Resmark Cos. of Los Angeles has become an equity partner in the rowhouse development planned as part of a sprawling residential complex slated to rise on a vacant 30-acre waterfront lot straddling Fishtown and Port Richmond.

The private equity firm is joining with the Bethesda, Md.-based Concordia Group and Philadelphia’s D3 Real Estate Development in the construction of 248 single-family rowhouses planned at the former shipyard property along Beach Street, near East Cumberland Street, it said in a release Tuesday.

Concordia and D3 also have proposed about 850 apartments spread across four seven-story buildings at the site. The rentals are to be developed separately from the partnership with Resmark.

The waterfront parcel at 2001 Beach St. was once part of the vast William Cramp & Sons Shipbuilding Co., which operated from 1830 until the end of World War II, producing battleships and naval cruisers.

Casino magnate Steve Wynn, who has since left his gaming company after sexual-misconduct allegations, had sought permission to build a $926 million resort at the site in 2013, pitting himself against others vying to build Philadelphia’s second gambling destination. He withdrew his proposal from consideration before a decision on the license was made.

Resmark previously partnered with Concordia and D3 on rowhouse developments at Manayunk’s Venice Island and in South Philadelphia’s Pennsport neighborhood.