"Sarah has been a tremendous leader within the agency, overseeing the start of the WOTUS rewrite as well as playing a vital role in our worldwide relations", Pruitt said in a statement.
Last year, Pruitt also directed Hupp's younger sister to reach out to a senior executive at Chick-fil-A to inquire about a "business opportunity".
Pruitt said in a statement that his scheduling director, Millan Hupp, 26, had resigned. EPA is doing really well.
Democrats continue to call for Pruitt to resign amid the growing list of controversies.
"Administrator Scott Pruitt, thank you. And you know, somebody has to say that about you a little bit", Trump said.
Weary Alexander Zverev out as Dominic Theim reaches last four
Play was suspended due to fading light, with Russian Daria Kasatkina leading 7-6 (5) 3-3 against second-seeded Caroline Wozniacki. He made a decision to carry on, but looked nothing like the player who had been tipped by some to win Roland Garros.
That official is referring to a new accusation that Pruitt had his office contact the CEO of fast-food giant Chick-Fil-A in an effort to secure a franchise for his wife, Marlyn.
According to one top EPA official, the 26-year-old was "tired of being thrown under the bus by Pruitt", and weary of seeing her name constantly appear in headlines about the agency. Senate Joni Ernst (R-IA) joined a chorus saying earlier this week: "He is about as swampy as you get here in Washington, D.C. And, if the President wants to drain the swamp he needs to take a look at his own cabinet".
Greenwalt, who also served as counsel to Pruitt in his previous position as Oklahoma's attorney general, was in the news most recently when Pruitt rescinded a hefty raise for her after public criticism of his use of a little-known clause in the Safe Drinking Water Act to come up with the money. The EPA gave no reason for her departure.
The aide to EPA chief Scott Pruitt who performed a series of personal errands for her boss on the taxpayers' dime - including trying to buy a used mattress from President Trump's DC hotel - is out of a job.
For his part, Pruitt suggested the criticism, investigations and unending stream of negative revelations about him were all political attacks motivated by his efforts to roll back environmental regulations.