Sevier Bridge Dam Rehabilitation, Phase II

Sevier Bridge Dam is located along the Sevier River near Scipio, Utah. The original dam construction began in 1903, and the dam was raised in 1917 to its current height. The embankment is 1,340 ft in length at the crest and has a structural height of 92 ft. The Sevier Bridge Dam impounds approximately 205,000 acre-ft of irrigation water. In 2008, the upstream embankment was rehabbed with the construction of a stability berm. Preliminary studies on the downstream embankment found that additional work would be needed on the crest and downstream portion of the embankment to bring it up to current standards. Hydraulic analyses performed by Bowen Collins & Associates (BCA) identified the need to enlarge the spillway to handle the spillway evaluation flood. The geotechnical design completed consists of stability and deformation analysis for the existing and the remediated dam section. The mitigation measures to bring the dam up to standards were stone columns in the foundation of the dam, stability berm, and then drainage blanket and chimney filter for the stability berm. This paper focuses on the geotechnical design and what mitigation measures were used to bring the dam up to minimum standards and increase the seismic resiliency of the dam. The construction of the stability berm and new spillway was completed successfully.