Dams, Ponds, & Rivers

Water’s Edge Ponds

A re-circulating pond and stream system are under construction for a new subdivision near Driggs, Idaho. Sanitary requirements dictate liners to isolate the ponds and streams from groundwater. WAI performed the field investigation and provided design specifications for liners, embankments, pond and stream layout, and erosion protection.

Huntley Irrigation Diversion, Ballantine, Montana

The Huntley Project Irrigation District diversion dam is a concrete gravity structure that diverts flows from the Yellowstone River. The dam was badly damaged during the record spring runoff of 1997, primarily by erosion of the downstream face. WAI recommended high strength grouted riprap armoring of the dam’s downstream face and a new fish passage channel. This repair scheme had the benefits of requiring a single construction event (thereby reducing cost), improving the Yellowstone River fishery, and improving public safety by eliminating the hydraulic jump typically found on the downstream end of low-head dams.

Burlington Northern & Santa Fe Railway Cumulative Impact Assessments

A major artery of the BNSF follows the Yellowstone River valley in eastern Montana. Erosion and undercutting is a long-term maintenance problem in areas where the rail line is adjacent to the river channel. The most common form of bank protection has been rock riprap. Six proposed bank stabilization projects were selected for Impact Assessments required by the Corps of Engineers. WAI analyzed geomorphic and riparian aspects to quantify changes in river morphology over the past 50 years. WAI also reviewed the performance of the projects, causes of instability, and potential remedial measures.

BNSF Slope Stabilization, Yellowstone River, Shirley, Montana

The BNSF railway line above the Yellowstone River near Shirley in Dawson County, Montana crosses the top of a steep 50-foot slope that has been subject to slope failures for many years. Slope retreat had moved within less than 20 feet of the rail, presenting an immediate danger to the rail. WAI, in association with Interstate Engineering, conducted a geotechnical investigation and recommended a combination of 2:1 slope angles, improved drainage conditions at the slope crest, smoothing of the meander bend in the river channel, and erosion control at the toe. A wildlife corridor and habitat enhancement were an integral part of the design, greatly easing the permitting process. The completed project has withstood an ice event equivalent to a 500-year flood.

River Property Boundary Issues

Because rivers serve as property boundaries, the origin of fluvial landforms has legal implications. WAI routinely analyzes historic maps and time-series aerial photographs to trace the geomorphic history of islands and bars. Ray Womack has been an expert witness and consultant in many river boundary disputes, most recently for oil and gas leases along the Yellowstone near Sidney, Montana.