The Doe Run Company (Doe Run) responded Tuesday to the Bonne Terre Chamber of Commerce request to investigate a hole in the ground that opened up on the chamber’s property near the Bonne Terre Mine.
Doe Run owns the mineral rights and underground mine workings in the area. The Bonne Terre Mine was operated by Doe Run’s predecessor, the St. Joe Lead Company.
“We were notified of a hole on chamber of commerce property in the area near the Bonne Terre Mine,” said Chris Neaville, asset development director at Doe Run. “We suspect that the extraordinary wet spring may have contributed to the opening of this hole.
“We are assessing the best means of permanently closing the opening." Neaville explained. "In the meantime, the Bonne Terre Chamber of Commerce has covered the hole and secured the area.”
At first, the hole was believed to be about 39 feet deep, but upon Tuesday's inspection, they found that it's actually much deeper than originally thought.
Using a down-hole camera, which is regularly used to inspect vent holes in working mines, the crew from Doe Run inspecting the sinkhole was able to see that the hole extends down into the mine and spotted large rock pillars and the waters of the billion gallon lake that fills the subterranean space which lies below the area.
The exploratory examination took approximately an hour to reach the bottom of the small diameter sinkhole as the down-hole camera operator had to maneuver the camera around tree roots and rocks.
Eventually, the operator was able to extend the camera apparatus to the bottom of the hole. They found that the hole was not completely vertical into the mine but instead inclined at an angle into the large cavity.
The owner of Bonne Terre Mine and West End Diving, Doug Goergens, said that the hole into the mine is in a remote area underground, far from where the mine tours or diving takes place.
He explained that neither he nor Doe Run was sure that it was a mineshaft at one time and could have possibly been the result of a number of different things.
According to Goergens, there may have been a tree that grew there at one time and it’s possible that the roots could have rotted away. This process would cause the cavities left by the roots to fill with soil and then the heavy rains the area has received lately may have washed the soil down into the mine causing a sinkhole.
He said that over the years, small sinkholes have appeared for this reason and others, but it's nothing unusual or anything to worry about.
Goergens added that the area hasn't had any sinkholes in a long time. Typically in the past when they have had sinkholes, Doe Run would come out and remedy the situation quickly after thorough examinations.
When the mine ceased operation, the St. Joseph Lead Company would completely seal up any large shaft openings with concrete for public safety.
“They were a very conscientious company,” said Goergens.
Doe Run assumes responsibility for any sinkholes or mine shafts related to their mining claim. The inspection crew on site Tuesday examined the hole from top to bottom and went down into the mine to inspect the area of the mine breach.
After the examination, the sinkhole was covered up again with a large concrete slab for public safety.
Not much is known at this stage in the process as engineers will need to analyze the video footage and mining records may have to be looked at to determine if the hole was indeed once a mine shaft and what the best method is for filling the crevice.
City Administrator Shawn Kay said that Goergens and the staff at the Bonne Terre Mine tour site have been very helpful with the whole process.