557 U.S. 261 (2009) (U.S. Supreme Court)
Coeur Alaska, Inc. v.
When a mining operation discharges tailings slurry that will raise the bottom elevation of a navigable lake, is the discharge governed by the Clean Water Act's §404 permitting regime for "fill material" (administered by the Army Corps of Engineers), or by EPA's §402 NPDES program and its New Source Performance Standards for froth-flotation mills, which would prohibit the discharge?
Under the Clean Water Act, the Corps has authority under §404 to issue permits for the discharge of "dredged or fill material" into navigable waters. EPA administers §402's NPDES program for other pollutant discharges and promulgates technology-based effluent limitations, including §306 New Source Performance Standards. Pursuant to a 2002 joint EPA–Corps regulation, "fill material" includes materials that change the bottom elevation of a waterbody, such as mine tailings. EPA's regulations also provide that discharges of dredged or fill material regulated under §404 are not subject to NPDES permitting. Where a discharge qualifies as fill material, permitting authority lies with the Corps under §404, and EPA's §402-based effluent limitations and NSPS do not apply to that discharge, absent contrary direction consistent with the statute and regulations. Courts defer to an agency's reasonable interpretation of the CWA and its own regulations (Chevron/Auer deference).
The tailings slurry to be discharged into Lower Slate Lake is "fill material" under the joint 2002 definition; therefore, the discharge is governed by §404, and the Army Corps of Engineers had authority to issue the permit. EPA's §306 New Source Performance Standards for froth-flotation mills do not apply to a §404 discharge of fill material. The Ninth Circuit's judgment was reversed.
The decision clarifies the boundary between the CWA's §404 and §402 programs and confirms that when a discharge qualifies as fill material, it is exclusively governed by §404 and the Corps' permitting process, not EPA's §402 NPDES regime or NSPS. For practitioners and students, the case is a prime example of Chevron/Auer deference, interagency coordination, and the regulatory consequences of definitional rules. It also highlights a policy tension: classifying certain mine waste as "fill" can avoid stringent technology-based limits, spurring debate about potential regulatory "loopholes" and prompting attention to EPA's oversight tools (e.g., §404(b)(1) Guidelines and §404(c) veto) and future rulemaking.