2009-06-18_PERMIT FILE - C1981018A ‎(6)‎

• Permit No: C1981018A
• IBM Index Class Name: Permit File
• Doc Date: 6/18/2009
• Section_Exhibit Name: Section V. Mine Surface Facilities Reclamation Plan
• Media Type: D
• Archive: Yes

• pH and chemical content of runoff from the disposal is monitored if discharged from the
sedimentation ponds (as indicated in Section IV). Groundwater is monitored as outlined in the
baseline hydrology report, Section II.C. If the runoff or groundwater develops adverse
characteristics, appropriate actions will be taken to remedy the situation. Waste banks already
constructed will be modified as required by the appropriate regulatory agency. In such a case, the
water in the ponds will be treated as necessary prior to release.
No ponds or coal banks will be located in areas over the underground mine. Therefore, no effects
on these structures due to subsidence are anticipated.
V.6.4 Sedimentation Ponds Design This section describes the ponds designed before mine
construction. The design of the mine facilities and Refuse Disposal Area drainage plan utilizes
diversion ditches where feasible to divert runoff from undisturbed areas away from disturbed areas
and into natural channels. Runoff from disturbed areas is directed to sedimentation ponds unless
exempted under small area exemption. The rugged terrain often dictates that the ponds be located
in less than ideal locations relative to the disturbed areas. Long collector ditches are constructed in
several places in the "D" Portal Area to get runoff to an area suitable for the construction of a pond.
These ditches are constructed in accordance with Section 4.05.3, as indicated on Maps 21 - 27.
The use and location of energy dissipation devices in these diversion ditches are field specified.
Ponds were sized and their outlets designed in accordance with the requirements of Section 4.05.6.
• In addition to the requirements of Section 4.05.6, sediment pond DP-1 is designed and constructed
in accordance with the requirements of 30 CFR 77.216 and 1973 Colorado Revised Statutes
37-87-105 or 37-87-122. Design storm data for 10-year, 24-hour; 25-year, 24-hour; and 10Q-year,
24-hour storms was obtained from Exhibit 2-3 in the SCS Field Enoineering Manual. Exhibit 2-3 is
a series of precipitation maps for the standard 24-hour storms prepared by the U.S. Weather
Bureau. The precipitation value used for the 10-year, 24-hour storm was 1.G inches, the value used
for the 25-year, 24-hour storm was 2.1 inches, and the value used for the 100-year, 24-hour storm
was 2.4 inches.
Sedimentation volume for ponds designed prior to mine constriction was determined using the
SCS Universal Soil loss Equation (USLE), The total required sediment for each pond is taken as
three years accumulation as calculated by the USLE. The values of the factors used in the USLE
were determined based on guidance from EPA-908-77-005 "Preliminary Guidance for Estimating
Erosion on Areas Disturbed by Surface Mining Activities in the Interior of the Western United
States" dated July 1977, and soils data taken from a soils survey of the area done by the SCS and
dated July 11, 1978. The various factors in the USLE are discussed below:
The USLE is A = (R)(K)(LS)(C)(P) where:
A =Sediment volume in tons per acre per year
R =Rainfall factor
K =Soil erodibility factor
• CS = CengtH-slope ractbr
Mid-Term Review 2002 (8/2002) V-8