EISEN| LETUNIC
TRANSPORTATION, ENVIRONMENTAL AND URBAN PLANNING
304 ½ Lily Street | San Francisco, CA 94102 | ph 415 552 2468 | www. eisenletunic. com
FINAL MEMORANDUM
To Rachel Hiatt, San Francisco County Transportation Authority
From Niko Letunic ( Eisen| Letunic) and Christopher Ferrell ( Dowling Associates)
Date January 10, 2007
Subject Establishing thresholds of significance under CEQA
Introduction
In December 2003, the San Francisco County
Transportation Authority ( SFCTA) Board
approved a Strategic Analysis Report ( SAR) on
“ Transportation System Level of Service ( LOS)
Methodologies.” The SAR recommended
alternatives to the current measure and
threshold of significance used by the City and
County of San Francisco under the California
Environmental Quality Act ( CEQA) for
evaluating the impact that proposed projects
might have on automobile level of service at
intersections. The SAR concluded that auto
LOS‐ based analysis under CEQA has
unintended negative consequences for the
City’s ability to implement the Transit First
Policy, and consequently, for the environment.
In July 2005, the Authority Board adopted
follow‐ up recommendations to the LOS
Methodologies SAR that were developed by a
Technical Working Group composed of city
agency representatives and public
stakeholders. The follow‐ up recommendations
included discontinuing use of the auto LOS
threshold for assessing CEQA impact and
replacing it with a measure of transportation
impact based on the number of automobile
trips generated ( ATG) by a proposed project.
A measure and significance threshold based on
ATG would not only be a more effective way to
gauge impacts to the city’s multi‐ modal
transportation system but would also be
consistent with the City’s “ Transit First” policy.
The replacement measure is also intended to
reduce the review burden on the SF Planning
Department.
The SFCTA recently hired a team of
consultants, led by Dowling Associates, to
conduct a study examining a number of key
issues related to replacing the automobile LOS
threshold. Specifically, the study will focus on
the following four issues ( which correspond to
the four main phases, or tasks, under the
study):
􀂃 The extent of technical and policy
justification necessary for the City to
establish a new threshold of significance
under CEQA ( Task 2);
􀂃 Alternative approaches for establishing a
threshold based on automobile‐ trip
generation ( Task 3);
􀂃 The advantages and disadvantages of each
alternative approach, including an “ after the
Ms. Rachel Hiatt January 10, 2007
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fact” evaluation of each approach under
CEQA’s review process ( Task 4); and
􀂃 The optimal strategy for the City’s adoption
and implementation of a new threshold of
significance ( Task 5).
The purpose of this technical memorandum is
to present the findings related to the first issue
above, namely the extent of justification
necessary for the City to establish a legally
defensible new threshold of significance under
CEQA. ( Findings related to the remaining key
issues outlined above will be the subject of
separate technical memoranda.) More
specifically, this memorandum examines, ( i)
the legal requirements, official guidelines,
formal guidance and case law concerning the
establishment of thresholds of significance; ( ii)
several case studies of thresholds established
by public agencies under a variety of
environmental impact areas; and, ( iii)
considerations related to abandoning the
automobile LOS threshold as part of the City’s
CEQA review.
I. Requirements and
guidance for establishing
thresholds of significance
Under CEQA, public agencies must review
projects under their jurisdiction and decide
whether they might have significant impacts
on the environment. Public agencies are
encouraged to develop thresholds of
significance as convenient tools to help them
assess the significance of potential impacts.
Thresholds promote consistency and
predictability in the environmental review
process. They also reduce duplication of effort,
and offer some assurance that potential
impacts are not being overlooked. Absent
thresholds of significance, public agencies must
evaluate the significance of impacts using
potentially inefficient and inconsistent case‐ by‐case
standards.
Thresholds of significance are not mentioned in
CEQA itself but rather in its implementing
guidelines, developed by the Governor’s Office
of Planning and Research ( OPR). The
guidelines— contained in Title 14, Chapter 3, of
the California Code of Regulations— are
binding on all public agencies in California
when implementing CEQA. Specifically,
Section 15064.7 of the guidelines (“ Thresholds
of Significance”) states:
􀂃 ( a) Each public agency is encouraged to develop
and publish thresholds of significance that the
agency uses in the determination of the
significance of environmental effects. A
threshold of significance is an identifiable
quantitative, qualitative or performance level
of a particular environmental effect, non-compliance
with which means the effect will
normally be determined to be significant by the
agency and compliance with which means the
effect normally will be determined to be less
than significant.
