Within the Sheep Mountain Project area, uranium mineralization is contained in the lower to middle Eocene Battle Spring Formation. The Battle Spring Formation, consisting of upper and lower members (designated the “A” for the lower and “B” for the upper), is a fluvial deposit. Mineralization is hosted by the Battle Spring Formation and has been described extensively since the 1960s and has been termed a ‘Wyoming Roll Front System’. These deposits are often organic-rich, fine grained lenses in tabular, or “roll front”, configurations. The uranium mineralization occurs primarily in the lower member of the Battle Spring Formation (Stephens, 1974).

Mineralization occurs throughout the lower A Member of the Battle Spring Formation and is locally up to 1,500 feet thick. The upper B Member is present only in portions of the project and may be up to 500 feet thick. The A Member of the Battle Spring is folded. The folding is considered to have focused mineralization in the troughs of the synclines (Stephens, 1974).

Although arkosic sandstone is the preferred host, uranium has been extracted from all lithologies. Grade and thickness are extremely variable depending on whether the samples are taken from the nose or the tails of a roll front. Typically the deposits range from 50 feet to 200 feet along strike, 5 feet to 8 feet in height, and 20 feet to 100 feet in width. Deposits in the Sheep Mountain area occur in stacked horizons from 7,127 feet elevation down to 6,050 feet elevation (Stephens, 1964)

The current mine design for the Congo Pit includes typical highwall heights in the range of 100 to 400 feet, and reaches a maximum depth of 600 feet in localized areas in the southeast pit corner. The open pit design employs similar design parameters and mining equipment configurations to those used successfully in past Wyoming conventional mine operations. Highwall design is based upon the performance of past projects in the Sheep Mountain and Gas Hills districts, and includes an average highwall slope of 0.7:1, which reflects the average of a 10-foot bench width and 50-foot wall at a 0.5:1 slope.

The Sheep Underground mine has operated as a conventional underground mine on three separate occasions. The historic mining method was a modified room and pillar method using conventional techniques. Jacklegs were used to drill out the rounds and underground track haulage was used to transport the ore to Shaft No. 1.

The mining method proposed going forward is also a conventional method using a modified room and pillar method, but utilizing modern mining equipment such as jumbo drills and 7 cubic-yard scooptrams for haulage. A new double entry decline will be constructed starting at the Paydirt Pit and ending below the deposit. Haulage from the mine will be accomplished via a 36 inch conveyor within one of the double declines. The existing shafts will be used for ventilation purposes only, with exhaust fans mounted at both locations. If the existing borehole ventilation shafts can be rehabilitated, they will be used as intake shafts. The deposit is comprised of 16 mineralized zones with a total thickness of approximately 350 feet. The deposit will be mined primarily from bottom to top.

Sheep Underground mining method summary:
- Development drifts will utilize dual openings. 10 by 15 foot openings will be used for haulage, and 8 by 10 foot openings will be used for transportation and ventilation.
- Mining panels will utilize multiple entries depending on the width of the zone. Entries will be approximately 12 feet wide, minimum of 6 feet high and averaging 7 feet high.
- Crosscuts will be placed on 100 foot centers.
- Mining will be completed by advance and retreat methods.
- Advance mining is accomplished by driving approximately 12 by 7 feet drifts within zones meeting cutoff grade. Multiple drifts will be driven parallel to one another with crosscuts on 100 foot centers. The parallel drifts will be 27 feet apart on centerline.
- This will leave a pillar with a dimension of approximately 15 feet wide and 90 feet long. On retreat mining, these pillars are removed if they meet cutoff grade.
- Blasting of the rock, both for development and mining, will be done by drilling 8 to 12 foot blast holes using jumbo drilling rigs and filling the blast holes with ANFO (Ammonium Nitrate and Fuel Oil).
- Haulage from the working faces to the haulage conveyor or to the loading chutes will utilize 7 cubic yard scooptrams which load, haul and dump mined product.
- Mined product will be hauled through development drifts directly to the decline or to two loading chutes to transport the mined product to the decline. The decline will be equipped with a 36 inch conveyor which will take the mined product and waste, when necessary, to the surface. Haulage drifts will be kept as level as practicable, not exceeding ten percent grades.
- The roof and sidewalls in the drifts, both mining and development, will be supported with rock bolts and wire mesh. A rock bolting machine which can drill holes both vertically and horizontally will place the rock bolts on approximately four foot centers as the drifts advance. There will be overlap of bolting and wire mesh between each round to ensure proper ground control coverage.
- Boreholes to construct loading chutes or to aid in ventilation will be drilled using raised boring methods.
- Waste rock, whenever possible, will be placed in mined out workings to minimize haulage of hauling the mined waste to the surface. When it is not possible, the waste will be taken to the surface where it will be stockpiled for final reclamation.
- Ground Support will, in addition to bolting and meshing, include:
- In areas that do not have mineralized zones directly above them temporary support will be placed such as timbers or concrete cylinders, and the pillars will be removed allowing the roof to ultimately fail.
- In areas with ore pods directly overhead, the adjoining rooms will be backfilled using a cemented backfill. The backfill will be a combination of waste rock mixed with three and one half percent cement and three and one half percent fly ash. This backfill will exceed the strength of the native rock and prevent the roof from failing and diluting the ore pods above them.

