Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole.
And I’m Brian.
Happy New Year!!
We’re off, taking in some much needed R&R. Making goals for 2023.
But we didn’t want to leave you hanging, so today we are bringing you one of our mini failures. This one is mini failure 22 about the Johnstown Flood or the Great Flood of 1889. Caused by collapse of the South Fork Dam upstream of Johnstown Pennsylvania.
Before we get into the failure, we have some engineering news. This one is about the Exchange Tower in Detroit Michigan.
● You might have heard about it, they are building it from the top down.
● The exchange tower is a 207 ft (63m) tall, 16 story residential tower using the LIFTbuild technology construction method.
● Essentially they are building floors on the ground, and hoisting them up to their final place in the tower.
● They started by building the core (or spine as they're calling it) , which is two concrete structures in the middle of the floor plate that hold the elevator and staircases. Then each floor is constructed on the ground and hoisted up into place by the spine.
● The construction method was chosen as a way to eliminate fall hazards and inefficiencies. And they are intended to reduce costs by 10-20% and schedule by 30%, which is a tall order.
● The lifts take about 7 hours per floor, and another 4 hours to lock them into place.
● This is a pretty cool construction method, something I haven’t quite seen before; although there are similar methods being used where parts of buildings are prefabricated off site before being installed with the rest of the building.
● That said, this building in Detroit has the same offset windows as a building we have in Calgary called the Hub and I hate it! For a variety of reasons, some of which are logistical and some of which are aesthetic, the windows are not in line and offset on each floor. And while I get it, I don’t want to look at it.
● So if you want to read more about the exchange tower in detroit, the link to the article can be found on the webpage for this episode at failurology.ca
Without further adieu, here is our mini failure on the Johnstown Flood.
Hi, and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole
And I’m Brian. And we’re both from Calgary, AB.
Welcome to our twenty-second mini-failure episode.
We’re bringing you engineering failures in bite-size pieces.
Make no mistake, these are still significant failures, but they either have pretty straightforward causes or not enough information available for a full episode.
These episodes are also just the failure, no news and no ads (for now at least).
It’s like Failurology-lite.
This week’s mini failure is about the Johnstown Flood, also known as The Great Flood of 1889.
● This flood happened on May 31, 1889 - 133 years ago - when the South Fork Dam 23km upstream of Johnstown, Pennsylvania, USA catastrophically failed after several days of extremely heavy rainfall.
● Fun fact, Johnstown is about 2.5 hours west of Three Mile Island that we covered in episode 41.
South Fork Dam
● The South Fork Dam was an earthen works dam. We’ve talked about these types of episodes, but to recap, they are essentially a mound of dirt that’s meant to hold back water. They are of course engineered for water forces and materials used, but to non dam builders such as myself, they look like hills of dirt.
● It was built on the Conemaugh (con-a-mauh) River between 1838-1952 by the state of Pennsylvania as part of a canal system to be used as a reservoir for the state's canal basin. It was sold to the Pennsylvania Railroad - which was eventually acquired by Amtrak - and then sold again to private groups. The group that owned the dam at the time of its demise was the South Fork Club - a hunting and fishing club.
● The dam was 22m high, 284m long, 3m wide at the crest and 67m wide at the base
● The outlet works included a stone-lined culvert with five valves for releasing varying flow. There was also a spillway on the east abutment; the plans called for a 45m wide spillway, but the actual width installed was only 21m wide.
● After a decade of poor maintenance, the outlet culvert collapsed and a portion of the dam washed out. The dam had sprung a number of leaks between 1881 and its demise in 1889.
● A previous owner had also sold three of the cast iron discharge pipes from the collapsed culvert for scrap - these pipes allowed a controlled release of water, which seems very important.
● In addition to failed portions of the dam, the South Fork Club also lowered the dam crest to allow carriage travel across it, adding a mesh screen on the spillway to prevent loss of fish and using brush, clay and hay to patch the washed out segments.
● When a low pressure weather system reached western Pennsylvania on May 28, 1889, it was the heaviest rainfall event ever recorded in that part of the US. An estimated 150-250mm of rain fell over 24 hours.
● When residents around Lake Conemaugh - the reservoir created by the dam - the water was nearly cresting the dam. They worked to unclog the spillway, which was blocked by a broken fish trap and debris. Another group tried to dig a ditch to divert water out of the reservoir before it could overtop the dam. And more residents tried to pile mud and rock on the face of the dam to save the eroding wall. All while raining intensely. None of these groups were successful.
