After years of delays, the Peabody Essex Museum is moving forward with its expansion plan, adding a gallery wing to the existing complex and a massive off-site facility for managing and conserving collections.

The plan, which the museum announced Wednesday, represents a significant departure from its earlier intent to build a 175,000-square-foot addition to the existing museum. The new design, by contrast, calls for 40,000 square feet in new gallery space and an 80,000-square-foot off-site facility known as the Collection Stewardship Center. The museum hopes to break ground next year, with a projected completion date in 2019.