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We granted review to determine whether an

Environmental Impact Report (EIR), issued as part of a master

plan to develop a partial retirement community in Fresno,

California, violates the California Environmental Quality Act

(CEQA) for failing to include sufficient information on topics the

Act requires. (Pub. Resources Code, § 21000 et seq.)1 Our task

is to review specific challenges to the final EIR2

that defendant

County of Fresno (County) and its Board of Supervisors adopted,

and the trial court approved. As we explain, we affirm in part

and reverse in part the Court of Appeal’s judgment.

FACTUAL AND PROCEDURAL BACKGROUND

The Friant Ranch project (Project) consists of real party in

interest Friant Ranch, L.P.’s (real party) planned development

of the Central Valley’s first master-planned “pedestrian

friendly” community on a 942-acre site (formerly zoned

agricultural) that sits adjacent to the unincorporated

community of Friant in north central Fresno County, just south



1 All further statutory references are to CEQA provisions as

codified in Public Resources Code sections 21000-21177 unless

otherwise indicated. Where applicable, the CEQA guidelines

(Cal. Code Regs., tit. 14, §§ 15000-15387) will be noted as

“Guidelines” throughout the text to distinguish between the

Public Resources Code and the Code of Regulations.

2 All references to the EIR are to the final EIR unless

otherwise indicated.

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

2

of the San Joaquin River. The County is the local governmental

entity that acted as the lead agency for the CEQA review and

for preparation of the Project’s EIR.

The Project includes the Friant Ranch Specific Plan

(Specific Plan), which contemplates the construction of

approximately 2,500 single and multi-family residential units

that are age restricted to “active adults” age 55 and older, other

residential units that are not age restricted, a commercial

village center, a recreation center, trails, open space, a

neighborhood electric vehicle network, and parks and parkways.

The Project also includes 250,000 square feet of commercial

space on 482 acres and the dedication of 460 acres to open space.

An additional Friant Community Plan Update expands the

Specific Plan area and adds policies that are consistent with the

Specific Plan and the County’s General Plan. The Project’s

construction is divided into five phases with an estimated 10-

year build-out.

Through its Board of Supervisors, the County received

written comments to the draft EIR, held a public hearing, and

prepared responses to the comments. After making the findings

required under section 21081, subdivision (a), for each

significant effect noted in the draft, the County issued a

Statement of Overriding Considerations (Statement) that is

required in CEQA approved projects to show that the Project’s

significant environmental effects have been identified, and

avoided or mitigated, or that unmitigated effects will be

outweighed by the Project’s benefits. (§§ 21002, 21002.1, 21081;

Guidelines, §§ 15091-15093.) The Statement noted: “The

Project implements and furthers important plans and public

policies adopted and endorsed by the County related to urban

growth.” The Statement also observed that the County “made a

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

3

reasonable and good faith effort to eliminate or substantially

mitigate the environmental impacts resulting from the Project

by requiring implementation of the environmentally superior

alternative—Project Alternative No. 3: Northeast Development

Configuration and the Beck Property alternative wastewater

treatment plant location—and various mitigation measures,

goals and policies identified in the EIR, General Plan, the

proposed Friant Community Plan Update, and the proposed

Friant Ranch Specific Plan.”

On February 1, 2011, the County’s Board of Supervisors

approved Project Alternative 3, certified the EIR, and approved

a version of the Specific Plan that prohibited the discharge of

treated effluent into the river from the wastewater treatment

plant. The County also adopted a Mitigation Monitoring

Program (MMP), which noted in part that compliance with the

mitigation measures would be “enforced through subsequent

conditions of approval for future discretionary actions,”

including use permits and tentative subdivision maps for the

Specific Plan area. By petition for writ of mandamus filed in the

trial court, plaintiffs Sierra Club, Revive the San Joaquin, and

League of Women Voters of Fresno (collectively, plaintiffs)

challenged the County’s certification of the EIR, alleging that it

violated CEQA in several respects. (Code Civ. Proc., §1094.5

[challenge to public agency’s determination based on alleged

CEQA noncompliance requires administrative mandamus

proceeding].) The trial court rejected plaintiffs’ challenges and

approved the Project, noting in its judgment that in reviewing

CEQA decisions, “it may not exercise its independent judgment

on the evidence, but must determine only whether the act or

decision is supported by substantial evidence.” In reviewing the

EIR, the court agreed with County’s findings on traffic impact,

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

4

biological resources, wastewater treatment, and air quality

impact, among other considerations. It stated that the court

“does not pass on the correctness of any EIR’s environmental

conclusions, but instead determines whether the EIR is

sufficient as an informational document. All conflicts in the

evidence and reasonable inferences must be resolved and drawn

in favor of the agency’s decisions and findings. The reviewing

Court does not reweigh the evidence.”

The court’s judgment also observed that regarding air

quality impacts, the County explained why the EIR’s mitigation

measures would reduce the Project’s greenhouse gas emissions.

The court agreed with the County that plaintiffs did not cite to

the record in sufficient detail to show any error.

At the end of its judgment, the court noted that it retained

jurisdiction to allow the County a reasonable amount of time to

circulate a Park Impact analysis on the Project’s effect on

adjoining parks, including Lost Lake Park and Millerton Lake.

This analysis is not at issue here. Otherwise, the court denied

all of plaintiffs’ claims and entered judgment in favor of real

party.

Plaintiffs appealed the judgment before the County could

implement the mitigation measures. They claimed in relevant

part that the Project’s EIR failed to comply with CEQA because

its discussion of air quality impacts was inadequate.

The Court of Appeal agreed with plaintiffs’ contentions

involving the EIR’s consideration of the Project’s air quality

impacts on the following grounds: “(1) the EIR was inadequate

because it failed to include an analysis that correlated the

[P]roject’s emission of air pollutants to its impact on human

health; (2) the mitigation measures for the [P]roject’s long-term

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

5

air quality impacts violate CEQA because they are vague,

unenforceable and lack specific performance criteria; and (3) the

statement that the air quality mitigation provisions will

substantially reduce air quality impacts is unexplained and

unsupported. These defects must be cured by the preparation of

a revised EIR.” The Court of Appeal reversed the trial court’s

judgment on those grounds only.

