Florida Sinkholes F.A.Q.

Sinkholes – or “sinks” – are depressions or holes in the land surface formed in “karst terrain” when slightly acidic groundwater slowly dissolves bedrock material (like Florida’s widespread limestone) creating underground caves, cavities or channels.

Eventually, these underground cavities enlarge to the point that the surface sediments and structures overlying the cavities become too heavy for the ceiling to support, and the earth collapses in to them.

In the less serious type of sinkhole, over time a bowl-shaped depression forms at the surface. In the much rarer but more catastrophic, the ground cover collapses suddenly into a large underground cavern. Sinkholes vary in size from a few feet to hundreds of feet in diameter.

Most situations that a homeowner is likely to confront can be repaired with proper soil stabilization procedures, and a home’s foundation with foundation underpinning. Those are our expertise, and we can help restore your property from the underground up.

“Karst” means that much of the terrain’s underlying bedrock is made up of carbonate rocks, like limestone, which becomes riddled with cavities of differing sizes and depths. Karst terrains often have drainage systems that appear on the surface as sinkholes, springs, disappearing streams or caves. A “sinkhole” is just one of its types of drainage features.

Since relatively few of the cavities in karst terrain ever collapse and directly affect roads or dwellings, karst terrains are rarely newsworthy. Headlines are made only when a house or road is located above one of the developing karst features. However, since much of Florida is karstic, these processes are continually taking place, and there’s always an element of risk.

So if you have not yet built or purchased a home, and you are in one of the more sinkhole prevalent areas of the state, you might want to consider having us do a preliminary assessment and perhaps obtaining a geological evaluation.

If there’s a possible problem, we have systems such as of pressure grouting to stabilize your soil, and we are specialists in pre-construction and remedial foundation underpinning to put you on solid ground.

There are three types of sinkholes in Florida:

• Solution sinkholes usually occur where there is very thin sediment cover over the limestone. So the rock easily dissolves at the ground surface or along joints or other openings.
• Cover subsidence sinkholes are the most common type and typically develop over long periods of time (sometimes years). They occur where thick, permeable sediments cover the limestone. As groundwater seeps down, it dissolves enough rock to create an underground network of channels. Over time these conduits grow until more and more surface soil is carried into the underground cavities in the limestone. Slowly, the ground surface usually develops a gentle, bowl-shaped, circular depression. However, if the sediments covering the limestone consist of a relatively thick layer of impermeable sediments, you may not see the subsurface collapse up on the surface.
• Cover-collapse sinkholes are rarer but quite dramatic. A circular hole typically forms and grows over a period of minutes to hours when the roof above a large cavity dissolves to the point that it can no longer support the weight of the sediment or structure above it. Then the surface elements plunge into the void. The dramatic cover-collapse is usually precipitated by some trigger – such as heavy rainfall, drought or a heavy load / structure.

It may take a day for the slumping of the sediments along the sides of the sinkhole to stop. Erosion on the sinkhole’s edge may even continue for several days, with sudden collapses along the sides, so it is important to stay well clear of the depression. Heavy rainfall can prolong the stabilization.

Possible triggers for sinkhole collapse might include man-made developments like retention ponds and new construction, especially new construction blasting, as well as changes in drainage patterns, heavy traffic, heavy ground loading or drilling vibrations.

Heavy ground-water pumpage and declining ground-water level can accelerate sinkhole formation.

Hurricanes, tropical storms and other heavy rains can permeate the soil and carry away sediments into the substrata, speeding sinkhole development, as can the shrinkage and cracking in the surface levels caused by drought.

Don’t worry about watering your lawn, though. Private lawn wells are typically not sufficient to impact the water table enough to cause sinkholes.

If you have sagging or cracking walls or ceilings… windows and doors that have begun to stick and are hard to open or developed new gaps around them… tilting or leaning chimneys, walls, lamp posts or trees… depressions in the ground, sidewalks, patios and driveways… or sinking ground around your foundation… you may have sinkhole activity, but not always.

Settling of the ground surface may be caused by other things such as broken pipes or decaying organic matter. Also, underground layers of clay may shrink upon drying and develop depressions, and poorly compacted soil from construction or excavations may settle.

