MT. PLEASANT, S.C. — Holder Properties is underway on Portside, a 120,000-square-foot office building located within Ferry Wharf, a master-planned development in Mt. Pleasant that includes office, retail, hospitality and residential projects. The development is located at the foot of the Arthur Ravenel Jr. Bridge along the Charleston Harbor. Holder Properties broke ground on Portside in March. The five-story building is approximately 45 percent preleased, including a recently executed lease with Serendipity Labs Coworking. Portside will share a parking deck with a new hotel under construction at Ferry Wharf. The office building will be available for occupancy in spring 2019. McMilan Pazdan Smith Architecture is designing the building, and Freese Johnson is the general contractor.