Rigging Throughout History: How the Hoover Dam was Built

Rigging Throughout History: The Hoover Dam

The Hoover Dam (originally known as the Boulder Dam) is one of American’s most famous landmarks—An engineering marvel of it’s time, that still remains one of the largest and most impressive dams to ever be created.

When the construction of the Hoover Dam was complete in March of 1936, it was the heaviest and tallest dam to exist, surpassing the next in line, The Arrowrock Dam, by double the height and triple the width.

This is impressive in any decade, right? Absolutely! But before we had the technology we have today that makes huge construction projects like these much easier, and more importantly, much safer, this feat was even more notable.

Read on to find out how, and why!

The Hoover Dam: It Begins

hoover dam inspection party 1931
An inspection party near the proposed site of the dam in the Black Canyon on the Colorado River.

The Hoover Dam was created to solve two different problems. If you’re not familiar, the Hoover Dam is located on the border of Nevada and Arizona, in the Black Canyon of the Colorado River. Prior to construction in 1931, the Colorado River would flood every spring, and often destroyed villages and crops along its path. This was one reason to create the dam, because water would be more controlled and displaced in calculated locations. Then, of course, the second reason is why most things get created—Income generation.

How does the Hoover Dam work? As water flows through large pipes inside the dam, turbines rotate, which then spins a series of magnets, past copper coils and a generator to produce electricity. This electricity helps support Nevada, California, and Arizona still, to this day!

As we mentioned before, this was not (and still isn’t) a simple task. Even today this wouldn’t be a construction project to scoff at, so you can imagine how difficult it was in 1931.

The Hoover Dam is 726.4 feet tall from the foundation of rock at the bottom to the roadway that runs along the top, and is constructed from 3.4 Million cubic meters of concrete. And if that’s not daunting enough, it was constructed in the middle of the desert, which at the time had no local workforce, no infrastructure, or transportation. The closest access to civilization was 30 miles away in Las Vegas, which had a railroad. This railroad became their one and only access point to bring in workers, materials, and supplies.

The construction of the Hoover Dam happened in the middle of the great depression, so despite it being in the middle of nowhere, it didn’t take long to get the workforce they needed. Within 3 weeks of the project being announced, the closest employment office in Las Vegas had received 12,000 applications for work. This wasn’t going to be easy work, but it was a stable income—Something many people at the time didn’t have.

black and white frank crowe hoover dam engineer
Frank Crowe.

Unfortunately, this made exploiting workers easy—If a worker wasn’t able or comfortable doing a task, they would simply be sent away and replaced with one of thousands of other men who’d happily step into the job.

An engineer named Frank Crowe was in the charge of the project, and had 7 years to complete it. If the project wasn’t complete within this timeline, there would be an approximate $3,000 a day financial penalty. Crowe was prepared to complete the project by any means necessary, and even earned the nickname ‘Hurry-Up Crowe’ for his constant efforts to ensure the project was unfolding on-time and on-budget.

A rushed project focused on speed above all else, is often not a safe project—And the Hoover Dam is a perfect example of this.

The Hoover Dam: Phase One

Allow me to set the scene for you—Thousands of untrained workers, in the middle of the desert, during one of the hottest summers on record (temperatures peaking at 49°C), faced with the monumental task of diverting one of America’s most powerful, dominating and unpredictable rivers—Sounds like a perfect storm…right?

In order to create a construction site in the riverbed, four diversion tunnels were driven through the canyon walls, two on the Nevada side and two on the Arizona side. These tunnels were 56 ft (17 m) in diameter and had a combined length of nearly 16,000 ft, or more than 3 miles (5 km). They also had to be sturdy enough to handle the powerful Colorado river, which meant about 850-cubic metrics of water a second.

The process of creating these tunnels involved  drilling holes into the rock, then packing the holes with dynamite. In 1931, this work was traditionally very slow and tedious, with each hole being drilled out individually with a simple drill or jackhammer. But, with a tight deadline in mind, Frank Crowe came up with a faster solution. Specialized 10-ton trucks were brought in that would each have 50 men on board, running 24-30 drills at one time. These trucks would be backed up along the walls of the tunnel, and half of the wall would be able to be drilled at a time. With 8 of these trucks and 500 drills, they were able to create the tunnels in record time. and 10 months ahead of schedule.

