Dam Safety Awareness Commemorates an Epic Flood

Dam Safety Awareness Commemorates an Epic Flood

The Johnstown Flood of 1889

It had been raining heavily for several days in late May of 1889.  People living below in the narrow Conemaugh Valley were eager for the spring rains to end. Just a month earlier, deep snow had lined the steep ravines of the Allegheny Mountains range and the ground was sodden with the heavy spring runoff. Floodwaters at the South Fork Dam high above the City of Johnstown, Pennsylvania were causing the lake level to rise, threatening to overtop the large earth embankment dam.

Before the dam breachAs the spring rains continued, life was about to change for the working-class city of 30,000 and other communities beneath the South Fork Dam.

Originally constructed in 1852, the South Fork Dam provided a source of water for a division of the Pennsylvania Canal. After a minor breach in 1862, the dam was hastily rebuilt creating Lake Conemaugh. By 1881, the dam was owned and maintained by the South Fork Fishing and Hunting Club, who created a recreational area by the large lake, enjoyed by their elite clientele from nearby Pittsburgh.

Lake ConemaughFor the pleasure of their private members, club owners soon began modifications to the dam. Fish screens were installed across the spillway to keep the expensive game fish from escaping. The dam was lowered by a few feet so that two carriages could navigate the carriage road to the clubhouse. Relief pipes and valves that controlled the water level and spill off from the original dam were sold off for scrap, and rustic cottages were built nearby.

Ignored Warnings

Notoriously leaky, repairs to the earthen dam had been neglected for years.  As torrential rains came down, swollen waters from the lake put tremendous pressure on the poorly maintained dam. With fish screens trapping debris that kept the spillway from flowing and with no other way to control the lake level, the water kept rising.

Aftermath of floodClub officials struggled to reinforce the earthen dam, but it continued to disintegrate. When the lake’s water began to pour over the top, it was apparent that a catastrophic collapse was inevitable and imminent.  Frantic riders were sent down the valley to alert the local communities and tell them to evacuate.  Sadly, few residents heeded the alarm being so often used to the minor seasonal flooding from the Little Conemaugh river.

This time, however, the flood danger was much more serious and deadly.

On May 31, 1889 at 3:10pm, the South Fork Dam washed away, leaving a wake of destruction that killed 2,209 people and wiped the City of Johnstown off the map forever. It took only 10 minutes for the raging torrent of 20 million tons or about 4.8 billion gallons of water to rip through the communities of South Fork, Mineral Point, Woodvale, and East Conemaugh.

Along the way, the deluge accumulated everything in its path, including all sorts of debris—from city buildings, houses, and barns. Piles of boulders, trees, farm equipment, rolls of barbed wire, horse carriages, and railroad cars churned in the turmoil. Embroiled in the devastation were also animals and people—both dead and alive.

By the time the raging waters reached Johnstown at 4:07 pm, the mass of debris was a wave 45-feet-tall, nearly a half mile wide and traveling at 40 miles per hour.

Despite the shocking immensity of this tragedy, relief efforts to the ravaged communities began almost immediately. Emergency shelters for homeless residents popped up and the grim task of cleaning up began.  Volunteers and donations poured in from across the country and world, sending tons of supplies and help. One of the first to arrive was Clara Barton, who had founded the American Red Cross just a few years earlier.

aftermathIt would take months to sift through all the wreckage to find the bodies and years to fully recover from the aftermath.

Lessons Learned

It is widely thought the South Fork Fishing and Hunting Club was to blame for the catastrophic failure of the South Fork Dam. Members of the club neglected to properly maintain the dam and made numerous dangerous modifications. Lowering the dam crest to only about four feet above the spillway severely impaired the ability of the structure to withhold stormwater overflow. The missing discharge pipes and relief valves prevented the reservoir from being drained for repairs and the elaborate fish screens clogged the spillway with debris. The club had also been warned by engineers that the dam was unsafe.

flood damageA hydraulic analysis published in 2016 confirmed what had long been suspected, that the changes made to the dam by the South Fork Fishing and Hunting Club severely reduced the ability of the dam to withstand major storms.1

The South Fork Dam was simply unable to withstand the large volume of stormwater that occurred on that fateful day on May 31, 1889.

Although the South Fork Fishing and Hunting Club failed to maintain the dam, club members were never legally held responsible for the Johnstown Flood after successfully arguing that the disaster was an “act of God.”

Due to what many perceived as an injustice and outrage towards the wealthy club members, American law was ultimately challenged and “a non-negligent defendant could be held liable for damage caused by the unnatural use of land”. This legal action eventually imposed laws for the acceptance of strict liability for damages and loss.