3



We granted real party’s petition for review on the issues

concerning the Court of Appeal’s reversal of the trial court

judgment upholding the air quality impact findings and

conclusions in the EIR’s chapter 3 (discussing air quality

impacts). The scope of our review concerns how courts should

determine the adequacy of an EIR’s discussion, including: What

standard of review a court must apply when adjudicating a

challenge to the adequacy of an EIR’s discussion of adverse

environmental impacts and mitigation measures, and whether

CEQA requires an EIR to connect a project’s air quality impacts

to specific health consequences. We must also decide whether a



3 Plaintiffs had also argued that the EIR’s discussion of

treated effluent from the proposed wastewater treatment

facilities was inadequate and that the EIR was inconsistent with

land use and traffic policies in the County’s General Plan. The

Court of Appeal concluded that the amount and location of

wastewater use and disposal, and the hydrogeology of the site

chosen for the wastewater treatment plant, were addressed in

sufficient detail during the environmental review process. The

Court of Appeal also concluded that the development plan was

consistent with the land use element (as changed from

agricultural to residential by amendment), and that the traffic

policy issues had not been properly exhausted during the

administrative process. The parties do not dispute the Court of

Appeal’s judgment on these issues, and we do not address that

aspect of the court’s opinion here.

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

6

lead agency impermissibly defers mitigation measures when it

retains the discretion to substitute later adopted measures in

place of those proposed in the EIR, and whether a lead agency

may adopt mitigation measures that do not reduce a project’s

significant and unavoidable impacts to a less-than-significant

level.

We conclude as follows: When reviewing whether a

discussion is sufficient to satisfy CEQA, a court must be

satisfied that the EIR (1) includes sufficient detail to enable

those who did not participate in its preparation to understand

and to consider meaningfully the issues the proposed project

raises (Laurel Heights Improvement Assn. v. Regents of

University of California (1988) 47 Cal.3d 376, 405 (Laurel

Heights I)), and (2) makes a reasonable effort to substantively

connect a project’s air quality impacts to likely health

consequences. As explained below, the EIR in this case failed to

do so. The EIR should be revised to relate the expected adverse

air quality impacts to likely health consequences or explain in

meaningful detail why it is not feasible at the time of drafting to

provide such an analysis, so that the public may make informed

decisions regarding the costs and benefits of the Project.

We further conclude that a lead agency may leave open the

possibility of employing better mitigation efforts consistent with

improvements in technology without being deemed to have

impermissibly deferred mitigation measures. A lead agency

may adopt mitigation measures that do not reduce the project’s

adverse impacts to less than significant levels, so long as the

agency can demonstrate in good faith that the measures will at

least be partially effective at mitigating the Project’s impacts.

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

7

We therefore affirm the Court of Appeal’s judgment

finding the EIR’s analyses of the Project’s air quality impacts

inadequate. However, we reverse the Court of Appeal’s

judgment that the EIR improperly deferred mitigation

measures by proposing to substitute more effective measures if

available in the future, and that the mitigation measures

proposed were impermissibly vague and unlikely to reduce

adverse health impacts to less than significant levels.

DISCUSSION

A. Adequacy of the EIR’s discussion of health impacts of

the Project’s long-term effects on air quality

Plaintiffs claim that the EIR was insufficient as an

informational document because it failed to adequately explain

how the air pollutants the Project generated would impact

public health. To address that claim, we must first decide what

standard of review applies to a challenge to the adequacy of an

EIR’s discussion of a required topic.

1. Standard of review

“The foremost principle under CEQA is that the

Legislature intended the act ‘to be interpreted in such manner

as to afford the fullest possible protection to the environment

within the reasonable scope of the statutory language.’ ” (Laurel

Heights I, supra, 47 Cal.3d at p. 390, quoting Friends of

Mammoth v. Board of Supervisors (1972) 8 Cal.3d 247, 259.)

“With narrow exceptions, CEQA requires an EIR whenever a

public agency proposes to approve or to carry out a project that

may have a significant effect on the environment. [Citations.]”

(Laurel Heights I, supra, 47 Cal.3d at pp. 390-391; see

Guidelines, § 15002, subd. (f).) The basic purpose of an EIR is

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

8

to “provide public agencies and the public in general with

detailed information about the effect [that] a proposed project is

likely to have on the environment; to list ways in which the

significant effects of such a project might be minimized; and to

indicate alternatives to such a project.” (§ 21061; see

Guidelines, § 15003, subds. (b)-(e).)4

“Because the EIR must be

certified or rejected by public officials, it is a document of

accountability. If CEQA is scrupulously followed, the public will

know the basis on which its responsible officials either approve

or reject environmentally significant action, and the public,

being duly informed, can respond accordingly to action with

which it disagrees.” (Laurel Heights I, supra, at p. 392.) The

EIR “protects not only the environment but also informed selfgovernment.”

(Ibid.)

The standard of review in a CEQA case, as provided in

sections 21168.5 and 21005, is abuse of discretion. Section

21168.5 states in part: “In any action or proceeding . . . to attack,

review, set aside, void or annul a determination, finding, or

decision of a public agency on the grounds of noncompliance

with this division, the inquiry shall extend only to whether there

was a prejudicial abuse of discretion.” (See § 21005, subd. (a)

[noncompliance with information disclosure requirements may

“constitute a prejudicial abuse of discretion”].) Our decisions

have thus articulated a procedural issues/factual issues

dichotomy. “[A]n agency may abuse its discretion under CEQA

either by failing to proceed in the manner CEQA provides or by

reaching factual conclusions unsupported by substantial



4 A “significant effect” is defined as “a substantial, or

potentially substantial, adverse change in the environment.”

(§ 21068.)

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

9

evidence. (§ 21168.5.) Judicial review of these two types of error

differs significantly: While we determine de novo whether the

agency has employed the correct procedures, ‘scrupulously

enforc[ing] all legislatively mandated CEQA requirements’

(Citizens of Goleta Valley v. Board of Supervisors (1990) 52

Cal.3d 553, 564 [276 Cal.Rptr. 410, 801 P.2d 1161]), we accord

greater deference to the agency’s substantive factual

conclusions. In reviewing for substantial evidence, the

reviewing court ‘may not set aside an agency’s approval of an

EIR on the ground that an opposite conclusion would have been

equally or more reasonable,’ for, on factual questions, our task

is ‘not to weigh conflicting evidence and determine who has the

better argument.’ (Laurel Heights I, supra, 47 Cal.3d at p. 393.)”

