# Why a Mormon Mega-Temple is Being Dug-Up Source: https://www.youtube.com/watch?v=mGa7PSWkf9U Recap page: https://rapidrecap.app/video/mGa7PSWkf9U Generated: 2026-01-21T15:42:03.575+00:00 --- ## Quick Overview The largest Mormon temple in the world, the Salt Lake City Temple, is undergoing a massive $2 billion retrofit project involving base isolation technology to protect it from potential major earthquakes, which experts estimate have a 57% probability of magnitude 6 or greater in the next 50 years. **Key Points:** - The retrofit project to save the Salt Lake City Temple is estimated to cost $2 billion US and involves decoupling the structure from ground motion using base isolation. - The temple took over 40 years to construct, completed over 130 years ago, featuring walls up to 9 ft thick and built from granite and quartz monzenite. - Geologists estimate a 57% probability of at least one earthquake of magnitude 6 or greater in the next 50 years, comparable in devastation to the 1994 LA earthquake. - The base isolation system will allow up to 1.5 m of horizontal movement during seismic activity by installing 98 base isolators, each weighing 8,000 kilos, beneath the structure. - Construction involved extensive underpinning techniques, including micro piles and consolidation grouting, before installing a new concrete foundation with over 423 km worth of post-tensioned cables. - The renovation is delayed, pushing completion to 2026 (with reopening in 2027), as teams are also reinforcing walls and spires while adding more space for ritual baptisms and increasing seating. - Salt Lake City's unique urban plan, established by Brigham Young, featured exceptionally large 200x200 m blocks and wide streets, which helped the city adapt to the automobile and supported the temple's historic role as the city's anchor. **Context:** The video examines the critical seismic retrofit of the Salt Lake City Temple, the largest temple belonging to The Church of Jesus Christ of Latter-day Saints, which was completed over 130 years ago. This undertaking is necessary because the temple was not designed to withstand earthquakes, and the Wasatch fault runs through the valley, presenting a significant risk of damaging seismic events, prompting the church to undertake a major, costly preservation effort mirroring seismic strengthening done on other historic structures like Christ Church Cathedral in New Zealand. ## Detailed Analysis The massive Salt Lake City Temple, a 130-year-old structure built from locally mined granite and quartz monzenite, is currently undergoing a $2 billion seismic retrofit to prevent collapse during earthquakes. The primary method employed is base isolation, designed to allow the building to move semi-independently from the ground, accommodating up to 1.5 meters of horizontal movement. This complex engineering required excavating down 10.6 meters, utilizing underpinning techniques like micro piles and tieback anchors to support the original footings, and installing a new concrete foundation system tied together with 423 km of post-tensioned cables. Ninety-eight 8,000-kilo base isolators sit between the new footings and transfer structures to absorb seismic energy. Beyond structural reinforcement, the renovation includes expanding ritual baptism space and increasing seating, pushing the completion date from 2025 to 2026, with reopening slated for 2027. This effort is crucial given the 57% chance of a damaging earthquake in the next five decades. Furthermore, the temple's existence is intrinsically linked to the history of Salt Lake City, founded by Mormons under Brigham Young in 1847, who engineered a deliberate urban grid with extremely large 10-acre blocks and wide streets, creating a unique, self-sustaining settlement model that has proven resilient over time, making the temple's preservation an important statement for the city's heritage. ### Seismic Retrofit Strategy - Base isolation is the core technique designed to allow up to 1.5 m of horizontal movement during strong seismic activity - 98 base isolators, weighing 8,000 kilos each, are being installed between new concrete footings and transfer structures - The system is vertically stiff but horizontally flexible, protecting stonework, masonry, and the interior. ### Construction and Engineering Challenges - The project involved excavating 10.6 m and using complex underpinning techniques like micro piles, secant piles, and consolidation grouting to support existing footings - Over 423 km of post-tensioned cables physically tie the temple structure into the new foundation system. ### Temple History and Scale - The temple took more than 40 years to construct, completed over 130 years ago, with walls up to 9 ft thick and 170 rooms - Initial construction faced major halts due to conflict with US troops in the late 1850s, and granite transport involved ox teams hauling stones 32 km from Little Cottonwood Canyon. ### Salt Lake City Urban Planning - The city layout follows the Plat of Zion, featuring a perfect grid aligned with cardinal directions - Blocks are 200x200 m, the largest in any American city, divided into eight 10-acre lots, enabling a hybrid rural/urban lifestyle and acting as firebreaks. ### Project Timeline and Scope - The project timeline has been pushed into 2026, with reopening expected in 2027, due to the complexity of retrofitting 19th-century stone - Renovations also include expanding space for ritual baptisms and adding a north addition wing for weddings.