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The Davis Campus: Built for world class science

In 2012 the Davis Campus was dedicated as the deepest underground science laboratory in the United States.
Left side is the Davis Cavern before outfitting. On the right is the Davis Cavern after outfitting

When you walk into the Davis Campus at Sanford Underground Research Facility, it’s easy to forget you are nearly a mile underground. Bright lights, white walls, freshly ventilated air and modern technology surround you. The only difference between this lab space and a similar one on the surface? The lack of windows.

Dedicated in 2012, this world-class research facility hosts two leading physics experiments in neutrino and dark matter research. The experiments go deep underground to escape the constant bombardment of cosmic radiation.

In the above left photo, Wendy Zawada Straub, former project engineer, stands on a muck pile in the Davis Cavern. The photo on the right is the same cavern after the lab was completed.

Throughout this page, you'll see numbers that represent deliveries to the 4850 Level during construction of the Davis Campus and quotes from people who were involved in the project. 

This is the story of how the Davis Campus came to be.

Scientists speak to reporters and guests in an underground laboratory.

Dedicated to science

On May 30, 2012, the Davis Campus opened its doors to science. Governor Dennis Daugaard, philanthropist T. Denny Sanford and other dignitaries attended a dedication ceremony on the 4850 Level. John Wilkerson, principal investigator for the Majorana Demonstrator project, spoke to dignitaries and reporters in the space that would become the home to Majorana's class-100 cleanroom. 

"I'm incredibly proud of this facility," said Mike Headley, executive director of the SDSTA. "The dedication of our employees, science collaborators and partners made all of this possible. The Davis Campus gives the United States an edge in the race to learn more about the origins of the universe." 

Scientists assemble the LUX dark matter detector

A world-class space

The Davis Cavern originally housed Dr. Raymond Davis Jr.'s solar neutrino experiment and was redesigned and enlarged for dark matter experiments. The first, the Large Underground Xenon experiment (LUX), operated from 2013 to 2016. The Davis Cavern gave the experiment the environment it needed to become the most sensitive dark matter detector in the world. 

When the Davis Campus became operational, so did LUX," said Rick Gaitskell, spokesperson for LUX. "So the Davis felt like home from the first day we were able to use it for physics."

This state-of-the-art laboratory features a 72,000-gallon (272,549 liters) water tank, which serves as additional shielding from cosmic radiation; and a water-deionization system, cleanroom and  control room for researchers. The researchers outfitted the Davis Cavern with a xenon purification system, servers, electronics and the experiment, itself. All will be in service once again for the next-generation dark matter experiment, LUX-ZEPLIN (LZ). 

Two machinist work in an underground cleanroom machine shop.

For world-class science

The Majorana demonstrator experiment is so sensitive, even a tiny speck of dust could ruin the results. The Davis Campus was engineered to provide clean filtered air to create one of the cleanest spaces on earth. 

"Having this space, allows us to make an important contribution in the global search for neutrinoless double-beta decay," said John Wilkerson, principal investigator for the Majorana Demonstrator. "It has been a wonderful experience and privilege to work together with the Majorana and SURF teams to build this experiment."

The Majorana lab spaces feature a class-100 clean room; the deepest, cleanest cleanroom machine shop in the United States; and an electroforming laboratory in which copper is grown to build the experiment. 

In what was once an environment in which miners carried pickaxes and shovels to mine for ore, scientists now carry computers and other technology into clean laboratory spaces to perform world-leading research. 

Transforming a former gold mine into a world-class research facility located nearly a mile underground, took meticulous planning and organization. Specialized materials and equipment couldn't be found at a hardware store. And if you forgot your tools—or lunch—on the surface, you were just out of luck. At least until the next scheduled cage.

It took a village of engineers, geologists, technicians, construction workers, electricians, administrators, information technologists and scientists to build the Davis Campus.  

Here's how we did it.

Removing the Davis neutrino tank.

Out with old

In the mid-1960s, Dr. Ray Davis Jr. began building his solar neutrino experiment on the 4850 Level. The Davis Campus is named for this Nobel-Prize winning scientist.

After nearly three decades of operations, the experiment was abandoned and the remnants left behind. One of the first steps we took in preparing to build this facility was to remove the 100,000-gallon (378,541 liters) tank (pictured above). 

Luke Scott, an infrastructure technician, was a member of the team that helped remove the stainless steel structure. "When I first walked into the space, I thought, 'we've got a lot of work ahead of us.'" He was right.

The tank was cut apart and stored in an empty drift three miles away. A support ring from the tank was later recovered and is on display outside the Sanford Lab Homestake Visitor Center in Lead. 

An engineer examines the empty Davis Cavern.

An empty slate

With the removal of the Davis tank, engineers and geologists began inspecting the cavern and planning the design for a dedicated state-of-the-art research facility. The existing cavern needed to be enlarged for the LUX experiment and a new cavern excavated for the Majorana experiment and the common corridor.

