It was reported in the news recently that a sink hole 10 meters wide and 20 feet deep opened up under the bedroom of a house, taking the man with it, who was in the bedroom, preparing for bed at the time. (view article here)
Sink holes can be caused by several different events, either by nature or as a result of man made error. Sink holes created by natural means happen when acidic rain water filters into the ground that then dissolves rock and in turn leads to underground caverns, then when the top layer collapses into the cavern a sink hole is born.
The other way a sink hole can occur is when a broken sewer or storm water pipe under the ground begins leaking water, eroding the soil around it and causing an underground cavern. A sudden heavy down fall of rain can then add increased weight to the surface layer of soil, making it too heavy for the cave beneath which then collapses.
Residents in Ocean Shores, NSW, just south of the Gold Coast awoke one morning this week to find a gaping hole that had opened in the middle of their street. The hole measures 90cm long, 40cm wide and at least two meters deep. (view article here)
The best way to avoid possible sink holes is to make sure you have good drainage, and that it is free from leaks or cracks. Make sure you have your sewer and storm water pipes checked to make sure they are not leaking or broken. Also ensure that your down pipes don’t just discharge onto the ground, but are properly connected to your storm water system.
Keep your eyes out for any tell-tale signs that may indicate you could be in danger of a sink hole in your back yard. Some things to watch out for are sagging trees or fence posts, doors and windows that no longer close properly and rain water collecting in unlikely places.