By 2008, Yucca Mountain was one of the most studied pieces of geology in the world; between geologic studies and materials science the United States had invested US$9 billion on the project. This site studied by the Nevada Bureau of Mines and Geology (NBMG) differs substantially from other potential repositories due to the finding of natural analogues of nuclear material that are currently being studied. The DOE estimates that it has over 100 million U.S. gallons of highly radioactive waste and of spent fuel from the production of nuclear weapons and from research activities in temporary storage. The cost of the facility is being paid for by a combination of a tax on each kilowatt hour of nuclear power and by the taxpayers for disposal of weapons and naval nuclear waste. Based on the 2001 cost estimate, approximately 73 percent is funded from consumers of nuclear-powered electricity and 27 percent by the taxpayers. The Total System Life Cycle Cost presented to Congress on July 15, 2008 by Director Sproat was $90 billion. This cost, could not be compared to previous estimates since it included a repository capacity about twice as large as previously estimated over a much longer period of time (100 years vs 30 years). Additionally, the cost of the project continued to escalate because of insufficient funding to most efficiently move forward and complete the project. By 2007, the DOE announced it was seeking to double the size of the Yucca Mountain repository to a capacity of , or 300 million pounds.