The Ross and Yates shafts are critical to science—today and in the future—at Sanford Lab. Last week's Deep Thoughts looked at the Ross rehabilitation project, its role in future research projects, and the unique challenges the crews face. This week, we're focusing on the importance of top-down maintenance in the Yates Shaft and the crucial role it, too, has in science at Sanford Lab.
So far this year, the Yates Shaft has moved nearly 1,300 loads of materials and supplies. Factor in the cages that carry people every day, and that number increases dramatically. When they aren't hauling loads or moving people, Yates crews perform top-down maintenance on the shaft.
Built 75 years ago, the Yates Shaft was constructed of timber, which expands and contracts, requiring more maintenance. "Every day we do top-down maintenance, we make that shaft healthier and safer," said Underground Access Director Will McElroy.
In preparation for the Long Baseline Neutrino Facility (LBNF) and the Deep Underground Neutrino Experiment (DUNE), the Ross Shaft is getting a facelift. The old corroded H-beam steel is being replaced with hollow-tubed steel beams that have a life expectancy of more than 50 years. The Ross will provide critical logistical support to LBNF/DUNE.
But the Yates Shaft will also play a critical role, said Josh Willhite, LBNF Project Manager. "The Yates will serve DUNE while LBNF is underg construction,? Willhite said. That includes continuing to move people, equipment and supplies. ?It will also be the avenue to installation of the next-generation dark matter experiment, LUX-ZEPLIN (LZ)."
Top-down maintenance involves inspecting almost every piece of timber and giving each a "grade," McElroy said. If a piece of timber is rated T-1, it means it?s in good condition and has a life expectancy of more than five years. A T-2 rating means the timber is in fair condition and has a life expectancy of at least five years. If a piece of timber is rated T-3, it needs attention sooner than later. Since 2013, nearly 4,000 components were addressed.
But top-down maintenance involves more than rating and repairing original timber pieces. "We're even more concerned about what's behind the lacing," McElroy said. As the crews move down the shaft, they remove the old wooden lacing and 75 years of muck (rock, timber and gravel) that has built up behind it. "On average, we remove almost 25 tons of muck every month," McElroy said. As the muck is removed, crews put in new ground support, repair timber pieces, and install new lacing where needed.
And through it all they keep moving people and supplies. "A normal day involves moving loads and people," McElroy said. "Night shift and four-day maintenance weekends are devoted to top-down maintenance."
At the Ross Shaft, the crews are focused solely on construction, while at the Yates, crews wear two hats: customer service and construction. "We have to balance access and top-down maintenance almost every day," McElroy said. "That's why we're adamant about limiting access outside scheduled times, but we try to be accommodating when necessary."
Although the scopes of work for both shafts are different, the goals are, ultimately, the same: to support current and future science at Sanford Lab. Completion of the Ross Shaft is two years out. While top-down maintenance on the Yates will continue for the next six years, McElroy said we hope to refurbish this shaft as well.
"This is one of the most significant projects of my lifetime and I want to thank everyone at the SDSTA who's been involved," McElroy said. "Whenever I've needed something, the men and women here have answered the bell. We couldn't do these projects without this dedicated team."