I live in Maryland where the soil in my area is clay. Just after a heavy Christmas snow followed by rain, I discovered a sinkhole in the middle of the front lawn. An agent from the county environmental services checked to ensure it isn't an old well, and the utility provider didn't find a leak. Even after the February blizzards, it remained dry until two weeks ago when it filled with groundwater, I guess from all the snowmelt. It has grown to three feet deep by five feet wide. Now that the ground has thawed, we need to get it drained and repaired, but I can't find the right kind of professional to do the job. Who do I call, and what should I expect to see to know that it's done properly?
You could fill it up as-is and see if it redevelops, the latter would indicate that there are still some subterranean caverns that are collapsing.
The worst case would be water actually flowing horizontally underground (aka an underground spring) and taking soil away with it and causing subterranean caverns to reform, then the ground up above collapses again and again.
Stop wasting time re-adjusting the pattern. Have several lawn sprinklers, one for each pattern.
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