There was a concern that if the explosion was successful, but the nuclear chain reaction did not follow, the 13 pounds of scarce and dangerous Plutonium would be blown all over the countryside. To contain the Plutonium if this happened the project designed a huge steel container. Several manufacturers reviewed the specs and refused the task. Steel fabricator Babcock and Wilcox of Ohio took the job in August 1944 and completed it in April 1945.
Named Jumbo, the container weighed 214 tons, was 25 feet long, 12 feet in diameter, had 15-inch thick walls comprised of 6-inches of steel plate and 9-inches of steel banding, and cost $12 million. Babcock and Wilcox moved Jumbo to Pope, New Mexico on a specially designed rail car. It was then transported 30 miles to a spot 800 yards northwest of ground zero on a special 64-wheel carrier. When loaded, it was pulled by a team of tractors to its front and rear.
The scientists and engineers decided to forego using Jumbo during detonation due to confidence in the bomb design, the potential to use increased quantities of plutonium without Jumbo, and concerns about how Jumbo would affect test results. Instead, it was placed under a steel tower, loaded with eight 500-pound bombs, lowered with one end resting on the ground, and detonated. The blast destroyed the tower and blew both ends off Jumbo. The rest of it was left intact. In 1979, the Army moved Jumbo to the spot near the ground zero gate where it is today.