Dam Safety & Security

Issue 5 and Volume 29.

U.S. Fish and Wildlife Service plans dam safety evaluations

The U.S. Fish and Wildlife Service (FWS) is preparing to conduct safety evaluations of its 233 dams and related water resources structures.

The work will involve contractors, who will perform Safety Evaluation of Existing Dams inspections for new dams; dams undergoing rehabilitation or modification; other hydraulic structures; and appurtenant facilities such as spillways, outlet works, and gates.

FWS plans to issue two indefinite-delivery, indefinite-quantity contracts for one year, with four option years. FWS estimates this would involve a maximum per contract year of $4 million per contract.

FWS’ dam inventory includes zoned and homogenous earth embankment, gravity and arched concrete, and roller-compacted-concrete dams ranging from 6 feet to 103 feet high, with reservoirs ranging from 15 to 109,000 acre-feet.

Corps to install seepage barrier at 135-MW Center Hill

The U.S. Army Corps of Engineers is proceeding with work needed to install a concrete seepage barrier at the main embankment of 135-MW Center Hill Dam on the Caney Fork River in Tennessee.

Center Hill has a history of seepage problems that have worsened in recent years. In February 2008, the Corps’ Nashville District awarded an $87.4 million contract to Kiewit–A.C.T. to install a grout curtain seepage barrier at the project.

The 250-foot-tall dam consists of a 1,382-foot-long concrete section and 778-foot-long earth embankment. The Corps plans to install a 900-foot-long concrete seepage barrier with a minimum 2-foot thickness, extending from elevation 696 mean sea level (msl) to 405 msl. The work is expected to cost $100 million to $250 million.

The barrier is to be installed through existing earthen embankment and underlying limestone foundation. Portions of the limestone foundation exhibit unconfined compressive strengths up to 32,230 pounds per square inch (psi), with a range of 5,000 psi to 32,230 psi. Therefore, the Corps prefers a combined wall of hydromill and circular pile elements.

Center Hill is among six dams the Corps identified as having a high risk of failure, in a screening program of 130 dams. In 2006, the Corps approved a $240 million rehabilitation plan to improve the dam’s long-term reliability by 2014.

Book available on dam-break problems and solutions

WIT Press announces availability of Dam-break Problems, Solutions and Case Studies.

To manage and minimize the risk of dam failure, it is necessary to identify hazards and vulnerabilities by understanding the causes that lead to dam failures, as well as the flow propagation process, say editors D. De Wrachien and S. Mambretti. Knowledge and advance scientific tools play a role of paramount importance in coping with flooding and other dam break problems. De Wrachien and Mambretti are with the State University of Milan in Italy.

This 368-page book covers:

– Practical aspects involved in dam failures;

– A range of laboratory tests and modeling techniques for dealing with shock waves and other disasters caused by dam failures;

– Dam break wave and flood routing;

– Dam break flow against obstacles and through river bed singularities;

– Dam break risk management and hazard mitigation;

– Economic evaluation of dams for flood protection; and

– Case histories to illustrate the topic of disaster management.

– To order the book for US$242, E-mail: [email protected]

Corps to upgrade monitoring system at 402-MW Dworshak

The U.S. Army Corps of Engineers is working to upgrade the dam safety monitoring system at 402-MW Dworshak Dam in Idaho.

The three-unit Dworshak plant began generating electricity in 1973 on the Clearwater River.

Work to be performed at this plant includes replacing vibrating wire sensors inside the dam, installing new sensors and communication cabling and related hardware, upgrading or replacing the automated data acquisition system, supplying and commissioning of network-based data handling and presentation software, and minor civil works.

Data collected using the updated system will be used to monitor the stability and performance of the dam. This work is being performed as a result of the Dworshak Dam and Reservoir Interim Risk Reduction Measures Plan. This plan was developed after a Screening Portfolio Risk Assessment identified deficiencies.

For information, contact Jacob M. Shaw, (1) 509-527-7225; E-mail: [email protected]

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