The Associated Press

SIOUX FALLS - A giant steel tank built 4,850 feet deep within the old Homestake gold mine to catch neutrinos might have more to contribute to science.

Physicist Ray Davis Jr. and his colleagues filled the 100,000-gallon storage vessel with cleaning fluid in the 1960s to help demonstrate that neutrinos are created in the sun as the result of nuclear fusion. Davis earned a share of the 2002 Nobel Prize in physics for the work.

Workers who soon will strip the cavern and rebuild it into the Sanford Laboratory will have to dismantle the tank, but it won't go unused, said Jose Alonso, Sanford's lab director.

The steel, of superb quality because it has been underground for decades, likely will be cut into strips and used for shielding for future underground experiments.

"Anything on the surface tends to be activated by cosmic rays, so this has been protected for so many years that in fact it's of a quality that you just can't get anywhere else," Alonso said.

The National Science Foundation has picked Homestake as the preferred site for a deep lab 7,400 feet underground, but in the interim, the state of South Dakota is building the Sanford Laboratory at the 4,850-foot level.

The first major experiment slated for the so-called Davis cavern is the Large Underground Xenon detector - or LUX - which seeks to detect dark matter, an unknown substance that may make up 80 to 90 percent of matter in the universe. Scientists know it exists because it has a gravitational force, but it's not visible.

Alonso said he'll attend a collaboration meeting in a couple of weeks with LUX's principal investigators, Tom Shutt of Case Western Reserve in Cleveland and Rick Gaitskell of Brown University in Providence, R.I.

Many physicists are interested in getting underground to begin their work, but there are also plenty of geologists, geophysicists and geobiologists looking to gain access.

Gov. Mike Rounds, in his State of the State address this past week, thanked legislators for having the foresight to appropriate state money for the interim laboratory ahead of the NSF's decision on a site for its deep underground national lab.

Scientists from various fields will visit Lead for a major workshop, the governor said.

"In April of this year, over 200 scientists will be coming to South Dakota for a special weeklong conference on underground science and to discuss experiments they want to do here at both levels in our laboratories," Rounds said.

But before any science starts underground, crews need to pump out the water that has been rising since Homestake's closure in 2003.

Crews have been working their way down the Ross shaft, one of two of the mine's access points, repairing any corroded steel, bearing sets or I-beams on the way down.

"We're not refurbishing the entire shaft," Alonso said. "We're just sort of looking at areas where there are high risks of problems and taking care of those right away."

Crews are hooking up electricity to water pumps at the 1,250-foot level and hope to turn them on in a couple of weeks to test draining a small nearby reservoir.

The mine has major pump stations at 1,250 feet, 2,450 feet, 3,650 feet and 5,000 feet.

"Each one of these has a sump, so that when you pump up 1,200 feet, you pump into that sump, Alonso said. "And then you empty that sump with that pump to go up to the next level."

The water in Homestake has reached 5,000 feet, and Alonso said it likely will reach the cavern at 4,850 feet by mid-February.

"We won't be able to get pumps down there and actually be able to mitigate that problem until probably April," Alonso said. "But it's not going to be a major problem because we have submersible pumps that we can just sort of drop down into the area and be able to get the water out from there once we have the system set up above that."

Workers also are preparing to enter the Yates shaft, which was built out of wood because of steel shortages during World War II.

Preliminary inspections a year ago and a follow up this past week showed everything is in good shape.

"For the steel, you want to keep the area as dry as possible," Alonso said. "For the wood, apparently you want to keep it wet. If it dries out, then it rots."

The lab's ultimate plan is to use the Yates shaft as the primary entrance and exit for science experiments.