Geochemical and Hydrogeological Evaluation of Former Yerington Mine Site

SSP&A has assisted the Atlantic Richfield Company for nearly a decade with the development and implementation of long-term management of contaminated groundwater at the Anaconda Copper Mine Site in Lyon County, Nevada. SSP&A has conducted various analyses of groundwater flow and geochemical conditions to assist in the selection of remedial actions at this large former copper mine site.

SSP&A conducted detailed analyses of plume stability and the processes affecting the migration of mine-related constituents in groundwater. A major element of the work included the construction of a complex groundwater model to simulate potential future migration of mine-related constituents, with calibration to historical groundwater-level and water-quality data. Other elements of the work included the evaluation of trends using multiple regression maximum likelihood (MLE) methods incorporating groundwater elevations as an explanatory covariate for concentration changes, the assessment of extensive irrigated agriculture in the vicinity of the mine site on groundwater quality, and assistance with preparation of the site Remedial Investigation Report.

Ongoing work includes assistance with the development of remedial alternatives and a recommended alternative for the Feasibility Study for groundwater issues, and implementation of remedies for other operable units. This work has included the assessment of monitored natural attenuation (MNA) as a remedial alternative as well as active remedial approaches, and was performed under the oversight of the U.S. Environmental Protection Agency (EPA) and the Nevada Department of Environmental Protection.

Project tasks included:

• Evaluation and revisions to Conceptual Site Model (CSM) and construction of groundwater model based on that CSM.
• 3D visualization of the CSM, mine facilities, and distribution of constituents in groundwater.
• Evaluation of multiple data types critical to estimation of fate-and-transport.
• Novel analysis of concentration trends using maximum likelihood to assess MNA progress.
• New insights into groundwater quality changes from irrigated agriculture.