30 CFR §250.1603

1. (a)Upon receipt of a written request from the lessee, the District Manager will determine whether a sulphur deposit has been defined that contains sulphur in paying quantities (i.e., sulphur in quantities sufficient to yield a return in excess of the costs, after completion of the wells, of producing minerals at the wellheads).
2. (b)A determination under paragraph (a) of this section shall be based upon the following:
   1. (1)Core analyses that indicate the presence of a producible sulphur deposit (including an assay of elemental sulphur);
   2. (2)An estimate of the amount of recoverable sulphur in long tons over a specified period of time; and
   3. (3)Contour map of the cap rock together with isopach map showing the extent and estimated thickness of the sulphur deposit.