Uranium Mine Dewatering Legacy Impacts on Soils and Shallow Alluvial Aquifers in the Grants Uranium Mineral Belt

Large scale uranium mining in the United States began in the 1950’s but a price decline and other factors in the early 1980’s effectively ended domestic production. Recent concerns related to global warming and greenhouse gas emissions from petrochemical energy sources have sparked renewed interest in nuclear power, leading to a number of new uranium mining and milling projects in the United States.  Because many projects are in areas that were previously mined for uranium, legacy issues from these mining activities will complicate permitting processes and establishment of background conditions. In the Grants Uranium District, New Mexico, extensive dewatering associated with uranium mining caused the development of shallow alluvial aquifers with elevated constituents of concern.  Surface impacts from dewatering may prove to be widespread throughout this district due to the large amount of water pumped from numerous mines in the area combined with the high evaporation rate in this arid climate.  This combination of factors can enrich surface soils in the least mobile constituents dissolved in discharge water.   It is currently unclear what the regulatory impact of this issue will be.   NMED has become aware that some soils and alluvial groundwater have been impacted, and they have requested further investigation.  This activity has the potential to draw increased interest and investigation from the EPA under the TENORM initiative.  A case study is presented to illustrate that constituents of concern are attenuated in the soils, and alluvial groundwater is limited in aerial extent and receding due to cessation of mine dewatering.