Building required teamwork and planning for safety purposes, efficiency and success.

Bryce Pietzyk, underground access director, remembers some of the challenges the teams faced. “Logistically, trying to find ways to fit large equipment and materials into a tight space was a challenge,” said Pietzyk. “But all of the teams worked together to come up with solutions.”

Once the necessary elements were in place, the cavern was ready for crews to begin blasting and installing ground support.

"I was here when we gained access to the underground and for initial dewatering. I had been fortunate enough to visit Soudan Lab in Minnesota, Gran Sasso in Italy and SNO Lab in Canada, so I had a pretty good picture of what the Davis Campus could become. You could say its like buying a home. You have to look past the flaws—the pink walls and bad carpet. We had to get past the muck and leftovers from when the site was 300 feet underwater and envision what it could be."

—Mike Headley, executive director, South Dakota Science and Technology Authority 

It took 2,000 cubic yards of engineered fill to cover the floor (1,529 cubic meters).

The amount of cubic yards (402 cubic meters) of concrete, which came in 300 bags each weighing 3,000 pounds (1,361 kilograms).

A new cavern in the middle of excavating.

Carving a new space

Excavating a new cavern to house the Majorana experiment had its own set of challenges to overcome. David Vardiman, a geotechnical engineer, recalled the difficulty in hauling excavated rock miles away to another underground area for disposal.

“It was an arduous and difficult process that was not easily done. It required a lot of manual labor and a lot of specialized procedures to do it safely,” said Vardiman. “We were successful because we were very good at overcoming challenges and adversity.”

The intent was for the design to last more than fifty years as a safe, permanent space in which scientists could work.

“This was an incredibly heroic effort,” Vardiman said.

Two men use jackleg drills to install ground support in a cavern.

Ground support

Developing a permanent space for science, required additional efforts to stabilize and strengthen the caverns. Ground support pins the rock together in a strong configuration, like a Roman arch, distributing the load and ensuring openings remain intact. Bolts reinforce the rock, while shotcrete and steel mesh keep smaller rocks from popping loose, providing a strengthening buttress effect that supports the opening.  

In a mining operation, ground support is temporary. But excavating for a large-scale, long-term underground construction project, requires more stringent standards for ground support design.

"We had to change the standards and protocols to bring them into a civil engineering quality standard," Vardiman said. 

 

"It was a pretty big team effort. Everybody on the crew takes pride in it. I’m proud of the guys that worked with me. They were highly dedicated and knowledgeable. They are great at what they do."

—Luke Scott, infrastructure technician

A batch plant for mixing concrete is slung in the shaft.

Building a "ship" in a bottle

Building a 30,000-square-foot (2,787 square meters) research campus nearly a mile underground was like building a ship in a bottle. Everything, from bolts to concrete to ductwork and people, had to be lowered down the Yates Shaft inside a 6-foot (1.8 meters) by 12-foot (3.7 meters) compartment. Most materials could be loaded inside the cage, but larger equipment, like this batch plant (cement mixer), had to be slung under the cage then lowered to the 4850 Level. 

Kevin Bauer, a hoist operator at Sanford Lab, said, "Once it's under the cage, it's just a matter of running the hoist at a slow and steady speed."

 

Loads of engineered filled are pulled on underground rail.

Tight spaces

Once underground, everything is moved by rail. But space is tight, so timing of the deliveries is critical. For example, you don't want to have 10 pallets of lead bricks in an area when there is only room for five. 

"Buying the nicest sofa in the show room is a great idea, until it doesn't fit through your front door," said David Vardiman. The same is true for any materials used in underground lab construction. For example, the LUX tank came down in pieces then was welded together in the Davis Cavern. 

"We overcame many challenges and I credit the incredible skill of our staff and contractors. We had a very strong partnership with science, the SDSTA and contractors and that allowed us to achieve this high level of success."

—Mike Headley, executive director

Shotcrete covers the rock walls in a cavern.

Bolting and wire mesh are the first line of defense in ground support. However, in laboratories spaces underground, we use an additional layer of protection. Shotcrete, a spray-on form of concrete is vital to constructing a safe space.

“The biggest challenge was trying to get the shotcrete mixed in a short time period going from a dry product to a wet product,” said Pietzyk.

In this photo, an engineer examines the recently shotcreted Transition Cavern. 

Davis Cavern after shotcrete was applied

In addition to providing a safe infrastructure for the space, shotcreting helped make the Davis Campus look like more than just an underground mining cavern.

“It was kind of like seeing the mine come to life again after it had laid dormant for so long,” said Zawada-Straub. “It was really exciting.”

This is what the Davis Cavern looked like after shotcrete was applied. 

“The proof is in the pudding! The facility is performing to design expectations and beyond. I’m quite proud of the work our crews did.”

