When the new Austin Convention Center opens in 2029, it will nearly double the site's rentable square footage, increasing from 365,000 sq. ft. to 620,000 sq. ft. The new center will have six city blocks of below-grade space, including the new exhibit hall, truck loading dock and other support areas.

But first, the 365,000 sq. ft. of the current center must be torn down, a process that began in January with enabling work off-site on the utilities. The workers had to tie together two separate pieces of underground electrical "ductbank" so that the electrical feed to the Convention Center could be disconnected without affecting power to other nearby buildings on the same electrical grid.

Then, in April, crews began encapsulating the site with fencing followed by selective demolition and the salvaging of some of the existing building's materials for re-use in the new building.

JE Dunn Construction photo

The $1.6 billion project is a 50-50 joint venture between JE Dunn Construction and Turner Construction. While the teams are totally integrated, each company takes the lead on its respective strengths. For example, JE Dunn has more experience with large excavations and concrete structures in downtown Austin, while Turner has more experience with convention centers and with long-span steel structures.

The demolition, which will be completed in the fall, is being accomplished without explosives. For the mechanical demolition, the companies are using a 750-ton long-reach excavator with a 130-ft. boom and hydraulic shear/claw that grabs and cuts concrete and steel off the building. It is joined by a 550-ton and 650-ton excavator, both with claws, to pull down smaller sections, as well as smaller pieces of equipment for sorting and managing the debris.

"They're track excavators that are modified to have special arms and equipment on them that allows them to do precision demo," said Chris Cordeiro, general superintendent of JE Dunn Construction.

While the demolition continues on the site, the placement of an earth retention wall begins on Aug. 1. Once a section of the building is demolished, another team will be right behind, installing a concrete soil retention diaphragm wall along the perimeter so that excavation can begin. This concrete diaphragm wall is poured in vertical panels into the earth.

The diaphragm wall will use a specialized cutter that will create 22-ft.-wide vertical excavations into the dirt and rock. These vertical panels are poured one by one creating a continuous concrete wall within the earth around the perimeter of the building.

"It's sometimes called a slurry wall, but is basically a concrete wall system, 60 ft. down into the rock," Cordeiro said. "They cut down into the dirt and rock and fill the excavation with slurry to prevent cave-ins and they start creating a diaphragm wall, called a diaphragm because we're basically retaining the soil. We have such a high water table, it also helps keep the water and moisture from getting into the hole when we start excavating."

"It cuts off the water and holds the earth back so that we can dig," added Greg Euston, vice president of JE Dunn Construction. "It's unlike a typical excavation or most typical excavations you see around town where we start digging and then the earth retention system goes in as you dig. In a diaphragm wall, the entire earth retention system is put in first, and then you dig out inside of it."

After each 22-ft-wide hole is dug, a crane will drop a reinforcing steel cage into the excavated hole. Then the concrete is pumped down to the bottom of the hole and as they fill the hole from the bottom up, the slurry gets displaced and pumped out.

JE Dunn Construction photo

"A vertical edge form is used on either side of the wall panel so that after the concrete is cured, they have a nice clean edge to their wall. So, when they dig out the next section, they can pour to that and you have your two different wall panels coming together," Euston said.

When completed, there will be a linear retention system of 3,000 ft. consisting of approximately 150 panels. "The entire perimeter is going to be a big basement wall," Cordeiro said.

The diaphragm wall will be finished in the spring of 2026 and excavation will continue through the summer of 2026.

Euston said the diaphragm wall also doubles as the new building's foundation system, supporting the structural steel and concrete structure that will bear on the diaphragm wall.

Chuck Baldwin, a project executive of joint venture partner Turner, said, "Convention centers are getting upgraded and replaced all across the country, and one of the features, or selling points, is to be able to sell exhibit hall space and ballroom space and to a smaller degree, meeting room space, with long spans without columns."

When the steel spans across a larger area, it means fewer columns and more uninterrupted area, he said.

The trusses, he said, will stitch across from one diaphragm wall on the east side to a diaphragm wall on the west side at grade and lend integrity to the entire structure. Perpendicular to the trusses, there will be a series of infill beams that create enough structure for a corrugated metal deck, which will support a cast-in-place concrete elevated deck.

The structural steel will start to be positioned in June 2026.

When completed, the new center will be the world's first zero-carbon-certified convention center, setting a precedent for environmental responsibility in the industry.

A structure can't be built without any carbon, Euston explained. There is a baseline established for how much carbon would normally be expended to build a building the size of the convention center. Zero carbon certification comes from a 20 percent reduction in that baseline. The contractors are taking steps both large and small to achieve that goal.

More than 90 percent of the existing building is going to be reused or recycled, including concrete, rebar, structural steel and metal studs.

The biggest contributors to the carbon footprint are concrete and steel and the builders are putting a lot of effort into finding steel and other materials that have reduced carbon impact in their mixes.

"We're trying to achieve the carbon reductions in all elements within the new building and where it's impossible to get there, which is the case with some of them, then as a team we're looking for other places where we can maybe beat those goals to make up for it," Euston said.

To the extent possible, the contractors are using electric- or solar-powered equipment on site to reduce diesel fuel usage and exhaust. This may include solid-state electrical generators in lieu of diesel-powered generators. They also are tracking fuel usage throughout the project.

There are approximately 100 workers on the site now but, at the peak of construction, there will be up to 1,000 trade partners on site. CEG