Lisa Jackson, administrator for the U.S. Environmental Protection Agency (EPA) told the agency on Dec. 27 that she is leaving her position, according to a report from the National Stone, Sand & Gravel Association (NSSGA),

No successor was immediately named, NSSGA reported, although it is expected that Robert Perciasepe, the EPA deputy administrator, will take over, at least temporarily.

Perciasepe was an EPA official under President Clinton and served as chief operating officer at the National Audubon Society, according to the EPA.

No official statement about Jackson’s resignation had been posted to the EPA website at the time of this posting.

NSSGA says in a Jan. 2 Special Legislative Update, that the next EPA administrator nominee “faces a difficult confirmation process” because Republicans have offered strong opposition to EPA’s regulatory agenda under Jackson.