A Novel Method for Conducting a Geoenvironmental Assessment of Undiscovered ISR-Amenable Uranium Resources: Proof-of-Concept in the Texas Coastal Plain

Abstract

A geoenvironmental assessment methodology was developed to estimate waste quantities and disturbances that could be associated with the extraction of undiscovered uranium resources and identify areas on the landscape where uranium and other constituents of potential concern (COPCs) that may co-occur with uranium deposits in this region are likely to persist, if introduced into the environment. Prior to this work, a method was lacking to quantitively assess the environmental aspects associated with potential development of undiscovered uranium resources at a scale of a uranium resource assessment. The mining method of in situ recovery (ISR) was historically used to extract uranium from deposits in the Goliad Sand of the Texas Coastal Plain. For this reason, the study’s methodology projected the following types of wastes and disturbances commonly associated with ISR based on historical ISR mining records: the mine area, affected aquifer volume, mine pore volume, water pumped and disposed during uranium extraction and restoration, and radon emissions. Within the tract permissive for the occurrence of undiscovered uranium resources, maps and statistics of factors were derived that indicate the potential contaminant pathways. The percentage of days meeting the criteria for air stagnation indicate the potential for radon accumulation; the geochemical mobility of COPCs in groundwater in combination with effective recharge indicates the potential for infiltration of surface-derived COPCs; the geochemical mobility of COPCs in groundwater combined with hydraulic conductivity indicates the propensity for transmitting fluids away from contaminated or mined aquifers; and finally, geochemical mobility of COPCs in surface water combined with the factor for climatic erosivity (R factor) indicates the potential for COPCs to persist in surface waters due to runoff. This work resulted in a new methodology that can be applied to any undiscovered mineral resource to better understand possible wastes and disturbances associated with extraction and identify areas on the landscape where COPCs are likely to persist.

Geoenvironmental Model for Roll-Type Uranium Deposits in the Texas Gulf Coast

“…The primary environmental concerns from 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. A conceptual source to receptor model developed for the geoenvironmental assessment of mining undiscovered U resources in the STU region (Figure 8; [12]) reinforces how some of these concerns might affect air, surface water, and groundwater. Pathway 1 represents the generation of radon during mining operations and(or) from waste associated with mining (concern 1).…”

“…Permissive tract 3 contains the youngest geologic units, the Goliad Sand, the Pleistocene Willis Sand, and Lissie Formation (Figure 4). Permissive tract 3 was the object of a proof-ofconcept application of a new geoenvironmental assessment methodology [12] to parallel U.S. Geological Survey's resource assessment methodology [13].…”

“…As this region is in the Texas Gulf Coast, there is a risk of facility damage by hurricanes and tornadoes. The variations in climate from southwest to northeast across this region contribute to greater potential for air stagnation, and hence to radon accumulation in the southwest versus greater potential for runoff of wastes and excursions to surface and groundwater systems in the northeast [12].…”

“…There may be a role for GEMs in sustainable mining practices and mine life-cycle models (e.g., [9,10]), but, again, no exact niche or format for GEMs in this realm has been identified, perhaps representing an opportunity for an evolution of GEMs beyond the scope of this paper. Herein, we present a descriptive GEM for the South Texas uranium (STU) region as part of the geoenvironmental assessment of these deposits [11,12], and as a complement to the USGS resource assessment of these deposits [13]. In this paper, a GEM is defined as a descriptive model that combines the characteristics of the deposit type-derived from literature review and a published oredeposit model-with the geographic, climatic, and regulatory framework existing where the ore deposits occur, to identify the potential environmental effects associated with mining the deposits.…”

“…In this GEM, we address these topics by first reviewing the geologic and geochemical characteristics of the mineral deposits and follow with discussions of potential environmental effects of mining derived from literature review and some analysis of existing data. The accompanying geoenvironmental assessment of a portion of the STU area [12] takes this analysis further in identifying geographic areas within the STU region where specific environmental concerns are more likely to occur.…”