LEAD - Water glistens off the gray rock lining the tunnel where the cold air carries the musty smell of decaying timber.

The tunnel is the Kirk Drift, 300 feet below the surface in the old Homestake gold mine in Lead. It was blasted out about three quarters of a century ago and served as a supply point to sink the nearby Ross Shaft.

Duane Ennis, a third-generation miner at Homestake, halts a group of 15 reporters and photographers tromping along the gravel rail bed in the drift to explain how explosives, timber and other supplies were brought in through the old drift dug 1,250 feet west from the side of the mountain.

Ennis, serving as a tour guide, says the 300 level is where some 21st century facilities are likely to be built for the Sanford Laboratory at Homestake, the state of South Dakota's precursor for the hoped-for Deep Underground Science and Engineering Laboratory.

The facilities could include a station to calibrate instruments that will go thousands of feet deeper in the mine to look for answers to some of science's deepest mysteries, according to Sanford lab spokesman Bill Harlan. It also could serve as a point to assemble materials for other experiments deep below, Harlan said.

The first big mystery scientists likely will pursue is that of "dark matter." Scientists are certain it exists because it has a gravitational force, but it is not visible. For example, astronomical studies show galaxies that rotate faster than their observable mass indicates they should.

That's the short explanation provided by Kevin Lesko, principal investigator for the Homestake DUSEL collaboration.

Lesko told reporters after the tour that the dark matter puzzle is one of the 10 biggest questions in physics today. "Finding an answer to that in the next several years would be revolutionary," he said.

Other deep labs throughout the world are already looking for dark matter.

Jose Alonso, director of the Sanford lab, said about 20 scientists will be joining the search for dark matter. "Dark matter is a big race," Alonso said.

But there will be many other experiments conducted at the Sanford lab's 4,850-foot level.

About 300 scientists and others from around the world gathered this week in Lead for the DUSEL Initial Suite of Experiments Workshop, where they talked about possible experiments to conduct in the Sanford lab, to be built by the state of South Dakota.

Alonso and Lesko were pleased with the response and the enthusiasm of the scientists.

"They're anxious and ready and knocking on the door," Lesko said.

Lesko said a major challenge will be fitting the different experimental collaborations into the Sanford lab so they can work without getting in each other's way.

The dark matter experiment, called the Large Underground Xenon detector experiment, or LUX, is a collaboration that includes researchers from Case Western Reserve in Cleveland, Brown University in Providence, R.I., and the University of California-Davis.

The LUX dark matter experiment will begin at the 4850 level - 4,850 feet below the surface - in the same cavern used by chemist Ray Davis, in experiments spanning from 1967-1985, to confirm the presence of particles called neutrinos. That work earned him a share of the 2002 Nobel Prize in physics.

Scientists need deep underground mines or caves to conduct such research because the thousands of feet of rock shield the experiments from much radiation, which, at the surface, would cloud the measurements.

To conduct the LUX, the Sanford lab must first pump water out that has been slowly filling the mine since it was sealed in 2003.

Alonso said the water level has reached 4,670 feet below the surface, covering the 4850 level.

But lab crews began pumping water Tuesday from a reservoir at the 2,450-foot level, Harlan said. That has intercepted about 40 percent of the water flow, Alonso said.

He said pumping from the main body of water would begin next month. Crews are installing pumps for a pumping station at the 3,650-foot level and placing smaller pumps even lower in the mine.

Alonso said the 4,850-foot cavern should be dry by August. After that, crews will make sure the cavern is safe, remove the old water tank that Davis used and mount a new, large tank for the dark-matter experiment, he said.

If all goes well, the hunt for dark matter in the old Homestake mine could begin early next year, Harlan said.

The DUSEL, which would include a lab 7,400 feet underground, will take longer.

At the Lead gathering this week, scientists worked to select experiments to pursue and to formulate a detailed cost analysis, which eventually will become part of a preliminary design report due to the National Science Foundation in about a year.

A formal presentation to the NSF governing board is expected in 2010, with the goal of NSF-funded experiments starting at Homestake in 2012.

Meanwhile, the scientists gathered in Lead were chomping at the bit to get into the mine and start their experiments, Alonso said.

During a series of tours of the 300-foot-deep Kirk Drift earlier in the week, the enthusiastic visiting scientists "looked like a bunch of school kids," Ennis said.

"We had represented every facet of science that you could imagine come through here."

Ennis said that, in effect, the scientists - not him - conducted the tours.

"If somebody asked a question, there was some expert in that field who could answer it," said Ennis, a third-generation miner who worked at Homestake for 22 years.

Contact Steve Miller at 394-8417 or steve.miller@rapidcityjournal.com