PERMFILE134006

• Permit No: C1994082A
• IBM Index Class Name: Permit File
• Doc Date: 4/25/2007
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-12
• Media Type: D
• Archive: Yes

FeGrnag 1999 1oartatare "1i-12 Drainer rmrCSeZmrrrt Cmrtro/Plan !
SENECA YOAST MINE
•` DRAINAGE AND SEDIMENT CONTROL PLAN
1.0 INTRODUCTION
Seneca Coal Company (SCC) proposes to develop the remaining coal reserves south of the e:dstin~
Yoast Coal Iwline operations in the Sage Creek drainage. To control run-off from the new development
area, SCC proposes to build three new sediment ponds (Pond 012, 013, and 014) and associated
ditches (ditch 13 ~ and 14x1). In additioq to access the new area, SCC will extend existing haul road $
and construct new haul roads C and D. The design of the haul road ditches aze included in this
attachment. The location of the proposed ponds, ditches and the haul roads are shown on Exhibit 12.
1, Operations Plan.
Once mining is complete, SCC will construct I1 post mining channels in conjuction with the
reclamation plan. The reclaimed topographe and channel locanons are shown on Exhibit 20-2, Pos}
Mining Topography (Tab 20). The design of the post mining channels are included in this attachment.
The following is the methodologg and assumptions that a-ere used in the designs of the ponds, ditches,
haul road ditches and culverts, and post mining channels.
The hydrologic, hydraulic, and sediment calculations used to model the ponds, ditches, and post
mining channels were performed utilizing the SEDCAD4 computer modeling pmgr;un developed by
Civil Software Design (Civil Softcaee Design, august 1998) and were analyzed according to the
following methodologies.
• 2.0 HYDROLOGIC CALCULATIONS
SEDCAD4 is the next generation of hedrologv and sedimentology modeling software that replaces
SEDCAD+. It is a comprehensive, computer-based model used to evaluate storm water, erosion, and
sediment control management techniques. The SEDCAD4 model calculates run-off and peak flow via
a numerical modeling technique based on user inputs of a design storm event (i.e., rainfall volume and
duration, selection of rainfall distribution, and convolution increment). He drographs are developed on
a subwatershed basis with the input of area, time of concentration, SCS Cun~e Number, and the
selection of 1 of 3 dimensionless double triangle unit hydrograph shapes. Calculated runoff is routed
to the carious strucmxes input into the model. Muskingum routing parameters are used.
Inputs to the hcdrologv component of the SEDCAD4 computer model include:
• Precipitation Distribution
• Storm Duration
• Remrn Period/Precipitation
• Hydrograph Response Shape
• Drainage Basin Area
• Time of Concentration
• Muskingum Routing Parameters
• Cun~e Number
Input values are explained in following sections'.
2.1 Precipitation Distribution
A precipitation distribution is input to model the run-off hcdrograph. SEDCAD4 allows the user to
DGintgomen~ \\~atson Jlining Group " 1G~ S. Onion L3uulecard, Juite 3G0 • Lakewood, Colorado 802?S' (303) iG3a110