Nuclear magnetic resonanance logs of fractured bedrock at the Hidden Lane Landfill site, Culpeper Basin, Virginia

In May 2018, the U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (EPA) collected borehole nuclear magnetic resonance (bNMR) logs in three boreholes completed in sandstone and siltstone of the Balls Bluff Member of the Bull Run Formation at a Superfund Site in Culpeper Basin, Virginia. The bNMR logs were used to aid in the evaluation of the aquifer by measuring the porosity, determining the mobile and immobile fractions of water, and estimating the hydraulic conductivity, to evaluate the potential storage and transport properties at the site. The bNMR method measures the transverse (T₂) decay in nuclear magnetism in response to radio-frequency pulses. The relaxation decay is related to water content and the size of the pores where the water resides. In addition, the relaxation decay parameters are used to estimate hydraulic conductivity. The results were compared to other borehole logs collected at the site and to regional groundwater investigations in similar rock formations.