In the Pumpkin Buttes Uranium District, which includes the Reno Creek, Moore, Bing, and Pine Tree deposits, important economic uranium deposits occur in medium to coarse-grained greywacke sand facies in the lower portion of the Eocene Wasatch Formation. The sandstone host rock is composed of poorly sorted, angular grains of quartz, feldspar and rock fragments ranging in size from 0.063 to 2.0 millimeters. Found between these grains is a finer-grained matrix or interstitial material consisting of silt, clay and some organic material. When mineralized, very fine-grained particles of uranium minerals occur scattered throughout the interstitial matrix. As described in Section 13, the permeability in the mineralized sandstone generally is above 1 Darcy (1000 md) across the project area. The uranium mineralization occurs along roll front trends formed at geochemical reduction-oxidation (redox) boundaries within the host sandstone aquifers. Roll front uranium minerals in the unoxidized zone are commonly coffinite and pitchblende (a variety of uraninite). Low concentrations of vanadium (less than 100 ppm) are sometimes associated with the uranium deposits.

Uranium deposits accumulated along roll-fronts at the down-gradient terminations of oxidation tongues within the host sandstones. The deposits occur within sandstones, which are intermittently interbedded with lenses of siltstone and claystone, commonly referred to as mudstones at the project due to the mixture of particle sizes. The thickness of the mineralization is controlled by the thickness of the sandstone host containing the solution front.

Uranium deposits are generally found within sand units ranging from 50 feet to 200 feet in thickness, and at depths ranging from 170 feet to 450 feet below ground surface. Uranium intercepts are variable in thickness ranging from 1 foot to 30 feet thick. Thin low-grade residual upper and lower limbs of the roll fronts are found in the less permeable zones at the top and bottom of oxidized sand units bounded by unoxidized mudstones.

While in solution, uranium is readily transported and remains mobile as long as the oxidizing potential of the groundwater is not depleted. When the dissolved uranium encounters a reducing environment, it is precipitated and deposited at the interface between the oxidizing and reducing environments known as the redox or alteration front.

Oxidation or alteration of the PZA sandstone in the Reno Creek area was produced by the downgradient movement of oxidizing, uranium bearing groundwater solutions. Uranium mineralization was precipitated by reducing agents and carbonaceous materials in the gray, reduced sands. The host sandstones, where altered, exhibit hematitic (pink, light red, brownish-red, orange-red) and limonitic (yellow, yellowish-orange, yellowish-brown, reddish-orange) alteration colors, which are easily distinguished from the unaltered medium bluish gray sands. Feldspar alteration, which gives a “bleached” appearance to the sands from the chemical alteration of feldspars into clay minerals, is also present. Limonitic alteration dominates near the “nose” of the roll fronts. The remote barren interior portions of the altered sands are usually pinkish-red in color.

AUC plans to mine the uranium using the ISR method. For purposes of operations, the North and Southwest Reno Creek Resource Units will be unitized into a single operation called the Reno Creek Resource Unit. Mining of the reserves will occur in the Reno Creek Unit and the Moore and Bing Units.

The basic requirement for ISR mining is that mineralization is located in water-saturated permeable sandstone bodies that allow effective confinement of mining solutions, typically confined between impermeable clay-rich strata.

Wellfields are the groups of wells, installed and completed in the mineralized zones that are sized to effectively target delineated ore and reach the desired production goals. One header house controls the operation of each wellfield. The ore zones are located within the geologic sandstone units where the leaching solutions are injected and recovered via wells in an ISR wellfield and it is bounded between aquitards.

The proposed uranium ISR process will involve the dissolution of the water-soluble uranium compound from the mineralized host sands at near neutral pH ranges. The lixiviant contains oxygen and sodium bicarbonate. The oxygen oxidizes the uranium, which is then complexed with the bicarbonate. The uranium-rich solution (typically ranging from 20 ppm to 250 ppm, but may be higher or lower) will be pumped from the recovery wells to the nearby processing facility for uranium concentration with ion Production Unit Boundaries were designated based on deposit locations and configuration of mineralization. Small and isolated blocks of measured and indicated resources were excluded from the proposed mine plan.

Mineral reserve head grade is projected to average approximately 45 ppm over the entire production schedule. Initial head grades in new wellfields can be several hundred ppm, while head grades from nearly mined out wellfields may be 10-20 ppm. As pregnant lixiviant is gathered from individual wellfields it is co mingled with solutions from other operating wellfields to make up an average head grade of about 45 ppm. Since there is a peak followed by a successive depletion in the amount of uranium extracted from the formation from a given wellfield, careful planning of mixing schemes from high yield wellfields and lower yield wellfields is required to maintain the head grade for the operation.

AUC plans to recover uranium from the lixiviant using the ion exchange (IX) process. This same method is typically and successfully used with the ISR method elsewhere in the United States and especially in Wyoming.

The proposed CPP will have four major process circuits: the uranium recovery/extraction circuit (IX); the elution circuit to remove the uranium from the IX resin; a yellowcake precipitation circuit; and the dewatering, drying and packaging circuit.

The systems within the CPP have been designed to recycle and reuse most of the solutions inside each circuit. A low-volume bleed (approximately one percent of flow) is permanently removed from the groundwater-based leaching solution to ensure a constant inward flow gradient to the PUs and ensure that the leaching solution in the target mineralized zone is contained by the inward movement of groundwater within the designated recovery area. This bleed solution will be routed to RO treatment, and the permeate will be used as process make up water. Brine will be disposed of via DDWs.

Pregnant lixiviant from the wellfields will be pumped to the CPP for processing as described below:

IX Circuit - Uranium dissolved from the underground deposits in the wellfields will be extracted from the solution in the IX circuit. This evaluation assumes an average uranium head grade of 45 ppm based on the production model and leach tests. Subsequently, the barren lixiviant will be reconstituted to the proper bicarbonate strength, and oxidant will be added, as needed, prior to being pumped back to the wellfield for reinjection. A low-volume bleed, approximately one percent during production and four percent of the circulating lixiviant flow during restoration, will be permanently removed from the lixiviant flow. The bleed will be treated by RO. A portion of the permeate will be returned to the wellfield, and a portion will be used as plant makeup water. Brine will be disposed of into a DDW.

Elution Circuit - When it is fully loaded with uranium, the IX resin will be subject to elution. The elution process will reverse the loading reactions for the IX resin and strip the uranium from the resin. The resulting rich eluate will be an aqueous solution containing salt and sodium carbonate and/or sodium bicarbonate.

Yellowcake Precipitation Circuit - Yellowcake will be precipitated from the rich eluate. The eluate from the elution circuit will be de carbonated in slurry tanks by lowering the pH below two standard units with strong mineral acid. The yellowcake product will be precipitated with hydrogen peroxide using sodium hydroxide for pH control.

Yellowcake Dewatering, Drying and Packaging Circuit - The precipitated yellowcake slurry will be transferred to a filter press where excess liquid will be removed. Following a fresh water wash step that will flush any remaining dissolved chlorides, the resulting product cake will be transferred to the yellowcake dryer which will further reduce the moisture content, yielding the final dried free-flowing product. Dried yellowcake will be packaged in 55-gallon steel drums.