Schafer Dam, formerly Success Dam, is located on the Tule River near the town of Porterville, California. Its reservoir provides flood risk management, water storage, and recreation benefits to the local community. The dam was built in 1961 using design standards that were current at the time. Beginning in 1992, a series of risk assessments indicated that Schafer Dam could fail in a major earthquake or be vulnerable to seepage and overtopping. In 2006, the U.S. Army Corps of Engineers began limiting the amount of water stored in the reservoir to minimize flood risk. In 2017, Schafer Dam was reclassified to a lower risk classification. However, it was determined that it was not tall enough to sustain a large flood event. This project involved the expansion of the dam’s spillway and the construction of a 10-foot-high concrete ogee weir, which increased the reservoir pool by 28,000 acre-feet.
GBI’s primary scope of work included 400,000 cubic yards of excavation, half of which was drilled and blasted. The dam’s spillway was widened by 165 feet to make it approximately 365 feet wide. To allow for the expansion of the spillway, a paved access road that passes through it had to be moved to the right abutment above the reservoir pool. As part of the road construction, GBI built gabion walls and placed rock fills to allow for the installation of rock bolts and culvert crossings. GBI’s paving crew completed the new roadway, and GBI’s subsidiary company, Blasting Technology, Inc. (BTI), was the primary subcontractor. There were some unexpected design challenges, but GBI worked closely with BTI and Central Environmental, Inc. (CEI) to remedy the design and schedule impacts while continuing to move the project forward through creative resequencing.
The raised spillway at Schafer Dam increases flood protection for the city of Porterville and a vast stretch of farmland below the reservoir, while also increasing the reservoir’s water supply capability. Local farmers had been pushing for this project for many years, and the additional capacity will provide them with much-needed water that is used primarily for irrigation in farming operations.