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Liberty Mining, LLC <br />DRMS 110 -d Permit Application <br />October 2013 <br />The crowned roadway section of the first project segment and first grading scenario forces the <br />drainage water collected from the hillside above the roadway into existing shoulder ditches or <br />swales. The drainage flow in the shoulder ditches or swales becomes channelized and <br />concentrated. This concentrated flow is then collected in strategically located culvert crossings <br />to carry the flow across the roadway where the flow is be dissipated and discharged through <br />rock check dams, to continue to the river below. This approach to managing the concentrated <br />flows from above the roadway provides for the drainage flows to be intercepted and removed <br />from the inside /uphill shoulder of the roadway before causing significant erosion damage to the <br />shoulder ditch /swale. In addition, the approach will not require significant re- grading on the <br />roadway or current shoulder ditch system, which could result in exposing newly cut soil to the <br />effects of erosion. This approach also allows concentrated flows to cross the road in a culvert, <br />minimizing erosion damage to the roadway. <br />The second grading scenario for the roadway, where the roadway is cross - sloped, allows the <br />drainage water coming from above the roadway to sheet flow across the road, as it currently <br />does and continue down the hill, in a sheet flow condition, to the currently established flow path <br />to the river below. This approach does not require that the flow be concentrated in channels, <br />thereby minimizing erosion impacts along the roadway or on the downhill slope below the road. <br />To mitigate possible silt transfer originating from the roadway due to sheet flow, erosion control <br />means or wattles, silt fences, straw bales, or other will be employed on the downhill side of the <br />entire roadway. <br />The second segment of the project, the operational site, assumed that the current grading of the <br />site would not be altered in any significant manner, except as necessary to ensure that drainage <br />water from the operational site was not allowed to leave the site. The site is currently graded to <br />contain all drainage water and is depicted in Exhibit 2 -Site Grading. <br />Entrance Road Analysis <br />The analysis of the entrance road began with the identification of the grading conditions of the <br />roadway. The grading conditions of the roadway were identified as crowned or cross - sloped. <br />The limits of each grading condition, i.e. where the grading condition started and stopped, were <br />identified. The drainage areas contributing to each section were delineated and the parameters <br />of each identified basin were detemlined. The parameters included the area of the basin, the <br />flow length of each basin, and the average slope of the basin from the top to the bottom. These <br />parameters were in addition to the described parameters of soil types, rainfall data, vegetation <br />cover, etc. See Exhibit U1- Drainage Basin Delineation, for basin configurations. <br />Using the Rational Method of analysis for determine runoff rates, a peak runoff, based on the <br />100 year, 24. hour rainfall event, was calculated. The analytical parameters and the results of <br />the calculations are presented in Table U(10 -1) -Peak Runoff Resulting from 100 - Year /24 -Hour <br />Rainfall Event. <br />Liberty Mining, LLC Moab; Utah SMA Ref. 5821857 Page 61 <br />