Hydro Review

Dam Safety & Security

ASDSO, DHS launch dam security resource center

The Association of State Dam Safety Officials and the U.S. Department of Homeland Security have launched a Dam Security Resource Center.

This Internet site — housed by ASDSO and supported by DHS Infrastructure Protection, Dams Sector — is intended to provide a comprehensive, open source resource center for dam security.

The site, at http://learningservices.us/asdso, features a variety of information, divided into tabs:

  • Understanding the threat discusses natural, manmade and cyber threats to dam security;
  • Key players elaborates on the roles of owners/operators, regulators, sector-specific agencies and other stakeholders/organizations;
  • Tools and resources provides access to handbooks, guides, and other materials on assessing risk, protecting facilities, crisis management, information sharing, training, conducting exercises, security awareness, cyber security and general topics; and
  • Regulatory information offers data on and links to federal and state regulations.

The site also offers steps for establishing a dam safety program, including conducting a risk assessment, implementing protective measures, developing plans and conducting exercises.

Dam owners and operators can access data on how to develop their expertise, such as learning more about threats, attending dam security events, and visiting other websites with relevant information.

British Columbia releases dam safety report

The Canadian province of British Columbia has released its first-annual dam safety report. The publication is one of a dozen recommendations made by the deputy solicitor general after the failure of Testalinden Dam in June 2010.

There were five dam incidents requiring action in British Columbia last year, in addition to the breach of Testalinden, which sent a wall of mud down on several homes and orchards near Oliver, B.C.

Testalinden Dam likely failed because the spillway and freeboard, the distance between the water’s surface and dam’s crest, were inadequate and insufficient, the dam safety report indicates. The breach has since been stabilized by the dam owner, according to the report.

The five remaining incidents took place at Goertzen Pond Dam near Osyoyoos, Grafton Lake Dam on Bowen Island, Eagle Rock Reservoir south of Chase, Allan Springs Reservoir in Saanich and John Hart Dam on the Campbell River. Dam owners were required to lower water levels, remove a beaver dam, clear a spillway of obstructions, remove vegetation and improve structural problems.

The number of dam owners who complied with reporting requirements increased to 93 percent, up from 87 percent the year before. However, those responses are inconsistent and difficult to interpret, reports indicate. The report recommends more concise questioning in the future.

There were 99 dam safety audits last year, which falls short of the target of 113 because staff were focused on the Rapid Dam Assessment program put in place after the Testalinden mudslide.

Of the 1,900 dams in the province, about 1,200 are considered low risk.

Full pool allows testing of Howard Hanson Dam work

In late June, the reservoir behind Howard Hanson Dam reached full summer pool at an elevation of 1,167 feet above sea level. Reaching this level allows the U.S. Army Corps of Engineers to run tests designed to gather date on the completed right abutment drainage improvements, as well as repairs still being completed.

The dam is a 235-foot-tall earth and rockfill structure on the Green River in western Washington, completed in 1962 for flood control, fish enhancement and water conservation.

In January 2009, the Corps discovered problems with water storage behind Howard Hanson Dam when, after a heavy rain, two depressions formed on the abutment, water levels increased in the groundwater monitoring wells and silty water entered the abutment drainage tunnel. During that storm, the Corps stored a record amount of water in the reservoir to prevent flooding.

The Corps determined there is no imminent risk of dam failure. However, the Corps was not confident about using the full flood storage capacity of the dam.

Work being performed or completed includes building a seepage barrier and improving drainage tunnel function. Nicholson Construction was hired under an $8.9 million contract to build the barrier, and Jensen Drilling Company was hired under a $900,000 contract to complete drainage tunnel work.

Among other things, the Corps is measuring seepage rates through the abutment and functionality of the new drains. The Corps says it will share the findings of its testing with national experts and will determine, before November, if the dam can return to its authorized flood risk reduction operation. The results will be used to determine possible further interim measures, as well as long-term repairs.

Virginia awards $855,000 for dam safety, floodplain work

The Virginia Department of Conservation and Recreation is awarding a total of $855,000 in grant money to 73 dam and floodplain projects.

Dam owners receiving the awards include cities, towns, water and service authorities, homeowner and recreation associations and individuals. Grant amounts ranged from less than $4,000 to more than $24,000. The grants will be used to fund dam break inundation zone analysis, mapping and digitization; emergency action plans; incremental damage analysis; and engineering costs related to dam repairs.

Local governments also were awarded grants for flood prevention and protection. Funds can be used for local flood warning and response systems, to improve local floodplain programs and to improve floodplain information and education programs.