(Vineyard Area Citizens for Responsible Growth, Inc. v. City of

Rancho Cordova (2007) 40 Cal.4th 412, 435 (Vineyard).)

This distinction between de novo review and substantial

evidence review has worked well in judicial review of agency

determinations. In most cases, the question whether an agency

has followed proper procedures will have a clear answer. Did

the agency provide sufficient notice and opportunity to comment

on a draft EIR? (§ 21092; Guidelines, § 15087.) Did the agency

omit the required discussion of alternatives? (Guidelines,

§ 15126.6.) As to these legal requirements, the agency has no

discretion, and courts will invalidate an EIR that fails to meet

them. In that sense, judicial review is de novo.

But the question whether an agency has followed proper

procedures is not always so clear. This is especially so when the

issue is whether an EIR’s discussion of environmental impacts

is adequate, that is, whether the discussion sufficiently

performs the function of facilitating “informed agency

decisionmaking and informed public participation.” (California

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

10

Native Plant Society v. City of Santa Cruz (2009) 177

Cal.App.4th 957, 988 [relying on Laurel Heights I, supra, 47

Cal.3d at pp. 404-405].) The review of such claims does not fit

neatly within the procedural/factual paradigm.

This court’s decision in Laurel Heights I illustrates how a

court should assess a claim of inadequate discussion. The case

involved a challenge to an EIR’s discussion of alternatives to the

proposed construction of the University of California, San

Francisco’s (UCSF) Laurel Heights campus. This court

concluded that the discussion was inadequate: “UCSF’s

treatment of alternatives was cursory at best. The draft EIR

identified three types of alternatives: no project anywhere,

alternative sites on the UCSF Parnassus campus, and

alternative sites off-campus. The three categories received a

scant one and one-half pages of text in an EIR of more than 250

pages. The EIR stated the obvious conclusion that the ‘no

project’ alternative, i.e., no relocation to Laurel Heights, would

not have the environmental effects identified in the EIR. It then

stated in a mere two-sentence paragraph that ‘. . . no alternative

sites on [the Parnassus] campus were evaluated as possible

candidates for the location of the basic science units of the

School of Pharmacy.’ This is not a sufficient discussion of oncampus

alternatives; it is merely an admission that such

alternatives were not considered.” (Laurel Heights I, supra, 47

Cal.3d at p. 403.)

Laurel Heights I continued: “Even if the Regents are

correct in their conclusion that there are no feasible alternatives

to the Laurel Heights site, the EIR is nonetheless defective

under CEQA. As we stated in a context similar to CEQA, there

must be a disclosure of the ‘analytic route the . . . agency

traveled from evidence to action.’ (Topanga Assn. for a Scenic

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

11

Community v. County of Los Angeles (1974) 11 Cal.3d 506, 515

[construing requirements of Gov. Code, § 65906 for zoning

variances]; [citation].) The EIR prepared by UCSF contains no

analysis of any alternative locations. An EIR’s discussion of

alternatives must contain analysis sufficient to allow informed

decision making. (San Bernardino Valley Audubon Society, Inc.

v. County of San Bernardino (1984) 155 Cal.App.3d 738, 751

[202 Cal.Rptr. 423].)” (Laurel Heights I, supra, 47 Cal.3d at

p. 404.)

In Laurel Heights I this court was clear that its inquiry

was not a matter of reviewing the record for substantial

evidence: “The Regents also contend the [project opponents]

failed to point to any evidence in the record that demonstrates

reasonable alternatives to moving the School of Pharmacy

research units to Laurel Heights. This argument is somewhat

disingenuous given the Regents’ own failure to provide any

meaningful information regarding alternatives. It is the project

proponent’s responsibility to provide an adequate discussion of

alternatives. (Guidelines, § 15126, subd. (d).) That

responsibility is not dependent in the first instance on a showing

by the public that there are feasible alternatives. If the project

proponent concludes there are no feasible alternatives, it must

explain in meaningful detail in the EIR the basis for that

conclusion.” (Laurel Heights I, supra, 47 Cal.3d at p. 405.)

Recently, in Cleveland National Forest Foundation v. San

Diego Assn. of Governments (2017) 3 Cal.5th 497, 514–515

(Cleveland National Forest), this court made a similar point that

the adequacy of an EIR’s discussion of environmental impacts is

an issue distinct from the extent to which the agency is correct

in its determination whether the impacts are significant. “[A]n

EIR’s designation of a particular adverse environmental effect

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

12

as ‘significant’ does not excuse the EIR’s failure to reasonably

describe the nature and magnitude of the adverse effect. (See

Berkeley Keep Jets Over the Bay Com. v. Board of Port Cmrs.

(2001) 91 Cal.App.4th 1344, 1371 [111 Cal.Rptr.2d 598] [‘The

EIR’s approach of simply labeling the effect “significant”

without accompanying analysis of the project’s impact on the

health of the Airport’s employees and nearby residents is

inadequate to meet the environmental assessment

requirements of CEQA.’]; Galante Vineyards v. Monterey

Peninsula Water Management Dist. (1997) 60 Cal.App.4th 1109,

1123 [71 Cal.Rptr.2d 1].) An adequate description of adverse

environmental effects is necessary to inform the critical

discussion of mitigation measures and project alternatives at

the core of the EIR. (See Guidelines, § 15151 [‘An EIR should

be prepared with a sufficient degree of analysis to provide

decisionmakers with information which enables them to make a

decision which intelligently takes account of environmental

consequences.’].)” (Ibid.)

However, there are instances where the agency’s

discussion of significant project impacts may implicate a factual

question that makes substantial evidence review appropriate.

For example, a decision to use a particular methodology and

reject another is amenable to substantial evidence review, as

Sierra Club concedes. But whether a description of an

environmental impact is insufficient because it lacks analysis or

omits the magnitude of the impact is not a substantial evidence

question. A conclusory discussion of an environmental impact

that an EIR deems significant can be determined by a court to

be inadequate as an informational document without reference

to substantial evidence.

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Opinion of the Court by Chin, J.

