The owners of Cordage Park in north Plymouth can now move forward with the first phase of a planned mixed-use development, after the local Planning Board approved a site plan for the work.

The initial-phase construction calls for 204 rental apartments — 51 of them designated as “affordable’’ — and 23,000 square feet of retail space on the vacant site of a former Walmart store.

The town created a “smart growth’’ zoning district in 2008 encompassing 55.8 acres of Cordage Park under the state’s Chapter 40R program, which encourages municipalities to set aside areas for dense residential or mixed-use projects that include affordable housing.

Cordage Park was formerly the site of the Plymouth Cordage Co., a large-scale rope manufacturer, and is today partially occupied by the Plymouth Commerce Center and the Plymouth MBTA station.

The plans for the overall development, Seaport at Cordage, call for 675 residential units, 33,500 square feet of retail space, a 180-seat restaurant, a 4,000-square-foot clubhouse, 21,000 square feet of office space, and a 300-slip marina.

The first-phase residential component calls for eight three-story buildings with 10 pocket parks disbursed among them, a community courtyard, and landscaped sidewalks. Details on the retail component will be offered later.

The state awarded a $2 million grant in 2015 in order to fund public utility, road, and sidewalk work in support of the project.

John Laidler can be reached at john.laidler-co@globe.com.