Total Capacity is the maximum volume of gas that can be stored in the storage facility, essentially the total volume of gas that would completely fill the entire reservoir pore space. The gas that fills the Total Capacity can be divided into two fractions, the Working Gas and the Base Gas.
The value is reported in MCF (thousand cubic feet of gas).
Follow this link to a more thorough discussion of < Terminology used to describe gas storage volumes >
U.S. Energy Information Administration, 2004, The basics of underground natural gas storage: U.S. Energy Information Administration Web site, http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/storagebasics/storagebasics.html., date accessed, July 21, 2011.