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Our Courts of Appeal have consistently recognized that

adequacy of discussion claims are not typically amenable to

substantial evidence review. As the court explained in County

of Amador v. El Dorado County Water Agency (1999) 76

Cal.App.4th 931, 945-946, “Substantial evidence challenges are

resolved much as substantial evidence claims in any other

setting: a reviewing court will resolve reasonable doubts in

favor of the administrative decision, and will not set aside an

agency’s determination on the ground that the opposite

conclusion would have been equally or more reasonable.

[Citations.] [¶] A claim that an agency failed to act in a manner

required by law presents other considerations. Noncompliance

with substantive requirements of CEQA or noncompliance with

information disclosure provisions ‘which precludes relevant

information from being presented to the public agency . . . may

constitute prejudicial abuse of discretion within the meaning of

Sections 21168 and 21168.5, regardless of whether a different

outcome would have resulted if the public agency had complied

with those provisions.’ (§ 21005, subd. (a).) . . . [W]hen an

agency fails to proceed [as CEQA requires], harmless error

analysis is inapplicable. The failure to comply with the law

subverts the purposes of CEQA if it omits material necessary to

informed decisionmaking and informed public participation.

Case law is clear that, in such cases, the error is prejudicial.

(Sierra Club v. State Bd. of Forestry (1994) 7 Cal.4th 1215, 1236-

1237 [32 Cal.Rptr.2d 19, 876 P.2d 505]; Fall River Wild Trout

Foundation v. County of Shasta (1999) 70 Cal.App.4th 482, 491-

493 [82 Cal.Rptr.2d 705]; Kings County Farm Bureau v. City of

Hanford (1990) 221 Cal.App.3d 692, 712 [270 Cal.Rptr. 650];

East Peninsula Ed. Council, Inc. v. Palos Verdes Peninsula

Unified School Dist. (1989) 210 Cal.App.3d 155, 174 [258

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Opinion of the Court by Chin, J.

14

Cal.Rptr. 147] (East Peninsula); Rural Landowners Assn. v. City

Council (1983) 143 Cal.App.3d 1013, 1021–1023 [192 Cal.Rptr.

325].)” (Italics added.) The court in that case concluded that

the EIR was insufficient because among other things it failed to

adequately describe environmental baseline conditions.

(County of Amador, at pp. 952–956.)

We also affirm that in reviewing an EIR’s discussion, we

do not require technical perfection or scientific certainty:

“ ‘ “[T]he courts have looked not for an exhaustive analysis but

for adequacy, completeness and a good-faith effort at full

disclosure.” ’ ” (California Native Plant Society v. City of Santa

Cruz, supra, 177 Cal.App.4th at p. 979; accord Laurel Heights I,

supra, 47 Cal.3d at p. 406; see Guidelines, § 15151 [“An

evaluation of the environmental effects of a proposed project

need not be exhaustive, but the sufficiency of an EIR is to be

reviewed in the light of what is reasonably feasible.”].)

Three basic principles emerge from our decisions and

those of the Court of Appeal: (1) An agency has considerable

discretion to decide the manner of the discussion of potentially

significant effects in an EIR. (2) However, a reviewing court

must determine whether the discussion of a potentially

significant effect is sufficient or insufficient, i.e., whether the

EIR comports with its intended function of including “ ‘ “detail

sufficient to enable those who did not participate in its

preparation to understand and to consider meaningfully the

issues raised by the proposed project.” ’ ” (Bakersfield Citizens

for Local Control v. City of Bakersfield (2004) 124 Cal.App.4th

1184, 1197 (Bakersfield).) (3) The determination whether a

discussion is sufficient is not solely a matter of discerning

whether there is substantial evidence to support the agency’s

factual conclusions.

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Opinion of the Court by Chin, J.

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The ultimate inquiry, as case law and the CEQA

guidelines make clear, is whether the EIR includes enough

detail “to enable those who did not participate in its preparation

to understand and to consider meaningfully the issues raised by

the proposed project.” (Laurel Heights I, supra, 47 Cal.3d at

p. 405; see Berkeley Keep Jets Over the Bay Com. v. Board of Port

Cmrs., supra, 91 Cal.App.4th at p. 1356 [“Whether an EIR will

be found in compliance with CEQA involves an evaluation of

whether the discussion of environmental impacts reasonably

sets forth sufficient information to foster informed public

participation and to enable the decision makers to consider the

environmental factors necessary to make a reasoned decision.”];

Guidelines, § 15151 [“An EIR should be prepared with a

sufficient degree of analysis to provide decisionmakers with

information which enables them to make a decision which

intelligently takes account of environmental consequences.”].)

The inquiry presents a mixed question of law and fact. As such,

it is generally subject to independent review. However,

underlying factual determinations—including, for example, an

agency’s decision as to which methodologies to employ for

analyzing an environmental effect—may warrant deference.

(Cf. Mountain Air Enterprises, LLC v. Sundowner Towers, LLC

(2017) 3 Cal.5th 744, 751; Crocker National Bank v. City and

County of San Francisco (1989) 49 Cal.3d 881, 888.) Thus, to

the extent a mixed question requires a determination whether

statutory criteria were satisfied, de novo review is appropriate;

but to the extent factual questions predominate, a more

deferential standard is warranted. (Connerly v. State Personnel

Bd. (2006) 37 Cal.4th 1169,1175.)

Real party draws a distinction for standard of review

purposes between claims that a required discussion has been

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16

omitted altogether and claims that a required discussion is

insufficient, with the former subject to de novo review and the

latter subject to substantial evidence review. But such a

distinction is neither consistent with our precedent (see Laurel

Heights I, supra, 47 Cal.3d at pp. 403–405) nor logically

defensible. Whether or not the alleged inadequacy is the

complete omission of a required discussion or a patently

inadequate one-paragraph discussion devoid of analysis, the

reviewing court must decide whether the EIR serves its purpose

as an informational document.

2. The EIR’s air quality discussion

The Court of Appeal’s opinion presents a concise summary

of the EIR’s discussion regarding the Project’s air quality

impacts on public health.

“The EIR’s discussion of Impact No.3.3.2, the long-term

area and operational emissions, estimated that, at build-out, the

proposed Friant Community Plan would emit approximately

117.38 tons per year of PM10 [particulate matter 10 microns in

diameter or smaller], 109.52 tons per year of reactive organic

gases (ROG), and 102.19 tons per year of nitrogen oxides (NOx).

