National Dam Safety Awareness Day

There are over 87,000 dams in the United States. With one-third of those dams posing a serious threat to people’s lives and property if they fail, dam safety is nothing to ignore. Dams are a critical part of our infrastructure providing flood protection, water supply, hydropower, irrigation, and recreation. Although dam safety may not seem to be a big concern, dam failure can affect people for miles and miles, with sometimes fatal results. National Dam Safety Awareness Day is a day to acknowledge the progress we have made in making our dams safe structures and the continuous progress we still have yet to make.

Damage caused by Lake Delhi Dam failure in Iowa, July 27, 2010
Damage caused by Lake Delhi Dam failure in Iowa, July 27, 2010

As our population keeps growing, our dams are getting older and some are even deteriorating. A dam can fail within hours of the first signs of breeching. Dam safety is a shared responsibility. Dam owners, engineers, community planners, along with federal and state leaders all have important roles in keeping dams running efficiently and safely.

The National Dam Safety Program (NDSP), led by FEMA, has been working for 30 years to keep Americans safe from dam failures. The NDSP assists states in establishing and maintaining dam safety programs along with providing technical training to state and federal dam safety staff. Their support for research and development has greatly helped raise awareness about improper dam safety along with lessening the impact on a community if a dam were to fail.

Why Dams Fail

One of the most frequent ways dams fail is overtopping. Overtopping is a strong indicator of an unsafe dam. This can happen due to a number of reasons but typically it is from inadequate spillway design, debris blockage, or settlement of the dam crest. Overtopping accounts for about 34% of all dam failures in the United States and can also lead to erosion of the downstream face of the dam. Without proper maintenance of the downstream face, the dam is at a heightened risk of failure. Wind and other harsh weather conditions can cause waves to erode the upstream face which can make the dam unsafe during heavy rainfall or flash floods.

Missouri River Flood: Breeching of the levee at mile 550 in Aitchison County, June 19, 2011
Missouri River Flood: Breeching of the levee at mile 550 in Aitchison County, June 19, 2011

Other important factors that can cause dam failure are seepage and foundation defects. These defects account for about 30% of dam failures in the US, typically due to slide failure. If seepage or other factors weaken the soil supporting a dam, the overall strength of the dam greatly diminishes, creating the potential for a landslide-like affect.

Improper construction measures such as insufficient soil testing also contribute to dam failures. When permeable cavities or course gravel are present in dam foundations, seepage is a big concern because it erodes the soil at a fast rate. This often results in the dam settling or sinking which causes failure. A dam can fail by water passing under, over, through, or around it. Every dam should be properly connected to the ground and constructed using the best materials and methods to meet current design and construction standards.

How to Prevent Failures

When constructing and maintaining a dam, taking the proper engineering steps is vital. For example, completing sufficient soil tests prior to construction helps ensure that the dam will be adequately supported. The soil on the actual site should be examined before any detailed planning is put into place. It is also important to confirm the existence of impervious clay to seal the excavation and form the core of the bank. Failures can be prevented if the contractor is aware of any soil limitations at the site.

Teton Dam failure, June 5, 1976
Teton Dam failure, June 5, 1976

Dam failures have taken the lives of hundreds of people in recent decades so it is important to hire the right contractors to do the proper work. Nothing can take the place of a reliable and reputable contractor. Having experienced engineers and machine operators greatly reduces the risk of failure. It is important to review every employee’s credentials before starting a job and to always seek professional advice from an engineer when planning and designing a dam. Improper construction and inspection can lead to a weak structure, which can be dangerous and, sometimes, even fatal.

Maintenance and inspection must be routinely completed in order to keep dams safe. If a problem associated with a dam is not addressed in a timely manner, it can become more dangerous as time goes on. Dam inspectors should document every inspection in order to accurately assess needed repairs. While maintaining a dam, vegetation control, erosion repair, and clearing debris from spillways should be a routine practice.  A healthy layer of grass can help prevent erosion, and any debris within 25 feet of the dam should be removed. A poorly maintained dam can cost the owner more to repair than a dam which is regularly inspected and checked for needed repairs.

