Another attempt to clean up 56 million gallons of nuclear waste at a World War II-era compound is rife with mismanagement, delays and cost overruns, a government watchdog found.

The Department of Energy's current waste treatment project at Hanford in Washington state has already faced several delays and cost increases, and poor oversight has set it up for more, the Government Accountability Office reported Thursday.

Hanford was created in 1943 during the Manhattan project and used nine nuclear reactors to produce plutonium for the nation's nuclear arsenal. The site closed its uranium operations in 1987.

The Energy Department has failed to treat a single drop of the 56 million gallons of toxic waste held underground, despite more than $19 billion invested over 25 years.

The most recent treatment project began in 2000 and was expected to be finished in 2011, at a cost of $4.3 billion. The completion date was extended in 2006 to 2019 at a cost of $12.3 billion. That estimate was also thrown out by 2011.

"As of March 2015, DOE and the state had not yet agreed to new deadlines," the report said.

The delays and cost increases were caused by technical problems with the treatment systems, among other issues.

Consequently, the Energy Department proposed two additional facilities in 2013 that would help treat some waste before the full project's completion. Officials estimated those projects would take from six to eight years and would cost at least $1 billion.

"These cost and schedule estimates, however, cannot be considered reliable," because the Energy Department didn't calculate the price or time commitment of certain essential technical components, the report said

"Without reliable estimates," the facilities could cost a "significant yet undisclosed" amount more than estimated and "will commit DOE to project time frames it may be unable to meet," the report said.

Also, instead of pinpointing the waste treatment program's shortcomings and assessing appropriate remedies, the Energy Department proposed the facilities and based its needs to fit the projects' capabilities.

"By narrowly defining the mission needs this way," the Energy Department didn't consider "other alternatives" that would expedite the nuclear waste treatment or address "potential danger posed by the leakage of waste from the tanks," the report said. "Potentially less costly or more effective alternatives will not be considered."

Investigators also noted that problems found in previous accountability office and inspector general reports haven't been solved.

For example, 12 systems used in the waste treatment process at one facility risk failure, a May 2014 report found.

"As of January 2015, DOE had not reviewed the remaining systems, and … officials told us they have no plans to do so," the report said.

Another facility's technical issues could cost nearly $1 billion to mitigate, or "radioactive contamination may spread," the report said.

Also, since a comprehensive review of all the facilities hasn't been conducted, the Energy Department "does not know the extent to which such problems may affect other facilities and systems," the report said.

This is not the first waste treatment program conducted at Hanford.

"DOE has considered and abandoned several different approaches to treating and disposing of this waste but, to date, no waste has been treated," the report said.

Hanford is only one site the Energy Department has struggled to clean.