Hydrologic Data and Evaluation for Model Validation Wells, MV-1, MV-2, and MV-3 near the Project Shoal Area

Abstract

In 2006, a drilling campaign was conducted at the Project Shoal Area (PSA) to provide information for model validation, emplace long-term monitoring wells, and develop baseline geochemistry for long term hydrologic monitoring. Water levels were monitored in the vicinity of the drilling, in the existing wells HC-1 and HC-6, as well as in the newly drilled wells, MV-1, MV-2 and MV-3 and their associated piezometers. Periodic water level measurements were also made in existing wells HC-2, HC-3, HC-4, HC-5 and HC-7.A lithium bromide chemical tracer was added to drilling fluids during the installation of the monitoring and validation (MV) wells and piezometers. The zones of interest were the fractured, jointed and faulted horizons within a granitic body. These horizons generally have moderate hydraulic conductivities. As a result, the wells and their shallower piezometers required strenuous purging and development to remove introduced drilling fluids as evidenced by bromide concentrations.After airlift and surging well development procedures, the wells were pumped continuously until the bromide concentration was less then 1 milligram per liter (mg/L).Water quality samples were collected after the well development was completed. Tritium scans were preformed before other analyses to ensure the absence of high levels of radioactivity. Tritium levels were less than 2,000 pico-curies per liter. Samples were also analyzed for carbon-14 and iodine-129, stable isotopes of oxygen and hydrogen, as well as major cations and anions. Aquifer tests were performed in each MV well after the bromide concentration fell below acceptable levels. Water level data from the aquifer tests were used to compute aquifer hydraulic conductivity and transmissivity. ACKNOWLEDGMENTS

Groundwater Model Validation for the Project Shoal Area, Corrective Action Unit 447

“…Based on the analysis of tritium in samples collected from the three wells, no evidence is found of testrelated radionuclides above natural background. Tritium was detected in MV-3, but the concentration was near atmospheric background levels (13 ± 9 pCi/L; Lyles et al, 2006). This validates the predictions of the Shoal transport model regarding the absence of transport to the locations of the MV wells at the present time.…”

“…Water level data recorded during aquifer tests were analyzed to compute aquifer hydraulic conductivity and transmissivity. Details of the MV well drilling and their hydrologic evaluation are presented in DOE (2006b) and Lyles et al (2006), respectively. This report uses the data collected from the MV wells to conduct the model validation process for Shoal as detailed in Hassan (2004a) andDOE (2006a).…”

“…The data should be diverse to be able to test the model structure, input, and output. This step has been completed and is described in (DOE, 2006b) and Lyles et al (2006).…”

Groundwater Model Validation for the Project Shoal Area, Corrective Action Unit 447

“…Water quality samples were collected after well development was completed. Samples were analyzed for tritium, carbon-14, stable isotopes of oxygen and hydrogen, as well as major cations and anions (Lyles et al, 2006). Aquifer tests were performed in each MV well.…”

“…Water level data recorded during aquifer tests were analyzed to compute aquifer hydraulic conductivity and transmissivity. Details of the MV well drilling and their hydrologic evaluation are presented in DOE (2006b) and Lyles et al (2006), respectively. This report uses the data collected from the MV wells to conduct the model validation process for Shoal as detailed in Hassan (2004a) and DOE (2006a).…”