NARRATOR: To support this building frenzy, huge concrete mixers were designed to churn out six tons of cement every minute. An ingenious railroad and cable system delivered this concrete in drop-bottom buckets. Crews with pneumatic vibrators shook air bubbles out of the cement as it settled.
Giant pipes, called penstocks, would funnel this water toward two electric generators. Each section of penstock weighed 40 tons, and moving them into place was treacherous business. Thousands of men risked their lives every day at TVA dams. The work was gritty, back-breaking, and above all, dangerous.