By Alison James

alison.james@fct.wpengine.com

Officials with Vulcan Materials were forced into some investigaton after a loud kaboom shook up Northwest Alabama Thursday morning.

“We did put off a shot … around nine o’clock,” said public affairs manager Jeff Johnson. But according to Vulcan’s seismographic readings, Johnson said, the “normal course of business type of shot” should not have caused the boom that followed.

“All our limits came in well under what the law requires and what Vulcan self-imposes,” Johnson said.

A volume of 133 decibels, Johnson said, is the legal limit. Vulcan restricts that to 125 decibels.

“We want to be well below what the law requires,” Johnson said. This morning’s shot in the quarry near Russellville was recorded at 124 decibels.

Johnson said in all other ways, besides the unusually loud noise, the shot was typical for Vulcan.

Concerned calls were made to Vulcan as well as to local law enforcement officials and the local EMA Thursday following the boom.

“That really scared a lot of people,” said fire marshal Justin Green.

Thursday afternoon the company began investigating possible causes of the loud noise. One theory they were pursuing was that of temperature inversion, and that is what they have determined was the cause.

“All the meteorological data we reviewed … supported that it was a classic temperate inversion on the weather the other day,” Johnson said Monday. “As the sun comes up, it typically warms up the air aloft before it warms the air closer to the ground, and so what that essentially does is create a ceiling,” – a ceiling that prohibits the sound from dissipating properly. Johnson said Vulcan conferred with National Weather Service to determine those conditions.

“What we’re going to do going forward is we’re going to push our shots back later in the day,” Johnson said. “That should help mitigate that problem.”