The Strategic Petroleum Reserve (SPR) operated by the United States Department of Energy is the largest emergency supply system of its kind in the world. The SPR presently consists of four underground storage facilities located in salt domes along the coastal regions of Louisiana and Texas, and has a total storage capacity of 700 million barrels of oil. These sites were chosen from among the more than 400 potential areas along the Gulf Coast of the southern United States after careful review of their relative geologic characteristics.

A salt dome is a body of rock salt surrounded by layers of sedimentary rock. Geologic characteristics considered in selecting storage sites include: 1) area geologic activity, 2) structural size 3) existence of a trapping mechanism, 4) salt geometry, 5) salt composition, and 6) surface conditions.

Geologic activity in the area of potential storage sites must be well understood. The coastal...