American Uranium Ltd (ASX:AMU, OTC:GTRIF) will begin hydrogeologic testing and resource expansion drilling at its Lo Herma In-Situ Recovery (ISR) Uranium Project in Wyoming’s Southern Powder River Basin during the fourth quarter of calendar year 2025.
The company confirmed that both programs are expected to be incorporated into an updated Mineral Resource Estimate (MRE) in the first quarter of 2026, with findings to also inform a Scoping Study later in the year.
Lo herma project exploration and infill drilling plan.
“Our upcoming resource expansion drilling and hydrogeology programs at Lo Herma represent major steps toward advancing one of America’s most promising ISR uranium projects. These programs will target both growth in the resource base and increased confidence in existing mineral resources along with further validation of the project’s hydrogeology,” CEO and executive director Bruce Lane said.
Hydrogeologic testing of Lo Herma aquifer
AMU will start hydrogeologic testing of four groundwater monitoring wells drilled earlier this year. The wells, screened across mineralised sands and completed with five-inch casing, demonstrated submergence of the Lo Herma mineralisation within the aquifer — a critical factor supporting ISR mining. Laboratory work has already returned hydraulic parameters consistent with efficient ISR wellfield operations.
Resource areas, monitor wells and proposed mine units.
The planned tests will include step-drawdown, or single-well pumping trials, to determine sustainable pumping rates, well efficiency and general hydraulic properties of the resource-hosting aquifer. These results will be compared to laboratory-scale permeability testing, with the aim of confirming that hydrogeologic conditions are conducive to ISR mining methods.
“The program is targeting an increase of the current 8.57 million pounds (32% indicated) eU₃O₈ Mineral Resource Estimate by converting Exploration Target Range mineralisation for Lo Herma, which currently stands at 5.6 to 7.1 million tonnes at a grade range of 500 ppm to 700 ppm eU₃O₈. This work is expected to feed into an updated Mineral Resource Estimate and Scoping Study in 2026, positioning us to deliver value from America’s nuclear energy revival,” Lane said.
Subject to confirmation, American Uranium intends to expand testing by installing additional monitoring wells and undertaking a long-term aquifer pumping program. This broader effort will support aquifer characterisation, a necessary component for progressing a mine permit application and refining near-term wellfield planning at the Scoping Study stage.
Resource expansion and infill drilling program
The resource expansion program will follow recent approval from the US Bureau of Land Management (BLM) and acceptance of the amended permit by Wyoming’s Land Quality Division (LQD). The approvals cover up to 121 drill hole locations for approximately 37,500 metres of drilling. Bond posting and formal LQD approval remain pending before mobilisation of rigs.
Once underway, drilling will target several objectives. Step-out holes will focus on expanding the resource north of proposed Mine Units 1 and 2 (MU1 and MU2). At the same time, infill drilling is designed to upgrade existing Inferred Mineral Resources to Indicated or Measured categories, increasing confidence in the current resource base.
The current Lo Herma Mineral Resource Estimate stands at 8.57 million pounds of eU3O8, with 32% in the Indicated category. The exploration target range covers 5.6 to 7.1 million tonnes at 500 to 700 parts per million eU3O8.
Converting this mineralisation into formal resources through drilling is expected to enhance the MRE and contribute to the 2026 Scoping Study, positioning Lo Herma as a key contributor to US nuclear fuel supply