The administration’s border wall troubles are spreading and have now infected President Biden’s nominee for undersecretary of the Air Force, who ran into trouble on Capitol Hill this week over her role in the Pentagon’s hasty and wasteful sell-off of the construction materials.

Melissa G. Dalton was pummeled by Republican senators who said in her current job as the Pentagon’s top homeland defense official, she presided over the fire sale, which saw the materials go at a 97% discount, all while misleading lawmakers over what was happening.

Under intense questioning Tuesday, Ms. Dalton also broke with Mr. Biden by saying she believes a wall can be effective to “mitigate” the flow of migrants, and she also acknowledged the Pentagon wasted money by selling the materials so hastily.

Senators said the Defense Department, which was roped into border wall construction thanks to the Army Corps of Engineers and President Trump’s use of emergency powers, was sitting on massive stockpiles of material after Mr. Biden halted all wall construction on his inauguration day in 2021.

First the government was paying $130,000 a day to store it, then when lawmakers started writing legislation to force the Pentagon to use the material or donate it to states, the Defense Department quietly began selling it off to the public through an auction site.

Sen. Roger Wicker of Mississippi, the top Republican on the Armed Services Committee, told Ms. Dalton it was “a clear effort to circumvent congressional intent.”

It was also poor budgeting. The department got just 3 cents on the dollar, he said.

Making matters worse, those buyers turned around and resold the steel tubing for 10 times that amount, said Sen. Joni Ernst, Iowa Republican.

“There’s a big scheme going on here where people are making a ton of money off of the taxpayers,” Ms. Ernst said.

Ms. Dalton admitted as much under questioning from Sen. Eric Schmitt. The Missouri Republican asked her if selling off the wall materials was a “good deal for taxpayers.”

“No,” she responded flatly.

Ms. Dalton said she’s made routine trips to the southern border to get a look at what’s going on. She said in her personal view, a border wall can stop illegal immigrants if it is “part of a system of border security management.”

“I believe a border barrier can mitigate the flow,” she said.

But she said she didn’t get to make those decisions, saying as a member of the administration she had to fall in line with Mr. Biden’s decision to halt construction.

As the wall issue was heating up last year Ms. Dalton signed a letter saying the Defense Department was still coming up with plans for what to do with the materials. In fact. Mr. Wicker said, it was already in the process of auctioning off the steel.

Ms. Dalton this week blamed colleagues, saying she was only transmitting the responses from “a number of components.”

“It was the best available information we had at the time,” said Ms. Dalton, who is currently the assistant secretary of defense for Homeland Defense and Hemispheric Affairs and is acting deputy undersecretary for policy.

Republican senators indicated opposition to her gaining promotion to the second-highest civilian job in the Air Force.

“We’ve established that you don’t take responsibility,” said Mr. Schmitt.

The wall has been a thorn for the Biden administration even before he took office. Mr. Biden’s promise not to build “another foot” of wall led to his Day One construction halt, not just on the barrier but also the sensors, lights and roads that constitute the wall system.

Local authorities say illegal immigrants and drugs pour through those unfinished sections.

Border Patrol agents are vocal in supporting the wall, saying it helps shape the flow of people and gives them a better chance at intercepting illegal immigrants when they do cross.

Mr. Biden has rejected their expertise, insisting the wall is not effective.

But sitting on the materials to build the wall, even as record-breaking numbers of illegal immigrants poured in, proved to be embarrassing, and that spurred the sell-off effort.

The procedures call for the material to be sent to the Defense Logistics Agency, which works with an auction company to sell it.

DLA said it stopped sales last year after lawmakers made clear their displeasure. The agency said the materials have since been doled out elsewhere in federal or state government, though DLA did not say who claimed it.

The Army Corps of Engineers did not respond to an inquiry for this story.

Part of the embarrassment for the administration is that it sold off the materials just months before Homeland Security Secretary Alejandro Mayorkas reversed himself and said he would build miles of new wall.

Mr. Mayorkas said his hands were tied by spending laws that Congress passed during the Trump administration, and he had to spend the money on wall-building.

It was tough to square that explanation with his official statement on the renewed wall building, published in the Federal Register, where he declared an “immediate” need for the wall and waived more than two dozen laws to speed construction. Among them were iconic environmental laws like the Clean Air Act, the Endangered Species Act and the Bald and Golden Eagle Protection Act.

• Stephen Dinan can be reached at sdinan@washingtontimes.com.