SAN FRANCISCO (KGO) -- Engineers are testing a new plan to prevent San Francisco's Millennium Tower from sinking further into the ground.
The Millennium Tower opened in 2009 and has sunk at least 18 inches, which resulted in a $100 million repair.
In August, repairs were halted after crews discovered the tower had sank another inch.
"It's reasonable to expect that there might be some lessons learned along the way," said Emily Guglielmo of the Structural Engineers Association of Northern California. "Some things we need to mitigate so it is not uncommon for a project to hit pause to revise installation procedures."
On Tuesday, crews installed a 36-inch steel cylinder 100 feet into the ground on Fremont Street.
Engineers believe the steel cylinder will reduce erosion and vibrations from construction and vehicles.
Crews have deemed the building structurally safe.