The 8 5/8-inch bore hole is aimed at a tunnel about 1,000 feet deeper in the Emery County mine than the section where the missing miners were working in the wee hours of Aug. 6 when a massive cave-in occurred.

No signs of life have emerged from deep underground since then. Images released Monday from a video camera lowered down another bore hole the previous evening showed more equipment in a tunnel near the missing miners' last known positions, but nothing of the men - Manuel Sanchez, Brandon Phillips, Juan Carlos Payan, Jose Luis Hernandez, Don Erickson and Kerry Allred.

Nevertheless, UtahAmerican Energy Inc., which owns and operates the mine, and federal mining regulators overseeing the rescue effort believe the catastrophic collapse would have pushed breathable air into the back of the mine, creating a life-sustaining pocket that the miners - if they survived the initial shock - might have fled to after determining their escape routes were impassable.

"That's why it's a priority area," federal Mine Safety & Health Administration boss Richard Stickler said Monday.

Like everything else in this weeklong rescue effort, however, the development of this new bore hole took longer than desired, further decreasing prospects of locating the six miners soon.

On Sunday, officials said they hoped to have the drill rig in operation before dawn Monday. But bulldozing a road 1,300 feet to a new drill site on the mountain above the mine took until dark, making it too dangerous to move the giant drill right to its cliff-side spot until first light Monday. Crews then spent the morning and afternoon getting the rig ready to start boring a 1,414-foot hole into the mine's deepest recesses.

The underground advance toward the trapped miners also continued to be difficult and dangerous.

Conditions described by mine co-owner Robert Murray as the worst he's seen in 50 years of mining have prompted 12 miners to ask to be relieved of rescue duties, he acknowledged. "They have been assigned to other work in the mine at other locations."

By midday Monday, miners working to clear the fresh-air tunnel of fallen rock and coal had moved forward just 65 feet in 24 hours. With that, they have advanced 645 feet in a week, a little more than a fourth of the way to the area where the missing miners were working when the cave-in took place.

It is unlikely the pace will pick up appreciably for some time.

Stickler noted that the next 1,000 or so feet of the tunnel is beneath the highest part of the mountain and subject to the greatest pressure from above. That pressure is so great, said Murray, that aftershocks moved an 80-foot-by-130-foot pillar of coal three feet. So that stretch of tunnel is likely to be filled completely with rubble.

To make matters worse, rescue organizers still have not determined the source of oxygen-deficient air found in the trapped miners' working section by monitors lowered down the first borehole.

Stickler said that on Sunday night, mine-rescue team members wearing breathing devices pierced the suspected source of the bad air - a sealed-off section to the north that had been mined out long ago. But the air-sampling equipment they installed showed that the bad air had not migrated into the working section from the north.

Now organizers are trying to determine if the bad air came from mined-out areas south of the trapped miners' working section, Stickler said.

"We need to know," he said. "Sooner or later, we're going to have large amounts of oxygen-deficient air we're going to have to dilute so that it's safe for the rescue workers."

The safety of those rescuers is paramount, Murray concurred.

"Progress is slow, way too slow, but not too slow to risk the lives of these rescuers," he said, announcing he will be taking two miners related to the missing men into the mine before dawn today [Tuesday], and will shoot video and still pictures of the work being done.

"I'm very disappointed to be telling you on the eighth day that we have not found six alive miners," Murray said. "It's heartbreaking, absolutely heartbreaking.

"As I've said before, the initial concussion of the seismic activity could have killed these miners outright and they would not have suffered. However . . . there are many reasons why one would believe they still may be alive," he added, citing earlier findings that cave-ins closer to the missing miners were only two feet deep and that this deeper section of the mine had good air and drinkable water.

If the missing miners did retreat to the back of the mine, Stickler said the drilling of the new bore hole could give them hope.

"I assure you they hear any drilling activity going on above them," he said.

mikeg@sltrib.com