Secretary of the Interior Ken Salazar is the latest key administration official who plans to step down after the beginning of President Barack Obama’s second term on Jan. 21.

Salazar, a former senator and attorney general from Colorado, said in a statement he would return to his home state by the end of March. “I am forever grateful to President Obama for his friendship in the U.S. Senate and the opportunity he gave me to serve as a member of his cabinet during this historic presidency," Salazar said in a statement on Wednesday.

Under Salazar, the Department of the Interior has authorized 34 solar, wind, and geothermal energy projects on public lands with a capacity of about 10.4 GW. Salazar also spearheaded the nation’s first blueprint for solar energy development in the West and established the nation’s first program for offshore wind leasing and permitting in the Outer Continental Shelf.

In December, Environmental Protection Agency (EPA) Administrator Lisa Jackson announced she would depart after the president’s State of the Union speech, to be delivered Feb. 12. Energy Secretary Steven Chu is also expected to step down, though he has not yet announced any plans.

According to The Hill, potential nominees to succeed the departing secretary of the interior include former Sen. Byron Dorgan (D-N.D.), outgoing Washington state Gov. Christine Gregoire (D), former Rep. Norm Dicks (D-Wash.), and former Montana Gov. Brian Schweitzer (D) .

Sources: POWERnews, DOI, The Hill