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Dam Safety & Security

Dams society issues paper on dam monitoring instrumentation

The U.S. Society on Dams (USSD) issued a white paper that emphasizes the importance of understanding the role of instrumentation in monitoring the performance of dams.

The USSD Committee on Monitoring of Dams and Their Foundations prepared the white paper, “Why Include Instrumentation in Dam Monitoring Programs?”

The paper says use of instrumentation is growing as a part of dam safety programs as the technology of instrumentation and ease of use improves. Thus, it says, it is important to understand how instrumentation can be used to provide comprehensive, timely information regarding the ongoing performance of a dam.

For purposes of the white paper, instrumentation is defined as a device that is installed to measure a particular parameter of interest. That can include seepage flows, seepage water clarity, piezometric levels, water levels, deformations or movements, pressures, loading conditions, temperature variations, or accelerations experienced by the dam during an earthquake. The measurement may be electronic or made using a mechanical device.

Topics covered in the white paper include:

 

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The white paper is available on the Internet at www.ussdams.org/instrumentation.PDF.

Significant-hazard dams must make failure analysis

The Federal Energy Regulatory Commission (FERC) is requiring owners of all significant-hazard-potential dams to perform Potential Failure Modes Analyses (PFMA) for their structures. Dam owners will be asked to propose a plan and schedule for completing analyses.

FERC already conducts PFMAs for high- and significant-downstream-hazard-potential dams that require inspections under Part 12D of the commission’s regulations for the safety of hydropower projects. (See Hydro Review, September 2008, page 86.)

The commission said the PFMA requirement is being extended to other significant-hazard-potential dams because they could cause substantial property damage in the event of a dam failure. It said it considered comments from the dam safety community before finalizing its proposal to expand the analyses to more dams.

PFMAs are conducted by reviewing information on a dam and then analyzing ways in which the dam could potentially fail. The process involves a facilitated discussion among representatives of the owner, including the owner’s consultant if applicable, and the FERC inspector.

FERC had considered applying the PFMA process both to significant-hazard-potential dams that do not require Part 12D inspections and to low-hazard-potential dams greater than 9 feet tall or that impound more than 25 acre-feet. However, it decided not to require PFMAs for low-hazard-potential dams at this time.

While FERC strongly encourages owners of low-hazard-potential dams to conduct PFMAs on their projects, at this time it will be voluntary, the agency said. Owners of low-hazard-potential dams have the option of voluntarily including the PFMA in dam safety inspections.

FERC said its regional offices would notify owners of significant-hazard-potential dams that they must perform PFMAs in accordance with Chapter 14 of FERC’s Engineering Guidelines for the Evaluation of Hydropower Projects, posted on FERC’s website, www.ferc.gov.

The initiative also is on the Internet at www.ferc.gov/industries/hydropower/safety/initiatives/final-initiative.asp.

U.S. awards 199-MW Folsom Dam auxiliary spillway

The Bureau of Reclamation awarded a $62.6 million construction contract for an auxiliary spillway to increase dam safety and flood protection at 198.72-MW Folsom Dam in California.

Interior Secretary Ken Salazar announced the award to Martin Brothers Construction of Sacramento. It is the second in a series of construction contracts for the new auxiliary spillway. Kiewit Pacific Co. of Concord, Calif., was awarded the first contract, for $16 million, in 2007.

Reclamation, the U.S. Army Corps of Engineers, Central Valley Flood Protection Board, and Sacramento Area Flood Control Agency are cooperating on the auxiliary spillway, being built as a joint federal project.

The auxiliary spillway project consists of an approach channel, a control structure with six submerged tainter gates, a concrete-lined spillway chute about 3,000 feet long, and a stilling basin to dissipate energy before water is discharged into the American River below the main dam.

The new contract includes spillway excavation, construction of a stilling basin coffer dam, relocation of a 42-inch water supply pipeline, and ancillary access roads. The work is to be completed in fall 2010. Phase III construction will follow thereafter, with the entire project expected to be complete by 2015, Interior said.

The spillway is to address the risk of possible overtopping of the dam and dikes during an extreme storm identified through Reclamation’s Safety of Dams evaluation program. The project also will achieve the Corps’ objective of doubling the flood protection for the city of Sacramento, to a 200-year flood.

A previous award for Phase II construction was made in September 2008. However, Interior said, a protest against the award was upheld by the Small Business Administration, and the contract rescinded. Discussions then were held with bidders who remained in the competitive range of the original solicitation, resulting in the new award, it said.

FERC proposes changes to hydro security program

The Federal Energy Regulatory Commission’s (FERC) Dam Safety and Inspections Division issued a draft revision of its Security Program for Hydropower Projects. The document provides guidance to FERC licensees and to commission staff in executing the security program.

FERC said the proposed changes in the draft reflect comments and recommendations FERC received from project licensees and from other agencies. FERC created the original program in November 2001, in response to terrorist attacks on the United States.

