U.S. Supreme Court Denies Review of Case Seeking to Overturn the Clean Water Act's Irrigated Agriculture Exemption
Published Thursday, July 2, 2026
On June 29, the U.S. Supreme Court declined to hear a challenge to the Grassland Bypass Project, letting stand a major ruling by the U.S. Court of Appeals for the Ninth Circuit. The high court’s decision affirms that agricultural irrigation projects are exempt from Clean Water Act permitting requirements, even if return flows contain incidental, nonagricultural pollutants mixed from nonpoint sources.
The Ninth Circuit decision, issued on Sept. 5, 2025, upheld the dismissal of a lawsuit alleging that the U.S. Bureau of Reclamation and the San Luis & Delta-Mendota Water Authority’s operation of the Grassland Bypass Project and the San Luis Drain violated the Clean Water Act. Environmental groups alleged that the project could not use the Clean Water Act’s irrigated agricultural exemption from federal National Pollutant Discharge Elimination Systems permits because the irrigation return flows mixed with other flows. The Ninth Circuit upheld the irrigated agricultural exemption, clarifying that minor commingling with nonpoint sources such as stormwater runoff, dust or groundwater seepage does not negate the exemption. California Farm Bureau, along with other agricultural groups, filed an amicus brief supporting the U.S. Bureau of Reclamation, San Luis & Delta-Mendota Water Authority and Grassland Water District, pointing out that the lawsuit conflicts with the congressional intent of the Clean Water Act and threatened irrigated agriculture in the West. California Farm Bureau Legal has been following this case since 2011.
Staff contact: Kari Fisher, kfisher@cfbf.com.
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