South Dakota Science and Technology Authority

Deep science for everyone Deep beneath the earth in South Dakota, engineers are building what will be the largest underground research lab in the world. The director of operations for the South Dakota Science and Technology Authority talks to Gay Sutton about the challenges of rehabilitating an old mine for science. The Homestake mine in South Dakota is rapidly returning from closure with a new and ambitious purpose. No longer are its operators searching for gold; the mine is being reopened and refitted with state-of-the-art research laboratories. The first experiments at the Sanford Underground Laboratories will be to search out and investigate altogether more elusive matter and phenomena: neutrinoless double-beta decay and relic dark matter.  However, the long-term aim is to develop the national Deep Underground Science and Engineering Laboratory (DUSEL), which will provide world-class research facilities for projects that require shielding from the noise and interference of cosmic radiation and human activity. The lab will be designed for and available to a wide variety of scientific disciplines, from particle and nuclear physics, through geology, hydrology and geo-engineering, to biology and biochemistry. The mine already has impeccable credentials. Not only is it the deepest mine in North America, but it lies in one of the most seismically stable locations in the nation. It was also home to groundbreaking neutrino research in the 1960s headed up by Dr. Ray Davis. It ultimately earned Davis a Nobel Prize in physics for his successful effort to be the first to count neutrinos emitted by the nuclear fusion taking place in the sun. His research did, however, throw up some serious questions. Only one-third the number of particles expected was actually recorded on DavisÔÇÖs equipment. The research continued at Homestake until 1994, along with parallel projects in Japan, the Soviet Union and Italy, but it wasnÔÇÖt until a new generation of detectors were used at the Sudbury Neutrino Observatory (SNO) in Canada that the riddle was solved. Neutrinos were found to oscillate between three ÔÇ£flavors.ÔÇØ The detector at Homestake counted just one flavor. Small wonder, then, that when Homestake was slated for closure in 2003, the scientific community in conjunction with the State of South Dakota came up with a plan to turn it into a world-class research facility. In 2006 the mineÔÇÖs owner, Barrick Gold Corporation, gifted the mine to the state through a Property Donation Agreement (PDA). ÔÇ£In June 2006 the South Dakota Science and Technology Authority (SDSTA) was created with four employees, one of them being me,ÔÇØ explains Greg King, director of operations. ÔÇ£My job is to open up the mine and develop the infrastructure for the labs.ÔÇØ SDSTA is headed up by Dr. Kevin Lesko, who had previously managed the SNO lab in Canada, and Dr. Bill Roggenthen from the South Dakota School of Mines. Their primary focus is to attract research projects and funding for DUSEL and to develop the facility into a world-class center for scientific research. ÔÇ£ThatÔÇÖs a lengthy process,ÔÇØ King says. ÔÇ£The first priority is to secure funding for the first major astrophysics project, and to have that money available by 2013 when weÔÇÖll be ready to start development work on the underground detectors.ÔÇØ In 2006, however, King began planning for the challenging and complex task of reopening a mine that had been closed for three years and beginning the process of rehabilitating it and turning it into laboratory space. Homestake has around 370 miles of open tunnels honeycombing an area of approximately 7,700 acres underground. The first task was to re-establish the hoist system on the main Ross shaft, which runs from the surface to a depth of 5,000 feet. ÔÇ£Although the mine is 125 years old, this shaft was first occupied in 1934, and the hoist dates back to this time. ItÔÇÖs an amazing piece of equipmentÔÇöa testament to the original engineering and to the care and upkeep all these years. During full production it was capable of carrying payloads of up to 20,000 pounds and running at about 40 miles per hour, going from the surface to the 5,000-foot level in about four minutes.ÔÇØ Ventilation also had to be re-established before any personnel could venture underground. ÔÇ£The mine actually has natural ventilation,ÔÇØ King explains. ÔÇ£We have two shafts, the Ross shaft and the Yates shaft. Because one is 40 feet higher than the other, the higher one acts like a chimney, drawing air out of the mine. We also have a series of interconnections to the surface, and weÔÇÖve installed a 3,000-horsepower fan to draw air out of the mine so that both shafts become intakes. Currently weÔÇÖre pulling around 140,000 cubic feet of air a minute through the system.