Page:Michigan v. EPA.pdf/33

 Cite as: 576 U. S. ____ (2015)

11

KAGAN, J., dissenting

theoretical) by sources of a similar type or character.” S. Rep. No. 101–228, pp. 168–169 (1989). Of course, such a standard remains technology-forcing: It requires laggards in the industry to catch up with frontrunners, sometimes at significant expense. But the benchmark is, by definition, one that some power plants have achieved economically. And when EPA made its “appropriate and necessary” finding, it knew that fact—knew that the consequence of doing so was to generate floor standards with cost considerations baked right in. Still more, EPA recognized that in making categorization decisions, it could take account of multiple factors related to costs of compliance—and so avoid impracticable regulatory burdens. Suppose, to use a simple example, that curbing emissions is more technologically difficult— and therefore more costly—for plants burning coal than for plants burning oil. EPA can then place those two types of plants in different categories, so that coal plants need only match other coal plants rather than having to incur the added costs of meeting the top oil plants’ levels. Now multiply and complexify that example many times over. As the Agency noted when making its “appropriate and necessary” finding, EPA “build[s] flexibility” into the regulatory regime by “bas[ing] subcategorization on. . . the size of a facility; the type of fuel used at the facility; and the plant type,” and also “may consider other relevant factors such as geographic conditions.” 65 Fed. Reg. 79830; see S. Rep. No. 101–228, at 166 (listing similar factors and noting that “[t]he proper definition of categories . . . will assure maximum protection of public health and the environment while minimizing costs imposed on the regulated community”). Using that classification tool, EPA can ensure that plants have to attain only the emissions levels previously achieved by peers facing comparable cost constraints, so as to further protect plants from unrealistic floor standards.