HILL AIR FORCE BASE — The Air Force will soon begin its 2015 season of large detonation operations at the Utah Test and Training Range.

The detonations, which involve destroying the rocket motors and solid propellant of Air Force and Navy ballistic missiles, will occur two or three times a week through October.

The destruction of these three-stage, solid-propellant motors — for the Navy’s Trident and the Air Force Minuteman missiles — is occurring to eliminate aged propellant and as part of international treaties to reduce the number of ballistic missiles.

“Detonation is the best environmental method for disposing of the rocket motors and propellant,” said Glenn Palmer, Hill AFB’s air quality program manager.

The warhead or payload portion of the missile is not destroyed at the UTTR, and no nuclear materials are involved in the detonation. During 2014, more than 140 rocket motors were destroyed at the UTTR.

Before each large detonation (those involving more than 10,000 pounds of net explosive weight) at the UTTR, the Air Force takes atmospheric readings to check wind speed, direction and other factors and enter them into a sound model to determine if conditions are acceptable for a large detonation.

“If the model predicts that noise is going to be louder than permitted levels at locations along the Wasatch Front, we delay detonation,” Palmer said.

During a couple of instances last year, however, residents near Hill AFB were startled to hear the detonations a few minutes after they occurred as the sound traveled 45 miles across the Great Salt Lake to Hill AFB and nearby communities.

“We believe weather conditions were conducive to amplifying the noise of those detonations and our sound modeling did not accurately predict sound levels along the Wasatch Front,” Palmer said. “We plan to collect additional sound-monitoring data this year to modify our model so it more closely reflects actual conditions here.”

The UTTR has played a major role in disposing of the nation’s missile motor inventory for more than 20 years and has destroyed more than 1 million pounds of missile motor propellant to date.

“The UTTR is the only location in the United States capable of destroying these missile motors,” Palmer said, “but we want to do this work without adversely affecting our neighbors.”