Uranium in Groundwater

Science Center Objects

The Issue: Recent groundwater monitoring in northeastern Washington has shown elevated levels of uranium in several community water systems and in private wells. Naturally occurring uranium is associated with granitic and metasedimentary rocks, as well as younger sedimentary deposits, that occur in northeastern Washington. The occurrence and distribution of uranium in groundwater, however, is poorly understood and warrants investigation in order to reduce uranium exposure, protect from toxic kidney effects of uranium, and reduce the risk of cancer.

How USGS will help: In close cooperation with water-resource agencies and stakeholders, USGS made a preliminary assessment of naturally occurring uranium in groundwater relying on existing information and limited reconnaissance sampling. A USGS Scientific Investigations Map was published to report on the current knowledge and data gaps regarding uranium in groundwater in northeastern Washington State.

Problem - Recent groundwater monitoring in northeastern Washington has shown elevated levels of uranium in several community water systems and in private wells. Naturally occurring uranium is associated with granitic and metasedimentary rocks, as well as younger sedimentary deposits, that occur in northeastern Washington. The occurrence and distribution of uranium in groundwater, however, is poorly understood and warrants investigation in order to reduce uranium exposure, protect from toxic kidney effects of uranium, and reduce the risk of cancer.

Objectives - The overall objective of the project was to conduct a reconnaissance style study involving: (1) compiling existing geologic, hydrogeologic, and radionuclide information for northeastern Washington State, (2) converting available data sets to GIS format, (3) preparing maps of available data sets in order to identify areas of known MCL exceedances of uranium in groundwater and to evaluate data gaps, (4) obtaining reconnaissance uranium-concentration data for selected wells (~20 wells) in areas without data, and (5) preparing and publishing a USGS Scientific Investigations Map summarizing available data, data gaps, and suggestions for further study in order to understand the occurrence and distribution of uranium and in groundwater in northeastern Washington State.

Relevance and Benefits - This study contributes to the goals of the USGS strategic science direction, identifying environmental risk to public health in America, as identified and described in the Strategic Science Plan of the USGS (U.S. Geological Survey, 2007). The study addresses groundwater quality which is a priority issue for both the USGS Water Mission Area and the USGS Washington Water Science Center. The project also serves the USGS mission by advancing the science of water- resource assessments of the region, by providing data useful to multiple parties, and by furnishing information that will help protect human health.

Approach - Documents and data sets from local, regional, state, and national agencies were obtained and reviewed, and selected data sets were converted to digital coverages for data analysis purposes. Limited new reconnaissance data was collected for private wells in areas where uranium-concentration data are generally lacking; water samples from those wells was analyzed at the USGS National Water Quality Laboratory. A USGS Scientific Investigations Map was published to report on the current knowledge and data gaps regarding uranium in groundwater in northeastern Washington State.

Fact Sheets:

U.S. Environmental Protection Agency, 2001, Radionuclides Rule: A Quick Reference Guide, EPA 816-F-01-003

Washington State Department of Health, 2011, Radionuclides in drinking water, Fact Sheet DOH 331-056 revised