● An engineer at the dam sent word to Johnstown twice, by telegraph, to warn them of the dangerous situation at the dam, but the message never arrived.
● By 1pm, exhausted from trying to protect the dam, the residents retreated to high ground.
● Between 2:50-2:55pm the dam breached. It took about 65 minutes to empty 14.55 million cubic metres (or almost 91 million bathtubs) of water in the reservoir once the dam started to fail.
● As the mass of water made its way down the Conemaugh River, it picked up trees, houses, and a lot of other debris. It reached a 24m high railroad bridge called the Conemaugh Viaduct and the debris jammed against the stone bridge’s arch; until it collapsed within 7 minutes.
● The flood reached Johnstown 57 minutes after the dam collapsed, water travelling at 64 kph and reaching a height of 18m in places - equivalent to a 6 storey building and double playground speeds.
● In Johnstown, the Stone Bridge, a seven-arch railroad bridge, created a temporary dam from the debris carried by the flood. This caused a surge rolling upstream, which thanks to gravity returned back to the dam and a second wave of water hit the city. To make matters worse, the debris caught by the bridge caught fire and burned for three days. The debris pile spanned 121,000 square metres and was 21m in height. It took workers 3 months to remove it all, mostly due to a huge amount of barbed wire from the ironworks factory entangled in the wreckage. They eventually used dynamite to clear it.
● An estimated 2,209 people died from the flood. This included:
○ 99 entire families
○ 396 children
○ 124 women
○ 198 men
○ 98 children were orphaned
○ 777 people were never identified
○ Human remains believed to be from the flood were found as far away as Cincinnati Ohio; which is a 6 hr drive west. Holy forking shirt balls folks. That’s a long way from home.
● 1,600 homes destroyed
● $17 million in property damage - $540 million in 2022 dollars
● 10 square kilometres of downtown Johnstown were completely destroyed
● Rail service was restored 2 days later by building a temporary trestle bridge in place of the Conemaugh Viaduct. This allowed food, clothing, medicine and other provisions to arrive and aid in the recovery.
● The founder and president of the American Red Cross, Clara Barton arrived 6 days after the flood and stayed for 5 months. The American Red Cross had only been in operation for about 8 years at this time.
● At its peak, the army of relief workers totalled about 7,000.
● Frank Shomo, the last known survivor died in 1997 at 108 years young.
Investigation & Legal
● The American Society of Civil Engineers appointed a committee five days after the flood to investigate the disaster
● James B Francis, one of the founding members of the ASCE, and a hydraulic engineer, led the investigation.
● They visited the dam, reviewed the original engineering design and modifications, interviewed eyewitnesses, commissioned a topographic survey of the dam remnants and performed hydraulic calculations
● For fear of being involved in litigation, the report was not made public until 2 years after the flood.
● The report found that even if the dam had been maintained to the original design specifications - with a higher embankment crest and five large discharge pipes. However a 2016 hydraulic analysis contradicts these results and confirmed that changes made to the dam significantly reduced its ability to withstand major storms. Lowering the dam by about 1m and failing to replace the discharge pipes reduced the capacity by half.
● Survivors blamed the South Fork Club for their modifications to the dam and accused them of failing to maintain the dam properly. However, the lawyers for the club, two of whom were members, argued that the flood was a natural disaster and the club was not held legally responsible and paid no legal compensation.
● Even so, several club members contributed thousands to the recovery and rebuilding of Johnstown and surrounding towns affected by the flood.
● The fact that survivors were unable to recover damages was due to a financial structure that kept personal assets separated from the club and that it was difficult to prove fault from any one particular owner. This was heavily criticised and in the 1890s, state courts adopted Rylands v Fletcher - a 1968 English Tort Law which had largely been ignored previously - this allowed a non-negligent defendant to be held liable for damage caused by unnatural use of land
● Johnstown was also hit with floods in 1894, 1907, 1924, 1936 and 1977.
● After the 1936 flood, the United States Army Corps of Engineers dredged the Conemaugh River to nearly 20 feet deep and built concrete river walls. But 275mm of rain in eight hours on July 19, 1977 put the city under 2.4m of water.
So there you have it, the Johnstown Flood or The Great Flood of 1889. The poorly maintained South Fork Dam, with a reduced capacity and no overflow capability, was ill-prepared for extensive rainfall and the towns downstream bore the brunt of those shortcomings.
Thanks for listening to this mini-failure episode. For our regular episodes, check out Failurology wherever you get your podcasts.
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Bye everyone, talk soon!