2010-05-07_PERMIT FILE - C2009087 ‎(55)‎

• Permit No: C2009087
• IBM Index Class Name: Permit File
• Doc Date: 5/7/2010
• Doc Name: Portal Area Sump Design Report
• Section_Exhibit Name: Exhibit 2.05.3-E2 Appendix 2.05.3-E2.F
• Media Type: D
• Archive: No

1.0 Introduction
• The Portal Area Sumps are two water management structures (Portal Sump #1 [PS -1] and Portal
Sump #2 [PS -2]) located on the portal pit floor. The primary purposes are:
• a storage /holding cell for mine water discharge; and,
• to collect surface runoff from precipitation falling on the portal entrance area (e.g., pit access
road, pit side slopes and pit floor)
The portal area sumps are non - discharging; the base elevation is below the native ground surface
and, consequently, they do not gravity drain to a sediment pond. The sumps are not designed as
sedimentation structures; consequently, they are not required to meet the requirements of Rule 4.05.6
and Rule 4.05.9. Water in the portal area sumps will be used to support the underground mine
operations or get pumped to the Coal Stockpile Sumps and ultimately Pond 002.
The Portal Sumps will be operated as follows:
•
The Portal Sumps will be excavated pits in native ground on the portal pit floor; they will not
have an embankment. The system is a non - discharging (there is no natural, gravity drainage
to a downgradient structure). While there is no principal or emergency spillway, there is a
culvert (SC -9) that will be used to convey water from PS -1 to PS -2. A MSHA safety berm
will be constructed along the side(s) of the sumps that abut the pit access road and pit floor
is as
safety measures.
•
Groundwater calculations indicate groundwater inflows to the underground workings will be
greatest during initial mine develop and stabilize after about 1,000 days. The peak
groundwater inflow rate is estimated at 75 gallons per minute (gpm) and the average long-
term rate is approximately 55 gpm.
•
The design is based on the peak groundwater inflow rate of 80 gpm.
•
There are 2.2 acre -feet (ac -ft) of storage in PS -2.
• the runoff volume from the 10 -year, 24 -hour event is 0.8 ac -ft
• the runoff volume from the 25 -year, 24 -hour event is 1.1 ac -ft
•
Assuming the water level in PS -2 will be conservatively maintained at approximately the
6,669.0 foot elevation — there will be sufficient storage capacity to contain all the runoff
from the 25 -year, 24 -hour storm event.
•
It is anticipated that mine water will be pumped to PS -2 at a rate of approximately 500 gpm
for approximately 30 minutes, as needed.
•
Two 1,500 gpm pumps will be used to pump water from the PS -2 to the Upper Coal
Stockpile Sump (UCSS), as needed. The pumps will be fitted with a floating siphon tube so
that the "cleanest" water will be pumped first.
•
The Portal Sumps will be cleaned of any sediment as needed.
•
They are temporary structures that will be reclaimed in conjunction with closure of the
•
portal.
2.05.3 -E2.F1 12/09