Emergency Action Plans

Damage left behind after the Teton Dam failure, Rexburg, Idaho, 1976
Damage left behind after the Teton Dam failure, Rexburg, Idaho, 1976

173 dams across the country have failed since 2005 so it is important to know what your community’s Emergency Action Plan (EAP) is if a local dam were to fail. An up-to-date EAP is critical to reduce the risk of lost lives and property damage. A good EAP accomplishes three main goals: identify the area below the dam that would be flooded, establish a line of communication for the dam owner and emergency response, and provide warnings and evacuations to be conducted by local emergency teams. Below are the six essential elements of a successful EAP.

  1. Notification Flowchart. This is to identify who should be notified by whom, and in what priority. This information is crucial for the notification of the persons in charge of taking emergency actions. The flowchart should have detailed information about each position in the chart such as title, office, and multiple ways of contacting that individual. EAPs should include the residents and businesses downstream of the dam that should be notified in case of an emergency. Proper communication and assigned roles can drastically reduce the impacts of a dam failure.
  2. Emergency Detection, Evaluation, and Classification. This ensures that the appropriate course of action is taken based on the urgency of the situation. Having procedures in place to classify an emergency situation properly will better prepare a community to activate their EAP before a catastrophe occurs. Early detection of a potential problem can save hundreds of lives and millions of dollars in property damage.
  3. Responsibilities. When an emergency occurs, everyone should know their role in reacting to the situation. Typically, the dam owner’s responsibilities include developing, maintaining, and implementing the EAP while state and emergency management officials are responsible for warning and evacuation. Without proper assignment of responsibilities, the EAP would be ineffective.
  4. Preparedness. This section outlines actions to be taken before an emergency occurs. Preparedness actions are taken to moderate or minimize the effects of a dam failure and to identify specific responses to be taken in emergencies.
  5. Inundation Maps. An inundation map identifies the areas affected if a dam were to fail. This map is important in identifying a strategy to notify and evacuate areas in danger. These maps graphically display flooded areas and show travel times for wave front and flood peaks at critical locations.
  6. Appendices. This section contains information directly applicable to the actions of the dam owner and the emergency management parties. The appendices provide information that supports the material used to develop the EAP such as maintenance requirements and dam break investigations.

In Conclusion

Dams serve an important role in our nation’s infrastructure. Millions of people in every state rely on dams to bring them benefits such as flood control, water supply, irrigation, recreational areas, and renewable energy. Safe operation and maintenance is important to sustaining these advantages and avoiding disasters which are very often preventable.  Dams fail for a number of reasons but the primary source of failure is poor inspection and maintenance, inadequate design, and improper operation. Know your risk when it comes to dam failure in your community. Getting familiar with your community’s EAP and level of risk from a dam failure can greatly help you in an emergency situation. National Dam Safety Awareness Day is an opportunity to raise awareness about our nations deteriorating dams and to take steps in making them safer structures for our community.

Happy National Dam Safety Awareness Day!

Subscribe-to-our-newsletter1

Dam Safety and the Criticality of Emergency Action Plans

Devastation from the Ka Loko Reservoir Dam breach in 2006

This month marks the ten year anniversary of Hawaii’s Ka Loko Dam failure on the island of Kauai. On March 14, 2006, after 40 days of heavy rainfall, the rising water finally overtopped the dam near the original spillway — which had been filled in by the owner. At the time, the State of Hawaii lacked resources and legal authority to properly ensure that the owner fully addressed safety concerns. The break sent almost 400 million gallons of water downstream four miles until it finally reached the ocean, and the water reached about 20 feet in height, destroying whatever was in its path, including trees, homes, and vehicles. The disaster, which was entirely preventable, killed seven people, including a pregnant woman and child, and caused millions of dollars of property damage as well as significant environmental damage. As a direct result of the disaster, Hawaii increased funding to its dam safety program, allowing for improved regulation of local dams.

