While a small sinkhole might cause a twisted ankle, a giant sinkhole could swallow a house. Therefore, the mere thought of a sinkhole near – or even under – your home is pretty frightening. The good news is USS can perform sinkhole repair potentially before the sinkhole causes loss of property or life.
What is a sinkhole?
Sinkholes are caused by water flowing through dissolvable rock. The water dissolves the rock, and eventually, underground voids form. When the surface can no longer support any weight – including its own – the ground collapses, and a sinkhole forms.
Sinkholes are dangerous because homeowners don’t always see them forming. Sometimes a visible depression will develop, but not always. Many times homeowners don’t realize a sinkhole is there until the ground suddenly collapses.
What causes sinkholes in Tennessee?
It’s all about geology. Two-thirds of Tennessee – most of it east of the Tennessee River – lies within an area categorized as karst. This is an area where shallow soil covers easily dissolvable limestone or dolostone bedrock. Over time, water causes caves, voids, and fissures to form in the bedrock. When these features develop near the bedrock’s surface, they can cause a visible sinkhole to form. We say “visible’’ because the hole was already there, but we couldn’t see it without special equipment.
In Tennessee, sinkholes form due to,
- Extreme weather fluctuations. For example, record rainfall immediately followed by severe drought.
- Improper grading that allows water to infiltrate the subgrade.
- The installation of underground utilities in a known karst area in a manner that allows water to travel and pond.
- Water leaks, sewer systems, unmanaged stormwater, drainage ditches, etc. Basically, anything that can cause water to seep into the subgrade can lead to sinkhole formation in a karst area.
Some conditions cause subsurface collapse features that resemble a sinkhole but aren’t caused by karst. These include abandoned wells or cisterns, collapsed septic tanks, broken drain lines, and buried trash pits containing building debris or tree stumps.
Sinkhole repair methods
The goal of sinkhole repair is to stabilize the area and prevent the sinkhole from reappearing. That means finding and eliminating the cause of the sinkhole. If water caused the sinkhole – and it usually does – then we need to get the water under control.
Sinkhole repair also involves excavation to expose the defect in bedrock that is allowing the soil to disappear. Once this is exposed, the throat can be packed with proportionately sized stone, the excavation lined with geotextile fabric and back-filled with compacted stone. The geotextile fabric can then be folded over the top of the gravel and the dirt placed back on top. This repair method is generally called and “Inverted Cone Filter” repair method.
Sinkhole repair is not a DIY project. It’s not enough to simply throw dirt into the hole. In fact, that could even make the sinkhole bigger. The sinkhole must be excavated entirely, cleared of all debris before adding the structural fill, and then the soil must be compacted using special equipment. While the specific approach might differ somewhat depending on the conditions, the goal is to create solid ground that will support your home.
What are the signs you might need sinkhole repair?
Signs you might need sinkhole repair include,
- Depressions in your yard
- New foundation cracks
- Ground cracks in your yard
- Tilting fence posts or trees
- A visible hole in the ground
Sinkhole repair and homeowners insurance
If you live in Middle or Eastern Tennessee, your home is in an area prone to sinkhole formation, and your homeowner’s insurance policy most likely does not contain coverage for damages caused by sinkholes. Fortunately, Tennessee Code TCA 56-7-130 states,
“Every insurer offering homeowner property insurance in this state shall make available coverage for insurable sinkhole losses.”
Insurance companies have no mandate to provide sinkhole coverage, but it must be made available if requested, and the provider may charge an additional fee.
United Structural Systems has been repairing sinkholes in Middle Tennessee, Southern Kentucky, and Northern Alabama since 1994. If you see signs of sinkhole activity in you’re in our service area, contact us today for a free inspection and estimate.