But, this did not come without consequence. Temperatures within the tunnels could reach upwards of 60°C, and the only solution presented for this was a team of people they called the “ice brigades” who would go into the tunnels to bring out exhausted workers to plunge them into ice water. Fourteen men died of heat exhaustion alone during the construction of the tunnels.

And the hazards don’t stop there – Many other workers were hospitalized or killed due to carbon monoxide poisoning because the tunnels didn’t have the proper ventilation to support the steady stream of trucks going in and out. Many of these deaths were reported as a pneumonia outbreak, according to doctors at the time, but it’s widely believed that it was misrepresented by the construction company to avoid paying death compensation.

The Hoover Dam: Phase 2

hoover dam high scaler 1931
One of the Hoover Dam “High Scalers”.

After the tunnels were complete, cofferdams (small enclosures so the water can drain) made from materials extracted from the tunnels were put in place, and water was drained from the construction site. In order for the dam to rest on solid rock, accumulated erosion soils and other loose materials in the riverbed had to be removed. Since the dam is an arch-gravity type, the side-walls of the canyon bear weight from the dam as well, so the side-walls also had to be excavated.

The team that performed these side-wall excavations was called “high scalers” and they would work suspended from the top of the canyon with ropes (NOT proper fall protection equipment) and would climb down the canyon walls removing any loose rock with jackhammers and dynamite. Falling objects were the number one cause of death on the dam site, with high scalers often being the victims of this hazard.

To protect themselves against falling objects, some high scalers took cloth hats and dipped them in tar, allowing them to harden. When workers wearing such headgear were struck hard enough to inflict broken jaws, they sustained no skull damage.

These hats went on to be called “hard boiled hats” and companies began ordering the hats and encouraging their use—One of the first versions of the modern hard hat (but not NEARLY as safe, so don’t get any ideas about dipping old hats in tar…please, buy a certified hard hat!)

The Hoover Dam: Phase 3

Once excavations were complete, the concrete staring pouring in, 6,600,000 tons of it to be exact. You may notice a squared pattern along the side of the Hoover Dam, and that’s because it’s made of a series of blocks of concrete—Not a large pour. This is because if they attempted to pour out the Hoover Dam in one continuous piece, it would still be drying today!

LEFT, A bucket holding 18 tons of concrete is maneuvered into positions. RIGHT, Concrete lowered into place.

When the ingredients of concrete are combined (cement, aggregate & water), they trigger a chemical reaction. This reaction generates internal heat, and slows down the curing process—The larger the pour, the longer it takes to harden. A series of interlocking blocks allows the concrete to harden in a more reasonable time-frame.

But there was also the opposite problem—Liquid concrete could harden too fast when attempting to transport it to the top of the dam, where the blocks were being formed, because of the intense desert heat.

To solve this problem, Frank Crowe designed an elaborate network of overhead cables and pullies that would move across the construction site carrying buckets of concrete. This was one of the largest rigging systems to ever be used on a construction site at the time! But I think it’s safe to say it probably wouldn’t pass a modern inspection (definitely not from our LEEA certified technicians)—So don’t start taking any notes!

The Hoover Dam: Lessons Learned

The Hoover Dam project was complete in 1936, 2 years quicker then the original timeline suggests. During construction, 112 people died.

Back in 1931, it wasn’t that uncommon to have a high fatality rate on construction sites. Some of that was because they didn’t have access to the technology we have today (or at least not as good quality), like fall protection equipment or modern hard hats, and other personal protective equipment (PPU). Some of it was also due to the fact that employers were not held accountable to ensure they weren’t putting their workers into unsafe working conditions – Like using the proper equipment and ensuring it’s been inspected and in full working order.

Construction is a dangerous industry, even today, but that doesn’t mean we should ever accept fatalities or even injuries. It’s not 1931 anymore—Employers and construction workers have the responsibility and the right to be able to perform their jobs safely. Now we DO have access to the proper means necessary to create a safe work environment, so there’s no excuse not to be using them.


LOOKING TO BRING YOUR WORKPLACE SAFETY TO THE NEXT LEVEL? CALL US FOR A QUOTE—HERCULES SLR OFFERS AN EXTENSIVE SUITE OF HIGH-QUALITY SAFETY TRAINING AND CERTIFICATION COURSES.

PPE-volution – How the Golden Gate Bridge Inspired PPE

Brooklyn bridge workers

America’s Industrial Revolution and ingenuity brought about many important advances in worker safety and PPE (Personal Protection Equipment).