Historic U.S. Dam Failures and Legislation

Unfortunately, the Ka Loko Dam failure in Hawaii was not an isolated incident. Dam failures in the United States have caused catastrophic damage and loss of life for well over a century:

Aftermath of the 1874 Mill River Flood in Williamsburg, MA
Aftermath of the 1874 Mill River Flood in Williamsburg, MA

May 16, 1874 – Williamsburg, Massachusetts
At 7:20 a.m., the 43-foot-high Mill River Dam above Williamsburg, Massachusetts failed, killing 138 people, including 43 children under the age of ten. At the time, this failure was the worst in U.S. history.

May 31, 1889 – Johnstown, Pennsylvania
Over 2,200 people — more than 20% of the residents of Johnstown — perished in the flood caused by the failure of South Fork Dam, nine miles upstream. To this day, the South Fork Dam disaster is the worst in U.S. history. National Dam Safety Day is celebrated each May 31 in remembrance of the catastrophe.

Around the turn of the century, many more dam failures occurred, resulting in the passing of some early state dam safety legislation.

March 12,1928 – San Francisquito Canyon, California
The failure of St. Francis Dam, which killed over 450 people and caused over $13 million in damage, the equivalent of about $180 million by today’s standards, was a landmark event in the history of state dam safety legislation, spurring legislation not only in California, but in neighboring states as well. It was also the worst civil engineering disaster of the 20th century, serving as the catalyst for the engineering licensure requirement in California.

Only one small section of the St. Francis Dam remained after its catastrophic failure in 1928
Only one small section of the St. Francis Dam remained after its catastrophic failure in 1928

In response to the St. Francis Dam disaster, the California legislature created an updated dam safety program and eliminated the municipal exemption. In addition, the State was given full authority to supervise the maintenance and operation of all non-federal dams. However, even in the wake of such a horrific disaster, most other states had severely limited dam safety laws — that is, until a series of dam failures and incidents occurred in the 1970s:

February 26, 1972 – Buffalo Creek Valley, West Virginia
The failure of a coal-waste impoundment at the valley’s head took 125 lives, and caused more than $400 million in damages, including destruction of over 500 homes.

June 9, 1972 – Rapid City, South Dakota
The Canyon Lake Dam failure took an undetermined number of lives (estimates range from 33 to 237). Damages, including destruction of 1,335 homes, totaled more than $60 million.

June 5, 1976 – Teton, Idaho
Eleven people perished when Teton Dam failed. The failure caused an unprecedented amount of property damage totaling over $1 billion.

July 19-20, 1977 – Laurel Run, Pennsylvania
Laurel Run Dam failed, killing over 40 people and causing $5.3 million in damages.

Damage from the Toccoa Falls, Georgia dam failure in 1977
Damage from the Kelly Barnes Dam in Toccoa, Georgia dam failure in 1977

November 6, 1977 – Toccoa Falls, Georgia
Kelly Barnes Dam failed, killing 39 students and college staff and causing about $2.5 million in damages.

In response to these tragedies, President Jimmy Carter implemented the “Phase I Inspection Program” that directed the US Army Corps of Engineers to inspect the nation’s non-federal high-hazard dams. The findings of the inspection program, which lasted from 1978-1981, were responsible for the establishment of dam safety programs in most states, and, ultimately, the creation of the National Dam Safety Program, which today supports dam safety programs in 49 states. Alabama is the only state in the nation that has yet to pass dam safety legislation, although Alabama State Representative Mary Sue McClurkin introduced a bill on March 18, 2014 which, if passed, would establish a state dam safety program.

Emergency Action Plans

One of the key components of a successful dam safety program for high hazard and significant hazard dams is a comprehensive, up-to-date Emergency Action Plan (EAP). Hazard level does not reflect the condition or age of the dam; rather, it indicates the potential for loss in the event of dam failure. According to FEMA, the classifications are as follows:

High hazard: Facilities where failure will probably cause loss of human life. Such facilities are generally located in populated areas or where dwellings are found in the flood plain and failure can reasonably be expected to cause loss of life; serious damage to homes, industrial and commercial buildings; and damage to important utilities, highways, or railroads.

