Ur-Energy's March 2026 technical report on the Lost Creek ISR uranium property in Sweetwater County, Wyoming, current to December 31, 2025, plans a separate wastewater treatment facility to add RO capacity and fines removal.
The Technical Report on the Lost Creek ISR Uranium Property, Sweetwater County, Wyoming, USA, was prepared by WWC Engineering for Ur-Energy, current as of December 31, 2025 and dated March 9, 2026. The Lost Creek plant has operated since August 2013. It has four main solution circuits: uranium extraction by ion exchange (IX), elution of the resin, yellowcake precipitation, and dewatering, drying and packaging. Most solutions are recycled within each circuit. A small permanent bleed creates a cone of depression in the well field, so that inflowing regional groundwater keeps the leach solution within the recovery area.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report date | March 9, 2026 | Not applicable | Current as of December 31, 2025; WWC Engineering for Ur-Energy |
| Plant operating since | August 2013 | Not applicable | Not applicable |
| Nominal well field flow | 6,000 | gpm | Basis for reagent estimates |
| Design production basis | 1,000,000 | lb U3O8/a | For the chemical consumption estimates |
| Header house capacity | Up to 90 | wells | Injection and recovery |
| Plant building | About 160 x 260 | ft | Metal building |
| Well field bleed | 0.5 to 1.5 | % of production flow | Not applicable |
| Wastewater to deep wells | 10 to 15 | gpm | Two deep disposal wells |
| Plant water use | About 10 | gpm | At full capacity |
| Propane and electricity | About 75,000 gal; 12.4 million kWh | per year | Plant heating, lighting and equipment |
| Product | Yellowcake in 55-gallon steel drums | Not applicable | Trucked about 1,270 miles to Metropolis, Illinois |
| Maximum staffing | 81 | FTE | 18 in the plant department |
Overview
Production fluid carrying dissolved uranyl carbonate is pumped from the well fields to the plant. Header houses hold manifolds, valves, flow meters, instruments and oxygen addition for the injection lixiviant, and each can serve up to 90 injection and recovery wells. Most process equipment is in a metal building of about 160 by 260 ft. Hydrochloric acid, propane and soda ash are stored in tanks and silos outside. The reverse osmosis (RO) system for bleed treatment and aquifer restoration is currently inside the plant. Ur-Energy plans a separate wastewater treatment facility next to the plant, with more RO stages and fines removal, and its cost is included in sustaining capital. The main laboratory work is done at Ur-Energy's chemistry lab in Casper.
Key Process Stages
Ion exchange. Uranium in the pregnant solution is loaded onto resin. The barren lixiviant is brought back to bicarbonate strength with sodium bicarbonate, or with carbon dioxide, which generates bicarbonate in the mine horizon. Its pH is corrected with carbon dioxide before reinjection.
Bleed treatment. The bleed is either disposed of directly or treated by RO. Clean permeate is reused or injected into Class V wells, permitted in 2016, and brine and excess bleed go to the two deep disposal wells (DDWs). A radium treatment step goes with primary and secondary RO.
Elution. Fully loaded resin is stripped, giving a rich eluate of uranyl carbonate, salt and sodium carbonate or bicarbonate.
Precipitation. The eluate is decarbonated by lowering the pH to about 2 with hydrochloric acid. Uranium is then precipitated with hydrogen peroxide, using sodium hydroxide for pH control.
Dewatering, drying and packaging. A filter press removes excess liquid, and a freshwater wash flushes out dissolved chlorides. The cake is dried to a free-flowing product and packed in 55-gallon steel drums.
Additional Interesting Data and Summary
Plant chemicals include hydrochloric acid, caustic soda, peroxide, salt, diatomaceous earth and make-up resin. Their annual use is estimated for an average 6,000 gpm flow and production of one million pounds of U3O8 a year. Hydrochloric acid, peroxide, salt and sodium hydroxide are stored with secondary containment. Solid waste includes spent resin and filtered fines, classified as contaminated or non-contaminated by their radiological characteristics, with about 700 yd³ a year of non-contaminated waste.
