Fifteen Years in the Making: First District Holds Res Judicata Bars Renewed CEQA Challenge to Richardson Grove Highway Project

In Bair v. California Department of Transportation, ___ Cal. App. 5th ___, 2026 WL 835777 (Mar. 26, 2026), the First District Court of Appeal held that a losing party in writ of mandate proceedings may not resuscitate a CEQA challenge it failed to appeal by filing a brand-new lawsuit raising the same underlying claims. The opinion brings to a close fifteen years of litigation over a highway improvement project running through a stand of ancient redwood trees in Humboldt County.

The project at the center of the dispute is Caltrans’ proposal to widen and reconfigure a one-mile segment of U.S. Highway 101 through Richardson Grove State Park—home to old-growth redwoods up to 300 feet tall and thousands of years old—in order to meet current design standards and accommodate larger commercial trucks. The litigation commenced in 2010, when local residents and environmental groups challenged the project’s EIR under CEQA. Four years later, the Court of Appeal invalidated the EIR, holding in Lotus v. Department of Transportation, 223 Cal. App. 4th 645 (2014), that Caltrans had failed to identify any threshold of significance for evaluating the project’s impacts on the redwood trees’ root systems and had improperly merged its impact analysis with its discussion of mitigation measures. The court directed Caltrans to correct those specific deficiencies, but did not require it to revisit the EIR in other respects. Caltrans then prepared an Addendum to the EIR, based in part on a certified arborist’s tree-by-tree rating system, which concluded that the project would not cause any significant impacts to the old-growth redwoods. It recertified the EIR with the Addendum in May 2017.

That recertification promptly gave rise to a second round of litigation. Many of the original petitioners, along with new parties, filed a second writ petition (Bair I) challenging both the substantive adequacy of the Addendum and Caltrans’ failure to circulate it for public comment. At roughly the same time, Caltrans sought discharge of the original Lotus writ, which the court declined to grant pending resolution of the CEQA issues in Bair I. The Bair I trial court ultimately granted the writ petition on the procedural ground alone—finding that Caltrans had violated CEQA by not subjecting the Addendum to public review and comment—but did not expressly reach the question of whether the Addendum’s substantive environmental analysis was adequate. Caltrans recirculated the Addendum and EIR for public comment and, in January 2023, reapproved the project and recertified the EIR and Addendum for a third time.

That brings us to the litigation that generated the current opinion. In February 2023, Caltrans filed a joint return to both the Lotus and Bair I writs, seeking their discharge. One month later, the petitioners filed consolidated objections to discharge while simultaneously commencing a third writ proceeding—this case—raising the same core claim they had pressed throughout: that the Addendum’s environmental analysis of the project’s impacts on old-growth redwood trees remained substantively inadequate under CEQA because it relied on an undefined and untested significance threshold and an arborist’s rating methodology unsupported by substantial evidence. In July 2023, the trial court granted Caltrans’ motion to discharge both writs in an unreasoned one-page order. Critically, the petitioners did not appeal that order. The trial court in the present case then ruled that the discharge of the Lotus writ precluded relitigation of the Addendum’s CEQA compliance under the doctrine of res judicata, and denied the petition on the merits in the alternative. This appeal followed.

The Court of Appeal affirmed on res judicata grounds, relying heavily on Silverado Modjeska Recreation & Park District v. County of Orange, 197 Cal. App. 4th 282 (2011). As in Silverado, the court reasoned that when a trial court discharges a writ of mandate issued in a CEQA case, it necessarily adjudicates on the merits whether the agency has complied with CEQA—and that determination becomes final and preclusive if not appealed. The petitioners had themselves argued, throughout the writ discharge proceedings, that the Lotus writ could not be discharged unless the Addendum fully complied with CEQA, and they had filed extensive briefing urging the court not to discharge the writ on precisely the grounds they sought to litigate in the third proceeding. Having litigated those issues before the trial court and lost, they could not start over in a new lawsuit. The court declined to follow a contrary suggestion in Central Delta Water Agency v. Department of Water Resources, 69 Cal. App. 5th 170 (2021), finding that case’s reasoning analytically flawed because it asked whether the revised EIR’s substantive adequacy could have been litigated before entry of the original judgment—which, of course, it could not have been, since the revised analysis did not yet exist—rather than whether it could have been adjudicated in response to the agency’s post-judgment request to discharge the writ.

The Court of Appeal closed its opinion with a pointed observation about the costs of protracted CEQA litigation. Caltrans’ work on the Addendum began in 2015, the court noted, and in the ten-plus years since, not a single trial court judge had found the Addendum’s analysis to be legally deficient. While acknowledging CEQA’s important purposes, the court repeated language from its earlier decision in Tiburon Open Space Committee v. County of Marin, 78 Cal. App. 5th 700 (2022): “CEQA was meant to serve noble purposes, but it can be manipulated to be a formidable tool of obstruction.” The CEQA battle over Richardson Grove, the court declared, had come to an end.

The decision has several notable implications for CEQA practitioners. Most directly, it confirms and extends Silverado’s holding that an order discharging a writ of mandate in a CEQA case constitutes a final adjudication on the merits of the agency’s CEQA compliance, with full preclusive effect in subsequent proceedings. Petitioners who believe a trial court has wrongly discharged a writ—whether because the administrative record was incomplete, the court failed to make express findings, or the court simply got the analysis wrong—must appeal that order or risk forfeiting their ability to raise the same CEQA claims elsewhere. The court’s explicit rejection of Central Delta Water Agency on this point creates a clear conflict among the districts that the California Supreme Court may wish to resolve, though given that Bair grappled with both cases, its framework may well prove more persuasive to trial courts in the interim.

More broadly, the decision has practical significance for parties who choose to pursue compliance with a CEQA writ through simultaneous proceedings—both by objecting to discharge in the original case and by filing a new writ petition. The court did not hold that this dual-track approach is procedurally impermissible (a question it expressly reserved), but it made clear that doing so creates a race to judgment, and that a party who loses that race cannot continue pressing claims in the surviving proceeding. As the court observed, the potential trap of claim preclusion in this situation might have been avoided by consolidating the proceedings—but here the petitioners failed to seek review of the trial court’s order denying consolidation, compounding the predicament they had created for themselves. Parties navigating similar circumstances would be well advised to move promptly for consolidation, to seek appellate review of any denial of that motion, and, most importantly, to appeal any writ discharge order they believe to be erroneous rather than seek to relitigate the underlying CEQA questions in a parallel proceeding.