Dia’s grand designs for a 34,000-square-foot slice of the High Line are moving forward, officials say, even as the art foundation’s longtime leader moves west.

The contemporary art institution has been in talks with the city to build a $55 million exhibition space on the forthcoming High Line Park in the meatpacking district. Last week, however, Dia’s director, Michael Govan, announced he was leaving the foundation to take over the Los Angeles County Museum of Art, raising questions about Dia’s planned move to the High Line.

Although Dia has not named a successor to Mr. Govan, foundation and city officials say they are committed to the High Line.

“I don’t think that Michael’s leaving will put that in jeopardy in any way,” the vice chairwoman of Dia’s board, Ann Tenenbaum, said.

The museum is planning to appoint a search committee to interview candidates for the director position.

Ms. Tenenbaum and other foundation officials stressed that discussions about the High Line were in the preliminary stages. The Dia wants to move to 820 Washington St. at Gansevoort Street, a plot the city owns. “It’s all contingent on a deal that works with the city,” Ms. Tenenbaum said.

The city’s cultural affairs commissioner, Kate Levin, said in a statement that the city “has been assured that the board and staff are committed to going forward. Michael Govan has been a great asset to the organization and to this project, and the groundwork he has laid builds a solid foundation for Dia’s future.”

Mr. Govan, 42, has led Dia since 1994 after serving as the deputy director of the Solomon R. Guggenheim Foundation. He has drawn effusive praise from colleagues, who credit him with spearheading the foundation’s extensive growth in the last decade.

In 1998, seeking a home for Dia’s permanent collection of contemporary art, Mr. Govan spotted an abandoned Nabisco box factory along the Hudson River in Beacon, N.Y. Five years and $50 million later, Dia:Beacon opened to rave reviews and crowds larger than those at the foundation’s space in Chelsea. After opening the Beacon location in 2003, Mr. Govan set his sights on revamping Dia:Chelsea, located on West 22nd Street since 1987. Dia:Chelsea closed in January 2004, but after seeing the estimated costs of renovations, Mr. Govan began to look elsewhere for a Manhattan home for Dia.

He settled on the High Line, the elevated railway where the city has begun work on a park scheduled to open in 2008. Dia’s plans call for 34,000 square feet of galleries over two floors in what Ms. Tenenbaum said would be a “simple, factory-like” space with entrances to the park.

Dia officials said Mr. Govan’s departure was not a surprise, as they assumed that after shepherding the foundation through a period of expansion he would be looking for new challenges. “I always thought that at some point he would get restless,” Ms. Tenenbaum said. She praised him as “a real visionary” and a “deal maker.”

A Dia trustee and Mr. Govan’s predecessor as the foundation’s director, Charles Wright, said Mr. Govan had put the foundation “in a position of great strength” for the future. “He’s allowed Dia to go forward with a dramatic period of growth without compromising its core values,” Mr. Wright said. “That’s pretty remarkable.”