Ask Dr. HOG About Water and Earthquakes: Water Tanks in Seismically Active Zones
Dr. HOG recently visited a school in Northern California that wants to install a large, round 1,500 gallon tank on a hill above the playground for decent gravity feed. They felt that steel was a sturdy, durable choice. What’s wrong with this scenario?
There’s a reason many steel tank manufacturers do not sell in California – and its all about rock ‘n roll. Well, actually its slip ‘n slide as the Pacific Plate and the North American Plate grind together. When the ground moves abruptly under a large or medium body of water contained in a tank the top section of water sloshes, and the bottom section moves with the tank body, effectively creating some very powerful shear. A riveted tank might just pop its rivets, pouring around 6 tons of water down onto the playground. A welded tank attached to a stiff foundation could shear in the middle.
The volume the school wants to store is not a viable project for Rainwater HOGs, so I recommended daisy chaining two 660-gallon round Bushman tanks with a secondary fastening system to the ground, and allowing room for an additional tank when funding became available. Daisy-chaining smaller tanks has a number of advantages to the monolith proposed: