Glen Canyon Dam, as featured in the popular film «Superman»
When designing, building and operating a dam, there are a few steps that ought to be followed in order to avoid large loss of life. Here are a few that I picked up at my first lecture in a series with the title that I have badly translated as “Conception of risky structures”:
1) Pay your workers well. The most dangerous period during the lifetime of a dam spans its construction, the filling of the reservoir and the first year of full service. Going on strike over pay during the construction is dangerous because the dam might not be ready for the winter’s flood waters and subsequently may get washed away.
2) When checking for cracks in the bedrock on to which the dam is to be founded, looking at 50 metre intervals is not good enough. A dam in Wako, Texas collapsed when a section of the bedrock between two cracks about 49 metres apart gave way.
3) If cracks have been found in the ground, it is unwise to leave them unfilled just because your client refused to give you any extra money to pay for this unforseen cost. To do so has led to death and destruction.
4) If you are satisfied with the conclusions of your ground survey that there are no cracks in the ground under your dam, don’t then move your dam a few metres downstream to make your lake a bit bigger without doing a new survey. Doh.
5) If when building, say, a 280m high dam in Italy, you notice that the mountain into which your dam has been founded has started moving(!) at a rate of several centimetres a day, don’t just carry on filling the dam and hope for the best. (In this case though the dam didn’t collapse, the mountain on one side of the lake gave way and a terrific landslide almost filled the lake that had been created, generating an enormous wave which swept over the dam and destroyed villages down-stream)
6) Finally, if your dam once built is not a profitable venture, don’t succumb to the temptation to sell it to a group of anglers. They may use it for stocking fish. This in itself is no problem. The problems arise in the rainy season when they may lose a significant portion of their fish down the overflow pipe. To prevent this loss, they may put a gauze over the pipe to keep the fish in, but which will also unwittingly get blocked with the leaves and branches which usually accompany storm waters, forcing the flood waters over the top, destroying the dam and killing 2000 people in the town below.
These six tips are from real examples of fatal dam failures.
When designing a dam, don’t just be safe, be dam safe.
Rose leaning over the Hoover Dam during our visit in March 2003