Much like the SC Supreme Court's ruling that the State has to provide only "minimally adequate" education (and the obvious ensuing question: Is that really our highest aspiration?).  Many federal standards are only "the floor", i.e., the minimally adequate, requirements. States have, in most circumstances, the power to require greater protections.

In many areas, such as the Clean Water Act provisions, this retained power of the States is explicit. See 33 U.S.C § 1370; 40 C.F.R. § 131.4(a); Natural Res. Def. Council, Inc. v. EPA, 859 F.2d 156, 174 (D.C.Cir.1988) (noting that “[i]n fashioning its guidelines … EPA endeavored to reconcile the competing objectives of regulatory uniformity and state autonomy by establishing a floor for … state enforcement authority, while ensuring that states have the maximum possible independence”)

The Vermont Supreme Court recently recognized this long-standing State right, while also holding that the State has the equivalent right of waiving its higher standards. (See article here.)

There are arguably very cogent reasons for allowing flexibility in State requirements above a certain minimum level. The huge disparity between different areas of our country (and even within a state itself) virtually negates the possibility of a one-size-fits-all rule. The ability of South Carolina to impose stricter requirements where necessary to protect environment and health is absolutely essential; however, any variance (above or below) such local requirements will be subject to scrutiny for those factors, both practical and immoral (if not illegal), which can influence local decisions.