Botanica Atlanta | Landscape Design, Construction & Maintenance

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Atlanta Garden Design

Sinkholes

Posted by Stuart DiNenno on October 17, 2009 at 6:19 PM

Sinkholes, those frightening depressions that appear suddenly in your yard after major rain events, are popping up (perhaps we should say dropping in)  in neighborhoods all over Atlanta and homeowners may be faced with another hazard of recent torrential rains along with flooded basements and crawl spaces, fungal diseases in the landscape and downed saturated limbs.  Whether caused by natural or manmade means, sinkholes must be addressed to maintain a landscape's safety, functionality and beauty.



Source: USGS


Georgia and Florida inherently have natural sinkhole tendencies due to a high percentage of limestone in the substrata.  Limestone is a soft rock and over time underground water movement and geological movement can erode the stone into a semi-solid status.  Heavy rains in turn cause settling of top soil in the spaces created by the reduction in limestone mass.  These are often imperceptible changes however there is great potential for a notable soil depression.


Manmade causes are also common.  Construction debris buried on site frequently leads to sink holes if the builder did not ensure proper grading and soil compaction before selling the property.  Broken water, sewer or gas lines can also create sinkholes.


Before you can properly repair a sinkhole you must first figure out what type of sinkhole you have and how big it is.  Dig beneath the sinkhole at the lowest point, and dig wider than the sinkhole to explore the cause.  If you encounter debris, you have a void that can be resolved with the help of a landscape professional. If you encounter limestone or granite bedrock, broken pipes and or water, you may want to get a city or county authority involved.


For the manmade sinkhole which is less than 3 inches deep, apply topsoil in a 2:1 mix ratio with sand.  Existing grass will grow through this easily or you may choose to seed if there was no lawn above the sinkhole.  Do not seed if there is existing lawn.  If the sinkhole is greater than 3 inches deep, remove the sod carefully, then apply topsoil and compact using a compactor and finally, replace the sod.  If greater than 1 foot of topsoil is required, compaction should occur once per foot of new soil.


If the sinkhole is a natural, substrate problem, remove all organic matter and debris and fill the bottom of the hole with rocks in graduated sizes from large at the bottom to gravel.  Apply landscaping cloth, then cover with sand until level with the top of the subsoil.  Compact, then add topsoil and compact.

 

Unless your sinkhole is small you should probably have a landscape professional help you assess the problem and suggest solutions.  If you encounter standing water or smell gas, call your city or county authority as well.


Categories: Landscape Construction

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