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 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.