BUTTE — What started as a 4-foot sinkhole in the backyard soon developed into a well that disappears into the guts of the Earth.
Tom Malloy, the reclamation manager for Butte-Silver Bow County, reported the sinkhole in the backyard of a residence in the 400 block of Iron Street. Malloy suspects the hole opened into a stope that was probably attached to the nearby Travona Mine.
City crews planned to fill the hole Tuesday with a concrete-based fill.
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Homeowner Dave Lammi first notice a sag in the ground a few weeks earlier when he brought in a trailer full of dirt to help a neighbor. A trailer wheel became stuck when the surface gave in a little.
It was after the big storm that hit Butte on Aug. 1, when the sinkhole opened to four feet deep. County workers sprayed water into the hole to flush it out and see how deep it went. The hole dropped about 20 feet deep but appears to go much deeper. Malloy estimates he finds about a dozen sinkholes in Butte each year.