Saved by Surveying, Satellite and Skill
Bob Long, an engineer technician living in Boswell, Pa., had just gone to bed when the telephone rang. Long had been getting up very early the past several days and was hoping to get some sleep to prepare for another long day. The date was Wednesday, July 24, 2002. It was summer, a good time of the year for Long. He had moved to Pennsylvania from Florida about three years before, and winters in southwestern Pennsylvania were not to his liking.
Long, who works for Civil, Mining and Environmental Engineering Inc. (CME) in Somerset, Pa., was hired on as an engineer technician and soon moved into the field as a surveyor, using the skills gained from surveying in Florida for more than 10 years. When CME purchased its first GPS system, a Trimble 4700 with TSC1 data logger (Trimble, Sunnyvale, Calif.), Long took the lead in learning and using the equipment. His skills soon payed huge dividends.
When Long answered the phone, he was surprised to hear his supervisor, Sean Isgan, PE, PLS, on the line. Isgan told Long there was a problem at the Quecreek mine in southwest Pennsylvania and that Long needed to get there right away with the GPS equipment. Isgan did not provide any details of why Long was needed; he just said he had to get there immediately. Long scrambled into some clothes and drove to CME’s office to pick up the equipment. Long gathered the batteries off their chargers, picked up his laptop and headed to the mine.
As Long drove to the mine, he was still not sure what had happened or why the mine needed a GPS surveyor at midnight. He had not spent much time at the Black Wolf Coal Co.-owned Quecreek Mine. There was a recent project in that area consisting of as-built locations of some facilities and a bit of topography work, all of which was tied in to the Quecreek Mine coordinate system. He had not been underground, as the Quecreek staff handles that work.
When Long drove through the gate at the Quecreek Mine, he was still unaware of what had happened but he knew it was something big. There were floodlights, satellite dishes, media trucks, police and emergency vehicles scattered everywhere. Only then did Long and Isgan learn that there had been an accident in the mine, and that nine miners were not accounted for. They were, at best, trapped somewhere in the mine—and they needed to be rescued.
Rescue Efforts BeginIsgan began his rescue efforts by going to the mine office for more details. Long set up the Trimble GPS equipment. He placed his base station (Base #1) in a convenient location about 2,200 feet south of the mine entry. He then used the HERE function on the Trimble 4700 to set an initial autonomous position for the RTK reference receiver. He then measured to the two control points he had used for the as-built survey. Fortunately, he also knew the Quecreek Mine used State Plane Coordinates running on NAD27, Pennsylvania South Zone. His initial checks to the control were off by about 23 feet with a rotation of just over one degree. This was well within the expected accuracy of the autonomous initial HERE position, so Long knew it was reasonable to proceed. He decided not to perform a calibration (localization), as he thought it would take too much time—and he knew time was of the essence. Instead, Long relied on his own skills. Working backward from the known control, Long developed a transformation to allow him to convert the Quecreek grid coordinate system to the one defined by the HERE position at the base. He thought it would be faster to do the computations manually than to perform the multiple measurements needed to develop and check his calibration using the data logger.
Meanwhile, Isgan had returned from the mine office. His plan was to drill small holes into an area of the mine where the miners were likely to be. The mine supervisors knew where the miners had been working and that there was accurate information—horizontal and vertical—on the mine layout. Based on where the miners were working, there was one place to which they could escape that would put them above the level of the water now filling the mine at a rapid speed. If the miners were not in that location, then they were most likely dead.
Isgan had received grid coordinates for the planned drill holes from the mine surveying and engineering staff. The drill holes were about 4,400 feet from the control points at the mine entry and 2,300 feet southwest of Base #1. The coordinates were in the mine system and Long was ready to locate. He converted the coordinates to the temporary coordinate system he had developed. After constant checking and rechecking of the math and fieldwork, Long and Isgan worked together to stake a point with GPS where rescue workers could drill. It was around 1:15 a.m. on Thursday morning, July 25, 2002. They had been on the site for less than 90 minutes. The miners, Long and Isgan believed, were 238 feet below their feet.
Saving-Grace SkillsBut there was more checking to do before the drilling could commence. A crew from Musser Engineering of Central City, Pa., consisting of Dave Zwick, industrial engineer, Dave Lucas, engineering technician, Ron Musser, PG, and Wade Tunnehill, mine surveyor, had been given the coordinates for the drill hole point. They traversed to the point using conventional SOKKIA SET 48 total stations with SOKKIA SDR 33 data collectors (Sokkia Corporation, Olathe, Kan.). Their final angle hit the stake Long had set and was within 0.2'. The conventional crew, working in the dark and confusion, provided an important confirmation that Long’s work was correct. A buried gas line in the area further complicated the rescue efforts. With no time to wait for location crews, the teams used a metal detector, shovels and some very delicate backhoe work to explore for the gas line. After going down about 5 feet, they concluded that the drill would not hit the gas line and drilling commenced.