—David Vardiman, project engineer

A mason builds a wall underground

Outfitting begins

With the completion of shotcrete, the SDSTA awarded an $8.1 million contract to Ainsworth Benning Construction of Spearfish to outfit the Davis Campus. Ainsworth-Benning constructed the concrete floors, lab modules, cleanrooms, air-handling infrastructure, electricity, fiber optic data cables and plumbing. 

"The guys from Ainsworth-Benning were proud of being a part of this project and blown away at what they had done," said Mike Headley, executive director of Sanford Lab. "James Benning said he was struck by the significance this facility—built in South Dakota—would have on science on a global stage."

"It was a wonderful experience and a privilege to work together with the Majorana and SURF teams to build the demonstrator. From hoist operations, to the warehouse, to technical support, the staff was always there to provide support. And the dedication to excellence was always apparent."

—John Wilkerson, principal investigator for the Majorana Demonstrator

of steel rebar were lowered 4,000 pounds (1,814 kilograms) at a time. 

cement blocks were used to build walls in the facility.

A contractor uses a level inside a wooden ring.

This circular wooden frame was built to form a concrete ring to hold the 72,000-gallon (272,549 liters) water tank that would house the LUX dark matter detector. 

The LUX water tank

The LUX water tank was transported in pieces and welded together in the Davis Cavern. 

"It feels good to know that it’s been able to operate for science without needing much in the way of maintenance or repair. Now, seeing the science happen is neat.”

—Bryce Pietzyk, underground access director

pounds of rectangular ductwork. (34019 kilograms)

pounds of spiral ductwork. (36287 kilograms)

Entrance to the lab before outfitting

Entrance before outfitting

This photo shows the entrance to the Davis Campus prior to outfitting. The drift on the left is part of the new excavation which would become the main entrance to the campus. On the right is the original access drift that Ray Davis would have walked to work on his neutrino experiment.

Entrance to lab after outfitting

Entrance after outfitting

Today the entrance to the Davis Campus is a finished space. All personnel, water, air, electricity, and data enter and exit here. The drift on the right is used for delivery of liquid nitrogen and as a secondary exit from the main campus.

"It doesnt get any better than the moment we were standing in the Davis with the LUX detector."

—Wendy Zawada Straub, former project engineer for the Davis Campus

miles of wiring. (48 kilometers)

miles of electrical conduit. (11 kilometers)

The floor of this corridor is covered in epoxy.

The Common Corridor

This hallway is known as the Common Corridor. It is a shared space where scientists can access both experiments. Lab spaces for Majorana are at the left and access to the dark matter experiment is at the far end of the hall. Click on the link below to watch a time lapse video of this space as it was outfitted.

A scientist examines his new lab space.

Majorana

John Wilkerson admires the new assembly space for the Majorana Demonstrator. Over the next 5 years he and his team of researchers, engineers will build the demonstrator. See the link before for a time lapse video of the assembly.

"This was far-sighted planning by Sanford Lab and something I wish we had been able to do with previous underground experiments as it ensured we had many engineering details worked out before going underground."

—Rick Gaitskell, LUX spokesperson

A fully outfitted laboratory ready for science to move in.

Ready for Science

The top floor of the Davis Cavern is ready for the LUX to move in. Stairs on the left lead to the ground floor and a control room on the right is used as a work space for researchers. Watch a time lapse video from the outfitting of this cavern.

A 72,000 gallon water tank.

A dark matter house

This 72,000-gallon ((272,549 liters) water tank serves as shielding and a veto system for the LUX experiment. The LUX detector was assembled in a laboratory on the surface and brought underground to be installed in this tank. Below is a link to a time lapse video of the 2-day journey LUX took from the surface to the Davis Campus.

The success of the Davis Campus project comes down to teamwork and partnership. The entire project was a success in terms of safety, as evidenced by only one recordable injury occurring throughout the work. Safety continues to be a priority at the facility. Addressing safety in a long-term underground facility is very different from how you approach it in mining. “It’s a much higher bar,” said Headley.

Continued safety checks and maintenance prove that the site is holding that bar up above standards. “When I’m doing inspections of the Davis Campus,” said Vardiman, “I’m looking at the shotcrete, I’m looking for cracks, I’m looking for failures in the stressed environment and the system of the design. I’ve seen none yet. It is performing to design expectations and beyond. I’m quite proud of the work that our crews did.”

“This dedication to safety and quality production is evidenced by the fact that team members can focus on other construction and projects at the facility without the hassle of constant repairs and maintenance. The Davis Campus is able to operate and doesn’t need a lot of maintenance,” said Pietzyk.

This article was written by Constance Walter, Matthew Kapust, and Christel Peters. Photography contributed by Matthew Kapust, Steve Babbitt and Roy Kaltschmidt.