Alta Mesa is a constructed ISR uranium project with a Central Processing Plant located in Texas, US. (Credit: enCore Energy Corp.)
Alta Mesa Wellfield Development. (Credit: enCore Energy Corp.)
The total operation capacity of the CPP is 1.5 million pounds of U3O8 (Triuranium octoxide) per year. (Credit: enCore Energy Corp.)

Alta Mesa is a licenced In Situ Recovery (ISR) uranium project with a Central Processing Plant (CPP), located in South Texas, US.

From 2005 to 2013, Alta Mesa produced approximately 5 million pounds of triuranium octoxide (U3O8). The operations were suspended due to low uranium prices.

The project is on standby, and it is expected to resume production in early 2024 following the completion of renovations and equipment upgrades.

Alta Mesa Project Ownership

The Alta Mesa Project went through several ownership changes since 1985. It was acquired by enCore Energy from Energy Fuels in February 2023 for $120m.

Besides Alta Mesa CPP, enCore operated two other fully licenced production facilities in Texas- the Rosita CPP and Kingsville Dome CPP. enCore commenced uranium production from Rosita CPP in November 2023.

In December 2023, enCore entered into a Master Transaction Agreement to sell 30% interest in the project to Australian ISR uranium producer Boss Energy.

As agreed, Boss Energy will pay $60m as consideration and invest an additional $10m into enCore common shares.

The Australian firm will also loan enCore up to 200,000 pounds of physical uranium for commercial use and will work to jointly develop enCore’s proprietary Prompt Fission Neutron (PFN) technology for uranium exploration and production.

Following the completion of the deal, slated in February 2024, enCore will establish a new subsidiary (JV Company) to hold the Alta Mesa project.

The JV will be 70% owned by an existing subsidiary of enCore and 30% by a new US subsidiary of Boss Energy.

Alta Mesa Project Location Details

The Alta Mesa CPP and Wellfield includes a fully licenced and constructed ISR uranium plant in South Texas. It is situated on a private land of around 200,000 acres.

The location is around 80-miles from the Rosita CPP and 75-miles from the Kingsville Dome CPP, both owned by enCore.

The project consists of two distinct properties- the 16,010-acre Alta Mesa and 47,088-acre Mesteña Grande.

According to a technical report released in 2023, the Alta Mesa property comprises the Alta Mesa mine area and processing facility, South Alta Mesa (SAM) and Indigo Snake.

Mesteña Grande includes Mesteña Grande Goliad (MGG) Mesteña Grande North (MGN), Mesteña Grande Central (MGC), Mesteña Grande Alta Vista (MGAV), and El Sordo.

Alta Mesa CPP and mine office are located within the Alta Mesa property, around 11 miles west of the intersection of US 281 and Ranch Road 755.

Geology and Mineralisation

The Alta Mesa Wellfield is located in Brooks County, while the Mesteña Grande Wellfields are mostly located in Jim Hogg County.

The wellfields include uranium mining and exploration leases for uranium ISR production (4,598 acres) and Mineral Options (195,501 acres).

The areas have uranium mineral-bearing sandstones of the Goliad, Oakville, and Catahoula Formations.

Around 5 miles of mineralised trends have been drilled out of approximately 52 linear miles of stacked geochemical REDOX and mineralised fronts.

Uranium mineralisation at both the wellfield locations was found as roll-front deposits contained in porous and permeable sandstones of the Goliad Formation.

The range of the mineralisation range from 300ft to 600ft beneath the surface.

Additional potential mineralisation may exist within the Goliad Formation at depths between 400ft and 500ft, and also within the Oakville Formation and Catahoula.

Reserves and Project Capacity

The Alta Mesa project is estimated to contain a National Instrument 43-101 resource of 3.41 million pounds at 0.109% U3O8 in the Measured and Indicated category.

The figure stands at 16.79 million pounds at 0.120% U3O8 in the Inferred category.

The total operation capacity of the Alta Mesa CPP is 1.5 million pounds of U3O8 per year. The CPP can process, dry, and package up to 2 million pounds of U3Oannually by installing additional IX resin processing circuits.

Alta Mesa CPP Operations

The project CPP leveraged ISR method in a non-invasive process using natural groundwater and oxygen, integrated with an ion exchange process, to recover uranium.

The Alta Mesa CPP is located on a 45-acre area within the existing mining lease. It is connected directly to the production areas via pipelines.

Additionally, the CPP can be modified to receive loaded resins transported from satellite IX systems for faraway uranium ore bodies.

The CPP facility is equipped with an automated control and monitoring system to enable remote monitoring. It can also shut down segments of the processing plant during an emergency.

The water supply required for project operations will be sourced from established and permitted local wells.

Liquid waste from the processing facility will be disposed via deep well injection through two permitted Underground Injection Control (UIC) Class I disposal wells, while solid waste will be disposed off-site at licenced disposal facilities.

Refurbishment Works

The refurbishment works at the site include revamping the processing circuits. The elution circuit, used to strip uranium from the ion exchange beads, has been refurbished.

Works also included replacing all the process pumps for the startup IX circuit including the main injection pumps.

enCore commenced the refurbishment of the yellowcake processing circuit along with the rebuilding of key components of the yellowcake storage systems and ordering components including the filter press and yellowcake transfer pumps.

The refurbishment of the yellowcake drying system is anticipated to be completed before production restarts.

The project may resume production in existing authorisations and within Production Authorisation Area 7 (PAA-7).

enCore is in the process of installing injection and production wells in the wellfield and staged the equipment required to install the pipelines to connect the wellfield to the CPP.