Save Our Heritage Organisation v. City of San Diego, 28 Cal. App. 5th 656

The City of San Diego approved the Plaza de Panama project in 2012; the project relocates vehicular access and creates a new underground parking structure and related improvements in Balboa Park.
Save Our Heritage Organisation (SOHO) previously litigated the original EIR and lost on appeal; post-approval physical changes and project refinements occurred while appeals were pending.
In 2016 the City adopted an addendum to the certified EIR describing several minor design and compliance changes (e.g., bridge supports, stormwater basins, ventilation, landfill elevation, energy upgrades) and concluded no new significant environmental impacts required a subsequent EIR.
SOHO petitioned for mandamus challenging the City’s adoption of the addendum, arguing (1) CEQA Guidelines §15164 (addendum process) is invalid and (2) the City was required to make new findings under Pub. Resources Code §21081.
The trial court denied relief; the Court of Appeal affirmed, holding SOHO failed to show §15164 invalid and that new §21081 findings were not required for an addendum.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Validity of CEQA Guidelines §15164 (addendum process)	§15164 is unauthorized by CEQA and conflicts with CEQA's public review requirements	§15164 properly fills a statutory gap, is consistent with §21166, and implements finality/efficiency without circumventing CEQA	§15164 is presumptively valid; SOHO failed to prove invalidity; Guideline is consistent with CEQA and reasonably implements §21166
Requirement to adopt new findings under Pub. Resources Code §21081 when approving addendum	City must adopt fresh §21081 findings because project changes remain significant	Addenda apply only to minor changes that do not create new significant effects; §21081 findings are not required when no new significant impacts are found	No new §21081 findings required for an addendum where the original EIR’s significant effects remain and the addendum identifies no new significant impacts

Jones v. Cal. Ins. Comm’r, 2 Cal.5th 376 (discusses review standards for quasi-legislative vs. interpretive rules)
Friends of College of San Mateo Gardens v. San Mateo Cmty. Coll. Dist., 1 Cal.5th 937 (guidance on agency gap-filling and deference to guidelines)
Muzzy Ranch Co. v. Solano County Airport Land Use Com., 41 Cal.4th 372 (standard of review in CEQA mandamus actions)
Save Tara v. City of West Hollywood, 45 Cal.4th 116 (deference to agency factual conclusions under CEQA)
Moss v. County of Humboldt, 162 Cal.App.4th 1041 (§21166 presumption against further review; finality of adopted EIRs)
Fund for Environmental Defense v. County of Orange, 204 Cal.App.3d 1538 (no new §21081 findings required when addendum used and no new significant impacts identified)
Laurel Heights Improvement Assn. v. Regents of Univ. of California, 6 Cal.4th 1112 (public comment/finality balance after EIR certification)
Bowman v. City of Petaluma, 185 Cal.App.3d 1065 (use of addendum to determine if further review is necessary)
American Canyon Community United for Responsible Growth v. City of American Canyon, 145 Cal.App.4th 1062 (discussing supplementary/addendum procedures under CEQA)
Gerawan Farming, Inc. v. Agricultural Labor Relations Bd., 3 Cal.5th 1118 (legislative acquiescence to long‑standing administrative practice)