The planned uranium recovery method at the Sheep Mountain Project is conventional heap leaching which includes: the mobilization of uranium values into solution from the mined material stacked on the heap pad via acid leaching, delivery of uranium rich solutions to a recovery plant (mill), and concentration of the uranium to a saleable product via solvent extraction, and precipitation systems that will be capable of producing up to 2 million lbs U3O8 annually.

Uranium recovery at Sheep Mountain will include the following processes:
- stacking of mined material on the heap leach pad;
- application of leach solution;
- collection of pregnant leach solution (PLS);
- filtering of sand and fines from PLS;
- solvent extraction to concentrate and purify the extracted uranium;
- precipitation of uranium oxide, “yellowcake”;
- washing, drying, packaging, storage and loading of yellowcake product;
- management of process solid and liquid waste and bleed streams; and,
- in-place reclamation of all “byproduct material”, within the meaning of Section11e.(2) of the Atomic Energy Act of 1954, as ameneded hereinafter refered to as (11e.(2)), in a double lined disposal cell, which will include the existing lined heap leach pad and the Raffinate and Collection Ponds.

The uranium recovery or “milling” process equipment will be housed in two buildings within the proposed mill boundary. All solvent extraction processing and equipment will be located within the SX Plant to isolate potential fire hazards associated with the organic solutions. Yellowcake processing, including precipitation, washing, drying, packaging, storage, and loading will be located within the Process Plant. Reagent storage and distribution systems will be located within or next to the process buildings.

Processing (‘milling’) begins as run-of-mine product is stacked on the double lined heap leach pad using covered belt conveyors and a covered radial arm stacking (RAS) belt conveyor. The stacked mined material is leveled with low ground pressure equipment forming a “lift”. A protective layer of gravel is place on top of the lift to mitigate fugitive dust and transport of radioparticulates from the heap. A drip irrigation system using conventional plastic piping is then installed on top of the completed lift, and the heap is ready for the application of leach solutions.

The process begins with the pumping of the leach solution from the Raffinate Pond to the top of the heap where it is applied using drip emitters. The leach solution consists of water; an oxidizing agent, such as sodium chlorate, to convert the uranium to a soluble valence; and a complexing agent, sulfuric acid, to complex and solubilize the uranium. The result of the heap leaching process is a pregnant leach solution (PLS) containing a mixture of uranyl trisulfate (UTS) and uranyl disulfate (UDS). PLS percolates through the stacked mined material via gravity drainage and is intercepted by the heap leach pad liner system and gathered into collection pipes, which drains by gravity into the collection pond. The PLS is then pumped from the collection pond into the solvent extraction (SX) Plant where the PLS is filtered to remove suspended particulates, and the uranium is recovered using organic phase ionic exchange solutions. The resulting, uranium depleted solution called barren leach solution or “raffinate,” flows by gravity from the SX Plant to the raffinate pond. This raffinate solution is refortified with additional acid and oxidant and additional make-up water and is then pumped back to the heap in a continuous cycle. From the SX Plant, uranium-rich strip solution is sent to the Process Plant for precipitation of a yellow, solid uranium oxide known as ‘yellowcake.’ The precipitated yellowcake is then washed, dried, and packaged into sealed 55 gallon drums for shipment. Yellowcake is shipped via truck to an enrichment facility in regular shipments approximately once every two weeks.