In summary, Lost Creek is an operating carbonate ISR plant that has run since 2013 on IX, elution, acid decarbonation and peroxide precipitation. The 2025 report's main process change is a planned stand-alone wastewater plant to cut the bleed sent to deep wells to 10 to 15 gpm.
Key Processes
- In-situ recovery with oxygen and bicarbonate lixiviant
- Ion exchange on resin
- Resin elution
- Hydrochloric acid decarbonation and hydrogen peroxide precipitation
- Filter pressing, washing and drying
- Drum packaging of yellowcake
- RO and radium treatment of bleed, with Class V and deep well disposal
Source: Technical Report on the Lost Creek ISR Uranium Property, Sweetwater County, Wyoming, USA, prepared by WWC Engineering for Ur-Energy, dated March 9, 2026.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Lost Creek ISR Uranium Property — 2022 Technical Report
This technical report describes a preliminary economic assessment for an in-situ recovery uranium property in Sweetwater County, Wyoming, with an effective date of December 31, 2021.
Report context
The report titled “PRELIMINARY ECONOMIC ASSESSMENT LOST CREEK ISR URANIUM PROPERTY, SWEETWATER COUNTY, WYOMING, USA” is dated March 7, 2022 and was prepared for a company headquartered at 10758 W. Centennial Road, Suite 200, Littleton, CO 80127. The report was prepared under NI 43-101 standards. The property location is in Sweetwater County, Wyoming, USA, and comprises mining claims, mineral leases, and surface use agreements.
Processing route
Mineral processing and metallurgical testing
Section 13.0 of the report addresses mineral processing and metallurgical testing. The report does not provide detailed flowsheet descriptions, performance data, or specific testwork results within the available evidence. No design parameters for processing are presented in this section from the original technical report.
Recovery methods
Section 17.0 describes proposed recovery methods. Plant processing is covered in Section 17.1. Section 17.2 addresses energy, water, and process materials. Liquid disposal is described in Section 17.3, and solid waste disposal is covered in Section 17.4. Plant personnel requirements are listed in Section 17.5.
Mining methods
Section 16.0 outlines the proposed mining methods. The mineral deposit amenability is discussed in Section 16.1. Mine development is described in Section 16.2. Piping is covered in Section 16.3, and header houses in Section 16.4. Wellfield reagents and electricity are addressed in Section 16.5. Mining fleet equipment and machinery are listed in Section 16.6, and mining personnel in Section 16.7.
Key reported parameters
The report does not provide a consolidated table of processing parameters within the available evidence. No specific design, actual operating data, or testwork parameters are reported in the report.
| Parameter | Value | Basis |
|---|---|---|
| No parameters reported | , | , |
Project website: https://www.ur-energy.com/projects/lost-creek
Technical qualifications
The report is a preliminary economic assessment prepared under NI 43-101. The qualified persons who supervised preparation are Benjamin J. Schiffer, P.G. and Ray Moores, P.E., both of WWC Engineering, 1849 Terra Avenue, Sheridan, WY 82801. The report includes sections on mineral processing and metallurgical testing (Section 13.0), mineral resource estimates (Section 14.0), mineral reserve estimates (Section 15.0), mining methods (Section 16.0), and recovery methods (Section 17.0). Mineral resource estimates are based on assumptions, cutoff selection, resource classification, methodology including mineral intercepts and GT contouring, and summary of resources, with resource estimation auditing and risk assessment covered in Sections 14.2.5 and 14.2.6.
Source: “PRELIMINARY ECONOMIC ASSESSMENT LOST CREEK ISR URANIUM PROPERTY, SWEETWATER COUNTY, WYOMING, USA” dated March 7, 2022, effective date December 31, 2021.
