Construction of a Low-Flow Channel in Barber Creek: Case Study in the Powder River Basin, Wyoming

Design and construction of low-flow channels to convey coalbed natural gas-produced (CBNG-produced) waters to higher-order streams is a relatively new water management option being employed in the Powder River Basin (PRB) of northeast Wyoming. In this case study, a low-flow channel was designed, constructed, and maintained on Barber Creek and South Prong Barber Creek in the PRB near Gillette, Wyoming. Engineering design challenges include large ephemeral flows, steep slopes, and cohesive soils. Initial design was based on aerial photography analysis, low-level reconnaissance flights, and field exploration. Existing channels were surveyed to establish representative channel sinuosity, depth, slope, and stability of streams in close proximity to the study area. The final design includes approximately 1,370 m (4,500 ft) of channel reconstruction on South Prong Barber Creek and 1,800 m (5,900 ft) of channel reconstruction on Barber Creek. Clay soils hardened by severe drought conditions presented an unexpected challenge during construction, as did several significant rainfall events which occurred immediately following initial construction, damaging design elements already in place. Automatic streamflow gages located upstream and downstream of the study area recorded the subsequent flood events. Post construction design considerations include stabilization of the existing channel and installation of erosion mitigation measures. This study provides a full range of design criteria, construction procedures, and mitigation efforts for consideration in the design of stable low-flow conveyance channels for CBNG-produced waters.