American Uranium (ASX:AMU) validates ISR hydrogeology at Lo Herma with Petrotek pump testing

American Uranium has reported the results of a hydrogeological pump testing program at its flagship Lo Herma in situ recovery uranium project in Wyoming’s southern Powder River Basin, with an independent review by Petrotek Corporation confirming that key aquifer parameters are consistent with those observed at permitted and operating ISR uranium mines in the district, ahead of a planned Mineral Resource Estimate update this quarter and a Scoping Study update in the second half of 2026.

Highlights

• Petrotek confirmed that hydrogeological test values are consistent with other permitted and operating ISR facilities in Wyoming’s southern Powder River Basin.

• Sustained well extraction rates and aquifer behaviour support the Scoping Study assumption of a 20 gpm pumping rate, which is typical of nearby ISR operations.

• Aquifer transmissivity and hydraulic conductivity values were established from single well step rate and constant rate tests across 4 monitoring wells completed in the Tongue River Member of the Fort Union Formation.

• The program is intended to de risk the project ahead of an intensive regional hydrogeological study in 2026 to support permitting and detailed wellfield design.

The November 2025 program comprised single well pumping tests at 4 monitoring wells within the planned production zones at Lo Herma, designed to determine aquifer transmissivity and to demonstrate permeability sufficient to sustain extraction rates of approximately 20 gpm.

The tests included step rate and constant rate pumping over periods of up to 4 hours, with water level responses analysed using confined and leaky aquifer models, including Theis and Hantush Jacob solutions, to derive transmissivity and hydraulic conductivity values.

Results showed transmissivity values in the range of 190 ft2/d to 285 ft2/d for 3 of the 4 wells, with a lower range of 65 ft2/d to 78 ft2/d at one location, while calculated hydraulic conductivity values ranged from 1.4 ft/d to 8.6 ft/d across the tested intervals.

These parameters are reported by Petrotek to be consistent with those recorded at other operating ISR uranium facilities in the southern Powder River Basin, and the observed drawdown behaviour demonstrated that sustained pumping at or near 20 gpm is achievable within the tested sands.

The work focused on the uranium bearing host sands of the Tongue River Member, including the locally defined B, C and TFL sand units, and was not designed to assess regional hydraulic confinement, which is a requirement for permitting and wellfield design.

Petrotek has therefore recommended the development of a regional hydrogeological conceptual model and longer duration regional pump tests, together with multi aquifer monitoring, to support future regulatory submissions and detailed production wellfield layout.

American Uranium CEO and Executive Director Bruce Lane commented,

“Aquifer testing at Lo Herma demonstrated sustained flows and minimal drawdown across all four wells, with Petrotek confirming aquifer conditions consistent with other permitted ISR uranium mines nearby in Wyoming’s southern Powder River Basin. These findings materially strengthen Lo Herma’s ISR development credentials.”

In parallel with the hydrogeological program, American Uranium has previously reported expansion drilling that confirmed a further 3 km of uranium mineralised trends north of Mine Units 1 and 2, with assessment of those results ongoing and further work programs to be announced.

Both the drilling and aquifer testing are stated to be directed toward supporting a higher confidence Mineral Resource Estimate and an updated Scoping Study.

From a broader industry perspective, the confirmation of transmissivity, hydraulic conductivity and sustained pumping performance within the Lo Herma host sands places the project on a comparable technical footing to other ISR operations in the Powder River Basin, a region long characterised by sandstone hosted roll front uranium deposits developed using in situ methods.

With regional hydrogeological modelling, additional pump testing and wellfield design studies planned, the next phase of work is positioned to provide the technical inputs required for permitting and for advancing Lo Herma toward the next stage of development in line with the company’s stated timetable for updated resource and scoping level studies.

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