Significant hazard: Facilities where failure would likely not result in loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities. Such facilities are generally located in predominantly rural areas, but could be in populated areas with significant infrastructure and where failure could damage isolated homes, main highways, and minor railroads or disrupt the use of service of public utilities.

Low hazard: Facilities where failure would result in no probable loss of human life and low economic and/or environmental losses. Such facilities are usually located in rural or agricultural areas where losses are limited principally to the owner’s property or where failure would cause only slight damage to farm buildings, forest and agricultural land, and minor roads.

Map courtesy of James S. Halgren, Office of Hydrologic Development, National Weather Service, National Oceanic and Atmospheric Administration
Map courtesy of James S. Halgren, Office of Hydrologic Development, National Weather Service, National Oceanic and Atmospheric Administration

Unfortunately, about 22% of high hazard dams and 40% of significant hazard dams nationwide still do not have EAPs, meaning that thousands of dams across the United States lack EAPs required by law. And dams are still failing. According to the Association of State Dam Safety Officials, 173 dams across the United States have experienced failures since 2005.

The lack of an EAP could be problematic in the event of dam failure, said Mark Ogden, project manager for the Association of State Dam Safety Officials, who also noted that while such worst-case scenarios are rare, they have happened. “An exercised, well-prepared emergency action plan is a valuable tool to help save lives,” Ogden said.

Ogden also noted that even when dams have an EAP, downstream residents often do not know where to find it. “There have been a lot of efforts in recent years to try to make the public aware of dams and the potential dangers, and to know if they live in an area downstream of a dam, the failure inundation zone, who to talk to – whether it’s the dam owner or more likely the local emergency management officials – to find out if there is an EAP for that dam and what they would need to do,” Ogden said.

Legislation

The Saville Dam in Barkhamsted, Connecticut is rated high hazard
The Saville Dam in Barkhamsted, Connecticut is rated high hazard

The good news is that most states have responded to the need for dam safety regulations and require EAPs for high hazard and significant hazard dams. The most recent legislation came in February of this year, when the State of Connecticut Department of Energy and Environmental Protection (DEEP) adopted new regulations concerning the preparation and update of EAPs for Class C and Class B dams. In 2013, fewer than 60% of regulated high hazard dams in Connecticut had an EAP, a statistic the State is hoping to drastically improve. The new EAP regulations include criteria for inundation mapping, dam monitoring procedures, formal warning notification and communication procedures, emergency termination protocols, and EAP review and revisions.

Currently, the only states without EAP requirements are Georgia, Illinois, Iowa, Kentucky, North Carolina, Vermont, Wyoming, and — ironically enough — California. Since Alabama still has no formal dam safety program, they also do not require EAPs.

Lake Martin in Alabama was created by the construction of the Thomas Wesley Martin Dam, which stopped the flow of the Tallapoosa River just southwest of Dadeville. It is the largest man-made lake in Alabama.
Lake Martin in Alabama was created by the construction of the Thomas Wesley Martin Dam, which stopped the flow of the Tallapoosa River just southwest of Dadeville. It is the largest man-made lake in Alabama.

ASDSO continues to work alongside the American Society of Civil Engineers (ASCE), American Council of Engineering Companies (ACEC), and other stakeholders to promote dam safety and to encourage legislation to protect the public and the environment from disasters such as the Ka Loko Dam failure in Kauai, Hawaii.

“The tenth anniversary of the dam’s failure reminds us of the potential dangers posed by dams and the critical importance of both responsible dam ownership and strong dam safety programs,” said Lori Spragens, executive director of the Association of State Dam Safety Officials (ASDSO). “Most dam failures are preventable disasters. Dam owners must keep their dams in the state of repair required by prudence, due regard for life and property, and the application of sound engineering principles. The quality of dam maintenance, emergency planning, and enforcement programs directly affects the safety of communities, as sadly demonstrated on Kauai. With more than 87,000 dams of regulatory size in the U.S., we all have a stake in dam safety.”Subscribe-to-our-newsletter1