Ms. Rachel Hiatt January 10, 2007
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􀂃 ( b) Thresholds of significance to be adopted for
general use as part of the lead agency's
environmental review process must
be… supported by substantial evidence.
The above section raises the question of what
constitutes “ substantial evidence.” The
concept is defined in Section 15384 of the
guidelines as follows:
􀂃 ( a) [ E] nough relevant information and
reasonable inferences from this information
that a fair argument can be made to support a
conclusion, even though other conclusions
might also be reached. Whether a fair
argument can be made that the project may
have a significant effect on the environment is
to be determined by examining the whole
record before the lead agency. Argument,
speculation, unsubstantiated opinion or
narrative, evidence which is clearly erroneous
or inaccurate, or evidence of social or economic
impacts which do not contribute to or are not
caused by physical impacts on the environment
does not constitute substantial evidence.
􀂃 ( b) Substantial evidence shall include facts,
reasonable assumptions predicated upon facts,
and expert opinion supported by facts.
Two other sections of the guidelines shed
additional light on the definition of substantial
evidence, even if these sections are not
concerned with thresholds of significance, at
least specifically:
􀂃 15063( a)( 3): An initial study may rely upon
expert opinion supported by facts, technical
studies or other substantial evidence to
document its findings.
􀂃 15064( b): The determination of whether a
project may have a significant effect on the
environment calls for careful judgment on the
part of the public agency involved, based to the
extent possible on scientific and factual data.
The guidelines do not suggest specific
thresholds or even discuss how public agencies
should go about establishing them. Appendix
G of the guidelines (“ Environmental Checklist
Form”) contains a long list of potential impacts
that public agencies should be mindful of when
reviewing projects under CEQA. However,
these impacts are described in fairly general
terms and the form provides little concrete
guidance in judging whether not the suggested
impacts might be environmentally significant.
Similarly, Appendix H of the guidelines— an
“ Environmental Information Form” for public
agencies to use in soliciting environmental
information from project applicants about their
projects— contains a checklist of environmental
“ red flags” but does not suggest ways for
public agencies to gauge their environmental
significance.
OPR GUIDANCE
To fill the void in guidance concerning the
development of thresholds of significance, OPR
published a paper in 1994, under its CEQA
technical advice series, titled “ Thresholds of
Significance: Criteria for Defining
Environmental Significance.” The paper—
while it is advisory in nature and does not
replace CEQA or the state’s CEQA
guidelines— provides clear, specific advice to
public agencies in developing thresholds.
Below are the paper’s key recommendations,
grouped by the section of the paper in which
they appear. ( In some cases, the
recommendations have been edited from the
original for the sake of brevity and readability.)
Thresholds of Significance
􀂃 Thresholds of significance should reflect the
agency’s policies.
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􀂃 The threshold of significance for a given
environmental effect is that level at which a
lead agency finds the effects of the project to
be significant.
􀂃 “ Threshold of significance” can be defined as a
quantitative or qualitative standard, or set of
criteria, pursuant to which the significance of a
given environmental effect may be determined.
􀂃 Ideally, a threshold of significance provides a
clear differentiation of whether or not the
project may result in a significant
environmental effect.
􀂃 A threshold may be based on standards such as
the following:
□ A health- based standard such as air
pollutant emission standards or noise levels.
□ Service capacity standards such as traffic
level of service or water supply capacity.
□ Ecological tolerance standards such as loss
of prime farmland or wetland
encroachment.
□ Cultural resource standards such as impacts
on historic structures.
□ Other standards relating to environmental
quality issues, such as those listed in the
Guidelines’ Initial Study Checklist or
Appendix G of the Guidelines.
􀂃 A threshold provides a rational basis for
significance determinations.
Establishing Thresholds
􀂃 Thresholds may be either qualitative or
quantitative. Some effects lend themselves to
numerical standards. Others are difficult to
quantify and must rely upon qualitative
descriptions. In either case, thresholds should
be based on legal standards, studies, surveys,
reports, or other data which can identify that
point at which a given environmental effect
becomes significant.
􀂃 The significance of an activity may vary with its
setting. In such instances, the Lead Agency
could adopt more than one threshold of
significance for a given effect or include
flexible standards which recognize differences
in setting.
