Tractor Towed Elevators on Garrison Dam

[MikePhua]

The Construction of Garrison Dam
When the Garrison Dam project began in the early 1940s along the Missouri River in North Dakota, it was one of the most ambitious civil engineering undertakings in the United States. Authorized as part of the Flood Control Act of 1944, it aimed not only to control flooding but also to generate hydroelectric power and provide water storage for irrigation. The project required moving an immense volume of earth—over 150 million cubic yards—making it one of the largest earth-fill dams in the world at the time. With such a vast workload, the contractors needed methods that could move soil efficiently before the age of ultra-large scrapers and articulated haulers.
The Role of Tractor Towed Elevators
Among the most critical machines in use during this period were tractor towed elevating scrapers, often referred to simply as tractor towed elevators. These machines combined a scraper bowl with a powered elevator chain that lifted soil into the bowl rather than relying solely on the forward motion of the tractor. This innovation allowed operators to load more effectively in softer or looser materials. Typical units of the time were pulled by heavy tractors such as Caterpillar D8 or Allis-Chalmers HD series, delivering the power needed to handle steep grades and long hauls.
Unlike self-propelled scrapers that would dominate later decades, these tractor-drawn versions required coordination between the tractor operator and sometimes an additional pusher tractor. Their efficiency lay in the balance of cost and output—being cheaper than purchasing fleets of self-propelled units while still delivering high volumes of earthmoving.
Technical Features of the Elevating Scrapers
A standard tractor towed elevator in the 1940s and 1950s typically featured:

• A scraper bowl capacity between 8 and 14 cubic yards, depending on model.
  
• An elevator chain powered by a secondary engine, often gasoline or small diesel, mounted directly on the scraper frame.
  
• A cutting edge with adjustable depth control to regulate soil intake.
  
• A system of rollers and chains designed to move earth into the bowl continuously, even in sticky conditions.
  

This mechanical design eliminated much of the wasted time associated with loading by push tractors alone. While push-loading was still common, the elevator scraper allowed for more consistent loading cycles, making it ideal for projects like Garrison Dam where massive amounts of material had to be shifted quickly.
The Scale of Earthmoving at Garrison Dam
During peak construction years, over 2,500 workers and hundreds of machines operated around the clock. Estimates suggest that at least 400 tractor towed scrapers of different models were in operation at various stages of the dam’s build. Daily earthmoving volumes exceeded one million cubic yards at the height of the project. The dam’s final size—11,300 feet long and 210 feet high—was a testament to the efficiency of these machines.
Challenges and Solutions in Operations
Operators faced several difficulties when using tractor towed elevators:

• Soil Variation: Missouri River banks offered a mix of sandy soils, clay, and gravel. Adjusting the elevator chain speed and cutting depth was critical.
  
• Maintenance: The elevator chain and roller system required frequent lubrication and replacement of worn parts. Breakdowns in the field could halt operations, so spare parts depots were set up nearby.
  
• Fuel Demands: With both tractor and scraper engines running, fuel logistics became a massive task. Reports from that era suggest that fuel trucks delivered thousands of gallons daily to keep the operation continuous.
  

Solutions included the introduction of preventive maintenance schedules, standardized training for mechanics, and staggered fueling rotations to minimize downtime.
Historical Development of Elevating Scrapers
The concept of elevating scrapers was developed in the 1930s as contractors sought alternatives to hand loading and cable scrapers. Companies like LeTourneau and Bucyrus-Erie pioneered designs that included powered elevators for faster loading. By the time of World War II, demand for large-scale earthmoving skyrocketed due to military base construction, highways, and dams, pushing manufacturers to refine their machines.
Garrison Dam was one of the proving grounds for these designs. Sales of tractor towed elevators rose significantly after the project, with LeTourneau reportedly selling thousands of units in the late 1940s and early 1950s across the United States and internationally. These machines helped shape infrastructure from irrigation canals in California to airport runways in Europe.
Impact on Future Equipment Design
The success of tractor towed elevators influenced the eventual development of self-propelled elevating scrapers in the 1950s and 1960s. These later machines combined the tractor and scraper into one unit, reducing the need for multiple operators and improving maneuverability. However, the lessons learned at Garrison Dam—regarding durability, soil adaptability, and high-volume efficiency—were central to those later designs.
Personal Stories and Anecdotes
Workers from the Garrison project often recalled the noise and dust that hung over the site. A common memory was the sight of long convoys of scrapers moving in lines, raising clouds visible for miles. In small towns nearby, children would watch the parades of machinery pass daily, sparking lifelong interests in engineering.
One story tells of a mechanic who managed to keep a worn-out elevator chain functioning by fashioning temporary links from farm equipment, allowing the scraper to continue working until proper replacements arrived. Such ingenuity was common, given the immense pressure to maintain production schedules.
Legacy of Tractor Towed Elevators
Today, Garrison Dam continues to serve its original purposes of flood control, irrigation, and power generation. The dam stands as a monument not only to engineering but also to the machines and people who built it. Tractor towed elevators may seem outdated by modern standards, but their role in mid-20th century megaprojects remains undeniable.
Their use demonstrates a pivotal transition in construction history—from manpower and horse-drawn scoops to mechanized earthmoving on an industrial scale. Without them, projects like Garrison Dam would have been far slower and costlier.