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• <br />RSN Operational Drainage to Pond 5 <br />Calculation Rational and Results Summary <br />Rational: <br />Calculated using Sedcad+ Ver. 3 <br />Areas, slopes and flow paths digitized from 100 scale topo maps flown in 11/94. The <br />attached 200 scale diagram represents the subwatersheds digitized. <br />The soil map, Exhibit 23, shows the area as Area 80 -"Stony Land". There is no defined <br />soil group associated with this soil therefore Table 5.1 in the Sedcad reference manual was <br />used to determine a soil group. Generally the soil samples for this and other disturbance <br />areas classifies the soil to be sandy to silty loam (Tab Section 9) which equates to a "B" <br />soil group. A "D" soil group was used for operations areas where clays from the mining <br />operations may be incorporated in the surface. The following CN were used in the <br />calculations: <br />86 - B soil group, fallow, bare soil. Used for topsoil piles, ponds and dirt slopes. <br />92 - D soil group, gravel road. Used for parking, storage and stockpile areas. <br />10 yeaz 24 hour storm event of 1.4" , 25 year 24 hour storm event of 1.8" <br />r1 <br />~J <br />The attached particle size distribution was estimated to represent the typical sand/siltJclay <br />proportions in the typical soil samples. The default specific gravity and submerged bulk <br />density were used. These numbers were required to run the sediment routine in Sedcad <br />but have no actual value for Pond 5 design because the pond will use a controlled <br />discharge system of trapping sediment rather than a calculated settling associated with <br />residence time during a continuous flow through. <br />The RUSLE method of soil loss calcuation was used to determine the sediment capacity of <br />the pond. Variables imput while nrnning Sedcad program include: <br />K = 0.24 Sandy loam soil type <br />CP = .24 Soil with a 20 % cover of weeds for topsoil stockpiles, pond and dirt <br />slopes <br />CP = .55 20% rock cover for parking, storage and stockpile areas. <br />R = 20 Sedcad table in Appendix D. <br />Results Summary: (other information may have been generated in this section but is not being <br />used in the site drainage design at this time) <br />Structure # Structure Description <br />• 111 Collection ditch west of <br />topsoil piles l :l side slopes, 1% grade, 1' min. depth <br />Design <br />RSN-20 <br />(New 3/1/96) <br />