Blasting is used in surface mining as a method to fracture rock. The rock is drilled with holes, which are then filled with explosive materials, usually nitroglycerin, then capped with an inert material. The blast then is set off with detonators that splits the rock and exposes the coal seam, which, in surface mining, usually lies a few feet beneath the surface.
When blasting occurs, energy is transferred through the air and through the ground through airblasts (the actual sound of the blast) and ground vibrations. The ground vibrations can cause structural damage to homes and other buildings because the vibrations cause the buildings to shake. Airblasts, depending on the proximity to the blasting, can be anywhere from bothersome to frightening.
What is even more problematic than ground vibrations and airblasts, however, is flyrock.
Flyrock is the rock that is loosened during blasting and thrown into the air during an explosion. The pieces of rock can vary in size and weight and have been known to cause injury or death to people and property damage when the rock is launched outside of the permit limits.
The Office of Surface Mining (OSM) is the government agency that regulates blasting. They oversee the certification of blasters, and set the limits for ground vibrations, airblasts, and flyrock. OSM states that the limits that they have set for ground vibrations “that reasonably protect most residential structures…[but] damage to homes is possible at vibration levels below the limits, particularly when structures aren’t representative of typical structures (e.g. adobe, log, or mobile homes)” (OSM). Airblasts that are well below the legal limits can prove to be extremely annoying, but the OSM only regulates what may potentially cause damage, saying that it “…does not regulate…potential annoyance” (OSM).
Flyrock, the most dangerous of potential blasting hazards, has proved fatal in some instances, from those who work on blasting sites to those who live in proximity to blasting. The CDC reports that between the years of 1978-1998, 1,008 non-fatal blasting injuries occurred, and blasting is responsible for the deaths of 104 persons, with an average of 5 deaths per year. They state that flyrock and blast area security issues account for 68.2% of surface blasting injuries (CDC). These staggering numbers hit particularly close to home for one Virginia family, whose 3 year-old son was killed by flyrock that hurdled into his bedroom as he slept soundly in his bed (The article on this story can be found here).
Citizens Coal Council member groups and individuals work to help citizens understand their rights under the law when blasting is set to occur close to their home. Our member groups provide information on the steps to a pre-blast survey, and how to address complaints to the proper government agencies when blasters violate the law.
Citizens Coal Council 125 West Pike St. Suite 2 Canonsburg, PA 15317