U.S. EPA's top water official, Pete Silva, announced his resignation today.

Silva, whom President Obama appointed the assistant administrator for water in July 2009, plans to return to his home and family in California, EPA Administrator Lisa Jackson said in a memo to staff.

The announcement of Silva's departure comes a day after his office made a controversial decision to revoke the permit of one of the largest mountaintop mines ever proposed in Appalachia (Greenwire, Jan. 13).

The decision on the West Virginia mine came as EPA's water office worked on regulations of ash from coal-burning plants and pollution limits for stormwater discharges. The office is also working on clarifying which waterways and wetlands it regulates under the Clean Water Act.

"During his tenure, Pete has led a wide range of important actions to help protect the water we drink and safeguard the health of millions of Americans," Jackson wrote. "We have greatly valued his service, and we offer him our deepest thanks as he prepares to embrace new opportunities. We are beginning the search for his successor."

Nancy Stoner, who came from the Natural Resources Defense Council to become the deputy assistant administrator for the water office, will serve as acting assistant administrator in Silva's absence. Silva leaves Feb. 12.

"Nancy is exceptionally talented and knowledgeable, and I am confident that she will continue to contribute significantly to the office's excellent work in this role," Jackson wrote.

Jackson also announced the appointment of Bicky Corman as deputy associate administrator for the Office of Policy and Joel Beauvais as senior adviser in the Office of General Counsel.