The $800 million the U.S. spent to build up the Afghan economy and infrastructure yielded few if any successes, Pentagon officials are expected to tell Congress on Wednesday.

The Special Inspector General for Afghanistan Reconstruction said in prepared testimony that projects run by the Defense Department's Task Force for Business and Stability Operations were usually well-intentioned but had "little-to-no chance of achieving desired outcomes." Problems in the task force resulted in "hundreds of millions" of dollars in unfinished projects that failed to meet stated goals.

John Sopko, the special IG, appeared before the Senate Armed Services Subcommittee on Readiness and Management Support alongside Brian McKeon, the principal deputy undersecretary of defense for policy, on Wednesday afternoon.

"SIGAR has not been able to find credible evidence showing that TFBSO's activities in Afghanistan produced the intended economic growth or stabilization outcomes that justified its creation," the prepared testimony said. "On the contrary, TFBSO's legacy in Afghanistan is marred by unfinished, poorly planned and ill-conceived projects."

Sopko wrote that over the past two years, his organization received more complaints of waste, fraud and abuse about the task force than any other group operating in Afghanistan.

In one example, the U.S. spent $43 million to build a gas station in Afghanistan between 2011 and 2014, or 140 times as much as the same gas station would have cost in Pakistan.

The Defense Department also failed to conduct any feasibility studies before beginning construction, so officials didn't know that Afghanistan lacks the infrastructure to transport and distribute natural gas. In addition, it costs about $700 per car to convert a gasoline-powered car to run on compressed natural gas, which is too expensive for the average Afghan, who makes just $690 per year.

The gas station project resulted in no gains and a net loss of $31 million, according to testimony. The status of the station today is unclear.

Reports released over the past few months also found the Pentagon wasted millions housing task force staff in plush villas and started projects to develop the country's oil, gas and minerals industries that didn't yield any results.

Another problem investigators discovered was that the first director of the task force would approve programs without knowing what they cost. Paul Brinkley, the founding director of the task force, said "he did not know the cost of any project; his managers simply established requirements and then removed themselves from the contracting process."

The Defense Department has largely been unwilling or unable to cooperate with investigators' requests about spending in Afghanistan, saying that it does not maintain the institutional knowledge to answer questions about the program since it ceased all operations in Afghanistan on March 31, 2015.

The testimony says this is "unfortunate" and raises questions, especially since some leaders within the program still work at the Pentagon or with the military. Sopko said this precedent makes him worried it will be difficult to conduct oversight and learn lessons from other projects in Afghanistan as the drawdown concludes.

A spokesman for the U.S. mission in Afghanistan said on Tuesday that the department welcomes "any constructive efforts to help in the transparency and accountability of the way U.S. tax dollars are spent here in Afghanistan."

Sen. Chuck Grassley, R-Iowa, and chairman of the Senate Judiciary Committee, has also asked SIGAR and the broader Defense Department inspector general to conduct a formal audit of the task force's spending.

"I need assurance that all this money was spent in accordance with the law," Grassley wrote in a letter this month.