FWS Red Rock Lakes NWS – Widgeon Dam

AESI provided the survey and geotechnical engineering services for the Widgeon Pond Dam project northeast of Upper Red Rock Lake in southwestern Montana. The project was conducted in response to findings in the Widgeon Pond Dam Inspection Report.

The topographic survey included elevations of the dam crest and upstream and downstream faces, inverts and crowns of water control structures and any other features of interest, and elevations of the downstream Hackett Creek, including five cross-sections along this creek. An AutoCAD base map was created based on the topographic data.

Information from the geotechnical borings, laboratory testing, and on-site assessments were utilized to provide the following information in a geotechnical report:

• Boring logs with soil descriptions and visual classification
• Visual assessment of the dam, outlet works, spillway, seepage conditions, etc.
• Vertical and lateral bearing strength of soils
• Plasticity and plasticity index of soils
• Assessment of any difficult soils encountered
• Groundwater levels
• Recommended subgrade treatment, engineered fill type, placement techniques, and construction methods
• Assessment of the existing dam material’s suitability for reuse in the rehabilitated dam