American Uranium (ASX:AMU) has commenced large‑scale hydrogeological pump testing at its Lo Herma In-Situ Recovery (ISR) Uranium Project in the Powder River Basin of Wyoming, US.
The program focuses on Mine Unit 1 and follows the company’s 4 August 2026 resource update, which reported total Lo Herma resources of 9.96 million pounds (Mlbs) triuranium octoxide (U3O8), including 4.79Mlbs indicated.
Within the proposed Scoping Study footprint across Mine Units 1, 2, and 3, resources increased to 7.38Mlbs, with 54% classified as indicated.
Testing intends to assess groundwater flow, hydraulic connectivity, and wellfield development parameters across the proposed initial mining area. Results are expected to inform American Uranium’s targeted Q4 2026 Scoping Study.
The test uses the existing LH MW‑003 pumping well, completed in the Middle C Sand, and incorporates monitoring wells across the target production horizon, overlying units, and an underlying sand interval.
The company installed seven additional monitoring wells at Mine Unit 1 in July 2026.
Technical testing builds on proven hydrogeological results
The program builds on 2025 testing by Petrotek Corporation, which included step drawdown and sustained pumping tests on four previously installed wells.
Those tests demonstrated sustained flow rates and minimal aquifer drawdown, with Petrotek concluding that the hydrogeological characteristics were consistent with other permitted and operating ISR uranium projects in Wyoming’s southern Powder River Basin.
The larger‑scale program is evaluating whether those conditions extend across the broader Mine Unit 1 area.
The test configuration includes four observation wells in the Middle C Sand, located approximately 122–152m from the pumping well to evaluate directional transmissivity.
Additional wells in the A Coal, D Sand, and an underlying sand unit aims to monitor whether pumping in the Middle C Sand produces responses in adjacent units.
CEO and Executive Director Bruce Lane says the updated resource and pump testing continue to strengthen the technical foundation for Lo Herma’s development pathway.
“With our updated 9.96Mlb resource completed and pump testing now underway, Lo Herma continues to advance toward development. The program will deliver key data for groundwater modelling, permitting, and ISR wellfield design,” Lane says.
“Pump testing is another important milestone as we progress toward our targeted Q4 2026 Scoping Study. Mine Unit 1 is our most advanced proposed mine unit and is currently expected to form the initial stage of development evaluated in that study.”
Lo Herma is American Uranium’s flagship ISR project, hosting a JORC‑compliant mineral resource of 9.96Mlbs U3O8.
American Uranium is a developer advancing ISR uranium projects in Wyoming, led by its flagship Lo Herma asset, alongside conventional uranium-vanadium properties in Utah.
Write to JC Villarba at Mining.com.au
Images: American Uranium
