Walton-Day, and four co-authors reported in mid 2022 that geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the Texas Coastal Plain.
Stratigraphic section showing Tertiary and Quaternary
geologic units along the Texas Gulf Coast, formations
that host uranium deposits and occurrences, known
uranium resources, permissive tracts, and hydrogeologic
units (aquifers and confining units). Modified from [16].
Stratigraphy from [25,26]. Geologic names conform to the USGS National Geologic Map Database Figure 4. Stratigraphic section showing Tertiary and Quaternary geologic units along the Texas Gulf Coast, formations that host uranium deposits and occurrences, known uranium resources, permissive tracts, and hydrogeologic units (aquifers and confining units). Modified from [16]. Stratigraphy from [25,26]. Geologic names conform to the USGS National Geologic Map Database [27]. Epoch boundary ages from [28]. Permissive tract extents from [13,16]. Hydrogeologic units from [29–31].
The model reviews descriptive and quantitative information derived from environmental studies and existing databases to depict existing conditions and
potential environmental concerns associated with mining this deposit type. This geoenvironmental model describes how features of the deposits including host rock; ore and gangue mineralogy; geologic, hydrologic, and climatic settings; and mining methods (legacy open-pit and in situ recovery [ISR]) influence potential environmental effects from mining.
Element concentrations in soil and water are compared to regulatory thresholds to depict ambient surface water and groundwater conditions. Although most open-pit operations in this region have been reclaimed, concerns remain about groundwater quality at three of the four former mills that supported former open-pit mines and are undergoing closure activities.
The primary environmental concerns with ISR mining are:
(1) radon gas at active ISR operations,
(2) radiation or contaminant leakage during production and transport of ISR resin or yellowcake,
(3) uranium excursions into groundwater surrounding active ISR operations, and
(4) contamination of groundwater after ISR mining.
Although existing regulations attempt to address these concerns, some problems remain. Geologists suggest that reactive transport modeling and a better understanding of geology, stratigraphy, and geochemistry of ISR production areas could minimize excursions into surrounding aquifers and improve results of groundwater restoration.
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