National Dam Safety Awareness Day

On May 31st, we commemorate the catastrophic failure of the South Fork Dam by recognizing this day as National Dam Safety Awareness Day.

The Johnstown flood or the Great Flood of 1889, as it was later known as, was the single deadliest disaster in the U.S at the time. This tragedy, 129 years later, is still a harsh reminder of the critical importance of the proper maintenance and safe operation of dams.

Earth embankment dams may fail due to overtopping by flood water, erosion of the spillway discharge channel, seepage, settling, and cracking or movement of the embankment.

Routine dam evaluations and inspections, as required by law, can identify problems with dams before conditions become unsafe.  Dams embankments, gatehouses and spillways, like other structures, can deteriorate due to weather, vandalism, and animal activity.  Qualified engineering firms can perform soil borings, soil testing, stability analyses, hydrologic and hydraulic modeling for evaluating spillway sizing and downstream hazard potential, arrange for under water inspections by divers, permitting, and assistance in applying for funding for repairs. Also required, are Emergency Action Plans (EAP) that identifies potential emergency conditions and specifies preplanned actions to be followed in the case of a dam failure to minimize property damage or loss of life.

The required frequency of dam inspections will vary depending on the state, but generally are based on hazard classification, with high hazard dams requiring more frequent inspection.   Generally dam inspections should be performed every two years for high hazard dams, unless the state requires more frequent inspections.  The best time of year for inspections is in the fall, when reservoir levels are typically low, and when foliage and tree leaves are reduced, allowing improved visibility around the dam.

A wealth of information on dam safety awareness, can be found at the Association of State Dam Safety Officials website

 

 

 

1Wikipedia.com

 

Dams: To Remove or Not To Remove?

The Hoover Dam created America’s largest reservoir, Lake Mead.

Dams are an integral part of modern day infrastructure, providing many benefits to society. Yet dams have also come under scrutiny in the past few years as they can potentially have a negative effect on an area’s ecology. Some people, including environmental groups, are vehemently calling for the removal of many dams, while others continue to promote the positive impact that dams have on our culture. To remove or not to remove? That is the question.

The Benefits of Dams

Dams have been in existence for over 5,000 years. The first known dam to be built was the Jawa Dam, which was constructed around 3,000 BCE in Mesopotamia. Since that time, dam engineering has progressed significantly, and there are now about 50,000 large dams in use worldwide. The United States currently has 87,000 dams over six feet in height, 2,000,000 dams in total, and 50 major dams — the most in the world. And though they may have an ecological impact, dams admittedly provide myriad benefits, both economically and socially.

Recreation

The most prevalent function of America’s dams is to provide recreation. Families flock to our nation’s lakes that are created by dams for vacations and downtime to enjoy boating, camping, picnic areas, water skiing, fishing, and water sports. Some of the most beautiful and enjoyable vacation spots in the nation are lakes created by dams. In fact, of the top ten most popular vacation lakes in the United States, eight are impounded by dams, including number one on the list, Lake Tahoe. These recreational areas bring in millions of dollars of tourist funds and are important to the economic health of the nation.

Flood Control

Flood control dams impound floodwater to help prevent loss of life and protect property caused by flooding. They also protect farmers’ crops from being destroyed by flood inundation. Protecting people, property, and crops also provides high economic benefit.

Water Storage (Fire & Farm Ponds)

While major dams create massive lakes, thousands of other dams create smaller reservoirs throughout the nation that supply water for industrial, municipal, and agricultural uses. Water from these human-made lakes supply water for livestock and fire protection for cities and towns, as well as industrial uses.

Irrigation

grand-coulee-irrigation
The Grand Coulee Dam in Washington state is a gravity dam on the Columbia River built to produce hydroelectric power and provide irrigation water.

Over ten percent of American crops are irrigated using water impounded by dams. This irrigated farmland provides thousands of jobs to hardworking American people, providing huge economic benefit to our nation.

Mine Tailings

Mine tailings are sometimes overlooked as dams, but there are actually over 1,300 mine tailings impoundments in the United States. The tailings allow for the mining and processing of coal and other minerals while protecting the surrounding environment.

Electrical Generation

While only 2.9% of our nation’s dams provide hydroelectric power, they account for over 35% of our nation’s renewable energy, over 6% of our total electricity, and around 10% of our nation’s total power needs. In fact, the United States is the second largest producer of hydropower in the world, second only to Canada. Hydropower is considered a clean energy source because it does not contribute to air pollution, climate change, or ozone depletion.

