 The sinkhole that developed Wednesday morning is believed to be tied to a nearby mining operation. A limestone quarry has been in operation in Alton for several decades, but a former Alton Township supervisor and local historian says the mining industry has roots in Alton dating back long before that. Don Huber tells the Big Z mining here is not a new thing. Limestone mining here in Alton goes back to its very origins. There were probably mining here on the bus even before the city was planted.