At the start of the American Industrial Revolution, worker safety and health were nowhere near the priority they are today. As manufacturing grew, so too did worker injuries and deaths. The idea of safe work grew slowly from a small glimmer to a bright flame inside the collective consciousness of the American workforce.

Although the creation of OSHA regulations was many decades away, the evolution of PPE progressed on its own with the creation of new types of protective devices and advancements in pre-existing devices. Much of this early PPE had a major influence on worker safety’s advancement and will continue to do so.

Hard-Headed PPE Golden Gate Bridge
San Francisco’s Golden Gate Bridge, built in 1933, is an excellent early example of PPE’s influence on safety. Constructing a cable-suspension bridge that was 4,200 feet long was a task that had not been attempted before, one that presented many hazards. The project’s chief engineer, Joseph Strauss, was committed to making its construction as safe as possible.

The bridge’s construction played a particularly significant role in the successful development of one form PPE: It was the first major project that required all of its workers to wear hard hats. Although the hard hat was in its infancy at the time, head protection wasn’t new; gold miners had learned long before the importance of taking steps to protect against falling debris. Michael Lloyd, head protection manager at Bullard – a company in business since 1898, said many early miners wore bowler hats, which were hard felt hats with rounded crowns. Often dubbed “Iron Hats,” these were stuffed with cotton to create a cushioning barrier against blows.

Inspired by the design of his “doughboy” Army helmet, Edward Bullard returned home from World War I and began designing what was to become known as the “hard-boiled hat.” The hat was made of layered canvas that was steamed to impregnate it with resin, sewn together, and varnished into its molded shape. Bullard was awarded the patent in 1919. Later that year, the Navy approached Bullard with a request for some sort of head protection for its shipyard workers. The hat’s first internal suspension was added to increase its effectiveness, and the product’s use quickly spread to lumber workers, utility workers, and construction workers. By the time of the Hoover Dam’s construction in 1931, many workers were voluntarily wearing the headgear. Soon after, the Golden Gate Bridge construction provided a true test of the hard hat’s protective capability because falling rivets were one of the major dangers during the project.

Other innovations came in the form of different materials. In 1938, Bullard released the first aluminum hard hat. It was more durable and comfortable, but it conducted electricity and did not hold up well to the elements. In the ’40s, phenolic hats became available as a predecessor to fiberglass hats. Thermoplastics became the preferred material a decade later for many head protection products; it’s still used by many manufacturers today.
PPE-Hard-hats
From Left to right: Vintage Bullard Miners hats, Vintage Bullard Hard Boiled Hard Hat 1930’s (Used on the Golden Gate Bridge Project, Hard Boiled aluminum Safety hard hat w/Liner and a current day hard hat

In 1953, Bullard introduced the process of injection-molded hats. “Before, [thermoplastic] was kind of laid out on a mold. In the injection-mold process you actually have a closed mold that you pump into. It makes a more consistent helmet and a higher-quality product, which in the long run is also going to be the same thickness all the way through. It’s going to be a safer helmet,” Lloyd said.

Despite the hard hat’s effectiveness and relatively low cost, its use wasn’t officially required at most job sites until the passage of the Occupational Safety and Health Act in 1970. OSHA’s head protection standard, 1910.135, obligated employees to protect workers and instructed manufacturers and employers to turn to the American National Standards Institute’s Z89.1 standard for the appropriate usage guidelines.

Many new materials have since been created, such as the use of General Electric’s high-heat-resistant polyphthalate-carbonate resin in firefighters’ helmets. New hard hats have been designed that provide side protection, which are designated type 2 hats in ANSI Z89.1. “A hard hat was originally designed to protect if something falls from that sky and hits you in the head,” Lloyd said. “But what happens if you run into something? What happens if you bend over and something hits your helmet?”

Because hard hats are a mature market, except for the development of other materials, most innovations will be comfort features and technologies enabling them to withstand different temperature extremes, Lloyd predicted. Easier-to-use designs are appearing that allow users to adjust a hard hat’s suspension with one hand. In the last couple of years, manufacturers have come up with different types of vented helmets designed to help workers keep cool. Hats are accessorized with attachable face shields, visors, and ear muffs, and some have perspiration-absorbing liners. Some come with AM/FM radios, walkie-talkies, and camcorders.

