PERMFILE134082

• Permit No: C1981038A
• IBM Index Class Name: Permit File
• Doc Date: 8/16/2004
• Section_Exhibit Name: 2.05 Operation and Reclamation Part 3
• Media Type: D
• Archive: Yes

2.05
2.05.6
(6)
(6)
•
(6)
I
TR 92-19
APPLICATIORd FOR PERMIT FOR SORF~ OR UDIDERGROZA~ID MiNIIJG ACPIVITIES -
MINIMUM RDQiTII2Et~NTS FOR OPERATION AAID RE7CLAMP,TiON PIS.
Mitigation of surface Coal Operation Mining Iaq~aots. (Oont'd.)
(f) (ii) (B) (I) (Cont'd.)
pillar recovery areas for attenuation of subsidence effects. Grout
columns or slurry injection are not conte~lated presently to be used
at the Orchard Valley mine.
(f) (ii) (B) (II)
Federal lease C-377210 stipulation "g" limits extraction beneath
Steven's G<alch and East Roatcap Creek to necessary development access
entryways below 600 feet of overburden thickness. In cca~g~liance with
BLM stipulation "g", ~V will drive access entryways only beneath the
Stevens Gulch and East Roatcap Creek drainage buffer zones under 600
feet of overburden. Permanent protective pillars will be left standing
to prevent all surface and subjacent disturbance to the overburden.
Protective pillars in these buffer zones will be designed to provide
safety factors in excess of 2.0 using the Wilson pillar design method
(refer to Pillar Stability Calculations in Volume 2). Panel designs
for specific development geometries and mining heights vary within
these buffer zones and are optimized to provide maxiimnn eoonomic
recovery of the coal resource, however, the miniminn safety factor
criteria for all panels developed within these buffer zones remains
constant at 2.0. Secondary extraction or retreat mining is limited to
the recovery of floor coal within previously developed entries. All
development entries are roof bolted in accordance with the approved
roof control plan in effect.
In the 600 to 800 feet overburden depth buffer zones defined in the
above mentioned drainages, permanent protective pillars are designed
to provide safety factors in excess of 1.5 using the Wilson pillar
design method. Panel designs for specific development geometries and
mining heights vary within these buffer zones and are optimized to
provide maxinnna economic recovery of the coal resouroe, however, the
minimum safety factor criteria for all panels developed within this
buffer zone remains constant (refer to Pillar Stability Calculations
in Volume 2) . Secondary extraction or retreat mining is limited to the
recovery of floor coal within previously developed entries. All
development entries are roof-bolted in accordance with the approved
roof control plan in effect. This zone of development mining between
600 and 800 feet of overburden also serves to dissipate abutment
stresses from full extraction to the. virtually solid buffer area
barrier blocks stipulated by the BIM. In essence, these subsidence
control measures of limited and partial extraction beneath Steven's
c~zlch and East Roatcap Creek will prevent subsidence in the areas
defined as Renewable Resource Iarxls, during subsequent permit terms.
(f) (ii) (B) (III)
Structures within the permit area are depicted on Map No. 9-7.
Revised 6/08/92
159