An international project to build the largest physics experiment ever constructed in the United States took a major step forward as a new phase of work began at the Sanford Underground Research Facility in South Dakota. When completed, a beam of neutrinos will be sent from Fermi National Accelerator Laboratory (CSA CSM) straight through Earth’s mantle to Sanford Lab.

Fermilab finalized an agreement with construction firm Kiewit-Alberici Joint Venture (KAJV) to start pre-excavation work for the Long-Baseline Neutrino Facility (LBNF). The South Dakota portion of the facility will be built a mile beneath the surface of Sanford Lab, ultimately housing enormous particle detectors for the Deep Underground Neutrino Experiment (DUNE).

“The start of LBNF pre-excavation work is a major milestone for the Sanford Lab and South Dakota,” says Mike Headley, executive director of Sanford Lab. “We’ve been working for years to get to this point, and we’re now starting construction on the largest science project ever attempted on US soil. It’s incredibly exciting.”

The contract with KAJV covers the next two years and includes everything that will be needed to support the next phase of work—the fast, safe and continuous removal of approximately 875,000 tons of rock to create the large caverns that will house the massive DUNE detector modules.

“After years of design and planning, it’s gratifying to put boots on the ground and begin this pre-excavation work,” says Chris Mossey, Fermilab’s deputy director for LBNF. “Getting to this point has been the result of a lot of work from the entire LBNF/DUNE team and our partners at KAJV, Arup, Sanford Lab and DOE; and we’re all ready for this next phase of the project to begin.”

The work includes restoring and refurbishing rock-crushing equipment that was once used for Homestake Gold Mine, where Sanford Lab now resides, and outfitting the Ross Shaft to carry loads of crushed rock. Much of the early pre-excavation work will take place underground at Sanford Lab or inside existing enclosures.

“Complicated tunneling, excavation and underground construction is what we do every day, but performing this work in support of a groundbreaking, international science experiment is a once-in-a-lifetime opportunity,” says Scott Lundgren, spokesperson for KAJV. “We are proud to be a part of this historic project and look forward to helping the vision for LBNF become a reality.”

DUNE, hosted by Fermilab, will be the world’s most advanced experiment dedicated to studying the properties of mysterious subatomic particles called neutrinos. Scientists are seeking to understand the role neutrinos played in the formation of our universe, and the DUNE detectors will enable them to study a beam of particles generated by an upgraded accelerator complex at Fermilab.

The DUNE collaboration includes more than 1,000 scientists from more than 30 countries around the world. A large prototype detector for the experiment, constructed at the European research center CERN, successfully began recording particle tracks in September 2018.