The Town of Moraga had a very rare occurrence of a sink hole opening up in the same location as a traffic signal pole.   My guess is that the soil around the traffic signal pole gradually washed away until there wasn't enough left to hold up the signal pole any more.   For those that don't know, the foundation for the traffic signal pole is about 9 feet deep and 2 feet around.  For the full story see http://www.sfgate.com/bayarea/article/Sinkhole-in-Moraga-swallows-light-pole-and-breaks-68888...
Continue reading ...