Wheeler will come to the EPA as Republican and Democratic lawmakers are investigating allegations that Scott Pruitt, the agency's administrator, acted unethically on expensive air travel, a condominium lease, and in arranging raises for close aides.
Trump says the changes were part of his effort to cut regulation and promote manufacturing growth.
On a conference call that included the EPA's liaison to the White House, Pruitt's security chief said he "didn't give a fuck who is on this call" when he described his plan to retrieve Chmielewski's credentials, according to the letter. The Democrats who signed the letter, Senators Tom Carper and Sheldon Whitehouse, as well as Representatives Elijah Cummings, Gerald Connolly and Don Beyer, said they found Chmielewski "to be a credible professional who continues to express deep loyalty to the President and Vice-President". Pruitt insisted in a recent television interview that he didn't know about the raises until after they were disclosed in media reports.
Chmielewski has confirmed numerous details previously reported in recent weeks, such as the EPA giving massive raises to two aides close to Pruitt and staff getting reshuffled or demoted for speaking out.
Pruitt is also accused of refusing to stay in Australian and Italian hotels that were recommended by the U.S. Embassy because of security concerns, instead demanding to stay at more expensive hotels that required even more taxpayer funds to pay for additional security.
Five congressional Democrats sent Pruitt a letter on Thursday detailing accusations made against Pruitt by Kevin Chmielewski, former Donald Trump campaign aide who served as Deputy Chief of Staff for Operations under Pruitt. Asked whether he had ever used a private email account while on the job, Pruitt told the Senate Environment and Public Works Committee: "I use only my official OAG [office of the attorney general] email address and government-issued phone to conduct official business".
Chmielewski told the staffers that Pruitt would order them to cook up some event he could attend in Oklahoma so he could fly home there on weekends.
Chmielewski, the lawmakers said, had laid everything on the table in a meeting with their staffs.
Pruitt, according to Chmielewski, designed his schedule around places he wanted to visit, and then would tell staff to justify the destination after the fact.
"We will respond to Members of Congress through the proper channel", the agency's spokesman, Jahan Wilcox, told CNN in a statement. While Jackson took responsibility earlier this week and said Pruitt had no knowledge of what transpired, Chmielewski said Pruitt was fully aware.
According to the letters, Pruitt would also frequently exceed his allowable USA government per diem rate, "sometimes even exceeding the 300 percent cap permitted in exceptional circumstances".
The letters put more pressure on Pruitt to resign as a ballooning scandal over accusations of rampant corruption and runaway spending continues into a third consecutive week. He also sought to fly on Delta Air Lines even when it wasn't the federal government's contract carrier on a certain route so that he could "accrue more frequent flier miles".