East Fork of Rock Creek Dam
East Fork of Rock Creek Dam is located in the Beaverhead-Deerlodge National Forest in southwest Montana, 15 miles south of Philipsburg. Primary deficiencies at the dam led the Montana Department of Natural Resources and Conservation (DNRC) to begin evaluating risk reduction measures for this high hazard facility. Schnabel was retained as a subconsultant for the feasibility study, which included a Potential Failure Modes Analyses (PFMA), site investigations, flood hydrology, alternatives development, cost estimating, and preliminary environmental studies.
Schnabel participated in the PFMA as geology, geotechnical, and hydraulic structure subject matter experts, and also served on the team to complete a review of the geotechnical analyses, alternatives, and development of the instrumentation plan. The evaluation included the development of conceptual modifications to address specific potential failure modes associated with the spillway, outlet works, and foundation seepage. Schnabel was subsequently hired as the lead firm for the design of the rehabilitation measures, including a replacement spillway (labyrinth, 600-foot-long chute, and stilling basin); a filter and toe drain system to mitigate internal erosion potential failure modes; the outlet works rehabilitation; and an extensive upgrade to the site instrumentation and monitoring systems.
Schnabel also prepared construction scheduling, cost estimating, and designed temporary construction works and temporary and permanent dewatering systems to facilitate construction of the spillway stilling basin. Schnabel performed all hydraulic, geotechnical, structural, and mechanical engineering. The design includes a new 100-foot-long single span vehicle bridge over the spillway approach channel to carry a US Forest Service roadway. Bridge design was by subconsultant, DOWL.
Schnabel provided bid-phase engineering services including preparation of contract documents with DNRC, leading the pre-bid meeting and site visit, preparing bid addenda, and reviewing bids received. Construction began in 2024 with Schnabel providing contract administration, technical services during construction, onsite resident engineering, and quality assurance. Construction is scheduled to be complete in fall 2026.