Intro

Using Concrete is almost as old as recorded history, albeit in different forms, nevertheless it is the building material responsible for some of history's most iconic structures. It’s prevalence has never really reduced, liquid stone is essential in almost any construction project from shed bases to today’s subject power stations, concrete is vital. And misjudgments in the process can have catastrophic results. Today I’m looking at the Willow Island disaster, my name is John and welcome to plainly Difficult.

Background

Background Our story begins and pretty much ends in 1970s Willow Island, West Virginia. The region is getting a new coal powered power station called The Pleasants Power Station. The new plant was to have 2 electrical generators producing a nameplate capacity of 1300mw. The new power station would requure 2 cooling towers, the first would be built during 1977, being completed in august of the same year. Soon after the second tower started to rise into the sky. Each tower had a base diameter of 358 ft (109 m) with a height of 430 ft (131 m) above the ground level. They were of the natural draft variety, now coal power plants are all about making steam to drive turbines, just like nuclear power plants. As such once turned into steam you want to recover your coolant this is where the towers come in, the ones at the pleasants plant took the hot water from the system and cooled through direct contact with fresh air. To increase surface area for the coolant the water is sprayed into the tower via nozzles. Cooling towers are a pretty interesting type of structure as it has a wider base than its top has different thicknesses and is circular, Because of this concrete is really the only feasible construction material, although brick chimneys and towers exist, brick laying takes time and a certain skill and this costs money. If your interested in brick towers check out Fred dibners life and career, he spent most of his life maintaining and ultimately dismantling these types of structures. Or just ignore my side tangent! Anyway how were the towers at the pleasants power station built? The construction method.

The Construction Method

The builders had to use a complex combination of formwork and scaffolding. This would follow the construction all the way from bottom to top to accommodate this the scaffolds would be physically attached to the rising building. This is different compared to other building methods where the scaffold is just mounted to the ground and rises up with the tower. To create each sections lift the forms were placed, then the concrete would be poured once cured the next section could be built. After each lift the formwork and scaffolding would be removed and placed above for the next lift . To raise up the concrete cranes were used, but rather than being fixed to the ground they were also mounted to the newly made lift, via the scaffolding. Now this seems like a lot of weight relying on fresh concrete, but I’m No expert just a faceless voice, yea you don’t want to see my face. The concrete would be reinforced with steel both horizontally and vertically. Now with over 400ft to build it’s no surprise a method for building the towers would need to be quick. The building would rise up at roughly 1.5m per day, or roughly 4ft. The method, although in theory cheaper than a massive pile of scaffolding, relies on the previous lifts concrete to be as strong as it Can be. It also vitally relied on correct geometry of the cranes and scaffolding for the whole system to have strength, and any weak link of the methods chain would yield not enough strength. But clearly it worked. The first tower was built using this method. The contractors used for the project were very well known in the industry at the time, New Jersey-based Research-Cottrell. Safe hands you might think, and until the 27th of April 1978 you’d have no reason for concern. The collapse.

Disaster

It is the morning of the 27th of April 1978, and the builders are planning to undertake another day of concrete work. So far 28 lifts had been completed with the scaffolding working it’s way up with the structure, cooling tower 2 is roughly 166ft 51m tall. At 0630 carpenters began removing wedges holding up the form work, some of the wood was discarded and new dimension wood was cut and set in place. This took place on the second level of the 4 level scaffolding. An hour later the iornmongers arrived and started hoisting the reinforced steel to the top of the tower. Around the same time the field engineer arrived and at 0830, the scaffolding was jacked up to its new position. The form work was being removed from the previous days lift and being repositioned for that days lift 29. Before 10am two buckets of concrete had been craned up to the top of the 4 level scaffolding, which was now anchored to the previous day's work. Cracking was heard from the tower as the second bucket was raised. After Roughly 1 cubic yard had been poured the next bucket was sent up, as the bucket went up to the platform, the 28th lift began to fail. The crane lifting the bucket of concrete fell into the cooling towers center. The previous days lifts peeled away from the tower sending scaffolding and the workers on top plummeting down into the hollow of the building. That morning there were 51 workers on the scaffolding; none survived the fall. Immediately other builders on-site rushed to help dig out anyone, at the same time calls went into 911 and ambulances and fire trucks from Belmont, Parkersburg, Vienna, and St. Marys in West Virginia, and Marietta in Ohio, arrived to assist. Co workers who had helped drag the victims out of the rubble were there to assist in identification. Sadly due to the damage many were only identified by the contents of the pockets. Osha was on the accident site pretty quickly to begin the process of investigation the same day as the disaster. With another team from the National Bureau of Standards arriving a couple of days later. These two organizations sought to find what caused the tower to fail, especially when the other had been successful in its construction using the same methods.

Investigation

The investigation. Investigators scoured the disaster site and found not much left of the 28th lift, it was thought that it had pulverized upon contact with the ground. Reinforcement bars were found to be bent, hinting that they hadn’t fractured, ruling them out as a cause. They also found that the scaffolding hadn’t failed causing the collapse neither did they find issues with the hoist cables. During the investigation they found that the concrete was not strong enough to support the scaffolding. This was theory officially published In the 1979 report the national bureau of standards summed up its conclusions: "the imposition of construction loads ... before the concrete of Lift 28 had gained adequate strength to support these loads." The concrete hadn’t cured enough. But that wasn’t the whole story, our good old friend corner cutting reared its ugly penny pinching head. Osha found that rather than following the carefully planned positioning of the cranes for raising the buckets, different positions were used to allow more buckets to be lifted, and thus pour the concrete more quickly. They also found a worrying lack of field tests of the concrete they were making, allowing inconsistencies in each lift. The anchoring for the scaffolding was also found to be lacking with some of its bolts missing and in other cases of an incorrect grade. It was also found that there was only 1 escape ladder, hindering any escape. On June 8, 1978, OSHA cited Willow Island contractors for 10 willful and 10 serious violations, which would result in a settlement of 85,5k a measly 1700 per victim. But the verdict on the cause of the disaster wasn’t agreed upon by everyone. The power plants main contractor hired a private engineering firm to investigate the failure. They were a bit more doubtful of the concrete theory, instead pointing the finger of blame at the feet of the unique scaffolding method. The consultants lev zetlin associates said: , "problems originated due to lack of understanding of the scaffold system by the workers, and also due to its systematic misuse. Lack of technical and management supervision was also an underlying cause to this collapse." Osha was aware of the problems with the scaffolding method, as early as 1977. Lawyer Ralph Nader began researching osha reports soon after the collapse and he found some worrying concerns. An osha inspector had seen that the scaffolding used in the first tower needed repairs and they had been modified without any knowledge of the engineers. Osha rejected the later Nader report, still upholding the concrete theory. The disaster would improve concrete and masonry standards across the industry. Which can only be seen as a good thing, but we know it was still not enough. Now I’m going to rate this disaster as a 3 oh balls people will remember this. And a 5 on my legacy scale. https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908824