California Supreme Court Clarifies “Negligible Expansion” Under the Class 1 CEQA Exemption

Sunflower Alliance v. California Department of Conservation (Case No. S287414.)

Why This Matters

After two years without weighing in on a CEQA case, the California Supreme Court has issued a significant decision clarifying the scope of CEQA’s Class 1 categorical exemption for minor alterations to existing facilities. For practitioners and agencies who rely on this commonly used exemption, the Court’s new standard for what counts as a “negligible expansion” of use is required reading, and its remand leaves an important secondary issue about permissible mitigation conditions still very much alive.

The Decision

On June 25, 2026, the Court issued its decision in Sunflower Alliance v. California Department of Conservation (Case No. S287414). The Supreme Court clarified what constitutes a “negligible expansion” of an existing or former use under CEQA’s Class 1 categorical exemption for minor alterations of existing facilities. (CEQA Guidelines §15301.) Notably, this was not the issue the Supreme Court initially accepted for review. The initial question was whether an agency may claim a categorical exemption while also adopting project conditions, pursuant to regulatory mandates, related to potential environmental effects.

Background

This case involved the agency’s use of this Class 1 exemption for the conversion of a dormant oil and gas extraction well, plugged in 1984. This well would be converted and used to re-inject treated wastewater, a byproduct of such drilling from other sites. Petitioners argued the use of the Class I exemption was improper as it did not meet the definition of a “negligible expansion.”

The Court of Appeal disagreed, concluding the “negligible expansion” should focus on whether “the proposed expansion would pose only a negligible additional risk of environmental harm.” The Appellate Court reasoned “no purpose is served by myopically focusing on whether a use is new, thereby excluding from the exemption many projects that would cause no environmental harm, precisely the type of borderline projects for which categorical exemptions are useful.” In the Supreme Court, Petitioner sought reversal, arguing that “negligible expansion” “excludes new uses from the scope of the class 1 exemption.”

The Supreme Court’s Ruling

The Supreme Court did not accept either Petitioner’s or Respondent’s definition of “negligible expansion,” instead concluding the California Natural Resources Agency (CNRA), which promulgates the CEQA Guidelines, was “closest to the mark.” The Supreme Court concluded that “an agency should examine the nature and scope of the proposed expansion of use, rather than its potential environmental effects, in making its exemption determination.” In doing so, the Supreme Court rejected Petitioner’s interpretation, that “‘expansion’ excludes new uses from the scope of the class 1 exemption.” The Supreme Court did not reach a final conclusion on the applicability of the Class 1 exemption to the project, instead remanding the case back to the Court of Appeal for reconsideration in light of this new definition.

What to Watch on Remand

On remand, it will be interesting to see whether Respondents pivot to any alternative CEQA exemptions, such as the common-sense exemption (CEQA Guidelines §15061(b)(3)), which allows for consideration of the scope of the project’s environmental impacts.

If so, this may reinvigorate the issue the Supreme Court initially accepted for review: i.e. What constitutes impermissible CEQA mitigation in a categorical exemption?

This issue continues to arise in numerous CEQA cases:

• Salmon Protection & Watershed Network v. County of Marin (2004) 125 Cal.App.4th 1098, 1102 [conditions constituted impermissible mitigation.]
• Wollmer v. City of Berkeley (2011) 193 Cal.App.4th 1329, 1353 [voluntary dedication by developer of land for turn lane to alleviate existing traffic conditions, not an improper mitigation measure.]
• Save the Plastic Bag Coalition v. City & County of San Francisco (2014) 222 Cal.App.4th 863 [bag fee was not an unlawful mitigation measure.]
• San Francisco Beautiful v. City and County of San Francisco (2014) 226 Cal.App.4th 1012 [“An agency may rely on generally applicable regulations to conclude an environmental impact will not be significant and therefore does not require mitigation.”]
• Citizens for Environmental Responsibility v. State ex rel.14th Dist. Ag. Assn. (2015) 242 Cal.App.4th 555, 574 [Manure Management Plan was not an impermissible mitigation measure.]

The Bottom Line

Agencies and project applicants relying on the Class 1 exemption should revisit their exemption analyses to ensure they focus on the nature and scope of a proposed expansion, not merely its potential environmental effects, and should watch for further developments on remand, which could reshape how mitigation conditions interact with categorical exemptions more broadly.

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