Photos via the Church Newsroom.
As part of the extensive and ongoing Salt Lake Temple renovation project, a tunnel is being constructed underneath North Temple to connect the parking lot of the Conference Center with the the underground facilities and entrance to the Salt Lake Temple.
The tunnel excavation is already about 80% complete. The photos below show the steel arches that are encased in “shotcrete” (a form of grout) to create the first layer of lining for these tunnel walls. These steel arches are spaced 4 feet apart.
A drilling machine is used to remove the upper portion of the soil and then an excavator hauls it away.
The temple itself has now had a “secant wall” added around three sides. These walls are installed directly adjacent to the bottom edge of the existing footings as a measure to contain and brace them in place. These types of walls are built by drilling deep holes where columns, alternating between steel and concrete, are installed. These overlap with one another to create a retaining wall.
As part of this bottom-to-top strengthening and renovating, the copper roof sheathing of the temple has also been removed. It has been replaced with a temporary roof in preparation for the coming installation of additional steel trusses. These are an essential part of the seismic strengthening of this sacred building.
The upper stones of the temple walls are also being gradually removed to prepare for structural concrete bonding beams that will also help brace the walls. Rest assured, the stones that are removed will then be reinstalled in their original positions. It sounds as though, in the end, the temple may not look very different on the exterior, but it will be strengthened in crucial and extensive ways.