Estimates were made for ROG and NOx because they are

precursors to ozone, which is formed when ROG and NOx

undergo chemical reactions in the presence of sunlight.

“The Air District’s thresholds of significance are 15, 10 and

10 tons per year for PM10, ROG and NOx, respectively. Because

the project’s estimated emission of PM10, ROG and NOx were

from seven to 10 times larger than that of the thresholds of

significance, the EIR concluded these air pollutants would have

a significant adverse effect on air quality. Because Mitigation

Measure 3.3.2 could not reduce these emissions below the Air

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Opinion of the Court by Chin, J.

17

District’s thresholds of significance, the EIR concluded that the

significant impacts were unavoidable.

“The draft EIR included a page of background information

about ozone and nearly a page of background information about

PM10. Each included a paragraph about the adverse health

effects associated with the pollutant. The discussion of the

adverse health effects, however, was not connected to the levels

of the pollutant that would be emitted by the completed project.

Instead, the discussion of adverse health effects was general in

nature. For example, the description of the health effects of

ozone noted that the effects were primarily to the respiratory

system and stated:

‘Exposure to ambient levels of ozone ranging from 0.10 to

0.40 [parts per million] for 1 to 2 hours has been found to

significantly alter lung functions by increasing respiratory rates

and pulmonary resistance, decreasing tidal volumes, and

impairing respiratory mechanics.’

“As to PM10, the EIR stated its adverse health effects

depended upon ‘the specific composition of the particulate

matter.’ The EIR, however, provided no information about the

composition of the particulate matter that was expected to be

produced by the Project.”

3. Adequacy of the EIR’s discussion of public health

impacts from air pollutants that the Project is

expected to generate

Real party contends that the EIR satisfied all CEQA

requirements because it analyzed the Project’s air quality

impacts and disclosed the Project’s likely general health

impacts. Plaintiffs argue that the EIR failed to satisfy

Guidelines section 15126.2, subdivision (a), which requires an

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Opinion of the Court by Chin, J.

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EIR to “analyze any significant environmental effects the project

might cause by bringing development and people into the area

affected.” In other words, they argue, the Project’s health effects

must be “clearly identified” and the discussion must include

“relevant specifics” about the environmental changes

attributable to the Project and their associated health outcomes.

The Court of Appeal held that the EIR’s analysis of air

quality impacts was inadequate because it did not connect the

raw particulate numbers and their effect on air quality with

specific adverse effects on human health in the built

environment. (See Bakersfield, supra, 124 Cal.App.4th at p.

1193.) Bakersfield considered EIRs relating to the construction

and operation of two shopping centers in the City of Bakersfield.

(Ibid.) The shopping centers featured a Wal-Mart Supercenter

as their primary tenant and anchor. (Id. at p. 1194.) Both EIRs

concluded that the projects would have “significant and

unavoidable adverse impacts on air quality.” (Id. at p. 1219.)

But neither EIR specifically identified the health impacts that

would result from the adverse air quality effects. The appellate

court criticized the EIRs because they lacked an

“acknowledgement or analysis of the well-known connection

between reduction in air quality and increases in specific

respiratory conditions and illnesses. After reading the EIRs, the

public would have no idea of the health consequences that result

when more pollutants are added to a nonattainment basin.” (Id.

at p. 1220.) Bakersfield concluded that brief references to

adverse health impacts on human respiratory health rendered

the EIRs in that case inadequate as a matter of law because they

failed to connect the adverse air impact with negative health

effects. (Ibid.) The court held that “the health impacts resulting

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

19

from the adverse air quality impacts must be identified and

analyzed in the new EIRs.” (Ibid., italics added.)

The Court of Appeal acknowledged that the EIR at issue

here went “much further than” the Bakersfield EIRs, noting that

the EIR not only listed the type and tons per year of the

pollutants the Project is expected to produce, but also provided

a general description of each pollutant and how it affects human

health. The Court of Appeal found, however, that the EIR was

inadequate under CEQA because its analysis failed to correlate

the increase in emissions that the Project would generate to the

adverse impacts on human health.

Real party had argued below that “the reader can infer

from the provided information that the Project will make air

quality and human health worse.” But the Court of Appeal

concluded that “although the better/worse dichotomy is a useful

starting point for analyzing adverse environmental impacts,

including those to human health, more information is needed to

understand that adverse impact.”

The EIR does include some discussion of the health

impacts of various pollutants and attempts to provide an

explanation for its lack of specificity. It offers a general

discussion of adverse health effects associated with certain

Project-related pollutants. Notably, it also recognized that

Fresno County suffers from the “most severe” ozone problems in

the state and acknowledged the relationship between adverse

ambient air quality and certain health risks to the respiratory

system that could affect asthmatics, children, and healthy

adults. These adverse effects, the draft EIR observed, could

include “breathing and respiratory symptoms, aggravation of

existing respiratory and cardiovascular diseases, alterations to

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

20

the immune system, carcinogenesis, and premature death.” The

EIR explained, however, that a more detailed analysis of health

impacts is not possible at this early planning phase. According

to the EIR, “Health Risk Assessments are typically prepared for

inclusion in development specific project EIRs when certain

types of development commonly known to have the potential to

result in a human health risk are being proposed (automobile

fueling stations [for example]). Due to the broad nature of the

planning approvals analyzed in this EIR, it is impossible to

conduct a human health risk assessment based on specific

proposed uses at specific locations within the boundaries of the

Project Area because such specific information has not been

determined.”

We agree with the Court of Appeal that the EIR’s

discussion of health impacts found in Impact No. 3.3.2 is

inadequate as an informational document, similar to what the

court found in Bakersfield, supra, 124 Cal.App.4th at p. 1220.

