S.C. Code § 48-1-30
The Department shall promulgate regulations to implement this chapter to govern the procedure of the Department with respect to meetings, hearings, filing of reports, the issuance of permits and all other matters relating to procedure. The regulations for preventing contamination of the air may not specify any particular method to be used to reduce undesirable levels, nor the type, design, or method of installation or type of construction of any manufacturing processes or other kinds of equipment. Except where the Department determines that it is not feasible to prescribe or enforce an emission standard or standard of performance, it may, by regulation, specify equipment, operational practice, or emission control method, or combination thereof. The Department may grant approval for alternate equipment, operational practice, or emission control method, or combination thereof, where the owner or operator of a source can demonstrate to the Department that such alternative is substantially equivalent to that specified.
S.C. Code § 48-1-30