Tonopah Public Utilities

Nye County, Nevada, Assessment of Potential Sources of Low Arsenic Content Groundwater and Well Field Augmentation

Tonopah Public Utilities existing Rye Patch well field, situated in central Ralston Valley, has been a source of municipal water to Tonopah for over 100 years. While a dependable and generally good quality source of water, the current arsenic standard of 10 ug/L is at times exceeded, and the well field consistently produces water near very near the threshold. Tonopah was confronted with either building and operating an arsenic treatment plant, or identify a source of groundwater with lower arsenic content to serve for blending. Prior to initiation of the study, it had been generally reported that arsenic was pervasive throughout central Ralston Valley, however, sparse data were available to define the conditions.

Interflow Hydrology conducted a multi-phased hydrogeologic and data collection effort to more thoroughly characterize groundwater quality in both the existing well field area, and at locations within reasonable proximity to existing facilities. Data on water chemistry and aquifer conditions were compiled from several sources, including existing monitoring wells from a nearby mining operation, an existing well at an abandoned gravel operation, stockwater wells in regions of interest, and through drilling of monitoring wells and a test well in areas of specific of interest. Through these efforts, a clearer interpretation of sources and occurrence of arsenic in groundwater at the well field was prepared, which successfully identify
ed an economical source of low arsenic content groundwater to integrate in as a blending source into the municipal system.

Interflow Hydrology provided well design, construction, supervision, and pumping tests for two new municipal wells, which were tied into the existing well field to provide a water quality blending source.