If you are unsure whether or not you live in an area with a high risk for sinkholes, you can check with your local, territorial, or national government offices to find out. Another source of information can be found in geological surveys such as the United States Geological Survey (USGS). However, it is not always easy to predict where a sinkhole event will occur.
While sinkholes can appear at the surface overnight, their development and evolution is a long and slow process. These natural disasters occur under the surface of the ground, and their development occurs long before any visible signs of damage or decay can be seen. Sinkholes occur due to a hole in the rock below. There are a variety of causes for sinkhole formation, including both natural calamities and human activity.
Scientists are currently working on developing effective methods to find underground cavities that have the potential to turn into sinkholes. They are able to do this utilizing radar, seismography, and electrical resistance. This works best because 10% of the world’s land area is estimated to contain karst topography (made of rugged and partially eroded rock). The development of such detection methods can go a long way in preventing the catastrophic damages that are associated with sinkholes.
Signs of sinkhole development to watch out for include the formation of small holes in the ground or cracks in the foundation. More significant signs include slumping trees or fence posts, water collecting in new areas, or the wilting of small circular areas of vegetation. The above warning signs can potentially indicate if there is a sinkhole that is currently forming on your property.
A sinkhole occurs when rainwater infiltrates the earth and liquefies soluble rock, such as limestone and clay. These spaces grow over time until the land above them cannot sustain them. This collapse is called a sinkhole, and they can cause severe damage to your property. If you have discovered a sinkhole that is threatening a house or another structure, be sure to immediately create distance. It is important to try and avoid a potentially dangerous situation. Then, contact your local emergency personnel and a building inspector. If you happen to discover a sinkhole in the middle of a road, be sure to contact local law enforcement right away.
What about insurance and permits?
In most cases, sinkholes that occur on a person’s private property are considered to be their own responsibility. Insurance companies are much more likely to cover an evaluation and repair if the sinkhole was naturally caused. This would be by way of a subsidence event, rather than if it is caused by people. Man-made interventions that can contribute to the forming of a sinkhole include a collapsed or broken sewer pipe and drainpipe, broken septic tanks, or buried trash. Another source of interference could be from improperly compacted soil following construction activities.
Most homeowners’ policies cover sinkhole repairs, but they may not cover the costs themselves. Luckily, insurance companies will cover these costs for you if the damage is due to sinkhole activity. Fortunately, it is possible to make an insurance claim when you notice a sinkhole in your home. Just be sure to ask for an estimate before you start work.
When you suspect a sinkhole is developing in your property, look for signs of damage. Cracks in the walls, windows, doors, and ceilings are signs of sinkhole development. Small circular areas of vegetation or a pond of rain can also be signs of a sinkhole. Additionally, a sinkhole may cause an area of the ground to become saturated and vulnerable to collapse.
Typically, permits are not required to fill a sinkhole on private property (check with your local authorities to be certain) for sinkhole repair. If the sinkhole contains groundwater (being connected to a local aquifer), then a sinkhole fill permit will likely be required by the local Environmental Protection Authority or Water Management District. This will ensure that the proper actions are taken to prevent groundwater contamination.
How to fix a sinkhole
Before you put your hand on that shovel, you need to distinguish a do-it-yourself sinkhole fix from a more challenging problem that only an expert can handle. If the sinkhole is not affecting a house or other structure and has a reasonable size (2 to 5 feet in both diameter and depth), then you can repair it yourself.
A large sinkhole will most likely require excavation and a more complex filling operation.
Here are six steps sinkhole repair:
- Determine the depth of the sinkhole with a sturdy stick, and whether or not the bottom and the surrounding ground are stable. Continue to monitor the sinkhole to make sure it does not grow any longer.
- Shovel away the outer edges of the sinkhole if they are unstable.
- Add a layer of dry-mix concrete or a concrete plug to the bottom of the hole to provide a solid base.
- Add clayey sand on top of the concrete. This will help to keep water from leaking out of the hole to prevent the sinkhole from growing larger over time. A local contractor should know where to obtain the clayey sand. If clayey sand is unavailable, pure clean sand works as well. Rocks can also be used to help fill in the hole at this stage.
- Add sand and topsoil on top of the previous layers in order to help things blend in with the surrounding landscape. Pack the soil down with an iron bar or the top of a sledgehammer.
- Water the filled-in sinkhole thoroughly. Watering helps the fill to settle and lets you know whether or not you will need to add more soil. That’s it!
After few days, check the filled-in sinkhole. It is possible that you will need additional soil if all layers are well packed, but the hole should eventually become stabilized.
But what about the very large… huge… and mammoth-sized sinkholes?
Large sinkholes typically require engineering professionals to properly repair them. They are trained to follow the necessary environmental requirements concerning local aquifers.
In some cases, cement and rocks are used to fill the very large sinkholes. However, it is possible that trying to use concrete to fill these big holes may actually cause water to concentrate in other nearby areas. This can potentially lead to additional sinkhole formation.
The most preferred method of sinkhole repair to fix these very large sinkholes is similar to the method that is outlined above. A technique for fixing smaller sinkholes, called the graded-filter technique, consists of layers of boulders, smaller rocks, and gravel. They are placed into the hole in that order. The advantage of this technique is that it fills the hole while still allowing for water drainage.
If the sinkholes are caused by decaying infrastructure, such as a leaky sewage system in urban areas, more sinkholes are likely to develop until the problem is fixed. This is especially the case if you live in a geographic area that is already vulnerable to sinkholes.
Fortunately, the dramatic type of large sinkholes that instantly swallow up buildings and cars are fairly rare.
Some caution is advised!
Because many sinkholes are connected to aquifers, it is important that you do not fill them with materials that could potentially harm the groundwater supply. These materials include trash and chemicals.
Hopefully, this article will help you to have patched up that annoying spot in your front or backyard that showed up slowly over time. For those of you dealing with a more serious sinkhole problem, you can find the appropriate solution of sinkhole repair from the appropriate sources.
If your residence is suffering from foundational damage due to a sinkhole “too close to home”, give Barrier Waterproofing Systems a call today at (615) 257-1060 | (931) 536-1168. We can evaluate your property for any foundational damage and waterproofing needs and make the necessary repairs to get your home in tip-top shape.
This post was originally published on 3/6/2020 and updated on 4/28/2022 for accuracy and a larger scope of information.