Netting a Safe Return
Although primitive by today’s standards, the solution for the problem of falls also was addressed during construction of the Golden Gate Bridge. Three years into the construction, delays had convinced Strauss to invest more than $130,000 (these were Depression-era dollars, remember) on a vast net similar to those used in a circus. Suspended under the bridge, it extended 10 feet wider and 15 feet farther than the bridge itself. This gave workers the confidence to move quickly across the slippery steel construction. There were reports of workers being threatened with immediate dismissal if found purposely diving into the net.

Strauss’ net was heralded as a huge success until the morning of Feb. 16, 1937, when the west side of a stripping platform bearing a crew of 11 men broke free from its moorings. After tilting precariously for a moment, the other side broke free and the platform collapsed into the net, which contained two other crew members who were scraping away debris. One platform worker, Tom Casey, managed to jump and grab a bridge beam before the platform fell; he hung there until rescued. The net held the platform and the others for a few seconds before it ripped and fell into the water. Two of the 12 men who fell survived.

Read the original article here.

At Hercules SLR we provide a wide range of PPE solutions, from Lanyards and harnesses, to hard hats and rescue equipment.  We also repair, service and certify PPE equipment. We stock leading industry brands and can provide you with expert advise on your PPE options depending on your project. Call us on 1-877-461-4876 for more information.

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Hercules SLR is part of the Hercules Group of Companies which offers a unique portfolio of businesses nationally with locations from coast to coast. Our companies provide an extensive coverage of products and services that support the success of a wide range of business sectors across Canada including the energy, oil & gas, manufacturing, construction, aerospace, infrastructure, utilities, oil and gas, mining and marine industries.

Hercules Group of Companies is comprised of: Hercules SLRHercules Machining & Millwright ServicesSpartan Industrial MarineStellar Industrial Sales and Wire Rope Atlantic.

A Brief History of Elevator Wire Ropes

Elevator rope

The humble hoisting rope occupies a unique place in the history of vertical transportation. A simple hemp rope lies at the center of one of the best-known elevator stories — Elisha Graves Otis’ demonstration of his Improved Safety Device at the 1854 Crystal Palace in New York City.

Currently, a sophisticated carbon nanotube “rope” is the primary innovation driving the conceptual (and possibly literal) development of the proposed “space elevator”. However, the wire rope retains pride-of-place in elevator history as the longest-serving suspension means. It is the subject of numerous 19th-century articles that questioned its safety, and has been featured in countless contemporary books, movies and TV programs that predicate disaster on its failure. Today, we look at the introduction of wire elevator ropes in the 19th century and its development into the 20th century.

The invention of wire rope more-or-less paralleled the invention of the passenger elevator, and, by the 1870s, wire rope had become the rope of choice for elevator use. Since they were new, both the elevator and wire rope faced similar challenges regarding safety concerns. The older hemp hoisting rope had a long history of use, and its strengths and weaknesses were well known. However, a rope made of wire was an entirely different matter. This difference was effectively summarized in the June 22, 1878, issue of American Architect and Building News, which included a brief article on elevator ropes. The article expressed the primary concern in its opening sentence:

“The sudden introduction in our large cities of elevators, most of which are hung by wire ropes, has led people to wonder what will happen when they have had a year’s wear, and why there should not, after a while, be a breaking of ropes, and consequent accidents all over the country.”

The key concern centered on the endurance of wire rope and its reaction to constant and repeated bending as it passed around winding drums and over sheaves. One of the aforementioned article’s key assumptions was that “everybody knows, at least, that reiterated bending weakens wire, whether it be by granulation or by the constant extension of its fibers.” The challenge was, in spite of “knowing” that this action occurred, there was no easy way to judge when a rope was no longer safe for use.

The ICS author also addressed rope replacement, noting that “particular attention must be given to the fastenings.” The chief recommendation was to “carefully reproduce the joint as it was originally made” by the elevator manufacturer. A typical shackle used by Otis Elevator is described below in figure 1.

Figure 1: “Otis Elevator Co. Shackle,” ICS Reference Library (1902).

