Understanding Sinkholes and Catastrophic Ground Collapse
Florida has more sinkholes than any other state in the nation, which form as part of a natural process inside the limestone layer located inside the land surface. Most sinkholes are approximately 10ft in diameter but can expand up to hundreds of feet in certain situations. Naturally, sinkholes cannot be prevented unless they are influenced by human activity.
Sinkholes are formed as rainfall enters and seep through the different soil layers, capturing chemicals and minerals that induce acidity in the water. This water can work its way down into the limestone layer, creating cracks and voids, and dissolving the limestone. This process creates weaknesses in the soil which often leads to sudden subsidence or collapse of the limestone, which sinks the clay and sand layers above.
This catastrophic geological process can also be influenced by human activities like well drilling, artificial ponds, or the over withdrawal of groundwater for example. This is why the water management agencies recommend keeping water tables high and issuing water restrictions to prevent sinkholes from occurring.
How to spot sinkholes
Being that this occurs gradually (and then suddenly), it may be hard to notice for the untrained eye, but some of the visible warning signs include:
Is sinkhole coverage included in homeowners' policies?
It depends. Some policies will specifically exclude sinkholes (and most earth movement-related damages) under their conditions. Florida law defines a sinkhole as "a landform created by subsidence of soil, sediment, or rock as underlying strata are dissolved by groundwater. A sinkhole may form by collapse into subterranean voids created by dissolution (the dissolving) of limestone or dolostone or by the subsidence as these strata are dissolved." Some policies may not provide "sinkhole" coverage, but they provide coverage for “Catastrophic ground cover collapse”. For this type of damage to be covered, the collapse must be abrupt, visible to the naked eye, and a government agency must issue an order to vacate the structure. It's important to carefully read your insurance policy or consult with a qualified insurance professional to better understand your coverage.
If you have ground subsidence damages, an engineering report would be your best bet in determining the cause and origin of these damages. Sometimes thorough testing and core samples of the soil would be necessary to accurately determine if the sinkhole occurred as described above, or if the damage is actually related to organic materials or unsuitable soils existing under the structure.
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How to repair or fix sinkhole damages?
It's very likely that nobody wants to live anywhere nearby a sinkhole or where a sinkhole previously developed. Nonetheless, there are some engineering solutions that can solve or mitigate ground subsidence situations. These solutions typically consist in pumping concrete grout or approved components to re-fill the voids affected by the sinkholes. It is very important to do these with qualified professionals and the appropriate testing equipment to guarantee the integrity of the ground afterward.
Sources
Please make sure to consult with a qualified professional if you believe your property has been damaged by a sinkhole.