2008-01-16_PERMIT FILE - C1994082A ‎(6)‎

• Permit No: C1994082A
• IBM Index Class Name: Permit File
• Doc Date: 1/16/2008
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-12
• Media Type: D
• Archive: Yes

February 1999 Yoart Mine * 13-12 Drainage and Sediment Cantrnl Plan • 1
SENECA YOAST MINE
DRAINAGE AND SEDIMENT CONTROL PLAN
1.0 INTRODUCTION
Seneca Coal Company (SCC) proposes to develop the remaini a coal reserves south of the existing Yoast Coal Mine
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 13A and 14A). A fourth pond,
Pond O12A, was designed for TR 36. Pond 012A will be used to assist Pond 012 to treat runoff' and sediment
from a portion of the South Mine mine area. In addition, to access the new area, SCC will extend existing haul
road B and construct new haul roads C and D. The design of the haul road ditches are 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 a series of post mining channels in conjunction with the reclamation
plan. The reclaimed topography and channel locations are shown on Exhibit 20-2, Postmining Topography Map
(Tab 20). The designs of the post mining channels are included in this attaclunent
The following is the methodology and assumptions that were 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 program developed by Civil Software Design (Civil Software
Design, 1998) and were analyzed according to the following methodologies.
2.0 HYDROLOGIC CALCULATIONS
SEDCAD4 is the next generation of hydrology 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 (Le., rainfall volume and duration, selection of rainfall distribution, and convolution
increment). Hydrographs are developed on a subwatershed basis with the input of area, time of concentration, SCS
Curve Number, and the selection of 1 of 3 dimensionless double triangle unit hydrograph shapes. Calculated runoff is
routed to the various structures input into the model Muskingum routing parameters are used.
Inputs to the hydrology component of the SEDCAD4 computer model include:
• Precipitation Distribution
• Storm Duration
• Retum Period/Precipitation
• Hydrograph Response Shape
• Drainage Basin Area
• Time of Concentration
• Muskingum Routing Parameters
• Curve Number
•
Input values are explained in following sections.
2.1 PRECIPITATION DISTRIBUTION
A precipitation distribution is input to model the run-off hydrograph. SEDCAD4 allows the user to
Montgomery Watran Mining Group * 165 S. Union Boulevard, Suite 460 * Inkewood, Colorado 80228 * [phone]
TR-36 Revised 08/07