Top of the Rock sinkholes may reveal caverns

The Ridgedale golf course known to host legends of the game and draw national media attention for its picturesque views and course design received media attention for off-course holes last week.

Four sinkholes were discovered at Big Cedar Lodge’s Top of the Rock golf course on the morning of May 22, and their sudden appearances could point to a yet undiscovered cave system, said Bass Pro Shops’ Director of Conservation Martin MacDonald.

The largest sinkhole measures roughly 60-by-80 feet and over 35 feet deep, according to an executive with the engineering firm working to assess the situation.

All four holes were near the Jack Nicklaus-designed driving range beyond player areas, and they have since been fenced off to protect the public, said Gary Pendergrass, a principal with GeoEngineers Inc. in Springfield. He said golf play has not been impacted and that heavy rains the previous week likely have caused the sinkholes above karst topography.

“We want to ensure the safety of the guests down there, but they are still using the driving range and still using the golf course,” Pendergrass said.

Officials say the sinkholes appear to have stabilized because there was minimal caving of the soil walls despite heavy rains over Memorial Day weekend. Pendergrass said the holes have not changed significantly since they were discovered around 5:30 a.m. May 22.

“We think we are at pretty much on the bedrock surface at the bottom of the hole right now,” he said of the largest sinkhole.

MacDonald said GeoEngineers representatives plan to work through early June with the Missouri Department of Natural Resources to determine the cause of the collapses and the best course of action moving forward. He said geologists speculate a previously unknown cave system exists in the area because it appears water that fed into the sinkhole is now on the floor of an underground chamber Bass Pro officials have called the Johnny Morris cave since discovering it about 12 years ago. Morris, who founded Bass Pro Shops in Springfield and Big Cedar Lodge on Table Rock Lake in Ridgedale, has not publicly addressed the situation.

“There may be a cavern down there,” MacDonald said. “There is much excitement from our founder and the geological team as to what might be there.”

The holes appeared about a month after Top of the Rock hosted the second-annual Bass Pro Shops Legends of Golf Tournament at Big Cedar Lodge. In its two-years at the course, the tournament has attracted such professionals as Tom Watson – who designed a putting course at Top of the Rock – Gary Player and Fred Funk.

That might be why several notable national media outlets called on Bass Pro in late May to learn details about the sinkholes. According to Bass Pro Shops Director of Communications Tammy Sapp, the geological event has been covered by The New York Times, Golf Digest, ESPN, ABC News, Fox News, USA Today and CNN. The story also has been picked up by BBC, The Weather Channel and the PGA.

Southwest Missouri is generally a hotbed for sinkholes with its caves and often Swiss cheese-like subsurface rock.

Brad Parrish’s geotechnical and civil engineering firm, Palmerton & Parrish Inc., firm is called to work on around a dozen relatively minor sinkholes a year.

“We see them quite a bit, but they’re not nearly as dramatic as Top of the Rock,” he said. “In the last 25 years, I can think of maybe only two of that magnitude.”

In 2006, an 80-foot sinkhole swallowed a car and half a house in Nixa, and Parrish said the Joplin area has been prone to sinkholes as well, due in part to the history of mining.

“Right now, we’re dealing with a mine collapse off of Rangeline Road in Joplin,” Parrish said. “It occurred after heavy rain. It was just a small opening in the parking lot, but you could see it opened into a larger feature.”

He said heavy rains are often a trigger because they can feed underground streams, which eat away at surface soil from the bottom up.  

Pendergrass said the collapses at Top of the Rock are thought to have filled in around the bedrock, and no new sinkholes are expected in or around the course.

“We see this all the time in southern Missouri,” Pendergrass said. “We’ll be doing a more complete investigation to really characterize all the sinkholes and how they interconnect with the caves on site.

MacDonald said Bass Pro had not estimated repair costs by press time, but said insurance would cover expenses.

From his experience, Parrish estimated a $500,000 price tag for a sinkhole that large.

“We are blessed with beautiful nature, but it also causes these sinkholes,” Parrish said.[[In-content Ad]]