SHELBYVILLE " A 20 foot deep, 12 inch diameter hole near the Lake Shelbyville dam has U.S. Army Corps of Engineers workers scratching their heads.

Maintenance workers at Lake Shelbyville found the hole while doing routine maintenance near the west berm of the dam.

"One of the workers saw a depression in the soil," said Lake Manager Ricky Raymond. "It was soft and with just a little poking the hole opened up."

What makes the hole interesting is that it is bored through natural soil and not materials used to build the dam and lake area. Lake Shelbyville was created over a network of old mines and farmland. Geological engineers routinely dig bore holes to test soil and map geological formations and sometimes use the holes to inject materials into abandoned mine tunnels. Raymond said engineers from the Corps' St. Louis office came within hours of the hole being found last Friday and determined it was not a threat to the Lake Shelbyville dam.

"It was important to check it out and find out what it was as quickly as possible," he said. "Anytime we find an anomaly like that we take it very seriously."

"The hole isn't an immediate threat," said Mel Baldus, chief of the St. Louis District's Engineering Division.

Another answer engineers are looking for is where water at the bottom of the hole is coming from. The land sits 25 feet above the water level of Lake Shelbyville, but there is water in the bottom of the hole. Raymond said the water was being tested to see if it was storm water runoff or a possible water main leak from the Shelbyville city water system.

"We'll be working with the city to figure this part out and take action," he said.

The mysterious hole is an unusual introduction to Lake Shelbyville for Raymond, who was named lake manager last month.

"It's interesting for sure," he said. "There's a lot of history in this area, and I'm getting a fast introduction to it."

Sharon Mosley can be reached at sharonhrnews@yahoo.com.