Some other uses for dams include debris control and navigation.

Negative Effects of Dams

While our nation’s dams provide many benefits, they also cause many concerns. First, the cost of maintenance sometimes outweighs any positive impact the dam may provide. In addition, dams can also have a negative effect on the environment, and some pose serious hazard to people and property. By 2020, about 70% of our nation’s dams will be over 50 years old and will require significant rehabilitation and repair. In fact, the Association of State Dam Safety Officials has estimated that it could cost over $51 billion to rehabilitate our nation’s non-federally owned dams. Therefore, it is imperative that we consider all aspects of dams and their environmental, economic, and social impact before making any rehabilitation decisions.

Many dams continue to provide benefit to our nation and its communities, while others have simply outlived their useful function. In these cases, it makes sense to remove them rather than to pour increasingly dwindling funds into their repair. Since 1912, over 1,300 American dams have been removed, 62 of these being removed in 2015 alone.

Maintenance vs. Removal

oroville-dam-spillway
The Oroville Dam in California, the tallest dam in the country, suffered spillway damage during controlled water discharges and forced the evacuation of almost 200,000 Californians in February 2017. Photo courtesy of  California Department of Water Resources.

Like all infrastructure, dams require routine and ongoing maintenance to keep them safe and functioning. Frequently, dams are allowed to deteriorate until they pose a threat to public safety, particularly when they have fallen out of usage. In these cases, it is prudent for dam owners to work with state and federal dam experts to determine whether it makes sense to simply remove the dam rather than repair it.

Environmental Impact

One of the most significant impacts that dams have on the environment is interference with migratory fish such as salmon. Dams block the migration of these fish to upstream spawning areas, while also limiting the movement of both sediment and woody debris necessary to the maintenance of downstream spawning grounds. Many environmental activists call for the removal of dams that interfere with fish spawn, citing disruption of local ecology. The good news is that once a dam is removed, species quickly return to their upstream spawning areas, regardless of the length of time that the dam has been in place.

Tourism

Free flowing rivers provide many tourism and recreational opportunities.

While dams provide significant recreational benefits, in some cases they can also hinder them. When a river is returned to its free-flowing state by dam removal, new recreational opportunities arise, including whitewater rafting, kayaking, and fly fishing. These activities can greatly benefit local economies by increasing tourism to these typically remote communities. Also, removing dams can increase the number of recreational and commercial fish species such as trout and salmon. Both commercial fisheries and recreational fishermen benefit from increased catch rates though additional revenue and increased tourism, respectively.

Decreased Cost-Effectiveness

Many aging dams were originally built to supply hydro power to nearby industrial facilities such as mills and factories, and they generate little electricity. Because the nation has shifted away from local power supply to a more regional production, the power generated by these older dams is expensive and, since many of the older factories and mills have permanently shut down, are oftentimes no longer even needed.

Cultural Implications

Many Native American populations place significant spiritual and cultural value on free-flowing rivers and the natural ecology, as evidenced by the long standoff between the federal government and the Standing Rock Sioux tribe. Because dams change the natural ecology and prohibit the free flow of rivers and waters, Native American tribes often view them in a negative light.

Property Value

Dams have the tendency to drive down property values, particularly smaller dams which are no longer used for their original purpose. These dams can present flood risk as well as lower water quality, and removal of these dams improves property values.

In Conclusion

Tata & Howard provided design and construction services for the rehabilitation of the Means Brook Dam in Connecticut. See here for details.

The question remains: to remove or not to remove? The reality is that there is no easy or right answer. The decision on whether to repair or remove a dam is complex, and all contributing factors must be considered carefully before determining the best course of action. The decision must include weighing the current value of the dam, including its social and economic benefits, against the costs of upkeep and the detrimental effects of the dam on the environment. When the dam has little social or economic effect either way, the long-term costs of maintenance versus the cost of removal must be considered.

Thousands of American dams have aged to the point that they require significant repair, while scientific understanding of our world’s delicate ecology and has grown exponentially. Also, advances in economic methodology has highlighted the positive impact that dam removal can have on local and regional communities. Because of these modern-day shifts, it is often considered prudent to remove dams that no longer properly serve their original purpose. At the same time, dams that still function and provide important benefits such as irrigation and flood control are often repaired and maintained. The fact remains that the answer is not clear or definitive. All aspects of a dam, its location, original use, state of repair, social and cultural implications, and surrounding environment must be considered prior to determining the best course of action.