Manderfield Dam, located in Beaver County, Utah was initially constructed in stages beginning as early as 1870. The dam has a structural height of 34.5 feet and a hydraulic height of 29.5 feet. A dam safety remediation project was recently undertaken to address deficiencies with the structure. These deficiencies included sinkholes that had appeared upstream of the dam and within the upstream slope, seismic stability, excessive seepage, inadequate spillway and outlet works. RB&G designed the dam safety modifications which included raising the embankment, installation of a new low level outlet, a low permeability zone on the upstream face of the dam, seepage collection and drainage features, seismic stability berm, new labyrinth weir spillway and partial blanketing of the reservoir basin. RB&G prepared plans and specifications, assisted the owner with bidding and contractor selection, and performed construction engineering management for the Owner. This reservoir is located at about elevation 8,000 feet with the owner requesting that the work not impact irrigation demands. Work began during the summer of 2013 and was completed in January 2014. The Utah State Engineer and U.S. Forest Service were regulatory agencies with the Utah State Division of Water Resources providing funding. The project was selected by the Association of State Dam Safety Officials (ASDSO) for presentation at the national conference held in San Diego in 2014.
Services: Geotechnical investigations; environmental documents; survey; coordination with Utah State Dam Safety, US Forest Service, and other stakeholders; seismic design; hydraulic design of spillway; seepage design; preparation of plans, specifications and estimates; and construction engineering management for the project.