David Marwell, the founding chief executive and director of the Museum of Jewish Heritage, is expected to leave his post after 18 years at the Battery Park City Museum.

In a resignation letter sent to Bruce Ratner, the museum’s newly appointed chairman, Marwell recalled the many memories over the past 18 years, including the 82,000-square-foot addition in 2002. “I have had a book project in mind for some time that will detail my involvement with the Josef Mengele investigation, and I think that now is the time to sit down and write it,” Marwell wrote.

Ratner praised Marwell’s brilliant guidance in a memo to the museum’s staff. “To say that David has left his mark on the museum is an understatement and he will be greatly missed,” he wrote.

Marwell has led the museum, known as ‘A Living Memorial to the Holocaust’, since its opening in 1997 at 36 Battery Pl. He was appointed as director of the museum in December 2000.

Ratner said he had asked the museum board to give Marwell the title of director emeritus.

According to a report by The Wall Street Journal, the museum is undergoing a challenging time.