A sinkhole in the backyard
Q. I have a sinkhole in the backyard next to my well house. We had a drought seven years ago and my well also got dry, so I stopped using well water. Do you think the well is filling up with water and causing the ground to become soft in the spot, and is starting to cause a sinkhole? Also, I had a fence built close to the well house and the digging could have created a problem. What do you suggest I do?
A. If a well goes dry, the soils around the well could shrink and a minor sinkhole could appear at the surface.
When you stop using the well, surface water likely will accumulate near the well shaft and the soils will swell and expand slightly rather than shrink as the water begins to soak into the upper soils.
My experience with sinkholes is mostly with mine subsidence, which occurs when an excavated mine shaft collapses deep in the earth. As soils above begin to fill the mine shaft, the soils will flow into the mine like the sands in an hourglass, creating sinkholes that can be as much as 50 yards in diameter at the surface. Any structure above the failed mine shaft will experience major structural damage.
Sinkholes also appear when groundwater dissolves and washes away limestone formations deep down. If you have a major sinkhole affecting a building near the well, it is likely the well did not “go dry,” but the flow of groundwater was redirected, leaving a cavity that filled with soil. Prolonged pumping can lower the water table, which in turn alters the direction of groundwater movement. The water is still there, but it is no longer near your well.
Lowering the water table can lead to contaminates entering the groundwater and can have an adverse effect on plant and animal life near the well.
If you decide to drill a new well, make sure to test the water for coliform and heavy metals before consuming the water.
It is very unlikely the fence posts caused a sinkhole to form.
Ÿ Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett at d.Barnett@insightbb.com.
Scripps Howard News Service