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<br />Z <br />7-~~s , <br />,o <br />SAE DENONSTRATION <br />FOR <br />EAST PORTAL STORAGE PAD AREAS <br />5'° <br />~ i3~ <br />The area referred to as the East Portal Storage Area consists <br />of 3 separate pad areas each having a graveled surface and <br />containment basins sized to contain the 25 yr. 24 hr. event. <br />Pad areas and containment sizes are as follows: <br />~ Pad #1 = 0.45 acres 2 at 0.029 ac.ft. each -7 <br />Pad #2 = 0.10 acres 1 at 0.01 ac.ft.~/ <br />Pad #3 = 0.37 acres 1 at 0.10 ac.ft./H~s~cY~ <br />See attached map for locations. <br />The following parameters were used within SEDCAD to model <br />these areas. <br />Soil type: Moyerson D. Which is the predominant soil type <br />for this area. <br />Land Use: 7, Paved area sheet flow. <br />Runoff curve #: 91 For paved areas with gravel surface. <br />Soil erodibility factor, R: .1, as determined for soil type <br />from conversation with DMG. <br />Control practice factor: 0.1, this is a conservative estimate <br />for a cp factor for gravel pads per conversation with SEDCAD <br />r~ <br />LJ <br /> <br />authors. <br />As demonstrated by the attached SEDCAD calculations the <br />existing containment structures should be more than <br />adequate to store the 25 year event. Containment structures <br />shall be dewatered after any storm where water depth in the <br />sump exceeds 1.0'. Sediment storage was not addressed since <br />calculations result in less than 1 cu. ft. of sediment. <br />Mine Permit Renewal li3 (Rev. 8/99) <br />O~~ <br />