SB 231 directs the Office of Land Use and Climate Innovation (OLUCI) to produce two related products to help local agencies apply CEQA: (1) a set of best-practice guidelines to live in a new Appendix O of the CEQA Guidelines and (2) a technical advisory offering suggested thresholds of significance for greenhouse gas (GHG) and noise effects. The office must consult other government entities while developing these tools and make the technical advisory publicly available online.
Why this matters: the bill attempts to narrow the biggest recurring source of CEQA fights—how to measure and declare a project’s GHG, transportation (vehicle miles traveled), and noise impacts—by supplying state-backed methods and area-specific suggested thresholds. That standardization could increase predictability for planners, counsel, and developers, while also creating frictions with local practices and resource-constrained agencies that currently set their own thresholds.
At a Glance
What It Does
SB 231 requires OLUCI to prepare CEQA best-practice guidelines to be adopted in Appendix O of the statewide CEQA Guidelines and to develop a separate technical advisory that provides suggested, area-specific thresholds of significance for greenhouse gas and noise effects. In making both products the office may consult regional, local, state, and federal agencies and must post the technical advisory on its website.
Who It Affects
Directly affects local lead agencies and planning departments that complete CEQA checklists and environmental impact reports, transportation and air-quality planners who prepare VMT and emissions analyses, noise consultants, CEQA counsel, and project applicants (developers). Air districts, MPOs, and state natural resources staff will be consulted and will see their technical standards reflected in guidance.
Why It Matters
By inserting state-developed best practices and suggested thresholds into the CEQA toolbox, the bill can change what analyses succeed or fail in environmental review, shift baseline expectations for mitigation, and influence litigation risk. The guidance is designed to foster consistency across jurisdictions while still allowing local agencies to adopt or adapt the suggested thresholds.
More articles like this one.
A weekly email with all the latest developments on this topic.
What This Bill Actually Does
SB 231 builds two complementary instruments to guide CEQA significance determinations for greenhouse gas emissions, vehicle miles traveled (VMT), and noise. First, it tasks OLUCI with drafting best practices to live in a new Appendix O of the CEQA Guidelines; those best practices are intended to steer how agencies complete Appendix G (the CEQA checklist) and to supply a uniform approach that lead agencies can follow when deciding whether a project’s effects are significant.
Second, OLUCI must produce a technical advisory that proposes thresholds of significance across the state and explains how those thresholds vary by place.
The bill requires the office to consider geographic and policy variables when tailoring thresholds: whether an area is urban or rural, which air district applies, and whether a community is designated disadvantaged under CalEnviroScreen. It also directs the office to ground thresholds in existing statutory frameworks—explicitly citing California’s Global Warming Solutions Act for GHG, the federal Clean Air Act for VMT-related considerations, and the California Noise Control Act for noise—while permitting the office to consult agencies that have subject-matter authority.Mechanically, the bill sets a fixed deadline for delivery (on or before July 1, 2027) and requires that the technical advisory be posted online.
The guidance process splits responsibility: the Secretary of the Natural Resources Agency is named to certify and adopt the Appendix O guidelines, creating a formal statewide guidance product, whereas the technical advisory contains “suggested” thresholds that local lead agencies may elect to adopt. That mix creates a state-level signal of best practices while keeping a degree of local discretion.For practitioners, the foreseeable effects are straightforward.
Planners and CEQA counsel will receive a state-developed menu of methodologies and numeric or methodological thresholds to consider when scoping and preparing analyses; transportation and noise consultants will likely need to align modeling inputs and reporting formats with OLUCI’s recommendations; developers should expect earlier, more standardized requests for specific VMT and noise metrics; and air districts and MPOs will find their regulatory frameworks explicitly feeding into CEQA thresholds. The bill therefore replaces some local customization with state-coordinated best practices while preserving an opt-in path for suggested thresholds.
The Five Things You Need to Know
Deadline: OLUCI must deliver the technical advisory and the Appendix O guidelines on or before July 1, 2027.
Two products: the bill mandates formal CEQA guidance in a new Appendix O (to be certified and adopted by the Secretary of Natural Resources) and a separate technical advisory of suggested thresholds that lead agencies may choose to adopt.
Statutory anchors: thresholds must consider the California Global Warming Solutions Act (AB 32) for GHG, the federal Clean Air Act for VMT-related factors, and the California Noise Control Act for noise.
Area-specific approach: suggested thresholds must be tailored across the state using factors such as urban vs rural designation, applicable air district, and CalEnviroScreen disadvantaged-community status.
Publication and discretion: OLUCI must post the technical advisory on its website, but the bill preserves local discretion by making adoption of the suggested thresholds elective for lead agencies.
Section-by-Section Breakdown
Every bill we cover gets an analysis of its key sections.
