Four behemoth live oak trees appear to float on air as a light breeze tugs at their limbs, and a litany of workers position themselves to slowly roll each gentle giant weighing in at more than 172,000 pounds — or about the weight of the Space Shuttle Endeavor — to its new home.

The move, undertaken in triple-digit temperatures at the height of a deadly heat wave in Texas, involves relocating four heritage live oak trees from a proposed development in Addison, Texas, and into a nearby new park by the end of this week.

The process shows the possibilities emerging for developers when they want to build where full-growth trees reside and save the trees. The implications are widespread as construction moves further into undeveloped areas — even as environmental preservation concerns grow.

The massive trees in Addison are being relocated with ArborLift technology, using giant, air-filled balloons to move the wooden platforms, helping to hold a plastic barrier and keeping the tree root balls intact until they reach their final destination.

"The root ball is the heaviest part of the tree when it's being moved with it not only including the soil and the roots, but also all the moisture needed for the tree," said Tara McCain, an urban forestry coordinator with the Texas Trees Foundation.

Chicago-based AMLI Residential is relocating the trees to make way for a $170 million residential development on nearly 14 acres in Addison, which is in the Dallas-Fort Worth area. AMLI plans to start construction on AMLI Tree House by early next year. The acreage includes the new 3-acre Redding Trail Park, a public park that will be the home of the four heritage live oak trees.

AMLI Tree House is one of the development firm's examples of integrating environmental design into a bigger development in a public-private partnership, said Taylor Bowen, president of AMLI Development Co. The firm is helping Addison create the future Redding Trail Park, which will be given back to the town, and its trail extension that would-be residents can use.

But there are challenges beyond the tricky combination of brute force and gentle care needed for the job. In addition to the patience of going through the process — and time is money — there's the expense. While the cost of the Addison project underway wasn't disclosed, those in the industry say moving a single tree can cost upwards of $100,000 depending on variables such as its size, the distance it's moved, and the type of machinery needed to make it happen.

But there are ways to manage the costs, including getting competing estimates and spreading variable costs like heavy machinery out by moving multiple trees in the same job.

As for AMLI Tree House, it is expected to include 370 apartments in its main building and 35 apartments in another building earmarked for senior residents. The project also includes 14 single-family rental homes and 30 single-family homes being offered for sale. The mixed-use project also includes 7,000 square feet of retail space.

AMLI plans to preserve many other older trees and plant more than 350 new trees on the acreage.

Construction on AMLI Tree House is scheduled for completion in early 2026. The developer partnered with Houston-based Environmental Design to move the four heritage trees to the tract designated for the new park.

Environmental Design spent four months preparing the trees and their root balls for transport on the air bag-type balloons, which cause the least damage possible to the limbs and roots of the giant trees, said McCain. An experienced large tree transplantation specialist, she's familiar with the project and formerly worked at Environmental Design.

In her new role at the foundation, she works with a team of professionals, adding to the urban forestry of Texas. The transport begins with root pruning after determining the size of the root ball, then fertilization and applying preventative insect and fungal sprays to help it stave off calamity when the tree goes into a type of "shock" from being uprooted, McCain said.

The heritage trees — defined as trees of significant size to the city in which they reside — are given first-class treatment to ensure they survive being relocated. Even with the hot temperatures in Texas, McCain said large trees can be moved throughout the year and survive — if treated right.

The root ball, encased in plastic, is then hoisted onto a metal platform atop airbags initially designed to move large ships in shipyards in China. Excavators will then push or pull the structure atop the airbags with the air cushion, helping limit root breakage and other damage, McCain said.

The heaviest part of the tree during a move is the root ball, she said, adding it not only includes the soil and the roots of the tree, but also all the moisture needed to help the tree survive its relocation.

"From the size of the platform to the size of the airbags, they have it down to a science," she added.