CHARLESTON, S.C. — Federal and state officials have signed an agreement that allows for the start of a project to deepen South Carolina’s busiest harbor.

The Army Corps of Engineers and the State Ports Authority signed what is called a project partnership agreement Wednesday over the work on Charleston Harbor.

The document allows the groups to begin work on the more than $500 million project to deepen the harbor by 7 feet (2 meters) to a depth of 52 feet (16 meters).

Port officials say the extra depth is vital to allow Charleston to bring in heavier, larger ships that are becoming more popular in global shipping.

Officials estimate the project could take anywhere from 3 to 6 years.