You need to know what’s causing these things and take effective action. Don’t take a chance, especially if the settling is affecting your home or business. Call Foundation Services for an assessment:

352-622-9218

We have evaluated and repaired thousands of these soil and foundation conditions with technologically advanced and innovative techniques. We work closely with the top geological engineers in Florida. We are also familiar with applicable insurance provisions and can give you guidance there. Let us help you solve your problem.

It is important to use only natural earth materials or concrete for the fill, since anything buried in the ground can potentially affect the groundwater. Do not fill a sinkhole with trash, chemicals, or other materials that could contaminate ground water.

Broken limestone rip-rap or a concrete plug in the bottom of a small sinkhole can sometimes create a stable foundation for the fill. Above that, you will want to add “clayey” sand, as clay helps form a barrier against water seeping downward through the hole and making it worse.

Sand and top soil should be added on top, and landscaping will strengthen the surface further. Although additional fill may be needed over time, most holes do eventually stabilize.

If the depression is near a structure, do not trust the do-it-yourself method. Call us for an evaluation – 352-622-9218 or toll-free 866-622-3723. Pressure grouting, chemical grout injection or another soil stabilization technique may be needed to protect your home!

Generally you do not need a permit to fill a new sinkhole on private property unless it contains ground water.

To fill those containing water (intersecting the underlying acquifers), you may need an Environmental Resources Permit from your local Water Management District (in southern Florida) or the respective district offices of the Florida Department of Environmental Protection (in northern Florida). District staff will assist in assessing your need for a permit and advise you of the approval process.

If Foundation Services is engaged to remediate the sinkhole and stabilize your soils, we will handle all permitting.

You should immediately try to rope off the hole, clearly mark it to warn cars and pedestrians alike, and contact local law enforcement to report the hazard. It is a clear and present danger to people and pets.

If it’s a public street, call your city or county road department to start the repairs. If it’s a private road, contact the property owner or homeowner’s association, as the repair will be their responsibility. If it’s your property, call Foundation Services immediately for an assessment and help – 352-622-9218 – and get it roped off and marked A.S.A.P.

Mark and rope off the hole, if possible, and keep people and pets away. Then immediately call us for a free evaluation and help – 352-622-9218. We can then provide the information you need to report this correctly to your property insurance adjuster and authorities.

Let us guide you through this. We work with all the top insurance companies and geological engineering firms in Florida. We have decades of experience assisting homeowners and business owners with the necessary explanations, details and coordination with the different entities, as well as having in-house seasoned experts in repairing your property from the underground up – from soil stabilization and foundation repair through structural and cosmetic restoration and landscaping.

Some small sinkholes require just filling with clean sand or soil. Let’s hope yours is that simple. If the hole is near your home or swimming pool, your insurance may cover the assessment and repair. Pressure grouting, chemical grout injection or another method of soil stabilization may be needed.

If there is a government agency that can help, we will know about it – such as local Emergency Management Offices who help when a home is endangered, personnel from the local Water Management District (especially if the sinkhole impacts local ground water), and any local agencies that might help with evacuating your home, if required. We can help you contact them.

The sinkhole should also be reported on the appropriate form and submitted to the Florida Geological Survey. We or one of the agencies can assist you.

It might be prudent to conduct a quick inspection of your property for any sinking or soft areas. But unless your neighbor’s sinkhole is very large and extends to your property, you probably have little reason for alarm.

Although the bedrock underlying this state is honeycombed with cavities of various sizes, most will not collapse in our lifetimes. While Florida’s sinkholes tend to occur along linear fracture trends – aligned northwest-to-southeast and northeast-to-southwest – most are isolated events.

No state or federal agency currently has responsibility and authority for sinkhole inspections in Florida, but Florida Geological Survey (FGS) encourages you to submit a report. It maintains a database of reported sinkholes that’s available through their website. [Find more in Resources.]

No government agency will help you fix a hole on your property, as private property is the responsibility of the property owner. In some cases your insurance may cover evaluation and repair of a sinkhole, depending upon your actual coverage, circumstances and the company’s policy.

Since the underground cavities are largely undetectable without expensive ground-penetrating radar surveys, resistivity tests or test drilling, there is no ready reference on sinkhole prediction or risk assessment. Broader references, such as regional maps of reported sinkholes, show zones of occurrences based on the local geology and historical sinkhole activity, with some excellent ones available from the Florida Geological Survey.

