The best method of sinkhole repair varies with the size and stability of the hole. For a smaller hole with firm ground at its lowest level, replacing dirt and repairing ground cover will suffice. Larger holes where the landowner can excavate to bedrock can be repaired by layering varying sizes of stone topped by gravel and dirt. Sinkhole repair for very large holes with unstable sides or low points should be carried out by professionals.
A sinkhole is a depression in the ground caused when ground water erodes subsurface rock allowing the dirt above it to sink. These holes range in size from about 3 feet (0.9 meters) wide and deep to 300 feet (91 meters) wide. Sinkholes can occur almost anywhere, but are most common in the southeastern United States. Manmade sinkholes are common as well, occurring when a depression in a piece of property has been filled with trash, branch cuttings or other debris and does not provide adequate subsurface support. Sinkhole repair methods are the same regardless of the cause of the hole.
Begin the process of sinkhole repair by testing the width and depth of the sinkhole with a long, sturdy pole or stick. If the hole is very large, the best method of repair likely is contacting a professional contractor who can excavate to bedrock and fill or reinforce as needed. If probing the extremities of the sinkhole with the pole does not lead to a firm base and sides, a professional should be called as well.
A smaller sinkhole in a residential property of about 3 feet (0.9 meters) wide and deep with a firm base and sides can usually be repaired by adding dirt. The property owner should layer in a few inches of dirt and tamp it down firmly. Repeat that process until the tamped dirt has filled the hole to surface level. If ground cover was lost, it should be replanted.
Sinkhole repair for a large depression, one of about 3 feet to 6 feet wide and deep (0.9 meters to 1.8 meters) in which the property owner can excavate to bedrock, involves layering in rock, sand and dirt. Begin by covering the bottom of the excavated hole with a layer of stones about the size of cabbages. On top of these stones, place a layer of smaller stones, about the size of billiard balls. Fill in the layers of stone with a layer of gravel.
On top of the layered stone, place a synthetic construction fabric, also known as a geotextile, over the gravel. This is a sturdy, stretch-resistant fabric that will help prevent layers of sand and dirt from washing away through the stone layers. Layer sand on top of the construction fabric and layer soil on top of the sand to ground level.