2013-10-30_PERMIT FILE - C1981038A ‎(2)‎

• Permit No: C1981038A
• IBM Index Class Name: Permit File
• Doc Date: 10/30/2013
• Section_Exhibit Name: Volume 8 Surface Drainage - Drainage - Design & Location
• Media Type: D
• Archive: Yes

COLORADO WESTMORELAND INC. O CT $ ,~
Orchard Va~ey WesPpMine MINEp ~NQ RECi.SMA1~A~'d
Small Area Exe tion A lication
October 2, 3986 CO10, Dept, 01 NeiurAl RQ+JOUrCt'
1. A map of the Orchard Valley West Mine site is attached and shows the areas
which would be included in the small area exemptions. The mine bench, cut
slopes, and the topsoil storage pile (north of the mine site) would drain
to the sedimentation pond. The fill outalopes could not drain to the pond
and three small area eaemptiona are requested for these areas. The three
small area exemptions include the north fill outslope, the west portion of
the south fill outslope, and the east portion of the south fill outslope.
2. As described in the attached "Erosion Control Plan for the Fill Outslopes
at the Orchard Valley Weat Mine" completed by Harney & Associates, Inc.,
consultant to CWI, erosion and sedimentation would be controlled by a
number of methods, including proper sequencing of topsoil salvage and
placement during construction, immediate seeding and mulching of the
topaoiled fill outalopes, placing erosion control matting or netting over
the mulched outalopes and the placement of erosion control mats and silt
fencing in strategic locations. Soil Conservation Service studies
indicate that soil loss from Delson soils with native vegetation cover is
5 tone per year. With the application of only hydromulch to the fill
outalopes, soil lose from the south fill is reduced to 4.8 tone per year
(from 9.14 tpy bare soil) and to 1.04 tone per year on the north fill
outslope {from 1.99 tpy bare soil). Sediment would be further reduced (by
approximately 75%) ae flows pass through silt fencing.
As construction would take place during November, December and January,
months of low precipitation and runoff, the potential for erosion and
sedimentation of East Roatcap Creek during construction would be low. CWI
proposes to place silt fencing or straw bale structures at strategic
locations below the area of the culvert and fill construction. As the
south fill is constructed, grades would be maintained so as not to allow
runoff from the fill and bench area, which is not intercepted by the
sedimentation pond, to flow over the outslope. Excessive accumulations of
water on the fill construction area would be pumped and transported to a
permitted sedimentation pond.
The surface of the topsoil on the fill outslopes would be "roughened up"
or furrows about 4-6" in depth would be constructed along the contours of
the outslopes to act as "pockets" to catch seed and retard flows over the
surface. Depending on the availability of materials, CWI proposes to
hydromulch over the hydroseeded and fertilized topsoil surface with
approximately two to three tone per acre of clean straw mulch utilizing a
"DOW" or other similar non-toxic, non-alkaline tackifier. An erosion
control matting or netting would be placed over the hydromulch for
additional protection and "tacking" of the mulch. Silt fences would be
constructed across the south fill's terrace, extending into and across the
perimeter drainages. Silt fences would also be constructed across the
toes of both the north and south fill outslopes and into and across the
. perimeter drainages. An eroslo^ control matting such as "Enkamat" would
be placed in the perimeter drainage of the south fill outslope from the
terrace to the toe of the fill.