Crews reach ‘key’ phase in seismic upgrade of historic Salt Lake Temple
Carter Williams, KSL.com
SALT LAKE CITY (KSL.com) — Dakotah Hansen is one of the crewmembers tasked with digging large horizontal holes underneath the Salt Lake Temple.
Hansen, a tunneling miner for HDD Willco, a West Jordan construction company that specializes in installing underground utilities without using trenches, spends most of his time in virtual darkness, chipping away at the deep soil with an air hammer. He’s making way for a 4-foot wide steel pipe that will fill the space he’s clearing out. He then tosses the dirt and rocks into a car behind him that removes the materials from the site.
“We have to go (down) there and dig it all out,” he said, in a video posted by The Church of Jesus Christ of Latter-day Saints on Friday about the ongoing temple renovation project. “Normally, we try to go 6 feet a day.”
His work is a part of what’s known as the jack and bore method, which is being used this summer to lay nearly 100 of these pipes underneath the foundation of the historic Salt Lake Temple — to keep the building stable in an earthquake. Church officials, in their Friday update, said this is a “key component” in the lengthy process of seismically upgrading the 187-million-pound building that opened in 1893.
Brandon Rowley, the superintendent over seismic upgrades for Jacobsen Construction, explained that pushing the pipes into place underneath the foundation is the “jack” portion of the method’s name. “Bore” refers to the process that clears out the space for the pipes.
It’s a process that is typically used when trenches aren’t feasible, such as laying pipes underneath roads or railways, according to the engineering and construction firm, Dewberry.
A boring machine is typically used in this method; however, Rowley said, this project uses manual labor because of the “accuracy that we need” under the temple. Crewmembers like Hansen hand measure where to dig before drilling away and removing dirt and rock.
“They’ve got to go in pretty much perfect every time,” Hansen said, regarding the pipes.
Once in place, a cement and sand-based grout is used to fill in the spaces between the pipes to ensure there isn’t a gap between the foundation and new piping underneath it. A rebar cage is also hauled in and inserted inside every pipe to make the pipe stronger.
Brad Bohne, general superintendent with Jacobsen Construction, adds that because the temple’s weight is unequally distributed, engineers took plenty of time customizing every underground pipe to ensure it’s sustaining the right amount of stress to balance the weight equally.
Church officials explain that the location of the pipes needs to be precise because they are the underground component of an “intricate system” of cables, rods, trusses and transfer beams that travel from beneath the foundation all the way up to the temple’s roof and spires. One of the next steps is to run a set of cables through the temple walls that will connect the top of the building to the new pipe casings underground.
This system will allow the building to move as “one solid structure” when there is an earthquake, officials said.
Once the jack and bore process is complete, Bohne said a “big, heavy” concrete footing will be installed underneath the pipes. Close to 100 base isolators will be installed between the pipes and footing. Every one of these isolators can support 800 million pounds of weight, serving as bearings during an earthquake.
There’s also a beam that will be installed to keep and jack and bore pipes together for more support.
“All of that works as a whole system to create a new foundation for the temple,” he said. “It’s an absolutely critical part of that system.”
Other construction updates
Meanwhile, other components of the massive Temple Square renovation project are also happening while the building gets a new foundation.
- Renovations to the Main Street Plaza began in April, with the giant reflection pool, gardens and other decorative landscaping being removed to repair and waterproof the decking that covers the parking garage underneath Temple Square. New stonework and pavers are replacing the old landscaping and pathways in the plaza between State Street and the temple.
- A new “contemplative” garden space is also being installed northwest of the temple. This is also the area where new bathroom facilities will be included.
- New planter boxes are being built as a part of a crosswalk between Temple Square and the Church History Museum, located on West Temple.
The entire project, which began in late 2019, was originally anticipated to be complete by 2024 but is now estimated to be completed sometime in 2025.