The program assigns all dams under FERC’s jurisdiction to one of three security groups, with specific requirements designated for each group. It defines requirements for vulnerability assessments, security assessments, security plans, and security measures for each of the three groups.

The security groups are based on potential dam hazard classification, project size, potential consequences, and installed generating capacity. Security Group 1 dams are inspected with a high level of scrutiny by FERC. Security Group 2 dams are inspected by FERC engineers at a high level of awareness, consistent with the potential threat level. Security Group 3 dams are inspected by FERC engineers as the dams come up for scheduled dam safety inspections, from one to three years.

The draft document is on FERC’s Internet site, www.ferc.gov. A PDF version of the 66-page document can be obtained from the site at www.ferc.gov/industries/hydropower/safety/guidelines/security/securityprogram-r2.pdf.

FERC postpones changes to security groups
FERC also is updating its security group classifications for dams, which originally were developed immediately after the Sept. 11, 2001, terrorist attacks.

The original groupings primarily were based on consequences. Since 2001, the dam sector security programs have more fully developed into a risk-based evaluation, which considers threat, vulnerability, and consequences.

FERC said it chose not to issue a tentative list of security group changes in 2009. Instead, it said it would wait until it can use an improved Dam Assessment Matrix for Security and Vulnerability Risk methodology to more accurately define the potential risk at hydroelectric projects.

FERC manages the largest dam safety program in the U.S., responsible for more than 3,000 dams. FERC’s Dam Safety and Inspections Division monitors security programs and measures implemented by dam owners.

U.S. awards security contract for 1,312-MW Glen Canyon

The Bureau of Reclamation awarded a $7.43 million contract to Basic Contracting Services Inc., which is to provide year-round security services at 1,312-MW Glen Canyon Dam.

Security services called for by the contract include armed guards, roving patrols, alarm and detection systems monitoring, and video surveillance equipment monitoring.

The services are to be provided as part of Reclamation’s larger efforts to detect, deter, or respond to threats to national critical infrastructure facilities from acts of terrorism, natural disasters, and other emergencies.

Basic Contracting Services, based in Artesia, N.M., will use currently employed, experienced, and well-trained security forces at the dam, Reclamation said. The company also plans to recruit and hire employees from the Northern Arizona labor sector and train the new workers in physical and electronic surveillance and detection methods.

Corps adds $24.4 million to Tuttle Creek Dam work

The U.S. Army Corps of Engineers said it will use $24.4 million from an economic stimulus bill to add to an existing contract for work on the Tuttle Creek Dam foundation project in Kansas.

The Corps announced in May it would add the funds to a contract previously awarded to Treviicos South Inc., Boston, Mass. Tuttle Creek Dam is included in a list of Corps projects to receive a total of $4.6 billion from the stimulus package.

In awarding a $50 million general contract to Treviicos in 2005, the Corps said work at Tuttle Creek represented the largest ground modification effort in the world involving an operational dam, and the largest dam safety modification project the agency had tackled.

The $200 million program includes activities to stabilize sands beneath the 157-foot-tall, 7,500-foot-long rolled earth and rockfill embankment dam, and structural modifications to 18 spillway gates. All construction associated with the dam safety assurance program is expected to be completed in 2010, the Corps said.

Without the improvements, the Corps said, a 5.7 to 6.6 magnitude earthquake could inflict significant damage to the dam. Thirteen thousand people live downstream of the dam. Located on the Big Blue River five miles north of Manhattan, Kan., the dam is part of a multipurpose project operated by the Corps’ Kansas City District.

Corps plans more testing below Taum Sauk breach

The U.S. Army Corps of Engineers plans additional testing of Missouri’s Clearwater Lake, which it claimed was fouled by the 2005 failure of the 408-MW Taum Sauk pumped-storage project’s upper reservoir.

The Corps’ Little Rock, Ark., District filed suit in December 2008 in U.S. District Court at Cape Girardeau, seeking damages from hydro project licensee Union Electric Co. of St. Louis, doing business as AmerenUE. In its suit, the Corps claimed the breach of the reservoir dumped sediment and debris into Clearwater Lake.

However, the assistant U.S. attorney dismissed the case without prejudice in April, with the Corps’ approval. Federal regulations provide the Corps one year from the dismissal to refile the suit, should it so choose.

“This should allow sufficient time for additional testing of Clearwater Lake,” Corps spokesman P.J. Spaul said. “We intend to run sediment ranges and take core samples over the next few months and then evaluate the results.”

In its suit, the Corps said it wanted damages and other relief from AmerenUE’s negligence in operation of Taum Sauk that led to failure of the reservoir. Corps said an unknown amount of sediment and debris was released into the Black River and Clearwater Lake downstream, reducing Clearwater Lake’s storage capacity and life span.

AmerenUE disagreed with the Corps’ arguments.

Taum Sauk has not operated since the reservoir’s ring dam breached, releasing 1.4 billion gallons of water down the Black River. A Missouri Public Service Commission probe cited a failure of utility management for the breach.


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