The EIR’s discussion of health impacts of the named pollutants

provides only a general description of symptoms that are

associated with exposure to the ozone, particulate matter (PM),

carbon monoxide (CO), and nitrogen dioxide (NOx), and the

discussion of health impacts regarding each type of pollutant is

at most a few sentences of general information. The disclosures

of the health effects related to PM, CO, and sulfur dioxide fail to

indicate the concentrations at which such pollutants would

trigger the identified symptoms. As in Bakersfield, “[a]fter

reading the EIRs, the public would have no idea of the health

consequences that result when more pollutants are added to a

nonattainment basin.” (Bakersfield, supra, 124 Cal.App.4th at

p. 1220.) And as mentioned above, a sufficient discussion of

significant impacts requires not merely a determination of

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

21

whether an impact is significant, but some effort to explain the

nature and magnitude of the impact. (See Cleveland National

Forest, supra, 3 Cal.5th at pp. 514–515.) The EIR in this case

fails to meet the standards articulated in Bakersfield and

Cleveland National Forest.

Even in the one area in which the EIR goes into some

detail about health effects––ozone––the analysis is inadequate.

The EIR states: “Exposure to ambient levels of ozone ranging

from 0.10 to 0.40 [parts per million of ozone] has been found to

significantly alter lung functions by increasing respiratory rates

and pulmonary resistance, decreasing tidal volumes, and

impairing respiratory mechanics. Ambient levels of ozone above

0.12 [parts per million] are linked to symptomatic responses

that include such symptoms as throat dryness, chest tightness,

headache, and nausea.”

At first glance, this information appears to potentially

illuminate the health impacts of ozone produced by the Project.

But the EIR presents no evidence of the anticipated parts per

million (ppm) of ozone as a result of the Project. Rather, the EIR

provides the estimated tons per year of reactive organic material

(ROG) and NOx, the two components that react with sunlight to

form ozone (i.e., ROG + NOx + sunlight → ozone). The raw

numbers estimating the tons per year of ROG and NOx from the

Project do not give any information to the reader about how

much ozone is estimated to be produced as a result. Therefore,

the disclosure of the health impacts associated with exposure to

0.10 to 0.40 ppm of ozone is not meaningful within the context

of the Project because the reader has no idea how much ozone

will be produced (i.e., whether the amount of ozone resulting

from the ROG and NOx pollution will bring the ozone ppm

within the 0.10 to 0.40 range).

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

22

Guidelines section 15126.2, subdivision (a) is instructive.

It mandates that an EIR “identify and focus on the significant

environmental effects of the proposed project . . . examin[ing] []

changes in the existing physical conditions in the affected area,”

that it identify and describe “[d]irect and indirect significant

effects of the project on the environment,” and that the

discussion should include, among other things, “relevant

specifics of . . . health and safety problems caused by the

physical changes.” It also suggests that a connection be drawn

between the two segments of information presented in the

EIR—potential project emissions and human health impacts.

Such a connection would meet CEQA’s requirements.

Relying on various amici curiae briefs submitted to the

court, the County and real party attempt to explain why the

connection between emissions and human health that plaintiffs

seek cannot be provided given the state of environmental science

modeling in use at this time. The parties may be correct; we

express no view on the question, except to note that scientific

certainty is not the standard. But if it is not scientifically

possible to do more than has already been done to connect air

quality effects with potential human health impacts, the EIR

itself must explain why, in a manner reasonably calculated to

inform the public of the scope of what is and is not yet known

about the Project’s impacts. Contained in a brief, such

explanation is directed at the wrong audience. The relevant

informational document here is the EIR, and the EIR must

communicate not to the reviewing court, but “the public and the

government officials deciding on the project.” (Vineyard, supra,

40 Cal.4th at p. 443.) For purposes of supplementing the EIR

and bringing it in conformance with CEQA, the information

contained in the briefs “is irrelevant [] because the public and

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

23

decision makers did not have the briefs available at the time the

project was reviewed and approved.” (Ibid. [“That a party’s

briefs to the court may explain or supplement matters that are

obscure or incomplete in the EIR [] is irrelevant . . . . The

question is [] not whether the project’s significant

environmental effects can be clearly explained, but whether

they were.”].)

We further reject real party’s argument that the EIR

sufficiently accounted for its lack of specificity by explaining

that a “Health Risk Assessment” is typically prepared later in

the CEQA process, in connection with development-specific

EIRs. A “Health Risk Assessment” is defined in the Health and

Safety Code as a type of analysis undertaken in connection with

the siting of hazardous substances, “a detailed comprehensive

analysis . . . to evaluate and predict the dispersion of hazardous

substances in the environment and the potential for exposure of

human populations and to assess and quantify both the

individual and population wide health risks associated with

those levels of exposure.” (Health & Saf. Code, § 44306.)

CEQA does not mandate such an in-depth risk

assessment. CEQA requires that the EIR have made a

reasonable effort to discuss relevant specifics regarding the

connection between two segments of information already

contained in the EIR, the general health effects associated with

a particular pollutant and the estimated amount of that

pollutant the project will likely produce. This discussion will

allow the public to make an informed decision, as CEQA

requires. Because the EIR as written makes it impossible for

the public to translate the bare numbers provided into adverse

health impacts or to understand why such translation is not

possible at this time (and what limited translation is, in fact,

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

24

possible), we agree with the Court of Appeal that the EIR’s

discussion of air quality impacts in this case was inadequate.

The Court of Appeal identified several ways in which the

EIR could have framed the analysis so as to adequately inform

the public and decision makers of possible adverse health

effects. The County could have, for example, identified the

Project’s impact on the days of nonattainment per year. But the

Court of Appeal was clear that, ultimately—though the EIR

must provide an analysis that is adequate to inform (Guidelines,

§ 15151)—the “County has discretion in choosing what type of

analysis to provide . . . .” We agree. The task for real party and

the County is clear: The EIR must provide an adequate analysis

to inform the public how its bare numbers translate to create

potential adverse impacts or it must adequately explain what

the agency does know and why, given existing scientific

constraints, it cannot translate potential health impacts further.

To be sure, “ ‘courts have looked not for perfection but for

adequacy, completeness, and a good faith effort at full

disclosure.’ ” (In re Bay-Delta etc. (2008) 43 Cal.4th 1143, 1175.)

But basic CEQA principles dictate there must be a reasonable

effort to put into a meaningful context the conclusion that the

air quality impacts will be significant. Although the EIR

generally outlines some of the unhealthy symptoms associated

with exposure to various pollutants, it does not give any sense

of the nature and magnitude of the “health and safety problems

caused by the physical changes” resulting from the Project as

required by the CEQA guidelines. (Guidelines, § 15126.2, subd.

