SINKHOLES

Classic Drainage, Inc. of Sterling, Virginia specializes in fixing sinkhole problems. We are experienced in sinkholes in the yard and also near strustures, outdoor stairs, and walkways. 

what is a sinkhole?
  

Depressions often develop in yards. These depressions technically are not real sinkholes. True sinkholes are formed in areas with limestone rock and karst geology, which can be found elsewhere in Virginia, but not in our Northern Virginia region. However, water can burrow through loose layers of soil or poorly compacted areas to create underground voids. These voids can become so large that the soil and grass “roof” sinks or collapses to form large holes. Since most people commonly call them sinkholes, we will also.

Sinkholes may occur along outside walls or in the lawn or garden. They can have various shapes and sizes and can grow or deepen either slowly or rapidly. In many cases, sinkholes can be repaired by the homeowner. Before any remediation work is done, the extent and cause of the sinkhole should be determined by calling Classic Drainage, Inc. for a free estimate and also roping off the area to prevent any injury to a person or animal. 

 
  

Sinkhole Near Structures, Stairs or Walkways

1. Sinkholes Near Outside Walls or Under Stairs

We first clean the area. Remove any trash, grass or other debris from the depression and determine the extent of the hole by careful excavation and probing. We fill the depression with fill soil that has a high amount of clay and low amount of sand. We do not use gravel or rock as a fill material, as this will let water trickle through the gaps in the gravel and create an even deeper cavity underneath. We continue this process until the depression is flush with the ground. We finish with grading so the area does not develop a "pool" when it rains. 

2. Sinkholes Under Sidewalks

Sinkholes under sidewalks or walkways. Sometimes depressions or holes can form under sidewalks or other walkways, with uneven concrete slabs creating a trip hazard. We install concrete under pressure that can be pumped under the sunken section of the sidewalk until it rises to the normal level. 

Sinkholes in the yard

1. Sinkholes from Large Debris in the Yard

These three scenarios have different causes, but the solutions are the same.

Buried, rotting debris. Often a sinkhole develops in a large open area of a lawn or garden. A common cause of this is buried brush, stumps or debris from past construction or other activities. Over several years, the brush and debris settle or decompose, leaving an underground void. The ground surface settles into the void, causing a depression on the surface. Remnants of the debris will often be evident with a little digging.

Tree Stumps Not Removed. Tree stumps that are left in the ground after a tree is cut down can rot and cause a sinkhole to form. Portions of the rotting stump may be found in the hole, or rot patterns on the surface may indicate the presence of an old stump.

Large Rocks in the Yard Fill. During home construction, when the yard is graded and compacted to its final shape, large rocks may be buried in the soil. Rocks prevent even compaction of the yard. The soil next to the rocks will be shielded from the compacting force of heavy machinery and remain lighter and less dense than the surrounding soil. Over time, this poorly compacted soil can become a preferred conduit for water which can scour out cavities and lead to a depression.

Our solution is similar to fixing sinkholes near outside walls and under stairs (as above) combined with other methods needed. Our experience is that sinkholes are never the same and require different solutions.  

Sinkholes Near a Buried Drainage Pipe, Water or Sewer Line

A sinkhole may occur near a buried stormwater, drinking water, or wastewater line, either because of poorly compacted soil or because of a leaking underground pipe.

Poorly compacted soil around buried drainage pipes, water or sewer lines. Depressions sometimes develop in utility easements, such as water and sewer lines, or stormwater drainage pipes. This usually occurs when the soil fill over the buried pipes was not properly placed and compacted. The poorly compacted soil settles over several years, causing a hole or shallow, linear trench on the ground surface. 

We commonly fix sinkholes near buried drainage pipes, water, and sewer lines. It is wise to verify with the utility companies before taking on the expense of repair youself, as they might fix it themselves.