In Wake of 'Earthquake', Quarry Promises New Practices

A correction has been made to this article. See below.

After an hour-long meeting Sept. 15, members of the Lyons Township Quarry Advisory Committee are satisfied with the explanations of a quarry operator about the cause of tremors that shook west suburban Cook County at 1 p.m. on Aug. 31.

Township Supervisor Russ Hartigan said the cause of the tremors was a freak occurrence, according to experts provided by Hanson Materials Service, which operates a quarry in McCook. The blast causing the U.S. Geological Survey to record a 2.7 magnitude 'earthquake' likely originated from a Hanson quarry near 47th Street and East Avenue.

In a telephone interview Sept. 17, Hartigan said it appeared the tremors that shook La Grange, La Grange Park and other municipalities were triggered by a combination of unusual atmospheric conditions and the composition of the explosives used.

"It looks like the atmosphere, it was a warm and muggy day with low cloud cover, combined with the composition of the blasting made for a greater explosion than estimated," Hartigan said.

In order to prevent another similar tremor, Hartigan said the company will not blast as long, and they will change the composition of the explosives, which will create smaller holes.

Representatives of Vulcan Materials Co., which also operates a quarry in McCook, presented information to the board at the same meeting, which showed they had not been blasting on Aug. 31, and therefore did not contribute to the tremors.

"This was an accountability meeting and we are satisfied with the explanation from the quarries," Hartigan said.

A spokesperson for Vulcan and Hanson could not be immediately reached.

In the minutes after 1 p.m. on Aug. 31, residents reported feeling tremors in municipalities across suburban Cook County and into parts of DuPage County. At first, people thought the shaking was caused by either an earthquake or sonic boom, Hartigan said. But those were quickly dismissed as more evidence pointed to blasting in one of the nearby quarries.

Hartigan said residents near the quarries are used to tremors from blasts, but said that day's shaking was unusual.

"We live in Western Springs and my wife was in the shower when it happened and she felt it," Hartigan said. "People in the area are now very aware that we have blasting in our area."

It was felt by officials in the La Grange Park Library, 555 N. LaGrange Rd., who posted on Twitter that the earthquake "shook the building."

Hartigan said the Township of Lyons offices were flooded with calls from concerned residents, several claiming they had minor damages from the shaking. However, Hartigan said officials have not discovered structural damage in any township home or business as a result of the explosion.

The Township will continue to monitor the activities of area quarries and maintain regular meetings with quarry officials. In addition, the Quarry Advisory Committee will maintain semi-monthly meetings.

"I just hope this incident was nothing more than an aberration," Hartigan said.

Correction: The first version of this article implied both Vulcan and Hanson were responsible for the Aug. 31 tremors, and that both were changing their practices. In fact, only Hanson was involved and is making changes. Paragraph six now clarifies Vulcan's involvement.