4The Dam Located on the border between Arizona and Nevada Blocks the Colorado RiverHoover Dam created Lake Mead behind itConstruction began 1931, initially on the four tunnels used to divert the river away from the building site
5The Dam Construction of the actual dam began 1933 Nothing of this magnitude had ever been attempted beforeAs a result there were many problems with untested solutions
6Site Preparation River water diverted This was done using four tunnels, two either side of the canyonIn total the tunnels spanned a length of 16,000 feet (3 miles)The tunnels were dug out using dynamite
7Site Preparation Scaling the cliff walls and removing any loose rocks This work was needed to ensure that when the dam was built it would stay firmly in place and not crumble away at the edges
8‘High Scalers’The men who were given the job became known as ‘High Scalers’The workmen were required to hang from ropes off the edge of the cliff and use jackhammers and dynamite to blast off loose rockThey weighed 44lbs
9High RiskMany men died from falling tools or slipping and falling off the cliffAs a result the men invented hardhats to stop them getting fractured sculls from falling objectsThey did this by filling cloth hats with tar
10RescueA spectaculuar example of the dangers involved is a story of a man who slipped and fell. 25 feet below another worker leapt off the cliff, holding onto his rope, and caught the man’s foot. Another worker pinned the man to the cliff until he could be rescued.
12Construction Construction began in 1933 The first problem engineers faced was the sheer amount of concrete needed to build the damA site to make concrete was first built upstream and later one was built on the edge of the canyon
13ProblemsAnother problem faced was the fact that concrete produces heat as it sets. Had the dam been created in one pour, the heat generated would have meant the dam would not have set for 125 years. This would have created cracking and erosion.
14Another solution A solution was devised by engineers The dam was to be built with a series of concrete pillars, trapezoidal in shape, joined with interlocking groovesWhen set, the blocks were pressure grouted together
16Problems and Solutions Pouring the concrete in separate blocks was only part of the solution to the concrete problemThe dam was in the middle of the desert and the heat was setting the concrete too fast
17PipesTo solve this problem, a system of pipes was woven throughout the concrete and filled with cold water. This slowed down the setting processLater the pipes were removed and the holes filled with grout