Technical advisory with suggested, area-specific thresholds
This subsection requires OLUCI to consult with regional, local, state, and federal agencies and to develop a technical advisory that provides suggested thresholds of significance for greenhouse gas and noise effects for all areas of the state. The advisory must account for local characteristics (urban/rural, air district) and environmental justice designations (CalEnviroScreen). Practically, the advisory is a nonbinding resource designed to harmonize approaches across jurisdictions while reflecting local conditions.
Voluntary adoption and public availability
The bill explicitly allows lead agencies to elect to adopt the suggested thresholds in the technical advisory rather than requiring mandatory adoption. It also obligates OLUCI to post the advisory on its website, creating a publicly accessible baseline. That combination makes the advisory an influential informational product without directly stripping local agencies of their authority to set thresholds.
CEQA best-practice guidelines to be added to Appendix O
Separately, the bill directs OLUCI to prepare best-practice guidelines for inclusion in Appendix O of the CEQA Guidelines and requires the Secretary of the Natural Resources Agency to certify and adopt them. Those guidelines are targeted at how agencies complete Appendix G (the CEQA checklist) and must include identifiable thresholds of significance based on specified state and federal laws. Certification by the Secretary makes these guidelines a formal statewide interpretive tool for CEQA practitioners.
Required considerations and statutory bases
The bill lists specific considerations OLUCI must use in developing thresholds: urban versus rural character, the applicable air district, disadvantaged-community status, and relevant state and federal statutes. It names the Global Warming Solutions Act for GHG, the Clean Air Act in the context of VMT, and the California Noise Control Act for noise—directing the office to root thresholds in these existing regulatory frameworks rather than inventing new statutory standards from scratch.
This bill is one of many.
Codify tracks hundreds of bills on Environment across all five countries.
Explore Environment in Codify Search →Who Benefits and Who Bears the Cost
Every bill creates winners and losers. Here's who stands to gain and who bears the cost.
Who Benefits
- Local planning departments: Receive state-backed best practices and suggested numeric thresholds that can shorten the scoping process and reduce consultant back-and-forth during CEQA review.
- CEQA practitioners and environmental consultants: Gain standardized methodologies and reporting templates that increase predictability and lower the time and cost of preparing VMT, GHG, and noise analyses.
- Disadvantaged communities: The bill requires consideration of CalEnviroScreen status when tailoring thresholds, which can make analyses more sensitive to cumulative burdens in overburdened areas if agencies follow the guidance.
- State agencies and regional planners: Air districts, MPOs, and OLUCI itself benefit from coordinated approaches that align CEQA practice with existing emissions, air quality, and noise statutes.
Who Bears the Cost
- Developers and project applicants: May face new or stricter area-specific thresholds that require additional mitigation, redesign, or more detailed modeling—raising project costs and delay risk.
- Small local jurisdictions: Will need staff time and possibly consultant support to evaluate, adopt, and implement the suggested thresholds or to defend locally tailored alternatives.
- OLUCI and Natural Resources Agency: Must allocate staff time and technical resources to consult, produce, and maintain the guidelines and advisory—an unfunded administrative burden unless resources are provided.
- Noise and transportation consultants: Will need to update modeling practices, tools, and deliverables to align with state-endorsed methods, which may require new training or software.
Key Issues
The Core Tension
The central dilemma is standardization versus local autonomy: the bill seeks statewide consistency and predictability for CEQA significance determinations by providing state-backed best practices and suggested thresholds, but doing so risks overriding locally tailored responses to differing environmental, social, and infrastructural realities—and it forces resource-strapped local agencies to either adopt state suggestions or justify departures in a more litigious environment.
The bill mixes a formal, Secretary-adopted guidance product (Appendix O) with a nonbinding technical advisory of suggested thresholds, which creates ambiguity about the degree of uniformity the state is imposing. Appendix O, once certified, will carry weight as adopted CEQA guidance; the technical advisory, by contrast, is explicitly elective for lead agencies.
That split raises questions: will courts treat Appendix O practices as de facto mandatory and give the technical advisory persuasive force, even though local agencies retain discretion? The bill does not define whether suggested thresholds must be numeric values, methodological prescriptions, or a combination, leaving implementation choices that will affect consistency.
Another implementation challenge is the bill’s direction to base thresholds on existing statutory regimes that operate on different metrics. The Clean Air Act addresses emissions and attainment status, not VMT directly; tying VMT thresholds to Clean Air Act obligations requires careful translation from VMT to emissions, modeling choices, and assumptions about fleet composition and local vehicle technology.
Similarly, calibrating noise thresholds across urban and rural contexts while incorporating CalEnviroScreen considerations will demand high-resolution data and resources many localities lack. These technical questions—plus the need to reconcile local General Plan policies or existing thresholds—open the door to litigation over whether an agency faithfully applied the statewide guidance or improperly deferred to the technical advisory.
Try it yourself.
Ask a question in plain English, or pick a topic below. Results in seconds.