It consists of a split rod, the two legs A, A of which are bulged out and provided with noses at the ends. A collar B straddles the legs and eventually abuts against the noses. The rope is brought through the collar, bent over a thimble C, and passed back again through the collar, after which the free end is fastened by wrapping with wire. The wrapped end of the sections that address elevator ropes serves as a reminder that different elevator systems required different types of rope:

Chapter 1: Standard Methods and Facilities for Testing Wire Ropes
Chapter 2: Materials Composing Wire Rope and Their Properties
Chapter 3: Standard Types of Wire Rope Construction
Chapter 4: Variety of Uses of Wire Rope
Chapter 5: Mechanical Theory of Wire Rope
Chapter 6: Practical Hints and Suggestions
Chapter 7: Instructions on Ordering Wire Rope
Chapter 8: Typical Applications of Wire Rope in Practice

“When ordering rope for elevators, state whether hoisting, counterweight, or hand or valve or safety rope is wanted, also whether right or left lay is desired. The ropes used for these purposes are different and are not interchangeable.”

The diversity of elevator ropes was reflected in the design of American Steel & Wire’s standard hoisting rope, which was produced in six grades or strengths: Iron, Mild Steel, Crucible Cast Steel, Extra Strong Crucible Cast Steel, Plow Steel and Monitor Plow Steel. The company’s standard iron rope was primarily designed for use on drum machines and was “used for elevator hoisting where the strength is sufficient” (Figure 2). It was also described as “almost universally employed for counterweight ropes, except on traction elevators.” Their Mild Steel Elevator Hoisting Rope was designed “especially for traction elevators in tall buildings where, on account of [the] usual quick starting and stopping, a stronger and lighter rope is required.” Shipper or control ropes (also called tiller or hand ropes) differed from standard ropes in that they were composed of six strands of 42 wires each, which were wrapped around seven hemp cores (Figure 3).

wire rope figure 3 and 4

Figure 5: “Side Plunger Hydraulic Elevator,” American Wire Rope: Catalog & Handbook, American Steel & Wire (1913).

wire rope fig 5
Figure 5

In addition to providing detailed information on a wide variety of wire ropes, the catalog included schematic drawings that illustrated their proper application. These included 17 elevator-related drawings that depicted direct-, side- and horizontal-plunger hydraulic elevators; geared and traction electric elevators; and electric and belt-driven worm-geared elevators. The drawings’ emphasis on the application of wire ropes makes them a unique resource. Two versions of direct-plunger elevators were depicted — one with a shipper rope and one with an in-car controller — and the presence of two elevation drawings for each system permits a thorough understanding of these elevators (Figure 4). The same level of detail was provided for side-plunger hydraulic elevators (manufactured by Otis) and horizontal-plunger hydraulic systems (Figures 5 and 6).

Figure 6: “Horizontal Hydraulic Elevator,” American Wire Rope: Catalog & Handbook, American Steel & Wire (1913)

Figure 5
Figure 6

The electric elevator drawings are of particular interest, because, in 1913, they represented the newest systems on the market. The electric drum machine featured an interesting array of sheaves for the car and counterweight ropes, while the worm-gear machine employed a winding drum located near the midpoint of the shaft (Figures 7 and 8). The traction elevator drawing effectively illustrated its inherent simplicity and the potential of this new design (Figure 9).

The variety of elevator types illustrated in American Steel & Wire’s catalog represented the diversity of elevator systems prevalent in the early 20th century, as well as the importance of wire rope to their operation. Part Two of this article will follow this story through the 1930s, which encompasses the continued development of the traction elevator and the writing of the first elevator safety codes.

Figure 7: “Electric Drum Machine,” American Wire Rope: Catalog & Handbook, American Steel & Wire (1913).

Figure 7

Figure 8: “Worm Gear Electric Elevator,” American Wire Rope: Catalog & Handbook, American Steel & Wire (1913).

figure 8

Figure 9: “Traction Elevator,” American Wire Rope: Catalog & Handbook, American Steel & Wire (1913).

Figure 9

Original article can be found here at Elevator World Inc. 

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Hercules SLR is part of the Hercules Group of Companies which offers a unique portfolio of businesses nationally with locations from coast to coast. Our companies provide an extensive coverage of products and services that support the success of a wide range of business sectors across Canada including the energy, oil & gas, manufacturing, construction, aerospace, infrastructure, utilities, oil and gas, mining and marine industries.

Hercules Group of Companies is comprised of: Hercules SLRHercules Machining & Millwright ServicesSpartan Industrial MarineStellar Industrial Sales and Wire Rope Atlantic.