More than $21 million has gone wasted on unused trash incinerators at U.S. bases in Afghanistan, with at least three bases building the expensive facilities and then letting them sit idle, according to a report by the Special Inspector General for Afghanistan Reconstruction.

Monday's report, the third in a series on money being burned -- figuratively speaking -- at these facilities, detailed the shoddy construction, multi-year delays and poor oversight of the incinerator project at Forward Operating Base Sharana in Paktika province, Afghanistan. Three years after they were supposed to be finished, the facilities were handed over to the Afghan Defense Ministry for scrap without ever being used.

"I don’t know what the U.S. Army Corps of Engineers considers success, but spending more than $5 million = on something that was never used is not what I call successful to the American taxpayer. This project appears to have been a complete waste,” said Special Inspector General John F. Sopko in a statement to the Washington Examiner.

The U.S. Army Corps of Engineers paid a Denver-based contractor $5.6 million to build the incinerators, which were slated for completion in August 2010. Two years after that deadline, the Corps paid the contractor fully and transferred the facilities to the base without testing to make sure they worked. When SIGAR investigators visited the base in May 2013, the incinerators were rife with electrical problems that left them unusable and would have cost another $1.1 million to fix.

The incinerators were so poorly constructed that even when fixed, they would have run only at partial capacity, and would have required manual labor to load and unload waste because the intended loading area was so narrow.

With a long list of problems and little incentive to pay to fix them, officials at the base decided not to fix the facilities, and the base closed soon after. Officials with the U.S. forces in Afghanistan told SIGAR the Afghans “have already deconstructed the incinerators, presumably for scrap.”

The incinerators were supposed to replace open burn pits, which go against Defense Department policy for permanent bases because they pose a health risk to troops living on the base. But while the half-finished incinerators sat useless, the trash pits at FOB Sharana kept burning.

The Corps told SIGAR its own review found the incinerators were built according to specification and transferred as usable facilities to Sharana in December 2012, and none of its contracting officers did anything wrong.

SIGAR disagreed.

"The fact remains that USACE paid the contractor in full for an incinerator facility that was never used to process solid waste, that experienced a 30-month delay, and that had a number of construction deficiencies," Sopko wrote.

The trash facilities at FOB Salerno, which SIGAR reported on in April, experienced similar problems. The $5 million incinerators, also contracted by the Corps, were transferred to the base unusable, and officials decided the cost of repairs and maintenance were too high to justify using them.

Another report in July found the larger two of four incinerators built at Camp Leatherneck for $11.5 million were unused.