Hydro Review

Dam Safety & Security

Act introduced to extend National Dam Safety Program

Senators Daniel Akaka (D-Hawaii) and John Boozman (R-Ark.) have introduced legislation that would reauthorize dam safety programs first authorized through the Water Resources Development Act of 1996.

The legislation, called the National Dam Safety Act of 2012, would continue the National Dam Safety Program, which provides support for state dam safety initiatives. Forty-nine states and the Commonwealth of Puerto Rico have established state dam safety programs, with Alabama being the lone exception.

Through the administration of the NDSP, the Federal Emergency Management Agency will continue leading national efforts to protect the public against dam failures by:

- Providing grant assistance for the improvement of state dam safety programs;

- Instigating and supporting dam safety research and technology transfer;

- Supporting public awareness efforts;

- Acting as a liaison for communication between state and federal agencies;

- Providing training of state dam safety staff.

The act is being applauded by the Association of State Dam Safety Officials, which has supported the legislation since its first authorization in 1996 through subsequent authorizations in 2002 and 2006.

"The NDSP is invaluable to the state programs involved with the day-to-day safety regulation of these vital, yet potentially dangerous, components of the national infrastructure," says ASDSO President Zahir Bolourchi.

ASDSO works with the American Society of Civil Engineers to issue national "infrastructure report cards" that assess the condition of U.S. dams. ASDSO says although the grades have remained a "consistent 'D'," the seeming lack of progress is somewhat deceptive due to overall improvements in many areas pertaining to dam safety.

ASDSO notes, however, that it would still take about $16 billion to rehabilitate the nation's most high-hazard dams, and funding for inspections and the enforcement of safety programs is sparse.

City looking to improve safety at 1.7-MW Lake Wohlford project

A decision made in August by the Escondido, Calif., city council should help improve the safety of California's Lake Wohlford Dam and its accompanying 1.7-MW hydro plant.

The council agreed to pay Black & Veatch US$3.5 million to design a $26 million replacement for the 116-year-old structure.

Since being deemed seismically unsafe during a 2007 federal review, the reservoir's capacity has been reduced by more than half due to concern that the structure's earthen portions might liquify during an earthquake.

Local sources say the city had been delaying a full replacement of the dam due to its price tag, but officials say state and federal grants should help cover much of the project's costs.

The work is expected to be done by mid-2017, per stipulations of state grants.

Corps changes safety rating of Idaho's Dworshak facility

The safety rating of Idaho's 402-MW Dworshak Dam has been upgraded by the U.S. Army Corps of Engineers, even though no repair or upgrade work has been done to the structure.

Instead, the Dworshak hydro plant, which had been listed as "unsafe or potentially unsafe," has been changed to "conditionally unsafe" after the Corps reevaluated the threats facing the dam.

According to the Corps, the biggest risks facing Dworshak, on the Clearwater River, are earthquakes, which are rare in the region. The report also says cracks and leaks in the dam don't present an urgent risk of failure.

The safety of the 717-foot-tall straight-axis dam was first brought into question in 2007, after it was evaluated under the Corps' new Dam Safety Action Classification System.

That evaluation prompted the Corps to solicit bids for improved safety monitoring systems, the last of which was awarded to Jensen Drilling Company in August 2010.

Drawdown performed after spillway breach at Corunna Dam

The Michigan Department of Environmental Quality initiated a drawdown of the water behind Corunna Dam in late July after a series of inspections revealed serious problems.

Inspections led DEQ personnel to the conclusion that the structure is at risk of sudden failure. The department issued an emergency order July 25 to the dam's owners, calling for immediate drawdown of the impoundment behind the dam to reduce an immediate threat to the health, safety and welfare of downstream residents and natural resources resulting from a breach that has formed in the dam's spillway. As the breach develops, sudden failure of the spillway could occur, releasing large volumes of water and sediment into the Shiawassee River, DEQ says.

Concrete embankment wall at Wolf Creek Dam complete

The U.S. Army Corps of Engineers moved a step closer to finishing a dam safety project in June at the 270-MW Wolf Creek Dam when crews completed installation of a protective concrete embankment wall, LEX18.com reports.

While this wall does not create a water barrier through the dam's karst limestone foundation, it completes a major stage of construction that is critical to the final stage - the main barrier wall, which is scheduled to be completed by December 2013.

The wall is 6 feet wide and up to 230 feet deep through the dam's clay embankment down to top of rock. It extends 3,800 feet along the length of the embankment. Its purpose is to protect the embankment while the main barrier wall is being constructed.

Treviicos-Soletanche Joint Venture has completed more than 70% of the concrete piles that create the main barrier wall. These piles extend up to 275 feet deep through the embankment and well into the limestone to block openings in the rock. The main barrier wall must be completed before Lake Cumberland can be raised back to its normal levels.

Foundation remediation began in 2008 when the Corps took aggressive action to reduce the risk of failure and to cut off seepage through the limestone caused by erosion of the dam's foundation from water pressure in the reservoir.

The Corps made an emergency decision in 2007 to maintain the lake at elevation 680 feet. Despite these lower lake levels, Lake Cumberland is still the third largest lake in Kentucky.

A refurbishment and safety project at Kentucky's 270-MW Wolf Creek facility is nearing completion after the crew finished construction of a protective concrete embankment wall.
A refurbishment and safety project at Kentucky's 270-MW Wolf Creek facility is nearing completion after the crew finished construction of a protective concrete embankment wall.

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