WASHINGTON -- When Claire McCaskill set out to crack down on waste and fraud in wartime contracting six years ago, the newbie senator from Missouri figured that finding ways to save taxpayer dollars in Iraq and Afghanistan would be a no-brainer project, even in the highly partisan halls of Congress.

"Like most who come to Washington for the first time, I assumed that this would not be a heavy lift," McCaskill said in a recent interview with McClatchy Newspapers. "I assumed that cleaning up war contracting and profiteering would be a consensus item that would fly through the process, and I learned quickly that that was very naive."

This month -- after half a dozen years of hearings, reports, overseas fact-finding trips, painful compromises and some last-minute, round-the-clock negotiating -- the first substantial overhaul of the federal government's wartime contracting practices since World War II finally became law, with McCaskill as its chief architect. The president signed it Jan. 2 as part of the 2013 National Defense Authorization Act, the day before McCaskill, a Democrat, was sworn in for her second Senate term.

In the end, McCaskill didn't get everything she wanted. Some of her proposals were dropped or scaled back, and she acknowledges that one consequence of the new law will be additional paperwork for the federal bureaucracy -- without any additional funding. But she said the bill was among the most satisfying accomplishments of her Senate career.

Among the worst examples of waste, fraud and abuse that the new law was designed to prevent were an ineffective water plant that Iraqis couldn't operate or maintain, a still-unfinished highway in Afghanistan that's wildly over budget at $176 million and a $300 million power plant near Kabul that Afghans can't afford to operate because the diesel fuel required to run it is too costly.

The power plant was a project by Black & Veatch, an engineering and construction firm based in Overland Park, Kan.

Black & Veatch referred questions about the feasibility of the plant to the U.S. Agency for International Development, which funded the project.

"Afghanistan is a very difficult place to work. We put our lives on the line for the government and the people of Afghanistan every day and we are proud of the work we've done in the region," the company said in a statement.

The plant typically runs at less than 10 percent capacity, according to USAID. Sheikeb Nesar, the head of operations for Afghanistan's national power utility, said the plant was used only during emergency situations when other power sources to Kabul were cut off.

"It is a big, hulking, overpriced, oversized generator, and you don't pay almost $300 million for a generator," McCaskill said.

But the senator defended Black & Veatch, a company that contributed $6,000 to her campaign in 2006 through its political action committee, and $1,000 in 2008. The PAC didn't donate to her 2012 campaign.

"They didn't do anything wrong," McCaskill said. "What was wrong was the analysis in the first place. . There was not an adequate sustainability analysis prior to the decision to build it."

Such an analysis is mandated by the new law, which should help prevent flawed ventures such as the plant, McCaskill said. The law requires government agencies to prove that taxpayer dollars won't be wasted on futile or ill-conceived projects before they allocate funds, strengthens the powers of inspectors general who investigate cases of fraud and abuse, and establishes a clear chain of authority for contracting oversight in the Defense Department, the State Department and USAID.

"Now someone has to take responsibility for the contract at the front end, so that if things go badly we know who to call on the carpet," McCaskill said.