In Cleveland National Forest Foundation v. County of San Diego (2025) 109 Cal. App.5th 1257, the Fourth District Court of Appeal invalidated two thresholds of significance adopted by the County of San Diego (“County”) that in certain circumstances would have avoided the need for a project proponent to perform an analysis of vehicle miles travelled. In finding both an infill and a small project threshold invalid, the court asserted that they were based on general assumptions, not local facts and analysis, and were thus unsupported by substantial evidence.
Background
In 2013 the California Legislature adopted Senate Bill No. 743 (“SB 743”) as part of a push to increase long-term sustainability and reduce greenhouse gas emissions by supporting denser infill development and public transit and reducing reliance on individual vehicles. To support these goals, SB 743 directed the Office of Planning and Research (“OPR”) to propose CEQA Guidelines revisions that would establish criteria for determining the significance of transportation impacts, suggesting vehicles miles travelled (“VMT”) as the appropriate measurement. The CEQA Guidelines were subsequently amended to reflect this mandate, and OPR also published a “Technical Advisory on Evaluating Transportation Impacts in CEQA” (“Technical Advisory”), in which it suggested that a per capita VMT that is fifteen percent below that of existing development was a reasonable threshold to use to determine the significance of a specific project’s transportation impacts.
But the Technical Advisory noted that in some cases thresholds of significance could be developed and relied on to “screen out VMT impacts using project size, maps, transit availability, and provision of affordable housing.” OPR suggested four screening thresholds based on these project characteristics: (1) small projects generating or attracting fewer than 110 trips per day; (2) projects located in areas where VMT is already below the 15 percent standard; (3) projects located within a half-mile of a major transit stop; and (4) projects consisting of 100 percent affordable housing built in infill locations.
In 2022 the County adopted a Transportation Study Guide (“Transportation Guide”) that attempted to implement the changes outlined in SB 743, in part by creating screening thresholds for general use that would obviate the need for project-specific VMT analyses in certain circumstances. For infill projects, the County identified infill areas using baselines of housing and intersection density and job accessibility associated with urban areas. Where the boundary of the infill area was not coextensive with a village’s boundaries, the County expanded the infill area’s boundary to match that of the village. And for small projects, the County adopted OPR’s recommended threshold; in doing so it did not adjust for local VMT or assess its relationship to the statewide data.
Shortly after the County adopted the Transportation Guide, Plaintiffs filed a petition for writ of mandate (“Petition”) challenging the infill and small projects thresholds. Plaintiffs argued that the infill threshold’s qualitative basis was not permitted and that both thresholds were unsupported by substantial evidence. The superior court ruled in the County’s favor, and Plaintiffs appealed.
Court of Appeal
The court first rejected Plaintiffs’ assertion that the infill threshold needed to be quantitative unless “existing models or methods” are unavailable to develop such a standard. The court pointed out that the CEQA Guidelines section upon which Plaintiffs relied, section 15064.3(b)(3), applies to specific projects and not thresholds of significance. And the court noted that by its terms CEQA does not prohibit a county from adopting a qualitative infill threshold. In support of this determination, the court last observed that OPR’s Technical Advisory recommends transportation screening thresholds based on qualitative project characteristics such as size, transit availability, and whether it is consistent with affordable housing.
However, the court upheld Plaintiffs’ assertion that the infill threshold adopted by the County lacked substantial evidence to support a finding of insignificance for infill projects. Although lead agency thresholds are given deferential review by courts, the court held that the County’s justifications for the infill threshold were not based on any evidence that developing infill, as the County chose to define it, would generally result in an insignificant transportation effects the local county level. Per the court, the County used general assumptions that development in denser areas—which includes infill development—would not significantly impact VMT, but failed to establish that those general assumptions were true for the County’s defined infill areas. Indeed, evidence in the record indicated that the County’s defined infill locations were too broad and had per capita VMT values that would not result in VMT-insignificant impacts.
The court also found that the County’s small project threshold was unsupported by substantial evidence. While OPR recommended a small threshold project based on statewide data, the court faulted the County for adopting that threshold without justifying its application specifically to the County. The court noted that agencies may adopt thresholds promulgated by other agencies only if that decision is supported by substantial evidence; thus, a statewide threshold must be shown to be applicable to local facts.
Key Takeaways
It is likely that many agencies across the state have incorporated OPR’s recommended screening thresholds. But unless agencies have substantial evidence demonstrating that OPR’s thresholds apply to local conditions, this decision would deem those thresholds invalid.
While agency thresholds are reviewed under the deferential “substantial evidence” standard, this case highlights the importance of relying on substantial evidence when crafting those thresholds. Generalizations or a failure to connect data to local circumstances may cause a threshold to be overturned.