Due to the by-product nature of propane production, the supply of propane cannot be easily adjusted to meet growing demand. About 90 percent of propane in the United States is produced domestically. [18] About 10 percent of the propane consumed in the United States is imported annually, with about 70 percent imported from Canada by pipeline and rail. The remaining 30% of imported propane enters the United States by sea from other sources. After being separated from crude oil, propane in North America is stored in huge salt caverns. Examples of these include Fort Saskatchewan, Alberta; Bellevue Hill, Texas; and Conway, Kansas. These salt caverns[19] can store 80,000,000 barrels (13,000,000 cubic meters) of propane.