Possible contributing factors explored:
The Sheriff’s Office recently contacted Naval Air Station Fallon and Hawthorne Army Depot in our neighboring state of Nevada. Both installations confirmed that they conduct daily ordinance explosions for various reasons. For example, Naval Air Station Fallon deploys aerial bombs and live ordinance detonations as part of their training regimen. High speed fighter/bomber aircraft that are assigned to the Station can break the sound barrier during flight. Flights are often higher in altitude than the elevation of the Sierra Nevada Mountains that separate us. They said they conduct these kinds of operations at various hours throughout the week.
Hawthorne Army Depot said it conducts ordinance disposal operations Monday through Friday between the hours of 11:00am and 2:00pm. These particular hours of operation are consistent with most of the explosions reportedly heard in the Swansboro area of the county. The Depot is housed on about 147,236 acres just outside of Hawthorne Nevada with manufacturing, storage, and demilitarization of conventional (non-nuclear) ordinance capabilities.
All of these explosions and operations coupled with atmospheric conditions, geography, altitude, and distances all play a factor in the way sound travels. Considering that the Naval Air Station in Fallon Nevada is about 160 miles away from the Mosquito / Swansboro area, while the Hawthorne Army Depot is located approximately 200 miles away, they are most likely the source of some noise. Military personnel from both locations confirmed it is possible for the sound created by these explosions and breaking the sound barrier at altitude can reach areas within El Dorado County. However, they remain somewhat skeptical that these detonations could be heard from this distance on a daily basis as atmospheric conditions change.
According to the Sheriff’s Office Records Division, no local explosive permits have been issued that could be the source or cause of this noise.