Phyllis Caldwell will leave her post as the chief of the Homeownership Preservation Office at the Treasury Department Dec. 9, according to an internal email obtained by HousingWire. Caldwell arrived shortly after the launch of the Home Affordable Modification Program in March 2009. She managed the development of the program from those early stages. Through September, participating mortgage servicers in HAMP started 856,000 permanent modifications and extended 1.7 million trials. Caldwell also oversaw the development of the $7.6 billion Hardest Hit Fund sent to 18 states to build additional foreclosure prevention and unemployment assistance programs for borrowers. "Phyllis’ depth of experience, judgment and leadership abilities have made her an invaluable member of OFS' and Treasury’s leadership," said Treasury Assistant Secretary for Financial Stability Tim Massad said in the email. Massad said Darius Kingsley, the deputy homeownership preservation officer, will take Caldwell's place. Kingsley joined the office of chief counsel at the Treasury in April 2009 to help with legal matters related to housing and other programs. Before that, Kingsley was a partner at the law firm McKee Nelson, now Bingham McCutcheon, where he specialized in mortgage-backed securities and other structured finance litigation. "It's a loss," Mortgage Bankers Association CEO David Stevens said about Caldwell's departure. "I think she did an extraordinary job. She took over HAMP at a very difficult time when there was so much pressure for the ability of these programs to be successful and getting the big banks to implement it effectively, coordinating with the administration and members of congress." Stevens worked closely with her while he was the commissioner of the Federal Housing Administration. The government reaction to the foreclosure crisis and the underwhelming performance of HAMP in particular have come under fire since the crisis began. The program was once estimated to help between 3 million and 4 million borrowers, but servicers were slow to convert the backlog of trials. Despite the various rule changes, the program is likely to prevent just over 800,000 foreclosures after redefaults – which equal nearly half of private programs – are taken into consideration. The problem, many critics have said, is that the Treasury never fully cracked down on servicers who have not performed well. The Treasury has maintained it lacked the legal authority to do more than withhold payments, which it has done temporarily for Bank of America (BAC) and JPMorgan Chase (JPM). "Phyllis had to testify often under unfavorable conditions, and she did it all with real grace," Stevens said. "She was stable, solid, persistent and very professional. She'll be missed." Caldwell will be spending more time with her family and will take an extended amount of time off before pursuing her next move, according to the Treasury. In addition to Kingsley's promotion, Massad will remain a central figure in housing policy. Assistant Secretary Mary Miller, President Obama's nominee to be Treasury's Under Secretary of Domestic Finance, is also expected to play a larger role in housing issues, pending confirmation. Jan Eberly, Treasury's assistant secretary for economic policy, will also maintain a role in housing policy. "(Kingsley) is outstanding," Stevens said. "I found him to be very responsive and hands on. He'll be a great steward of the office." Write to Jon Prior. Follow him on Twitter @JonAPrior.