(a).) Perhaps it was not possible to do more. But even in that

case, we would have found the EIR insufficient because it failed

to explain why it was not feasible to provide an analysis that

connected the air quality effects to human health consequences.

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

25

B. Mitigation measures

1. “Substantially reduce air quality impacts”

At the outset of the discussion of proposed Mitigation

Measure 3.3.2 (discussed more fully in part D below), the EIR

stated that “Implementation of the following mitigation

measures will substantially reduce air quality impacts related

to human activity within the entire Project area but not to a

level that is less than significant.”

The Court of Appeal concluded that the EIR’s use of the

term “substantial” to describe the impact the proposed

mitigation measures would have on reducing the Project’s

significant health effects, without further explanation or factual

support, amounted to a “bare conclusion” that did not satisfy

CEQA’s disclosure requirements.

We agree with the Court of Appeal on this point. (See

Laurel Heights I, supra, 47 Cal.3d at pp. 404 - 405 [“ ‘To

facilitate CEQA’s informational role, the EIR must contain facts

and analysis, not just the agency’s bare conclusions or opinions.’

”].) Here, the EIR included no facts or analysis to support the

inference that the mitigation measures will have a quantifiable

“substantial” impact on reducing the adverse effects. The EIR

must accurately reflect the net health effect of proposed air

quality mitigation measures. (Cleveland National Forest, supra,

3 Cal.5th at p. 514 [“an EIR’s designation of a particular adverse

environmental effect as ‘significant’ does not excuse the EIR’s

failure to reasonably describe the nature and magnitude of the

adverse effect”].)

2. Deferral of mitigation measures

We next decide whether, as the Court of Appeal concluded,

the County, as the lead agency, impermissibly deferred

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

26

mitigation measures when it approved real party’s EIR, which

included mitigation measures to “at least partially reduce” the

Project’s air quality impacts, as well as a substitution clause for

future mitigation methods. Plaintiffs contend that the Project’s

EIR is insufficient, because “the mitigation analysis is devoid of

criteria for measuring the effectiveness of mitigation measures.”

(Guidelines, §15126.4, subd. (a)(1)(B); see Sundstrom v. County

of Mendocino (1988) 202 Cal.App.3d 296, 306-307 [improper to

defer formulation of mitigation measures until after project

approved].) Plaintiffs agree with the Court of Appeal’s

conclusion that the formulation of future substitutions in this

case was improperly deferred.

The general rule is that an EIR is required to provide the

information needed to alert the public and the decision makers

of the significant problems a project would create and to discuss

currently feasible mitigation measures. Mitigation measures

need not include precise quantitative performance standards,

but they must be at least partially effective, even if they cannot

mitigate significant impacts to less than significant levels.

(Laurel Heights I, supra, 47 Cal.3d at p. 404; §§ 21051, 21100;

Guidelines, § 15370.)5



5 Guidelines section 15370 provides that legally adequate

mitigation measures must be capable of “(a) Avoiding the impact

altogether by not taking a certain action or parts of an action.

[¶] (b) Minimizing impacts by limiting the degree or magnitude

of the action and its implementation. [¶] (c) Rectifying the

impact by repairing, rehabilitating, or restoring the impacted

environment. [¶] (d) Reducing or eliminating the impact over

time by preservation and maintenance operations during the life

of the action. [¶] (e) Compensating for the impact by replacing

or providing substitute resources or environments.”

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

27

In the present matter, the Project’s EIR noted that the air

quality impacts will be significant and unavoidable. But the

EIR’s 12 mitigation measures in Mitigation Measure 3.3.2 were

designed to reduce the Project’s air quality impacts by providing

shade trees, utilizing efficient PremAir or similar model

heating, ventilation, and air conditioning [HVAC] systems,

building bike lockers and racks, creating bicycle storage spaces

in units, and developing transportation related mitigation that

will include trail maps and commute alternatives.

Mitigation Measure 3.3.2 includes a substitution clause

that allows the lead agency to “substitute different air pollution

control measures for individual projects, that are equally

effective or superior to those propose[d] [in the EIR], as new

technology and/or other feasible measures become available

[during] build-out within the [Project].” In other words, the

County retains the discretion to modify or substitute the

adopted mitigation with equally or more effective measures in

the future as better technology becomes available, unless the

changes increase a project’s significant impacts. (See

Guidelines, § 15162, subd. (a)(3).)

The County concluded that the Project’s air quality

impacts will be significant, and that the 12 mitigation measures

set forth in the Specific Plan should be at least partially effective

in reducing the significant impacts. The substitution clause will

allow for additional and presumably better mitigation measures

when they become available and it should be encouraged. (See

Napa Citizens for Honest Government v. Napa County Bd. of

Supervisors (2001) 91 Cal.App.4th 342, 357−358 [recognizing

county must have power to modify land use plans].) Allowing

future substitutions for equal or more efficient technology to

mitigate a project’s acknowledged significant effects promotes

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

28

CEQA’s goal of environmental protection and is not an

impermissible deferral of mitigation or an abuse of discretion.

It is simply a recognition that substitutions of adopted

mitigation measures may be implemented to further minimize

the Project’s environmental impacts.

3. Failure to reduce impacts to less than significant

levels

Plaintiffs also ask us to decide whether a lead agency

violates CEQA when its proposed mitigation measures will not

reduce a significant environmental impact to less than

significant levels. We conclude that as long as the public is able

to identify any adverse health impacts clearly, and the EIR’s

discussion of those impacts includes relevant specifics about the

environmental changes attributable to the project, the inclusion

of mitigation measures that partially reduce significant impacts

does not violate CEQA.

We have stated that protection of the environment and of

California’s resources has long been considered of the utmost

importance. However, in enacting CEQA to protect the

environment, the Legislature did not seek to prevent all

development. Section 21081, subdivision (b) allows a project to

continue even if there are significant environmental effects that

have not been mitigated, if “the public agency finds that specific

overriding economic, legal, social, technological, or other

benefits of the project outweigh the significant effects on the

environment.”

