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How to Use the Images

 

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Visual Evidence

Photo 4: "Drilling Jumbo"

[Photo 4] with link to larger version of photo. (Bureau of Reclamation; Ben Glaha, photographer)

Six Companies came up with a number of new and ingenious ways to drill the four diversion tunnels more quickly, and one was the “drilling jumbo.”  Eight of these jumbos were built, each mounted on the back of a 10-ton truck.  The jumbos backed up to the working faces in the tunnels so that men using all the drills could work at the same time and higher on the wall without the need for scaffolds.  The men filled the holes they had drilled with dynamite and then the jumbos drove away.  After the dynamite was detonated, the rock dislodged by the explosion was taken out of the tunnel.  Eventually they removed 1.5 million cubic yards of rock.

Questions for Photo 4

1.  Look carefully at this image. Look for the drills (they look a little like machine guns). How many of them can you count?

2. Why do you think Six Companies developed this process?  How do you think they might have done this work without the jumbos?  Why do you think Six Companies was so anxious to get this part of the project done quickly?  Refer to Reading 2 if necessary.

3. Internal combustion engines produce carbon monoxide.  State laws prohibited using them in enclosed spaces like tunnels for health and safety reasons, but Six Companies used the jumbos anyway.  What kind of danger does carbon monoxide present?  Why do you think Six Companies disregarded the state law?

4. What other hazards do you think the men working on the jumbos might have faced?

5. How large is 1 cubic yard? Measure your classroom and figure out how many cubic yards it could hold. How many of your classrooms would it take to hold 1.5 million cubic yards?

Click here for a larger version of Photo 4.

 

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