Drafting Thresholds
􀂃 The first step should be to identify those effects
for which thresholds are to be drafted.
􀂃 The next step should be to gather and evaluate
existing information relative to the chosen
effects. At what point or under what
circumstances was a given effect deemed
significant? Are there effective criteria by
which to measure significance?
􀂃 The agency should also rely upon its general
plan as a source of environmental standards.
Whenever possible, thresholds should be based
on or otherwise reflect the community's
adopted planning policies and regulations.
􀂃 The agency should also survey other agencies
for adopted standards which might lend
themselves to thresholds. Thresholds should be
based on existing environmental laws and
regulations whenever possible.
􀂃 Previously prepared studies and research are
additional sources of thresholds, provided that
they offer clear standards for assessing
significance.
Contents
􀂃 A threshold should contain, in some form, the
following elements:
□ A brief definition of the potential effect.
□ Reasons for its significance.
□ Threshold criteria for significance.
□ Geographic scope of the criteria, if
applicable.
□ References to the facts or data upon which
the criteria are based.
􀂃 The threshold may also contain a menu of
standardized mitigation measures. These
Ms. Rachel Hiatt January 10, 2007
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should be flexible enough to be tailored to
individual projects.
􀂃 In a jurisdiction with diverse locales, there may
be more than one or even a sliding scale of
thresholds for a single effect.
􀂃 There may be certain effects … which for one
reason or another are not easily described.
There is no advantage to adopting a threshold
which does not clarify or otherwise improve the
process of determining significance.
Ten Tips for Thresholds
􀂃 Write the threshold criteria clearly and
succinctly. Thresholds, whether quantitative or
qualitative, should be as objective as possible
so that they can be applied in a consistent
manner.
􀂃 Enact only those thresholds with a basis in fact
or in adopted policy, and reference that basis.
A factual basis may be developed as part of the
process of preparing thresholds. Further, the
standards or regulations upon which the
thresholds are based must be enforceable.
􀂃 Do not force an issue. If a clear threshold does
not exist, or existing policies are vague and
unenforceable, simply do not adopt a threshold
for that effect.
􀂃 Harmonize the thresholds with those of other
agencies to the extent possible, particularly the
technical thresholds of regulatory agencies.
􀂃 Adopt quantitative rather than qualitative
thresholds whenever reasonably possible.
􀂃 Base thresholds on existing standards and
regulations whenever possible.
CASE LAW
Given the role of the courts in interpreting
legislation and regulations, we reviewed
analyses of CEQA‐ related legal cases for
additional information on the requirements
governing thresholds of significance. We
learned of several cases that dealt with the use
of standards for determining environmental
significance under CEQA ( even if the
standards had not always been adopted as
thresholds of significance).
A number of such cases revolve around
questions relative to the conformity of
proposed projects with general plans. In
general, courts have indicated that just because
a proposed project conforms with the
applicable general plan does not mean that the
project might not cause significant impacts
[ City of Antioch v. City of Pittsburg ( 1986); Gentry
v. City of Murrieta ( 1995)]. More specifically,
courts have indicated that compliance with a
standard found in a general plan does not
justify a determination of insignificance if it can
be reasonably argued, using other substantial
evidence, that a project will have significant
environmental effects [ Oro Fino Gold Mining
Corporation v. County of El Dorado ( 1990)].
In a case related to the above, Kings County
Farm Bureau v. City of Hanford ( 1990), the court
rejected the use of regional air quality
emissions standards as the sole gauge for
determining the significance of air quality
impacts. The court found that the standards
applied only to on‐ site emissions from the
project and not to the secondary, off‐ site
emissions of trucks and rail traffic serving the
project. By relying on such standards alone,
the environmental review for the project
assessed the significance of some, but not all,
air quality impacts related to the project. In
other words, the court found that the City of
Hanford analyzed the project’s direct, on‐ site
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( i. e., stationary‐ source) emissions but not the
project’s traffic‐ related air quality impacts. 1
By way of contrast, the court in the Gentry case
cited two cases in which standards applied by
public agencies had been adequate for the
determination of significance: Schaeffer Land
Trust v. San Jose City Council ( 1989) and Citizen
Action to Serve All Students v. Thornley ( 1990).
The court stated that the agencies in both of
those cases had used “ predetermined
engineering standards to judge the significance
of a traffic impact.” In one case, the
environmental review for the project relied on
a level of service policy articulated in the
general plan; in the other, it relied on the
conclusions of a traffic report conducted for the
project that applied predetermined standards.