This money comes from the Virginia Dam Safety, Flood Prevention and Protection Assistance Fund.

Gate failure temporarily drops water levels in river

Heuvelton Dam, on the Oswegatchie River in New York, suffered a failure of one of the spillway gates in early June, resulting in a significant drop in water levels in the river, media reports indicate.

Heuvelton Dam, owned by Brookfield Renewable Power, impounds water for a 900-kW hydro project. The powerhouse, one of six in the Oswegatchie Project, began operating in 1924.

Brookfield says the dam has six flood gates, two of them inflatable. On June 7, one inflatable gate ruptured and deflated. This is the second time it has failed in 10 years. The possible cause of the rupture could be a failed compressor.

Water levels in the river upstream from the dam began to drop. Representatives from the New York Department of Environmental Conservation visited the dam to determine if there was any damage to the environment as a result of the rupture, such as drying of smallmouth bass nests or sediment washing downstream.

Brookfield secured the gate and installed a temporary bulkhead upstream. The company then planned to conduct an investigation to determine the actual events.

Working group focuses on dam and levee safety

The Dam and Levee Safety Technical Working Group focuses on the development of sound monitoring techniques and specific decision criteria implementation to provide the best detection, decision-making and notification of an event at a dam or levee that would warrant warning and evacuation of the affected populace.

This working group is part of the Data Collection Sub-Committee of the National Hydrologic Warning Council.

Implementation strategies of the technical working group include:

  • Education for dam and levee owners of the risk that their structures pose to the downstream and protected populations;
  • Promotion of the ideas of providing effective warnings through adequate detection and specific decision criteria implementation;
  • Encouragement of dam and levee owners to interface with the local response officials and emergency managers through dam and levee emergency action plan development and exercises;
  • Technical support through shared experiences, resources and reviews of consultant proposals; and
  • Guideline development to provide documentation support for dam and levee owners.

For more about this group, E-mail: dam-levee@hydrologicwarning.org.

The National Hydrologic Warning Council is a non-profit organization dedicated to assisting emergency and environmental management officials by providing expert advice on the use of real-time, high-quality hydrologic information from automated remote data systems. The council was formed in 1993 and incorporated as a stand-alone organization in 2005.

David C. Curtis, Ph.D., vice president of WEST Consultants Inc., is president of the council.

Board approves raising, strengthening Forebay Dam

The El Dorado Irrigation District board of directors recently approved a recommendation to buttress and raise the El Dorado Forebay Dam in California, said GEI Consultants Inc., the firm that made the recommendation.

El Dorado Forebay Dam is on the Long Canyon River in El Dorado County, Calif., and is used for recreation, among other things. The 88-year old Forebay Dam will be raised about 10 feet once construction is complete. The project will improve dam safety, increase the reliability of domestic water supply and increase hydroelectric revenue.

El Dorado Forebay Dam has been found to not meet the California Division of Safety of Dams (DSOD) seismic stability criteria. The District tasked GEI Consultants with conducting a detailed evaluation of various project alternatives that would meet DSOD’s criteria and as well preserve the district’s water supply and hydroelectric power generation.

The district has commissioned GEI to continue with design of the selected project and guide it through the DSOD and FERC review. GEI will also assist in preparing technical information for the environmental review process.

Corps prepares for more work at Canton Lake Dam

The U.S. Army Corps of Engineers is preparing for the second phase of work to be performed at Canton Lake Dam on the North Canadian River in Oklahoma.

This work includes construction of a concrete weir and hydraulic structures as part of an auxiliary spillway. Canton Lake, a 68-foot-tall, 15,140-foot-long earth-filled embankment, includes a 778-foot-wide spillway at the right abutment with 16 tainter gates. Corps hydraulic studies found the spillway is unable to discharge a probable maximum flood and the dam is likely to fail during a major flood.

The Corps has begun construction of an auxiliary spillway at the right abutment. Under the current contract, a 480-foot-wide auxiliary channel has been partially excavated. Fifty-foot-tall vertical diaphragm walls line the channel. The Corps chose a Fusegate system from Hydroplus Inc. for the new spillway.

The next phase of the work includes placement of a concrete weir about 35 feet deep and 70 feet long spanning the width of the channel. Other work includes a 40-foot-tall water intake monolith with a 47- by 15-foot base; 250 feet of 11-foot-diameter conduit; 30-foot-tall, 50-foot-wide Fusegates; diaphragm walls with anchors; and stop-log manufacture. The work is valued at $25 million to $100 million.

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