CEQA Case Report: Understanding the Judicial Landscape for Development[i]

By Christopher W. Garrett, Daniel P. Brunton, Diego Enrique Flores, and Samantha K. Seikkula

In an unpublished opinion issued May 18, 2018, Responsible Development for Water Tank Hill v. County of San Mateo, Case No. A150883, the California Court of Appeal affirmed the trial court’s judgment denying Responsible Development for Water Tank Hill’s (Petitioner’s) petition for writ of mandate, finding that the County of San Mateo (County) had properly analyzed the potential environmental impacts of San Mateo Real Estate, Inc.’s (Developers’) proposed housing development (Project) and that the County’s determinations were supported by the substantial evidence. In summary, the court determined:

  • An EIR’s analysis of noise impact should be site-specific and should consider qualitative factors as well as technical factors
  • When an EIR finds, based on substantial evidence, that an impact would be less-than-significant, further mitigation is not required.
  • An agency may rely on statewide emissions-reduction goals when determining mitigation measures to reduce a project’s significant GHG impacts.

Background for Appeal

After several rounds of public comment, the San Mateo County Planning Commission (Commission) approved the Project. The County Board of Supervisors denied an appeal of the approval and upheld the Commission’s decision. Petitioner then filed a petition for writ of mandate seeking to set aside the Project approvals as inadequate under CEQA. Petitioner argued that the approvals were inadequate because:

  • The environmental impact report (EIR) failed to adequately analyze impacts
  • The County failed to adopt feasible mitigation measures
  • The County’s findings were not supported by substantial evidence
  • The County failed to recirculate the final EIR after making changes that constituted significant new information

The trial court rejected Petitioner’s specific challenges to the County’s environmental analysis of air quality, aesthetics, hydrology, and noise, finding that the County had properly analyzed the potential environmental impacts of the Project and that the County’s determinations were supported by substantial evidence. Petitioner appealed the decision with respect to air quality and noise.

County’s Noise Analysis Was Appropriately Site-Specific and Comprehensive

Petitioner argued that the final EIR was inadequate because noise levels during construction would sometimes exceed 60 decibels adjusted for frequency, and would remain a significant impact, even with mitigation. Petitioner argued that in determining whether construction noise impacts are significant, the County was required to apply the same 60 decibel standard it had used to assess whether an exterior land use activity generates excessive noise.

Citing Berkeley Keep Jets Over the Bay Com. v. Board of Port Cmrs. (2001) 91 Cal.App.4th 1344, 1380–1381, the court noted that “CEQA requires the lead agency to use a ‘site-sensitive threshold of significance for noise,’ and recognizes that ‘[a]n ironclad definition of significant effect is not always possible because the significance of an activity may vary with the setting. For example, an activity which may not be significant in an urban area may be significant in a rural area.’” The County’s analysis took a multi-faceted approach, incorporating various standards included in City and County ordinances, as well as other factors, to determine that mitigation would reduce the Project’s potential noise impacts to a less-than-significant level. Thus, the court found that the substantial evidence supported the County’s determination and that focusing on a fixed 60-decibel standard, as demanded by Petitioner, was “myopic.”

No Further Mitigation Was Required for Air Quality Impacts

Petitioner claimed that the final EIR’s analysis of the Project construction’s air-quality impacts was flawed. First, Petitioner argued that the final EIR was inadequate because it did not require Developers to use “Tier 4 construction equipment,” which Petitioner described as a “feasible and commonplace mitigation measure necessary to bring emissions down to levels safe for local residents.” Under CEQA, public agencies must not approve a Project without requiring feasible mitigation measures that would substantially lessen the Project’s significant environmental effects. Here, the court found that the final EIR adequately explained that the mitigation measures in place, which required Tier 2 construction equipment, would already reduce the air quality impacts to a less-than-significant level. Petitioner presented no evidence disputing that finding. Therefore, the court found that Petitioner’s argument was without merit and no further mitigation was required.

Additionally, Petitioner argued that the County violated CEQA by ignoring the adverse impact of diesel particulate matter (DPM). But the court explained that the final EIR had used the state-approved emissions estimator model, CalEEMod, to thoroughly analyze the potential impacts from DPM. The final EIR acknowledged that DPM can have serious health effects, but determined that emissions would not exceed thresholds set by the Bay Area Air Quality Management District and were therefore less-than-significant.

County Properly Relied on Statewide Metrics in Creating GHG Mitigation Measure

Petitioner relied on Center for Biological Diversity v. Department of Fish & Wildlife (2015) 62 Cal.4th 204 (CBD) to argue that the County’s use of a mitigation measure modeled on statewide emissions reduction goals was improper. In CBD, a statewide greenhouse gas (GHG) emissions reduction goal was improperly used to determine that a project’s emissions were less-than-significant and required no mitigation.

Here, the court distinguished CBD on two grounds. First, the court noted that CBD dealt with the emissions from operation of a “massive development project,” whereas here, Petitioner challenged the analysis of mitigation for only the construction-related emissions of the much smaller Project (19 single-family homes). Second, in contrast to the lead agency in CBD, the County assumed that the GHG impact would be significant. The County then imposed mitigation on the project for construction emissions, including purchasing carbon dioxide emissions-reduction credits to fully offset the project’s construction emissions. Petitioner did not provide any reason or authority for challenging the sufficiency of the mitigation measure. Therefore, the substantial evidence supported the County’s determination.


Accordingly, the court affirmed the trial court’s judgment. The County’s environmental analysis was proper and its findings were supported by substantial evidence.

  • Opinion by Justice Smith, with Acting Presiding Justice Streeter and Justice Reardon concurring.

[i]California court decisions on California Environmental Quality Act (CEQA) related cases can impact business not only in California, but more broadly in other US jurisdictions (e.g. under the US National Environmental Policy Act (NEPA), though statutory provisions may differ). Latham’s case summary series provides a comprehensive archive of both published and unpublished cases, in order to track judicial interpretations of CEQA and new legal developments. Unpublished or “non-citable” opinions are opinions that are not certified for publication in Official Reports and generally may not be cited or relied on by other courts or parties in any filing with California courts in other court proceedings. (see California Rules of Court, rule 8.1115).