Mining Feature: Inundations Can Put Miners at Risk by Blocking Escape Routes
Saturday, June 30, 2012
An unusually large amount of rain that fell Monday, June 20, near a coal mine in Kentucky flooded portions of the mine, trapping three miners. While the amount of rain that fell is unusual, water inundating a mine unfortunately is not.
Inundation, or water suddenly entering a mine, is not that uncommon. In fact, there are four ways excessive water can enter a mine and cause problems:
- Flash floods (as in the case of Monday's incident) where heavy rainfall or swollen creeks and rivers dump large amounts of water into a mine entrance. This rapid inflow of water can trap miners by blocking escape routes. Water settles into the low areas of a mine tunnel or drift.
- Mining into an adjacent, abandoned mine that is flooded is another way to cause an inundation. Safety experts say this is an infrequent, but a very preventable type of inundation. Older mines may be poorly mapped meaning the boundaries are not accurately known. Mining next to one of these sites can be dangerous if the new mine workings break into an older mine that is flooded. This can be avoided by drilling ahead with a small probe that could expose a possible flooded drift in an adjacent mine, so as to avoid exposing the flooded area to the newly mined area.
- Another way a mine can incur inundation is when coal slurry, or left over mining waste, is not properly contained in an impoundment (a banked in area that holds the mineral/water mixture left over from mining). If this impoundment fails, slurry can also enter and quickly flood a mine.
- Mines can also become inundated by mining under an aquifer, such as a lake, when the ground above the mine is damaged by the mining activity.
Typically, water rapidly enters a mine in one of these four scenarios, cutting off escape routes for miners. Coal mines are particularly vulnerable to inundation due to their relatively flat orientation. As water enters, it flows to the lowest point, blocking the escape route. Mine engineers are constantly reminded of the need to provide multiple, independent escape routes for miners to prevent them from being trapped in cases such as this.
How Big is the Problem?
- 249 inundations have occurred in the past 10 years (2000-2009) with 76 pct of them in coal mines.
- None of the incidents have resulted in any fatal injuries.
- The most recent incident in 2002 was the Quecreek event, which resulted in 9 miners being trapped for 3 days before being rescued through an escape shaft drilled into the mine.
When inundations trap miners, the initial response is generally to bring in additional pumps to lower the water level and permit miners to escape. If the flooded area is very large, extreme measures such as drilling a rescue shaft may be required. A shaft was used to rescue miners at the Quecreek mine.
The NIOSH Office of Mine Safety and Health Research has conducted studies on safe designs of impoundment areas and escape training in the case of inundation. Please see the links on this page to read papers on the topic of inundation.