How common are residential sinkholes? If there’s a hollow spot under the sidewalk, is that cause for worry? I have a bit of rockery next to the sidewalk and, several years ago, saw that a rock had been displaced, went to put it back and found a small hole that seemed to lead under the sidewalk. I poured some sand in the hole, then some more, then poked a stick in there when I ran out of sand. It moved freely under the sidewalk. Every time I see something about a sinkhole in WS I think of the hollow under my sidewalk and wonder if it’s something I should be concerned about. Naturally I’ve taken the ostrich route and haven’t looked at it since.
Usually, not always… a sink hole means running water is erroding the supporting soils. I would call the city…I would suspect a broken/leaking water line or a broken sewer line…. Is there a drainage line going to the street to take water runoff to a nearby manhole? If it is a sewer line.. don’t dig to invesitgate !!