The entire state is underlain by carbonate rocks, so sinkholes could theoretically form anywhere. However, there are definite regions where sinkhole risk is considerably higher than others … areas where limestone is close to the surface, or areas with deeper limestone but with a conducive configuration of water table elevation, stratigraphy and aquifer characteristics.

The Florida Geological Survey maintains a database of sinkholes that have been reported since 1954, so these tend to cluster in populated areas where they are readily seen and might affect roads and houses. Of course, those occurring in fields and forests often go unseen and unreported. Sinkhole information for a specific area (by county) can be found in their Subsidence Incident Reports.

A variety of tests to locate buried cavities can be performed by professional geologists and geotechnical engineering consultants. These tests include ground penetrating radar surveys, electrical resistivity tests, and borings.

However, test results may be affected by the local geology and elevation of the water table, they are not always conclusive, and they can be quite costly.

We and other sinkhole contractors and engineering companies routinely repair sinkholes and the foundation problems they cause using various techniques, from deep compaction grouting / pressure grouting and chemical grout injection to more advanced systems of engineered reinforced plugs, steel pins and piers and porous concrete.

Generally, if the repair has been made by a qualified contractor, certified by a licensed engineer and completed to the satisfaction of the homeowner’s insurance company, the house is probably safer than a neighboring one that has not been repaired.

We and a few other top contractors have been specially approved to offer transferable warranties guaranteed by the country’s largest warranty company and re-insured by an A.M. Best “A+” rated global insurer. Nevertheless, since we are dealing with natural systems, there can be no guarantees that a repaired sinkhole will never cause future problems.

If Foundation Services did the repair, you can rest assured it’s not only the highest quality, technologically advanced and reliable work, but also that the repair work is covered with the most comprehensive Foundation Stabilization Warranty in the industry. The warranty is on the property itself and would transfer to you, the purchaser. With over 2000 sinkhole and foundation repair jobs under our belt just since our merger in 1991, we have never had to go back for future repairs.

Unfortunately, an insurance company has the right to refuse issuance of a policy based on sinkholes in the (ambiguous) “area.” In fact, many insurance companies rely heavily upon regional maps showing zones of sinkhole occurrences based on the general local geology and historical sinkhole activity.

Insurance company policies vary and some are more liberal, so you may wish to shop around. Once you have homeowners insurance available, you will also want to understand the difference between sinkhole and cover collapse insurance.

No. Chapter 627.707 (8), Florida Statutes specifies that it is illegal for an insurer to cancel or refuse to renew an insurance policy because you filed a claim for possible sinkhole damage.

For further insurance information or to issue a complaint, the HELP LINE for the Florida Department of Insurance is 1-800-342-2762.

The team at Foundation Services (1-866-622-3723) has years of experience repairing everything from the most minor crack to a full-blown sinkhole collapse, working with all major insurers in Florida. They are familiar with sinkhole insurance in the state and “catastrophic ground cover collapse” insurance. So before you call your insurance agent, get a free assessment from the Foundation Services team to find out what’s going on underneath your home and how best to describe it to your insurer.

Are you covered? … Click here for a better understanding of sinkhole insurance in Florida and the insurance industry’s definitions of “sinkhole” and “catastrophic ground cover collapse.”

YES. We are proud to announce that our reputation as one of the highest quality sinkhole and foundation repair specialists earned our approval to provide you with the most comprehensive Foundation Stabilization Warranty Coverage in the sinkhole remediation and repair industry.

It is guaranteed by the largest national warranty provider, then reinsured by an “A+” rated global insurer in A.M. Best’s highest financial size category. Our warranty is the industry’s FIRST and ONLY 10-Year TRANSFERABLE warranty for foundation stabilization in Florida. So if you want to sell your property, this improves its value by increasing the purchaser’s confidence and assurance of long term soundness.

We note that since sinkhole activity involves natural systems, there can be no absolute guarantees that a repaired sinkhole will never cause future problems. However, our remediation, stabilization and repair processes use the most advanced techniques and best products in the industry. With over 2000 successful sinkhole and foundation repair jobs just since the merger that formed Foundation Services in 1991, we have never had to go back to the same job.