A 6" drill hole broke through to the trapped miners at about 5:30 a.m. Thursday morning. The miners announced their presence by pounding on the drill bit with hammers. The above ground teams heard the noise and only then did anyone know that there was at least one surviving miner below. This was doubly good news to Long and Isgan, who had worried that the drill might come down into a pillar supporting the mine ceiling, rather than in a tunnel or “void.” It also proved that the maps of the Quecreek Mine were very accurate. The tunnels were 20' wide, but there was the constant worry that the drill might drift, or that the mine maps were off a bit. The miners were nearly a mile from the entrance, so the underground mapping and control had to be very good.
While the drilling of the 6" hole proceeded, Long established a new base station, Base #2. By now, he had enough measurements to establish a base station in a new location better suited to staking the dewatering holes, and he wanted his base station in a location that would ensure good radio frequency data links in the rolling, brush-covered terrain. His transformation was working well and he could quickly transform the mine coordinates to his own system. The next task was to mark locations for large 30" rescue shafts and for a number of holes for pumps that would pull water from the mine. The 6" hole was now being used to pump warm air down to the trapped miners. When mechanical problems stalled progress on the 30" shaft, drilling on a second rescue shaft was started. Long then marked that one.
As Long worked to stake the additional holes, he encountered radio interference that disrupted his RTK radio data links. Randy Musser, PE, determined that the interference was caused by the extensive radio traffic from the news media, which had by now gathered in large numbers. At Musser’s request, the Pennsylvania State Patrol moved the media out of the area where he was working and his GPS work resumed. In total, Long staked 15 drill holes and marked the locations for the two rescue shafts using GPS. He said later that his equipment performed perfectly throughout the operation and he had encountered no problems. Even the GPS satellites seemed to cooperate. Long said that he always had at least nine satellites working and recalled tracking nine at one point.
Once the dewatering holes had been drilled, diesel pumps were set up to pump water out of the mine—a massive effort. The dewatering pumps used 10" pipes with 350 hp engines to pump water over 300 feet up and out of the mine. Long made numerous measurements for elevations around the mine entrance, checking the elevation of the water as the pumping progressed. He could see that the pumps were working and the water level was going down. This was important because if the drill holes did not work, the only way to reach the trapped miners was to go through the tunnels.
A Hard Day’s NightLong worked almost continuously from midnight on Wednesday until Saturday morning. Volunteers from the Red Cross had been active on the site, making sure that the rescue teams were supplied with food and water. But there had been no time to rest. Isgan was able to get a little rest on Friday, but Long had never felt fatigued. Finally, after over 50 hours of continuous effort, Isgan grabbed Long and insisted he get some sleep. Long found a cot in a tent and laid down. His rest was interrupted by an alarm system in an ambulance parked nearby. After a few minutes, it was evident to Long that the ambulance driver was not around to switch off the alarm. He went to the ambulance and disconnected the battery, finally silencing the alarm. Only then was he able to get a couple hours of sleep.
Once the drill holes were marked and checked, there was not much for Long and Isgan to do other than monitor the water elevations. That was one way to work off the tension. Isgan noted that after the initial hammering on the 6" drill, they had heard nothing further from the trapped miners. While the miners had hammered at intervals, rescue teams on the surface had not heard their messages. Commotion from the people and equipment drowned out the tapping from below.
Long, Isgan, the other rescue workers, family, friends and people around the country would soon find out that all nine men were alive, despite their horrendous ordeal underground.
That Thursday afternoon a 30-in diameter drill arrived from West Virginia to drill a shaft large enough for a bucket to pull the miners to the surface. Despite the setback of the drill breaking and having to be repaired, by Saturday night drillers broke into the chamber where the miners were trapped. Rescuers lowered a phone to contact the miners, resulting in the almost unbelievable news that all nine of them were alive and clamoring to get out of that hole. Around 1 a.m. Sunday morning, July 28, 2002, true success manifested: the first of the nine miners was pulled from the rescue shaft. The others followed in 10- to 15-minute intervals.
Both Long and Isgan attribute the success of the rescue operation to the work done by the Quecreek surveying team: Chad Mostoller, Quecreek Coal Co. Vice President Joe Gallo and Black Wolf Mining Co. President Dave Rebuck. Quecreek is a relatively new mine, only about two years old. As the mine grew, Quecreek surveyors developed and maintained accurate maps of the tunnels and rooms underground. The underground facilities are tied to coordinate points on the surface, so everything should fit. Long and Isgan were able to use the Quecreek maps directly on their laptop computers. Both Quecreek and CME used SurvCADD CES software (Carlson Software, Maysville, Ky.), and there was no difficulty in reading the mine’s data. The miners were trapped over 4,000 feet from the control points at the mine entry, which was the only link that Long’s GPS equipment had to the underground surveys. Despite the potential for error, everything fit well and only one drill hole failed to come into a tunnel.
With the miners finally safe and reunited with their families, there was time to reflect on the efforts that resulted in the rescue. Much of the credit for the successful rescue belongs to the Quecreek Mine teams that developed and maintained accurate maps of the mine and to the people who knew where to look for the miners—including Long and Isgan. Bob Long’s skills with the computer and GPS equipment played a major role, as did the constant checking and rechecking of the calculations and fieldwork. The most important factor of the rescue was the teamwork and cooperation of every person involved, each of whom did everything necessary to bring the miners home. It’s a lesson for all of us.