Geoprobe®: Investigation of Uranium in Drinking Water
Project Logs

For information on uranium and other radionuclide regulations go to www.epa.gov/safewater/radionuclides/basicinformation.html. Additional information about this investigation and the specific field methods applied and equipment used is available by contacting Wes McCall at Geoprobe Systems®, 1-800-436-7762 or at mccallw@geoprobe.com.

	The first HPT log run near the South PWS well and test well. Note increasing baseline is due to hydrostatic pressure. Peaks in the log indicate increased water pressure in the HPT probe due to fine-grained materials in the formation. Lower pressures indicate sands/gravels in the formation. The PWS well is 12-in. diameter, stainless steel screen and casing. The test well is 4-in. PVC and was backfilled to the surface with sand.
	This figure indicates how screen intervals were selected and screens placed based on the HPT log response. Nominal 0.75 in. x 5 ft. prepacked screens were placed to sample different sand intervals in the aquifer that are separated by fine-grained materials. This was done to see if aquifer chemistry changed with depth, especially uranium concentration.
	The Specific conductance and analyte concentrations in the groundwater decrease with depth in the aquifer as shown by the DP wells. However, the Specific conductance and analyte concentrations in the 4-in. well is high when compared to the DP wells screened over similar intervals. These results indicate that the sand-packed annulus of the 4-in. well is permitting shallow groundwater with high analyte concentrations to flow down the aquifer unimpeded. Note the high uranium in the 4-in. well is greater than any result from the A-Group DP wells.
	Again at the B-Group wells, the Specific conductance and analyte concentrations generally decrease with depth, but with one clear exception. The uranium concentrations in the B4 and B5 wells are much higher than any of the other DP wells at the B- or A-Group locations. These results indicate that soluble uranium is present only in selected zones of the aquifer and is heterogeneously distributed. The B4 and B5 zones of the aquifer appear to be the source for the elevated uranium observed in the 4-in. test wells and PWS wells.