Installation of a groundwater monitoring-well network on the east side of the Uncompahgre River in the Lower Gunnison River Basin, Colorado, 2012

Abstract

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized. The U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board and the Bureau of Reclamation, has established a groundwater-monitoring network on the east side of the Uncompahgre River Basin. Ten monitoring wells were installed during October and November 2012. This report presents location data, lithologic logs, well-construction diagrams, and well-development information. Understanding the groundwater system will provide managers with an additional metric for evaluating the effectiveness of salinity and selenium control projects.

Groundwater quality and hydrology with emphasis on selenium mobilization and transport in the Lower Gunnison River Basin, Colorado, 2012–16

“…The random site-selection process divided the study area into 30 equal-area polygons and then generated three potential groundwater-monitoring sites in each polygon: a primary, secondary, and tertiary site. When establishing sites, the primary site was considered first, followed by the secondary and tertiary sites (Thomas and Arnold, 2015). Final well locations were established based on landowner permission and site accessibility.…”

“…Final well locations were established based on landowner permission and site accessibility. Monitoring wells were drilled and installed during 2012 and 2014 (table 1); the process is described in Thomas and Arnold (2015) and Thomas (2015). The boreholes were drilled with a truckmounted drilling rig and advanced with 4.25-in.…”

“…Split-spoon samples of geologic materials were collected to correctly identify formation intervals for well installation. Lithologic logs were developed based on visual inspection of split-spoon samples and auger cuttings (Thomas and Arnold, 2015;Thomas, 2015). Of the 12 holes drilled in October and November 2012, three were dry (well identifiers 8,11, and 13), indicating discontinuous saturated conditions in the study area (Thomas and Arnold, 2015).…”

“…Lithologic logs were developed based on visual inspection of split-spoon samples and auger cuttings (Thomas and Arnold, 2015;Thomas, 2015). Of the 12 holes drilled in October and November 2012, three were dry (well identifiers 8,11, and 13), indicating discontinuous saturated conditions in the study area (Thomas and Arnold, 2015). All 30 monitoring wells were developed to remove mud and any foreign material and to help improve the hydraulic connection of the well with the aquifer.…”

“…All 30 monitoring wells were developed to remove mud and any foreign material and to help improve the hydraulic connection of the well with the aquifer. Well development information and well construction diagrams are provided for each well in Thomas and Arnold (2015) and Thomas (2015).…”