What’s the Dirt: All About Caissons

When you see a massive construction crane reaching into the sky, you may not stop to think about how it got there. The answer is unfolding at Shady Grove Medical Center’s tower site: lots of prep work and a few 7-foot-wide foundations known as caissons -- with a little help from a crane friend.

The weight of a 190-foot steel crane means you can’t just drive it into place. Crews need to anchor it into the ground, and then build it on the job site. To begin this process, and to create the foundation for the tower itself, crews at the start of July 2023 brought and assembled a caisson drill rig at the site. Since then, they’ve been busy installing the first of 108 caissons: 10 have gone in along the hospital’s ambulance driveway and 15 supports for the first floor are in place. Crews also placed four caissons to support the construction crane.

Crews then poured a 6-foot-thick concrete pedestal for the crane. Right now, strength testing is underway to make sure the pedestal can hold the crane, which will move up to 25,000 pounds. The crane comes in pieces, delivered by a tractor-trailer, and will be built over a day or so later this week, Aug. 3-4. It is built with a 300-ton assist crane and once it’s up, a third-party certifier will ensure the crane is safe for action. Once the construction crane goes into service, it will be hard at work on the tower site for one year.

In our next What’s the Dirt, we’ll highlight the crane’s installation and other fun facts about our project’s giant new helper. For all the latest on the tower, including features it’ll bring to the hospital and ways to support our project, visit AdventistSGMC.com/NextLevel.