If, after the feasible mitigation measures have been

implemented, significant effects still exist, a project may still be

approved if it is found that the “unmitigated effects are

outweighed by the project’s benefits.” (Laurel Heights I, supra,

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

29

47 Cal.3d at p. 391.) Even when a project’s benefits outweigh its

unmitigated effects, agencies are still required to implement all

mitigation measures unless those measures are truly infeasible.

(City of San Diego v. Board of Trustees of California State

University (2015) 61 Cal.4th 945, 967.) We recently held that

“the lead agency must adopt feasible mitigation measures or

project alternatives to reduce the effect to insignificance; to the

extent significant impacts remain after mitigation, the agency

may still approve the project with a statement of overriding

considerations. [Citations.]” (Center for Biological Diversity v.

Department of Fish & Wildlife (2015) 62 Cal.4th 204, 231.) The

inclusion of a mitigation measure that reduces an

environmental impact is permitted even if the measure will not

reduce the impact to a level below the threshold of significance.

4. Enforceability of mitigation measures

Plaintiffs argue that mitigation measures involving the

installation of HVAC systems and tree planting, and any

required mitigation efforts that “are fully enforceable through

permit conditions, agreement, or other measures,” are

unenforceable. (§ 21081.6, subd. (b).) We note that the

measures referred to in this section are proposed as “guidelines”

that “shall be used by the County during review of future

project-specific submittals for non-residential development . . .

with [the] intent that specified measures be required where

feasible and appropriate.”

The Court of Appeal found the EIR mitigation “provision

about equipping HVAC units with a catalyst system does not

identify who will determine if the system is ‘reasonably

available and economically feasible’ ” and is unenforceable. In

its analysis, the court omitted the next sentence, “[c]atalyst

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

30

systems are considered feasible if the additional cost is less than

10% of the base HVAC cost.” This definition of what constitutes

“economically feasible” catalyst systems eliminates the need to

have individuals make such determinations. The Court of

Appeal also found the phrase “ ‘PremAir or similar catalyst

system’ ” vague for not defining what performance criteria must

be met to be a “ ‘similar catalyst system.’ ” The term is not

vague. PremAir is a brand name for an HVAC catalyst system.

The individuals proposing new projects, or those tasked with

evaluating the proposals for approval, would necessarily have

knowledge of HVAC systems and catalyst systems, including

PremAir. It is also impossible to require specific performance

criteria, given that the type, size, model, and efficiency levels of

the HVAC systems being installed in these future projects are

unknown. Given the uncertainty of these future proposed

projects, the language “ ‘PremAir or similar catalyst system’ ” is

sufficient under CEQA to provide an enforceable mitigation

measure for any HVAC systems associated with those projects.

The Court of Appeal similarly found that the mitigation

measure requiring trees be selected to provide shade did not

specify the person(s) responsible for selecting which trees to

plant. The measure instructs that “ ‘[t]rees selected to shade

paved areas should be varieties that will shade 25% of the paved

area within 20 years.’ ” The instruction provides sufficient

guidance for selecting appropriate shade trees. Any plan that

the County approves must be complete, and must contain

information about the trees selected for this mitigation

measure. It seems clear that the person(s) selecting the trees

would be the individuals or entity submitting the plans to the

County for approval. The measure is not vague.

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

31

In finding the mitigation measures cannot be enforced

through permit conditions, agreements, or other measures, the

Court of Appeal also misinterpreted section 21081.6, subdivision

(b) and its significant effects provision, which provides that a

public agency may set forth conditions of project approval

required to avoid significant effects in “referenced documents

which address [or incorporate the] required mitigation

measures . . . into the plan.” (§ 21081.6, subd. (b).) The Project’s

MMP places the burden of enforcement on the County to “ensure

that all construction plans and project operations conform to the

conditions of the mitigated project.” The Specific Plan

additionally states that “The County shall monitor compliance

with the Specific Plan and mitigation measures,” and it provides

the stages of planning at which certain mitigation measures

must be completed. These measures are not vague as to how

they will be enforced; the County will enforce them during the

approval process of future nonresidential development.6

Indeed,



6 The Statement and MMP have this language: “The

following guidelines shall be used by the County during review

of future project-specific submittals for non-residential

development within the Specific Plan area and within the

Community Plan boundary in order to reduce generation of air

pollutants with intent that specified measures be required

where feasible and appropriate.” To clarify, this aspect of the

Statement and MMP deals with the specific air quality issues

discussed in the EIR, which issues are considered “nonresidential.”

The off-site created HVAC catalyst systems (that

are eventually inserted into each home), tree planting, bicycle

trails, and any other mitigation that affects air quality and

comprises this aspect of the MMP are considered “nonresidential

development” for architecture and engineering

planning purposes. Of course, they each are part of the greater

“residential development” in the project, but for EIR purposes

SIERRA CLUB v. COUNTY OF FRESNO

Opinion of the Court by Chin, J.

32

if the County were to approve a project that did not include a

feasible mitigation measure, such approval would amount to an

abuse of discretion, which could be corrected in a court

mandamus proceeding. (See Rominger v. County of Colusa

(2014) 229 Cal.App.4th 690, 727 [holding dust control mitigation

measures left to the county’s discretion are enforceable through

a judicial writ of mandamus]; see also, e.g., California Oak

Foundation v. Regents of University of California (2010) 188

Cal.App.4th 227, 247.)

CONCLUSION

In our view, the EIR’s air quality impacts discussion and

its mitigation measures meet CEQA requirements for specificity

and enforceability with one exception: The EIR fails to provide

an adequate discussion of health and safety problems that will

be caused by the rise in various pollutants resulting from the

Project’s development. At this point, we cannot know whether

the required additional analysis will disclose that the Project’s

effects on air quality are less than significant or unavoidable, or

whether that analysis will require reassessment of proposed

mitigation measures. Absent an analysis that reasonably

informs the public how anticipated air quality effects will

adversely affect human health, an EIR may still be sufficient if

it adequately explains why it is not scientifically feasible at the

time of drafting to provide such an analysis. Otherwise, the EIR

is generally clear about the potential environmental harm under

the Specific Plan, and it outlined mitigation measures to address

those effects with factual support and scientific consensus.



are considered “non-residential” since they involve cleaning the

air, planting trees, and creating bicycle trails.

Based on the foregoing analysis, we affirm in part and reverse in part the Court of Appeal’s judgment and remand the matter for additional proceedings consistent with this opinion.