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hlal' 1999 C)y~Hr Tmnrgmile * Pond D Era/uahan 1 3 <br />2.7 Muskingum Routing Parameters, K, X <br />• The I\lusldngum routing pazameters were also calculated using the NRCS upland method. The <br />hydraulic lengths, drainage heights and associated slopes were deterrrwted from scaled drawings. The <br />values calculated between each structure and/or subwatershed are shown in the SEDC.~1D 4 printouts. <br />2.8 Curve Number, CN <br />• <br />The run-oft curve number is a factor relating the amount of rainfall to the amount of rvn-off for a <br />given area. Curse numbers were assumed based on supplied vegetation and soils information. \\~Itere <br />no vegetation or soils data was available, average conditions were assumed. \r'here multiple conditions <br />existed within the watershed, a weighted average curve number was assigned. A summan~ of the cun•e <br />numbers used for this evaluation is presented in Table 1.1, Pond D \Vatershed Curve Numbers. <br />TABLE 1.1 <br />POND D WATERSHED CURVE NUMBERS <br />Area <br />Condition Cover Type Hydrologic <br />Condition Hydrologic <br />Soil Grou Curve <br />Number <br />Reclaimed Reclamation Seed i.lix Good (>70%) C 7d <br />Pre-Law <br />Reclaimed Natural Reclaimed <br />Partial, Seeded Fair (>50%) C 79 <br />Disturbed None - C 90 <br />Retuse None - - - - - - 86 <br />Facilities None - - - C 90 <br />Ref: (SCS, 1986) <br />2.9 Mine Pumping and Spring Water Inflow <br />As indicated in the introduction of this report, there is a continuous water inflow into Pond D. \\'ater <br />enters the Pond from natural springs and water pumped from mining operations. Pursuant to the <br />request by Dtv(G, (\•1\G has modeled Pond D to include this water inflow. The combined water inflow <br />has been estimated by TCC as follows: <br />Current mine pumping 0.5 cfs <br />Springs 0? cfs <br />Possible increase in pumping 0.2 cfs <br />Total 0.9 cfs <br />In order to simulate this continuous inflow, the permanent pond water level has been set at 683i.~1, <br />which is slightly above the lowest hole in the riser. This water elevation results in an equivalent head <br />pressure on the principle spillwa[ to continuously pass R9 cfs. (Refer to SEDCAD 4 printouts initial <br />warer elevation.) <br />3.0 SEDIMENTATION CALCULATIONS <br />The sediment calculations used to model Pond D were performed utilizing the SEDCAD 4.0 <br />• Computer Modeling Program developed by Civil Software Design. The SEDC.~D ~4.0 Computer <br />model calculates annual sediment yield using the Revts'ed Universal Soil Loss Equation (RUBLE). The <br />input paramerers used in the sedimentation analyses- are presented in the following sections. <br />Afomgomeq~ \\'aeson ~Lnmg Group' 1G5 ti. l,'n~un I3oulecard, Su¢e JIn' Lakewood, Colorado 8P2?8' (3113) 7G3-S1aU <br />D-7 <br />