I study here http://www.thardeep.org/thardeep/loan-based-on-future-sales/ lending expo  Such a level at Cushing, based on the amount of oil needed to be left to prop up tanks' floating roofs, would be about 10 percent of total shell capacity, or 8 million barrels, said Mark Shaw, executive director at E3 Consulting LLC, an engineering firm that has reviewed Cushing tanks designs.