Dam Safety & Security

More than 140 dams to be repaired in British Columbia

The Canadian province of British Columbia is requiring remedial work on more than 140 dams, based on the results of a rapid assessment of structures after the collapse of Testalinden Dam in June 2010.

Testalinden Dam is a privately-owned structure built in the 1930s for water storage and irrigation. On June 13, 2010, the dam failed, causing a torrent of debris and mud that affected 14 private properties, including three with homes.

An independent review revealed that the Ministry of Environment issued several concerns and warnings to make repairs to maintain the dam’s integrity. There is no indication the repairs were made or that the owner was being held accountable to make those repairs. Two days before the failure, a hiker noticed that water from the lake was overflowing onto the road. This was not deemed to be urgent because it was a “non-status road” (as opposed to a forest service road). Thus, the information was not reported to the proper authorities before the collapse.

This rapid assessment included a rating system for dams. Of the more than 600 dams assessed, the ministry ordered immediate actions in three cases. Another 140 dams were not deemed as urgent, but repairs are necessary to ensure their continued safe operation.

Environment Minister Barry Penner also has instructed his deputy to produce an action plan that addresses the 12 recommendations made in a report on the Testalinden Dam collapse. These recommendations, intended to prevent a recurrence, include several for the Environment Ministry:

– Review and update the dam safety regulation to “incorporate best practices on dam safety found in other jurisdictions;”

– Consider further regulatory oversight to enhance enforcement and compliance; and

– Ensure the consistent oversight and regulation of all water-related structures.

Spillway control structure to be installed at Folsom Dam

The U.S. Army Corps of Engineers has awarded a $125.9 million contract to California-based Granite Construction Company to build an auxiliary spillway control structure for 198.72-MW Folsom Dam on California’s American River.

The auxiliary spillway is being built to address the hydrologic risk to Folsom Dam identified by the Bureau of Reclamation’s Safety of Dams program. The work is a joint federal project by Reclamation, the Corps, California Department of Water Resources, and Sacramento Area Flood Control Agency.

The control structure includes foundation excavation and preparation, submerged tainter gate fabrication, and installation and mass concrete placement. The structure includes two 89-foot-wide independent flow-through monoliths flanked by three non-flow-through monoliths. Each flow-through monolith is to house three submerged tainter gates, 23 feet wide by 34 feet tall.

The spillway itself is being built by Oregon Mt. Construction Co. under a $48.8 million contract awarded in 2008.

The Interior Department said in April that Reclamation would invest $22.3 million in stimulus money from the American Recovery and Reinvestment Act of 2009 to address dam safety concerns at the high-risk Folsom Dam.

CDA 2010 attendees discuss dam safety, other topics

The Canadian Dam Association (CDA) held its annual conference recently at Niagara Falls, Ontario, Canada, highlighting a range of dam-related topics. The association also has announced plans for 2011’s annual conference.

The CDA 2010 Niagara “Partnering for a Safer Future” event, held October 2-7, provided a unique professional development opportunity on a broad range of subjects, including dam safety.

CDA 2010 offered a total of eight workshops, providing delegates opportunities to improve their understanding, develop skills, and discuss with peers and experts in their field. Topics discussed at the conference include dam safety reviews, surveillance and monitoring, internal erosion of embankment dams, risk management, emergency preparedness, extreme floods, seismic analysis, slope/stability analysis, case histories of failures, public safety measures, new techniques in dam construction and rehabilitation, and concrete technology.

CDA has planned its 2011 annual conference for October 15-20 at the Delta Fredericton Hotel in Fredericton, New Brunswick. The event will include workshops, technical paper presentations, tours, exhibitor presentations, and other features.

For more information about the CDA 2011 conference, visit www.cda.ca.

Grout curtains to be installed at two Corps dams

The U.S. Army Corps of Engineers plans to install two grout curtains as part of emergency dam safety repairs to 270-MW Wolf Creek Dam at Jamestown, Ky., as well as construct a grout curtain at 112-MW Beaver Dam’s Dike 3 near Eureka Springs, Ark.

The Corps previously identified the earthfill and concrete gravity dam at Wolf Creek as being critically near failure or having extremely high life or economic risk. Money to repair the dam was included in economic stimulus appropriations approved by Congress. A 2008 assessment of equipment at nine Corps hydropower plants on the Cumberland in Tennessee and Kentucky, including Wolf Creek, found a need for up to $470 million in repairs.

The Corps awarded a $341.4 million contract for a 4,200-foot-long concrete seepage barrier at Wolf Creek to Treviicos Soletanche JV of Boston in 2008. The cutoff wall is the primary element of the seepage rehabilitation project. Work began in fall 2008; the contract performance period is four years.

The Corps now plans to commission installation of a grout curtain from the right end of the gallery to the base of the right abutment, constituting a grout line about 1,500 feet long and 140 feet deep. Also included is a separate grout curtain in the power plant plaza adjacent to an existing diaphragm wall. The 600-foot-long plaza grout curtain requires drilling and installing casing through about 70 feet of soil prior to constructing a 60-foot-deep grout curtain in rock.

The work is expected to cost $5 million to $10 million.

The multi-purpose Beaver Dam was completed in 1966 on the White River. The dike’s embankment consists primarily of clay with a dolomite rock foundation. The top of the rock averages 15 feet deep. The grout curtain is needed to deal with seepage through the dike.

In October 2010, the Corps’ Little Rock District awarded a $1.7 million contract to Pennsylvania-based Nicholson Construction Company to install a 700-foot-long grout curtain with holes drilled on 6-foot centers to a depth of about 60 feet. Either a single-line or triple-line grout curtain is to be constructed, depending on the condition of the foundation rock and results of grouting the first single line.

FEMA releases poster on identifying dam risk

The Federal Emergency Management Agency (FEMA) offers Identifying High Hazard Dam Risk in the United States, a poster.

In 2009, more than 1,800 dams were classified as high hazard, meaning the failure or misoperation of these dams likely will result in loss of life. The American Society of Civil Engineers and Association of State Dam Safety Officials say the cost to repair deficient dams is $50 billion for all of them or $16 billion for only high hazard dams.

FEMA leads the National Dam Safety Program, a partnership of states, federal agencies, and other stakeholders formed to encourage individual and community responsibility for dam safety. Activities of the program include providing grants for the improvements of state dam safety programs, funding dam risk reduction research initiatives, delivering training to state dam safety staff and inspectors, and providing for the education of the public (including state and local officials) in the hazards of dam failures.

The National Dam Safety Program covers more than 83,000 dams. This poster features a map of the U.S. that identifies the location of each of these dams and their hazard categories: high, significant, or low. It also breaks down these dams by owner (federal, state, local, private, public, and unknown). The poster features a bar graph that illustrates how the number of high-hazard dams in need of remediation has grown over the years.

– To download the poster, visit www.fema.gov, click on Search for Resources, and search for keyword “identifying,” hazard type “dam/levee break.”

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