2010-12-27_PERMIT FILE - C1981012A ‎(6)‎

• Permit No: C1981012A
• IBM Index Class Name: Permit File
• Doc Date: 12/27/2010
• Section_Exhibit Name: Section 2.05 Operation and Reclamation Plan
• Media Type: D
• Archive: Yes

• Ditch 27 will direct runoff from Warehouse 1 to Containment Area 2. The total drainage area is
2.9 acres. A total of 0.28 acre -feet of storage is required to handle the 10 -year 24 -hour event and
0.38 acre -feet of storage is required to handle a 25 -year 24 -hour event. The three -year sediment
volume is 0.02 acre -feet. Ditch 28 will direct disturbed runoff from a 15.45 -acre disturbed area
to Containment Area 1. A total of 1.51 acre -feet of storage is required to handle a 10 -year
24 -hour event and 2.01 acre -feet for a 25 -year 24 -hour event. The three -year sediment storage
volume is 0.07 acre -feet. Containment Area 1 also controls drainage from the non -coal waste
disposal area.
Ditch 29 collects runoff from 67.2 acres of undisturbed runoff and directs this runoff to the
laydown area without impacting any disturbed area. Culvert C -27 has been installed at the east
end of the laydown area to handle peak flows from Drainage Basins CC and DD as shown on
Map 13A— Drainage Basins.
Ditches 39a and 39aa are proposed to route stormwater around the cut slope of the substation and
rock dust system to maintain the integrity of the slope. At the time of construction, the slope
material characteristics will be evaluated to determine if a drop structure is necessary to carry the
cut slope runoff. The details of the cut slope are included as Figure 2d.
Culverts C -21 through C -25 direct undisturbed runoff south of the fan and substation to the
Purgatorie River. Sizing data is provided in Exhibit 19— Sediment Design Specifications.
Culvert C -25 was inspected and found to be draining all runoff adequately. The Operator is
unsure if it is a drop structure or simple culvert. (It would be necessary to excavate the inlet to
determine what type of structure exists.)
• Pond 004 was surveyed in 1995 and found to have 7.19 acre -feet of volume. A 10 -year 24 -hour
storm of the contributing watershed is 0.9 acre -feet, a 25 -year 24 -hour storm is 1.13 acre -feet and
a 100 -year 24 -hour storm is 1.5 acre -feet. There are 3.78 acre -feet below the lowest dewatering
hole, of which SEDCAD+ estimates there are three years of sediment storage between 0.98 and
1.28 acre -feet. The Operator retains the option to use all 4.03 acre -feet as a combination of
sediment or permanent pool storage. Sediment would be cleaned out at an elevation of 7,449
feet. The Operator periodically stores drilling fluids in this pond to the elevation of the lowest
dewatering orifice and, depending on existing water storage in the pond, there would be a
maximum of 2.75 acre -feet (895,950 gallons) of fluids in this pond. The duration of storage will
depend upon the quality of the pond's water and the size of subsequent storm events.
The Operator constructed the preparation plant in the spring of 1984. After several months of
operation, it was determined that a plant process pond was required to accommodate plant
discharges. The Operator submitted a permit revision whereby Pond 006 was taken out of the
surface drainage plan and modified to a plant process pond. Pond 007 was sufficiently oversized
to handle the additional runoff formerly reporting to Pond 006.
Exhibit 19— Sediment Design Specifications and West Portal Drainage Plan, confirm that
Pond 007 (as- built) has sufficient storage capacity to
TR 54 Page 2.05 -10 Revised 1 -3 -2011