The County of San Diego's thresholds for exempting certain projects from vehicle miles traveled (VMT) analysis were not supported by substantial evidence showing they were appropriate specifically for the County. Cleveland National Forest Foundation v. County of San Diego, No. D083555 (4th Dist., Apr. 28, 2025).
In 2013, the state legislature shifted the metric used to assess transportation-related environmental impacts under CEQA from traffic congestion and automobile delays to VMT. The CEQA Guidelines and the Governor's Office of Planning and Research (“OPR”) set forth guidance for adopting these standards.
In 2022, the County adopted a Transportation Study Guide, implementing the changes to transportation analysis set out by the state. The County included thresholds of significance for transportation impacts to be used in completing CEQA analysis. At issue on appeal were the thresholds of significance set by the County for infill development and small projects.
The County's infill threshold focused on the location of the development, identifying certain “infill village areas” where projects would be exempt from VMT analysis. The County's small-project threshold was set at projects that generated fewer than 110 daily vehicle trips. For projects that met either the infill or the small-project thresholds, there would be a presumed finding of no significant impact and thus no VMT analysis required under CEQA.
Plaintiffs challenged both thresholds, arguing they were based on unsupported assumptions and that the infill threshold did not set a numeric VMT target.
The court found that while County could set a qualitative – as opposed to quantitative - infill threshold, substantial evidence did not support the use of the threshold in this instance. The County relied on several unsubstantiated assumptions that development in more dense areas, such as infill development, did not significantly impact VMT. The County should, instead, have provided data showing that development in the designated areas would actually result in lower VMT to meet the substantial-evidence standard. The County also expanded the areas characterized as infill even though some of those areas did not match its infill definition.
As to the small-project threshold, the court found that the County adoption of OPR's threshold recommendation without any evidence as to why it was appropriate specifically for San Diego County did not satisfy the substantial-evidence requirement. OPR's small project threshold was developed by evaluating projects across the state, and specific analysis for San Diego County should have been conducted to support the 110-trip threshold.
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