The U.S. Government's Social Security Administration signed a 10-year lease at 439 South Union St. in Lawrence, MA. The building is a five-story, 243,000-square-foot, Class-B flex building located in the Heritage Place complex. The Social Security Administration will occupy 12,242 square feet on the second floor. The administration will be relocating within the building into newly built-out space in March of next year. Ellen Keller of Ozzy Property Management Inc., represented both the tenant and the owner, Heritage Place LLC.