Sinkhole Primer for Public Adjusters

Florida. Land of sunshine, beautiful beaches, sinkholes and public adjusters!
For more than 60 million years, ancient shallow seas covered what is now the state of Florida. Factors relating to the chemistry of the water and the chemistry of the plants and animals that lived here resulted in limestone being deposited beneath these ancient sears. Eventually, the seas lowered to where they are today leaving a base of predominantly limestone bedrock covered with sand and clay for us to build houses and buy insurances policies.

What is a sinkhole? 

Sinkholes are depressions or holes in the land surface that occur throughout Florida. They can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone. Hydrologic conditions, including lack of rainfall, lowered water levels, or, conversely, excessive rainfall in a short period of time, can all contribute to sinkhole development.

Sinkholes are a common naturally occurring geologic phenomenon and one of the predominant land forms in Florida. Many of the lakes in Florida are relic sinkholes. Sinkholes can be classified as geologic hazards sometimes causing extensive damage to structures and roads resulting in costly repairs. Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them.

As the rock dissolves, spaces and caverns develop underground. Sinkholes are dramatic because the land usually stays intact for a while until the underground spaces just get too big. If there is not enough support for the land above the spaces then a sudden collapse of the land surface can occur. These collapses can be huge and can occur where a house or road is on top. Abrupt collapse-type sinkholes have become more common over the past twenty-five years, primarily due to activities of humans such as withdrawal of groundwater, diversion of surface water, or construction of ponds.

Geologists refer to three categories of sinkholes occurring in Florida.

Limestone Solution Sinkholes are common in areas where limestone is exposed at the surface or is covered by a thin layer of soil. Pasco, Hernando, Citrus and Levy counties are areas where this geology is prevalent. This leaves the limestone subject to both physical and chemical processes that break down the rock. When this breakdown occurs, it usually forms a saucer or bowl-shaped depression. Due to the natural dissolving of limestone, these sinkholes develop continuously, but slowly.

Cover-Subsidence Sinkholes occur where the sand layer may be as thick as 50 to 100 feet, with very little clay below it. Dissolving limestone is replaced by granules of sand that cascade down to fill the void. This type of sinkhole is referred to as a cover-subsidence sinkhole. These sinkholes are only a few feet in diameter and depth. Their small size is due to the fact that the cavities in the limestone cannot develop to appreciable size before they are filled with sand.

Cover-Collapse Sinkholes Generally, the deeper the soils, the more clayey the soils tend to become. This clay provides some cohesiveness to the soil material above it, allowing it to bridge any existing cavity in the imestone. If this “bridge” collapses, it results in what is call a cover-collapse sinkhole. The size of the sinkhole depends upon the size of the cavity. Cover-collapse sinkholes form the same way as cover-subsidence sinkholes but differ mainly in the bearing strength of the soil above the cavity and whether the sinkhole subsides slowly or collapses abruptly.

The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. 

Sinkholes are covered events

In 1981 the Florida Legislature mandated sinkhole insurance for this commonly occurring natural hazard. Florida Statute §627.706 requires every insurer authorized to transact business in the state of Florida to make sinkhole coverage available and required coverage for both structures and contents. Included in this legislation is the following definition of a sinkhole:

‘Sinkhole loss’ means actual physical damage to the property covered arising out of or caused by sudden settlement or collapse of the earth supporting such property only when such settlement or collapse results from subterranean voids created by the action of water on a limestone or similar rock formation. 

In addition to requiring sinkhole coverage, the Florida Legislature added provisions mandating minimum standards for investigation of sinkholes. Insurers are required, at a minimum, to:

1. Make an inspection of the premises after receiving a sinkhole claim
2. Must obtain written certification of person qualified to determine if sinkhole has occurred before the claim can be denied.
3. Must disclose qualifications of expert.
4. Sets standard for denial as an investigation that can eliminate sinkhole activity as the cause of damage within a reasonable professional probability.

Finally, the sinkhole legislation prohibits an insurer from nonrenewal of a policy of insurance on the basis of a claim for partial loss by sinkhole as long as the insured complies with the recommended scope of repairs on which the insurance company’s claim payment is based.

An insured that files a claim for sinkhole damage and causes an insurance company to incur the cost of a mandatory sinkhole investigation can be liable for 50% of the cost of the investigation, not to exceed $2,500. In order to assess the insured the cost of sinkhole investigation it must be found that there was no good faith grounds for submitting the claim.

Document the good faith grounds for making a sinkhole claim. Some indicators of possible sinkhole activity are:
• Tree roots are now exposed that were not before.
• Doors and windows fail to close properly.
• Depressed areas on property that were not there before.
• Muddy water or turbidity in well water.
• Structural failure, cracks in walls, floors or pavement.
• Small ponds of rainfall where water has not collected before.
• Fence posts that start sagging or slanting of trees.
• Exposure of exterior footer or separation of soils from floor slabs.
• Cracks in the ground.
• Changes in vegetation (dry and wilting).
• Heavy amounts of rainfall in recent weeks.


Other possible causes of sinkhole-like damage, most of which are excluded under typical insurance policies, are:
• Subsidence related to the decay of land clearing debris buried when a home or structure was built
• Decay of tree stumps or large roots
• Leaking water pipes or fittings
• A cracked or leaky swimming pool 
• Cracked storm water piping that carries away soil with the storm water run-off
• Poor compaction of soil around utility lines and foundations
• Run-off from roofs, gutters, or pavement.
• And the catchall excluded cause