GENERAL55787

• Permit No: M1999002
• IBM Index Class Name: General Documents
• Doc Date: 8/18/1998
• Doc Name: COMMERCIAL MINE PLAN SUBMITTED TO BLM SECTION 8
• Media Type: D
• Archive: No

• • conventional mining with above ground retorting
• modified in situ retorting
• true in situ methods.
Conventional mining has been attempted at several pilot operations (Colony, Anvil
Points, Unocal, Mobil, etc.) on the southern boundary of the Piceance Creek Basin.
These operations all targeted the rich Mahogany Zone between the A-Groove and
the B-Groove. Conventional mining used drill-and-blast with truck haulage and
room-and-pillar layouts. This method is sensitive to depth and rock quality. The
economics of mining decrease with increasing depth and with poor quality (highly
fractured) rock.
At the Yankee Gulch leases, the Mahogany Zone is at moderate depth and is more
highly fractured than the rock encountered at the pilot mines in the southern
Piceance Creek Basin. Therefore, the economics of mining the Mahogany Zone by
conventional mining methods would be poor. Conventional mining of other high
grade oil shale zones above the Dissolution Surface is likewise highly unlikely
because of increasing depth, lower oil shale grade, very poor rock quality, and the
presence of large volumes of groundwater.
Mining oil shale in the nahcolite-bearing zone using conventional mining methods
• (e.g., drill-and-blast, room-and-pillar) may not be possible, but other methods such
as shrinkage stoping or sublevel open stoping could be possible. However,
conventional mining of oil shale below the Dissolution Surface is unlikely because
of depth and low oil shale grade. Solution mining could enhance the economics of
mining oil shale below the Dissolution Surface because the removal of 25 to 30
percent of the volume of the formation by removing the nahcolite would increase
the oil shale grade on a per-ton basis, thereby lowering unit mining costs.
Furthermore, the resulting porous/permeable formation might make the oil shale
ore somewhat easier to mine. However, because of the depth and difficulty of
providing access via deep shafts, mining the oil shale resource below the
Dissolution Surface by conventional means (with above ground retorting) is
impractical and uneconomical, and, hence, the oil shale resource in this zone is not
minable whether or not nahcolite solution mining has occurred.
In the modified in situ methods demonstrated to date, intensive and costly mining
and subsequent blasting are required to create aporous/permeable or rubblized bed
in the retort for processing. The minability of the oil shale using modified in situ
retorting, as demonstrated by Occidental at Logan Wash and Standard Oil at the Ca
oil shale tract, could be enhanced by solution mining of nahcolite because, after
solution mining, the resulting cavities would be filled with porous, permeable,
enhanced-grade oil shale, which could then be subjected to in situ retorting.
True in situ methods include both multiple and single bore hole techniques.
• Heating of the rock mass can be accomplished using a variety of methods.
American Soda, L.L.P. 8_4
Commercial Mine Plan
August 18, 1998