material consists of sandstone, claystone, and mudstone particles with small amounts of fines, <br />14 <br />PAMpls\06 CO\26\06261003 MCC Refuse Pile Site Review & Permit\WorkFiles\Permit Application\2014 Revision\Exhibit 82 2014-05- <br />29.docx <br />