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 Success Dam photos

Documents

Final Deviation Environmental Assessment - June 6, 2017

Historic water levels graph - Apr. 3, 2014

Study timeline - Apr. 3, 2014

Review plan - Oct. 5, 2013

Contact Information

For more information on the Success Dam Safety Modification Study, please contact us at the following:

Phone:
916-557-5100

Email:
spk-pao@usace.army.mil 

Mailing Address:
U.S. Army Corps of Engineers,
Sacramento District
Success Dam Safety Modification Study
1325 J Street, Room 1513
Sacramento, CA 95814

Success Dam Safety Modification Study

Success Dam is located on the Tule River, about five miles east and upstream of the town of Porterville, Tulare County, California. Success is an earthen dam 145 feet (44 meters) tall and 3,490 feet (1,060 meters) long. The dam and reservoir were authorized as part of the Tule River Project under the Flood Control Act of 1944 and construction was completed in 1961. The reservoir provides flood risk management, water storage and recreation benefits to the local area.

The dam was built using design standards that were current at the time of construction, and built well. Seismic reanalysis that began in 1992 indicated that the alluvial (loose soil or sediment) foundation underlying the dam is susceptible to liquefaction, which in a major earthquake could cause the dam to fail.

In 1999, Congress authorized the U.S. Army Corps of Engineers to study how to address seismic risk to the dam. The study revealed additional concerns about seepage and overtopping, requiring further study and funding authorizations. In late 2006, the Corps began limiting the amount of water stored in Success Lake to minimize flood risk to the public while the Corps studied the dam and developed a solution.

New requirements and modifications to the Corps’ dam evaluation process since 2004 required additional analysis and a new type of report. Upon completion of this report in 2010, the Corps’ national dam safety program required the district to perform a baseline risk assessment - a comprehensive analysis of all the dam’s safety risks using the same methods now being applied to Corps dams throughout the nation. This re-evaluation demonstrated that the risk associated with liquefaction (dam failure during an earthquake) and seepage is significantly less than early study results indicated, and the Corps approved April 11, 2014, raising the operating restriction of the reservoir behind Success Dam to the maximum authorized storage capacity of 82,291 acre-feet, or a storage elevation of 652.5 feet.

The baseline risk assessment for Success Dam is currently being reviewed and is scheduled to be completed in summer 2014. At that time, the determination will be made as to whether the dam needs a significant fix or not.

Frequently Asked Questions

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Overtopping is the main threat that could cause the dam to fail. Overtopping results from a huge, although rare, flood (about a 1/13,000 probability in any year) that could fill the reservoir too quickly, leading to overtopping and erosion of the dam. During this extremely rare flood event, Success Dam is not tall enough to store such a high volume of water. Through rigorous engineering analysis and investigation, seismic and seepage risks have recently been determined to be minimal concerns.
Success Dam is not in danger of imminent failure and is regularly inspected and monitored. The primary concern is overtopping in a huge flood and the public would get notice far in advance of this happening.
The Corps' study of the level of risk at Success Dam and whether work to reduce that risk is needed is still ongoing, so no fix has yet been determined. The review process for the baseline risk assessment for Success Dam is under way and is scheduled to be complete in summer 2014. When that is approved, a permanent change to the water level restriction will be considered. Also, the Corps will determine if any fixes are necessary for Success Dam.
The Corps is still studying the risk at Success Dam, so there are currently no plans for construction. The review process for the baseline risk assessment for Success Dam is under way and is scheduled to be complete in summer 2014. When that is approved, a permanent change to the water level restriction will be considered. Also, the Corps will determine if any fixes are necessary for Success Dam.
The Sacramento District is still studying the risk at Success Dam so it is too early to say if the spillway will be widened or raised. The review process for the baseline risk assessment for Success Dam is under way and is scheduled to be complete in summer 2014. When that is approved, a permanent change to the water level restriction will be considered. Also, the Corps will determine if any fixes are necessary for Success Dam.
Projects to fix existing infrastructure like Success Dam are often more complicated and take longer than building new infrastructure. Technical investigations and analysis of the geology, weather patterns and environmental concerns needed to plan a major project like a dam upgrade take years, and require review by regional and national Corps experts, as well as experts outside of the agency. Study progress also depends on steady funding, which is not always guaranteed. Additionally, Corps technical standards and policies evolve with advances in science, engineering and technology, and occasionally require reconsideration of studies that are already in progress to ensure that projects are built to the most modern specifications. While lengthy, this deliberate process is designed to ensure that recommended projects make the most efficient use of taxpayer dollars and provide the most long-term public benefit.
$54 million. Some of the major costs include drilling boreholes and collecting samples for analysis, geophysical tests, seismic modeling and the design of potential fixes. Many federal dams, including Success Dam, were built more than 50 years ago, and require continual investment in studies and maintenance to ensure they continue to offer the best balance of benefits to the public.
Access current reservoir status, monthly reports and historical water data since 1990 at http://www.spk-wc.usace.army.mil/. From the homepage, select “Midnight Reservoir Status”, then “COE”.
Funding was appropriated in fall 2011 to purchase high-risk properties directly below the dam. The Corps has purchased three high-risk properties and is in the process of purchasing one additional property. There are currently no additional plans or authorization to purchase any other properties.
Living directly below a dam always has risk, regardless of the condition of the dam. The Corps’ top priority is minimizing the safety risk to the public. The Corps will continue to take steps to minimize risk for those living directly below dams.