ÔÇØ The ventilation is not only essential for establishing suitable air quality for human habitation, but also for cooling purposes. Below ground, the rock warms by roughly one degree for every 100-foot drop in elevation. Therefore, at the 4,550-foot level, for example, the temperature would be 90 degrees Fahrenheit, with 100 percent humidity. The labs were scheduled to be located lower than that, at the 4,850-foot level where the original 1960s research had been conducted. ÔÇ£Today, with our ventilation system, that area is maintained at about 66 degrees, and the relative humidity has dropped to about 50 percent,ÔÇØ King says. Rehabilitating the mine has been a painstaking process, and the emphasis has been on safety and thoroughness. All the way down the Ross shaft, at intervals of 150 feet, tunnels radiate horizontally from the shaft in a north-south orientation and extend for about a mile in each direction. ÔÇ£What we had to do was rehabilitate the shaft from level to level, and then walk every one of those horizontal tunnels, checking ground conditions and air quality and ensuring there was no stored water that could potentially inundate the shaft,ÔÇØ King explains. Each level then required careful cleaning, geological testing and structural repair where necessary. Much of this was also a race against time. Homestake generates about 750 gallons of water a minute, and since the pumping systems had been shut off at closure, the mine had spent three years steadily filling with water. ÔÇ£Our goal was to get to the water before it got to the 4,850-foot level where we planned to site the labs. However, the rehabilitation took a little longer than expected, and we met the water at 4,529 feet,ÔÇØ King continues. ThatÔÇÖs where the long dewatering process began. The mineÔÇÖs original pumping system, which had been part of the PDA, was now brought into action. However, because the water had been gathering for so long in the mine, it had leached a considerable amount of iron out of the rock, so an additional process was added to the system that removes a staggering 200 pounds of iron a day. ÔÇ£WeÔÇÖve been at the 4,850-foot level for about eight months now,ÔÇØ King continues. ÔÇ£Initially we had to test the stability and geological structure of the rock, restabilize it where necessary and then clean up.ÔÇØ The original rail system that had been left behind on closure was reinstated, and all the utilities were reintroduced. Four years later, the SDSTA has a staff of 90 working in the mine, some 75 percent of whom had previously worked at Homestake mining for gold. Reopening the mine has required considerable financial investment, and this has been supplied by a $10 million federal HUD grant and $33 million from the South Dakota legislature, which generated a further $8 million in interest. ÔÇ£We also have a benefactor, T. Denny Sanford, who has donated $70 million to the project. His main interest is educational outreach,ÔÇØ King says. ÔÇ£He could see the opportunity the mine presented, not only for research students but also for young people from kindergarten through 12th grade. So we will ultimately have a large educational center here on site.ÔÇØ A portion of the Sanford donation has already gone toward excavating a series of tunnels and caverns at the 4,850-foot level to house the first underground campus at the Sanford Underground Laboratory. ÔÇ£The excavation work is probably about 60 percent complete, and we should be finished by June 1 this year.ÔÇØ Once that is done, the rock surfaces will be finished by shotcreting, and then work will commence on constructing and fitting out the labs. Sanford financing has also gone into initiating some early scientific research. ÔÇ£We currently have two research endeavors that are in various phases of construction,ÔÇØ King explains. The LUX project will be hunting for dark matter using a liquid underground xenon (LUX) detector, and the Majorana project will be looking for evidence of neutrinoless double-beta decay. One of the surface facilities has been repurposed as a cleanroom for the construction and testing of the LUX detector, while a cleanroom is currently under construction at the 4,850-foot level for the manufacture of the ultra-pure copper plates required for the Majorana detector, which will then be assembled and tested in situ. Both projects will be handed over to the science community shortly: Majorana in October this year and LUX in January 2011. The focus will then switch to preparation for the prestigious DUSEL labs. ÔÇ£One of the big challenges weÔÇÖre going to face is how to continue running the LUX and Majorana projects while we do major blasting and excavation work nearby. WeÔÇÖre looking to create a large cavern for DUSEL that is 55 meters in diameter and 55 meters in height. Big enough to hold all four of Mount RushmoreÔÇÖs heads, itÔÇÖll be one of the largest facilities ever built.ÔÇØ Word is getting out about the scale and importance of the facilities being created at Homestake. The educational outreach program has been set in action with public lectures entitled ÔÇ£Deep science for everyone.ÔÇØ There have been teacher workshops and tours down to the 300-foot level for the science community, students, teachers and the public. Engineers are currently working on plans for the educational center, including both surface and underground campuses. So the future looks bright for those with an interest in science as well as those engaged in cutting-edge research.