A blast at a quarry in suburban McCook was well within safety limits, according to state officials who said Wednesday they cannot explain a subsequent tremor seconds later that rattled windows and frazzled nerves throughout the Chicago area.
The Illinois Department of Natural Resources sent an inspector to the Hanson Material Corp.'s quarry after the U.S. Geological Survey reported a seismic event occurred Monday in the area. A two-day inspection of the site and a review of the company's blast recording and measurement data found it was under limits set for vibration levels, the agency reported.
The blast was picked up by instruments and was followed by a "second event that was also picked up by the instruments … about seven seconds later," said Department of Natural Resources spokesman Chris McCloud. "But it wasn't a blast."
Although McCloud said the agency does not know what caused the second event, officials from the USGS continued to stand by their statement that the tremor — which measured a magnitude of 3.2 — was not an earthquake.
"The waveforms generated from the event indicate that it was a blast from a quarry in the area," said Julie Dutton, a geophysicist at the agency.
U.S. Rep. Daniel Lipinski, D-Ill., sent letters Wednesday morning to the U.S. Department of Labor and the Bureau of Alcohol, Tobacco, Firearms and Explosives, requesting that the agencies investigate whether the blast caused the second tremor.
Lipinski noted that his home was also rocked by the incident and said that the disturbance to residents and their property was unacceptable.
"Unfortunately, homeowners and businesses in the western suburbs are accustomed to being disturbed and startled by frequent quarry blasting, but the incident that took place earlier this week demands additional scrutiny," Lipinski said in a statement.
"Residents of the area deserve some answers. I was sitting at my kitchen table at my home in Western Springs when my house started to violently shake for five seconds. This is something that no one should have to tolerate."
Officials from Lehigh Hanson Inc. — the parent company of the quarry — acknowledged a routine blast occurred at about 12:35 p.m. Monday, and said the Department of Natural Resources report confirmed their earlier statements that the tremor was unrelated to activity at the mine. Nonetheless, a spokesman said the company will fully cooperate with any further investigations into the cause of the tremor.
"The report confirms what we already knew," company spokesman Jeff Sieg said. "We are going to keep looking into this. We are still very concerned what caused the tremor. We are going to look at things such as blasting patterns."
The U.S. Department of Labor's Mine Safety and Health Administration sent an inspector to the quarry Tuesday, and a spokeswoman said that while the investigation continued, the inspector found no violations or signs of unsafe activity.
A spokesman for the ATF said investigators in the bureau's Chicago office had not been notified of Lipinski's letter.
"We were surprised by that release (from Lipinski)," Sieg said. "We have tried to reach out to his office and make contact with him. ... We welcome a discussion with him. If there are any agencies that want to investigate, we will be happy to work with them."
Walberg is a Tribune reporter; Ruzich is a freelance reporter.Copyright © 2015, The Baltimore Sun