The U.S. Court of Appeals for the Ninth Circuit ruled on the Grassland Bypass project into the San Luis Drain, stating that it qualifies for the Clean Water Act's irrigated return flows exception since "discharges that 'do not contain additional discharges from activities unrelated to crop production."

 
This phrase means that under the Clean Water Act, "point source" discharges - which do not include return flows from irrigated agriculture as long as they don't include certain additional discharges - require a federal permit. Furthermore, the court states that the return flow can't include additional pollution, such as a storm drain, and permits mixed water from irrigation systems as long as it's not sourced from foreign sources.

The Ninth Circuit court interpreted the language to mean that the exemption isn't lost because of non-point pollutants like dust or runoff. However, the ruling determined that the pollutant sources mean that the Grassland Bypass Project is outside the permitting requirements.

Irrigation and landscape professionals are affected by this because if the drainage serves agricultural or landscape irrigation return flows, it remains exempt. Further, designers must prevent crossover connections with drainage or stormwater outfalls to maintain an exempt status, allowing practitioners to not have a NPDES permit requirement, operational flexibility, and reduced costs.

The Irrigation Association (IA) published an article explaining the ruling and its effect on the industry.