The location map of the Lost Creek ISR Uranium Property in the Sweetwater County, Wyoming. (Credit: Ur-Energy Inc./ PRNewswire)
View of Lost Creek processing plant under construction from the south looking north. (Credit: PRNewsFoto/Ur-Energy Inc.)
Lost Creek had produced 2.7 million pounds of triuranium octoxide until December 2021. (Credit: PRNewsFoto/Ur-Energy Inc.)

Lost Creek in-situ recovery (ISR) Uranium Property is located in Sweetwater County in south-central Wyoming in the US. It commenced operations in 2013.

The property comprises six individual contiguous projects namely the Lost Creek, LC East, LC West, LC North, LC South, and EN.

The Lost Creek is the core project with production occurring in mine units MU1 and MU2, while the other five projects are known as Adjoining Projects and serve as extension and exploration targets to recover additional feed to the Lost Creek production facilities.

The facility is owned and operated by uranium mining company Ur-Energy.

In 2021, Lost Creek secured a licence amendment to expand mining activities within the existing Lost Creek Project and the adjacent LC East Project. This will also enable to increase annual plant production up to 2.2 million pounds U3O8.

The company expects additional expansion-related approvals in 2023.

As of 31 December 2021, Lost Creek had produced 2.7 million pounds of triuranium octoxide (U3O8).

Location and Site details

The Lost Creek ISR Uranium Property is located in an unpopulated area, northeast of Sweetwater County in the Great Divide Basin (GDB) and in Wyoming.

The property is approximately 15miles southwest of Bairoil, around 38miles northwest of Rawlins, and about 90miles southwest of Casper in Wyoming.

Overall, it covers an area of over approximately 35,400acres.

History of the property

In 1936, uranium was discovered in the GDB. In the early 1950s, exploration activities started to increase after the Gas Hills District discoveries and continued to grow in 1960s with the discovery of additional occurrences.

The earliest operators Wolf Land and Exploration (later became publicly traded as Inexco), Climax (Amax), and Conoco Minerals made significant discoveries of low-grade uranium mineralisation in the Battle Spring Formation in 1968.

In 1969, Conoco Minerals entered into a joint venture with Inexco and gained control over the property in 1970. The joint venture continued their exploration in the area known as Project A. The joint venture identified the eastern half which is referred to as the Main Mineral Trend (MMT) in the Lost Creek Project and EMT in the LC East Project.

It also included large portions of current LC North, LC South, EN Projects.

The Lost Creek Project area passed through multiple ownerships to New Frontiers Uranium in 2000. Later, the company transferred the property, along with its other Wyoming properties, to NFU Wyoming.

In 2005, Ur-Energy USA, a wholly owned subsidiary of URE, acquired full ownership of NFU Wyoming and commenced drilling and mining permit applications within one year.

Geology, Mineralisation and Mineral Resource Estimate

The uranium deposits in the GDB are found in the Battle Spring Formation, which contains Lost Creek resources.

The lithology consists of approximately 60%-80% poorly consolidated, medium to coarse arkosic sand beds up to 50ft thick, and 20%-40% interbedded mudstone, claystone, siltstone, and fine sandstone.

The outcrop is within the Battle Spring Formation occurring largely as a sub-crop beneath the soil.

The mineralisation of the property consists of roll front type uranium deposits occurring in sand horizons within the Battle Spring Formation of Eocene age.

Most of the significant resources occur within two stratigraphic horizons- HJ and KM horizons.

The HJ horizon hosts most of the currently defined mineral resources including the current production zones. It is divided into four stratigraphic subhorizons with highest occurrence of uranium mineralisation found in MHJ1 and MHJ2 sub horizons.

The KM horizon is situated beneath the HJ horizon and will be targeted for future production.

As per the Mineral Resource report of the Lost Creek ISR Uranium Property in 2021, the measured and indicated mineral resource estimates for the property is 11.9 million pounds U3O8 equivalent (eU3O8). The figure stands at 6.6 million pounds eU3O8 in the Inferred category.

Mining and Ore processing

ISR is used at Lost Creek as it supports effective recovery of roll front mineralisation and is more environmental friendly compared to conventional open pit or underground recovery techniques.

This mining method involves using injection wells to introduce lixiviant mining solution into the mineralized zone. This converts the uranium compounds from a relatively insoluble +4 valance state to a soluble +6 valance state.

It leads to the formation of uranyl carbonate, which is recovered through a series of production wells and piped to a processing plant.

The groundwater is re-fortified with the oxidizer and complexing agent and subsequently moved to the wellfield to recover additional uranium.

The processing plant features uranium recovery or extraction circuit, elution circuit to remove the uranium from the IX resin, yellowcake precipitation circuit, and dewatering, drying, and packaging circuit.

Most of the process equipment is placed within an approximate 160ft by 260ft metal building.

In October 2012, Ur-Energy began the construction of the Lost Creek plant and installation of Mine Unit 1 (MU1).

Production operations in MU1 began in August 2013.

Other project infrastructure

Other project infrastructure includes roads (primary access roads, secondary access roads, temporary wellfield access roads, and well access roads), laboratory equipment (inductively coupled plasma emission spectrometers, auto-titrator, specific conductance meter, and other materials as per the requirement), a pre-existing 34,500v power line, a new overhead raptor resistant power line, 12 water wells for supply, and two holding ponds among others.

Contracts and Supply Agreements

The amended S-K 1300 Initial Assessment Mineral Resource Report of the property dated 19 September 2022 was prepared under the supervision WWC Engineering.

TREC prepared the technical report and Preliminary Economic Assessment for the property.

Groathouse Construction won the contract for building plant and other infrastructure facilities for the project.

NuCore provided uranium marketing advisory and professional services to Ur-Energy, Fagen was selected as the general contractor.

In December 2022, Ur-Energy announced that it has expanded the quantity to be delivered into a previously announced sales agreement.

Instead of the agreed annual delivery of 200,000 pounds of U3O8 over a six-year period, the company will supply an additional 100,000 pounds from 2024.

As of December 2022, the company’s total sales quantity will be 600,000 pounds U3O8 per year beginning in 2024.

The National Nuclear Security Administration (NNSA) has also contracted Ur-Energy for 100,000 pounds of domestically produced U3O8 to the national Uranium Reserve.