Cosmic depth: LBNF featured in Tunnels and Tunnelling

LBNF cavern at SURF
LBNF cavern at SURF
LBNF caverns at SURF; Credit: Sandbox Studios

Excavation and construction of a science lab one mile underground is the first step in better understanding of neutrinos, one of the unexplained mysteries of the universe. Nicole Robinson, editor of “Tunnels and Tunnelling North America,” a publication of the Tunnelling Association of Canada (TAC), reports on the Long-Baseline Neutrino Facility.  (The text here is excerpted from the full article, linked with permission.)

An RFP (request for proposal) released in late June (by LBNF) focuses on building a new underground facility (for DUNE) at a former gold mine in Lead, South Dakota. The project concerns the underground excavation of approximately 350,000 bank cubic yards (267,000 cubic meters) and will be constructed one mile underground (the “4850-foot level”). The particle accelerator in Illinois will beam neutrinos straight through the earth to four detector (modules) in the new South Dakota facility. Fermilab says the project has been getting a lot of support and is gaining momentum.

Fermilab is bidding the project through a Construction Manager/General Contractor (CM/GC) approach, listed with a construction magnitude of USD 250M to 350M.

“We started this year executing some reliability projects for the (South Dakota facility) infrastructure,” explains Chris Mossey, Fermilab’s deputy director for LBNF. “We hope to transition to the pre-excavation work, which is building systems that will support the excavation — such as rock handling systems — in 2017, then switch to production excavation in 2018. Virtually all that work will be done through the CM/GC contract and we’re very excited it’s out on the street.”

The existing network of hundreds of miles of horizontal drifts in South Dakota has been advantageous for the project team.

“In the roughly 2,500 ft (762 m) of horizontal borings that we’ve done we had rock quality designation values that were excellent for all but about 25 ft (7.6 m) of the cores,” said Tracy Lundin, Fermilab’s LBNF conventional facilities project manager. “And the fact that we’ve got miles and miles of existing drifts very close to us — We feel like we have a really, really good handle on the geology.”

“The most interesting aspect of the project’s design is to overcome the logistical issues,” says Amirreza Ghasemi, senior tunnelling engineer at Arup, the project designer. That is specifically the logistics of getting people and excavated material from the 4850 level up to the surface.

Another key challenge (during LBNF excavation) is preventing disturbances to existing science experiments to the degree possible. Discussions with the existing science facilities are focused on peak particle velocity of about 2 in/s (51 mm/s).

“Based on work at another deep underground facility in Canada, SNOLAB, we believe that 2 in/s is a careful balance between what the existing science would like versus what the underground excavators would like,” says Lundin.

Priority has been given to developing the facilities in South Dakota, and on the heels of that will come design and construction in Batavia, Illinois, at Fermilab to support LBNF.