By L. Findlater

At about 9 pm on July 24, 2002 a work crew of nine men from the Quecreek Coal Mine in Somerset Pennsylvania (Fig. 1) nearly lost their lives when they inadvertently drilled into the adjacent abandoned Saxman Mine, liberating an estimated 50-60 million gallons of water into the active mine. The men were trapped in an air pocket within a 48-52 inch coal seam 240 feet underground for more than 3 days. Miraculously, the nine men survived the incident, in part due to a well-planned and executed rescue operation. The story of the Quecreek Mine flooding is a reminder on how dangerous mining can be and how critical a good understanding of hydrogeological situation in vicinity of the mine can be.

Figure 1. Location Map (scroll down).

 

Rescue Operation

The rescuers first decided to drill a 6 inch diameter exploratory hole (Fig. 2) to try to locate the miners and allow them to blow compressed air into the tunnel to create/maintain the air bubble. The hole was located using about $60 000 (USD) worth of GPS surveying equipment, operated by a local engineer technician. Within 5 hours of locating the drill site, at about 5:30 am on July 25th, the drill penetrated the air chamber and the rescuers heard the trapped men tapping on the drill bit with their hammers. That afternoon, using a 30 inch diameter drill bit (Fig.3), the rescuers started drilling a rescue shaft large enough for a rescue capsule (Fig. 4) to be lowered to the miners. Early in the morning on the 26th, the drill bit broke and fell into the shaft while drilling through dense rock. Later that morning, the rescuers started drilling a second rescue shaft while others tried to retrieve the broken drill bit from the first hole. By that evening, the workers successfully retrieved the broken drill bit and resumed drilling the first shaft while also drilling the second shaft (Fig. 5).

Figure 2. Drill rig at exploration hole.

Figure 3. Drill bit used at second rescue shaft.

Figure 4. Capsule lowered down rescue shaft.

Figure 5. Photos of drill rigs.

Another challenge faced by the rescuers was to drop the level of the water in the mine by a total of 30 feet so that the integrity of the air pocket would not be compromised should the rescue shaft enter the it (Fig. 6). As of the morning of the 25th, the water levels in the Quecreek and the abandoned Saxon mines were at an elevation of 1870 feet above sea level, with the men trapped in the air bubble at an elevation of approximately 1820 feet. At this point, about 9 pumps (Fig. 7) were in place and removing 12 000 gal/min of water from the site, effectively dropping the water levels in the mine by one foot per hour. By the afternoon of the 26th, the pumping rate had increased to 20 000 gal/min which included a submersible pump pumping 1600 gal/min.

Figure 6. Schematic cross-section of flooded mine. Diagram courtesy of Pennsylvania DEP.

Figure 7. Pumps used to dewater flooded mine. Photo courtesy of MSHA.

Some nearby homeowners needed to be provided with an alternative water supply when theirs was lost due to the shaft dewatering.

By the afternoon of the 27th, rescuers put a plate over the first rescue shaft to stabilize the air pressure. At this point the shaft was 214 feet deep (about 23 feet from the air pocket) while shaft two was 190 feet deep. A couple of hours and 10 feet later, the rescuers stopped drilling the first shaft to install an air lock. By 10 pm, the rescuers had succeeded in lowering the water levels in the mine by 30 feet and shortly afterward the first rescue shaft penetrated the air chamber. By 3:00 am on the 28th of July, all nine men were retrieved safely from the mine (Figs. 8, 9, 10).

Figure 8. Rescued miner.

Figure 9. Rescued miner.

Figure 10. Rescued miner.

 

Post-Flooding Mine Rehabilitation

As reported on August 23rd on the Pennsylvania Department of Environmental Protection (DEP) website, the Black Wolf Coal Company, operator of the Quecreek Mine, continues to drain the Quecreek Mine at rate of 1500 gal/min (Fig. 11). Throughout the mine dewatering, the DEP has been continuously monitoring the quality of the discharge. During the rescue effort, the DEP monitored the water quality at the Quemahoning Dam Reservoir, where the mine water was being discharged, and found that the turbidity and pH levels were slightly elevated but within normal ranges.

Figure 11. Partially flooded entrance of Quecreek Mine. Photo courtesy of MSHA.

A few days after the rescue, however, the water quality declined with the iron levels exceeding the limit allowed in the Quecreek Mining Inc.'s permit. The DEP officials advised the Black Wolf Coal Co. that they could no longer pump water out of the mine that they couldn't treat. In response, Black Wolf Coal Co. had to shut down its submersible pumps and only operate pumps near the main entrance of the mine whose water could be fed into their existing water treatment facilities. Within one day of shutting down the submersible pumps, the water level in the mine rose 5 feet. Quecreek Mine officials agreed to build additional treatment ponds to supplement their treatment facilities, which were completed within 5 days.

As of August 23rd, the water level inside the mine had been lowered enough to allow Black Wolf Coal Co. employees into the mine as far as the mine pool location. Progress beyond this point is slow as they have to rehabilitate each section of the mine before they move forward. Preliminary observations carried out by DEP and Fish and Boat Commission biologists indicate no significant impact on Quemahoning Creek from pumping the Quecreek Mine pool.

 

Lessons Learned

One major issue that has arisen from this near disaster is the accuracy of the maps of the abandoned underground Saxman Mine, which closed in the early 60's. The maps show the Saxman mine to be 300 feet away from where the crew was drilling. The US Department of Labor's Mine Safety and Health Administration (MSHA) is conducting an investigation of the incident and is starting a national project to identify old mines, along with reviews of mine maps, technological innovations, and regulations and practices to prevent these incidents.

In a letter to state Attorney General Mike Fisher, two state lawmakers wishing to convene a grand jury on the incident wrote: "Based on the common knowledge that much of the area around the Quecreek Mine was undermined and that historic mining maps are notoriously inaccurate, the department [Pennsylvania DEP] should have been more diligent in requiring the company [Black Wolf Coal Co.] to evaluate the hydrological consequences of the proposed mine."

As recent events in Somerset have shown, one can never underestimate the importance of groundwater in the mining life cycle, even nearly half a century after a mine closes.

The Pennsylvania Department of Environmental Protection's website includes documented developments in the investigation. The DEP released its final investigative report on the Quecreek disaster in 2003 (see DEP website). The report found that the accident occurred because of inaccurate maps depicting the historic mine workings and underscored the need for the state to improve deficient map verification methods and revamp mine permitting processes. Since the accident, DEP issued administrative orders to all bituminous and anthracite mines operating near known abandoned mine voids to provide credible evidence—in the form of accurate maps, drilling or other means—that they know for certain where the actual mine void is located. Bituminous mine operators now have to provide hard data as to the location of mine boundaries once they reach 500 feet of an abandoned mine void. Anthracite operators have to provide this information at 300 feet. The previous distance for both was 200 feet.

The DEP has since catalogued mine maps in its repositories, electronically scanning some 3,900 maps, and designed a database for entering mine production data collected from hard-copy mining reports over the past 130 years to enable searches that will allow comparisons with known maps to get a more accurate picture of mine voids and mine workings.

The MSHA also maintains a website with a photo gallery, news and maps relevant to Quecreek Mine.