Strategic Petroleum Reserve (United States)  The Strategic Petroleum Reserve (SPR) is a supply of petroleum held by the United States Department of Energy (DOE) for emergency fuel. It is the largest emergency supply in the world, and its underground tanks in Louisiana and Texas have capacity for . The United States started the petroleum reserve in 1975 after oil supplies were interrupted during the 1973–1974 oil embargo, to mitigate future supply disruptions. The current inventory is displayed on the SPR's website. , the inventory was . This equates to about 635.0/18.49 round 0 days of oil at 2013 daily U.S. consumption levels of  or 635.0/9.859 round 0 days of oil at 2013 daily U.S. import levels of . However, the maximum total withdrawal capability from the SPR is only , so it would take over 635.0/4.4 round 0 days to use the entire inventory. At recent market prices ($17 a barrel as of April 2020), the SPR holds over $10.8 billion in sweet crude and approximately $18.3 billion in sour crude (assuming a $15/barrel discount for sulfur content). In 2012, the total value of the crude in the SPR was approximately $43.5 billion, while the price paid for the oil was $20.1 billion (an average of $28.42 per barrel). The SPR management office is located in Elmwood, Louisiana, a suburb of New Orleans. The reserve is stored at four sites on the Gulf of Mexico, each located near a major center of petrochemical refining and processing. Each site contains a number of artificial caverns created in salt domes below the surface. Individual caverns within a site can be up to below the surface, average dimensions are wide and deep, and capacity ranges from . Almost $4 billion was spent on the facilities. The decision to store in caverns was made in order to reduce costs; the Department of Energy claims it is roughly 10 times cheaper to store oil below surface with the added advantages of no leaks and a constant natural churn of the oil due to a temperature gradient in the caverns. The caverns were created by drilling down and then dissolving the salt with water. Access to the reserve is determined by the conditions written into the 1975 Energy Policy and Conservation Act (EPCA), primarily to counter a severe supply interruption. The maximum removal rate, by physical constraints, is . Oil could begin entering the marketplace 13 days after a presidential order.