American Uranium Finds Stronger Groundwater Case for Lo Herma ISR

Mine Unit 1 Test Supports ISR Development Pathway

American Uranium Limited (ASX:AMU) has cleared an important technical hurdle at its Lo Herma uranium project in Wyoming, with a large-scale aquifer test showing the proposed production zone can sustain pumping at a rate close to the company’s current Scoping Study assumption.

The Mine Unit 1 pumping well delivered an average 19.2 gallons per minute for 48 hours, the maximum available from the test pump. Drawdown stabilised at about 16.9 feet in the pumping well, while four observation wells positioned 426 to 452 feet away recorded between 0.6 and 0.9 feet of drawdown. The company said the results demonstrated hydraulic communication across the tested production aquifer and provided project-specific inputs for mine planning.

The test is the next step after the large-scale aquifer testing initiated at Mine Unit 1 in August, which was intended to refine groundwater-flow and wellfield-design parameters for the planned study. The results support the use of an approximately 20 gpm per-well assumption in the Scoping Study, although the pumping rate was constrained by equipment capacity rather than by the aquifer itself.

Confinement Results Support Continued ISR Evaluation

Petrotek Corporation, American Uranium’s independent hydrogeological consultant, estimated transmissivity of roughly 510 to 605 square feet per day across the four observation wells, with hydraulic conductivity of approximately 7 to 11 feet per day. The relatively narrow spread between directional results indicated little variation in flow properties across the tested area, supporting standard production-well patterns as a preliminary mine-planning assumption.

Vertical responses were also broadly supportive, but not uniformly conclusive. The underlying sand recorded only about 0.2 feet of drawdown against 16.9 feet in the pumping well, indicating hydraulic separation at the test location. The overlying A Coal showed no pumping-related response and had a potentiometric elevation about 73 feet above the production zone, consistent with its interpretation as a confining unit. However, the overlying D Sand recorded approximately 1.6 feet of drawdown and requires further characterisation.

That distinction matters. The company says the findings are supportive of ISR evaluation, but they do not amount to a permitting determination. The observation-well drawdowns were small, barometric pressure affected the readings, and the aquifer-property estimates depend on the analytical solution used. Petrotek also identified unresolved differences between transmissivity estimated at the pumping well and at the observation wells.

Scoping Study Moves Ahead, With Permitting Work Still to Come

American Uranium said the hydrogeological results are sufficient for the base case of its planned Lo Herma Scoping Study. The study is being prepared using the 4 August 2026 Mineral Resource Estimate as its primary resource basis; Lo Herma currently hosts 9.96 million pounds of U3O8 reported under the JORC Code.

The final study footprint, any production target and the development sequence have not yet been determined. The company plans higher-rate and longer-duration testing in a production-style well, additional work on the D Sand, preliminary groundwater modelling and testing at Mine Units 2 and 3 as those areas advance.

It also intends to begin groundwater-level measurements and water-quality sampling through the Mine Unit 1 monitoring network. That baseline work is intended to support potential future aquifer-exemption and Class III Underground Injection Control applications, but the company explicitly states that monitoring would not constitute submission or approval of a permit application. The technical case has strengthened; the regulatory case remains unfinished.