These cases suggest that courts might be
predisposed to favor quantitative thresholds
based on established standards.
More recently, Section 15064( h) was struck
from the CEQA guidelines pursuant to
Communities for a Better Environment v.
California Resources Agency ( 2002). The former
guideline specified that a change in the
environment was not a significant effect if it
complied with a standard found in a statute,
ordinance, rule or regulation. The court held,
instead, that an agency must prepare an
environmental impact report ( EIR) if it can be
“ fairly argued on the basis of other substantial
evidence that the project could still have a
significant environmental effect.” The court
reasoned that “[ a] public agency cannot apply
a threshold of significance… in a way that
forecloses consideration of any other
1 In contrast, the BAAQMD’s CEQA guidelines recommend
calculating the emissions from both stationary and mobile
sources for various pollutants ( CO, ROG, PM10, NOx, etc.) and
then applying thresholds developed specifically for each kind
of pollutant, reflecting the idea that the type of pollutant is
more important than its source.
substantial evidence showing there may be a
significant effect.”
This finding was reinforced by the Protect the
Historic Amador Waterways v. Amador Water
Agency ( 2004) case. In that case, the judge
ruled that a threshold of significance “… does
not relieve a public agency of the duty to
consider the evidence under the fair argument
standard.” A similar scenario was addressed
even more recently, in Mejia v. City of Los
Angeles ( 2005). In that case, a potentially
significant traffic impact was found to exist,
based on other substantial evidence, even
though the project did not meet the local
threshold of significance for traffic impacts.
These rulings emphasize that, if a reasonable
argument can be made that an impact is
created which isn’t captured by any of a public
agency’s thresholds, then that agency must
analyze that impact on a case‐ by‐ case basis ( i. e.,
without the help of thresholds). 2
Nevertheless, rulings have encouraged public
agencies to develop thresholds of significance
as convenient tools for analyzing commonly
encountered environmental impacts. The court
in the Communities for a Better Environment case
upheld Section 15064.7 of the CEQA
guidelines, which encourages local agencies to
determine their own thresholds of significance.
The court determined that “[ a] lead agency’s
use of existing environmental standards in
determining the significance of a project’s
environmental impacts is an effective means of
promoting consistency in significance
determinations and integrating CEQA
environmental review activities with other
2 One way of limiting the universe of potential impacts is to
argue successfully— as San Francisco did concerning
parking— that a certain effect does not constitute an
environmental impact. See the final section in this
memorandum for further discussion on this topic.
Ms. Rachel Hiatt January 10, 2007
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environmental program planning and
regulation.”
From the above‐ cited cases, it could be
concluded that any framework of thresholds
for determining significance should be
comprehensive enough to cover all reasonably
conceivable and measurable impacts that a
project might generate. By ignoring or
overlooking a particular impact source, a
jurisdiction could leave itself vulnerable to
legal challenges stating that a project results in
significant negative environmental impacts
that are not captured by the thresholds.
The above‐ cited cases appear, in some cases, to
contradict each other. Specifically, Schaeffer
Land Trust and Citizen Action to Serve All
Students reinforce the notion that CEQA allows
local jurisdictions latitude in defining their
own significance standards while other cases
found in favor of challengers to locally
determined thresholds. It might be possible to
summarize case law on the subject as advising
public agencies to employ thresholds as tools
that can assist in determining significance but
not as the determinant factors. The ultimate
determinant of environmental impact
significance should be the whole record of
substantial evidence available to the public
agency. As mentioned in OPR’s “ Thresholds of
Significance” paper, “ thresholds do not
substitute for the agency’s use of careful
judgment in determining significance.”
The above‐ cited cases contain several
implications for the City’s effort to develop a
new CEQA threshold of significance to replace
the auto LOS measure. For one, rulings
support the idea that a project might comply
with an adopted statute, ordinance, rule,
regulation, policy or plan, and yet still have a
significant negative effect on the environment.
Following from this, various rulings support
the development and application of thresholds,
especially quantitative ones, for determining
environmental significance, rather than having
public agencies rely simply on compliance with
existing policies ( for example, on San
Francisco’s Transit First policy, in the City’s
case).
Finally, the case law makes clear that an
agency’s formulation of significance thresholds
does not define the range of potential
environmental effects. Thus in the existing
context, an ATG threshold would not capture
all of a project’s potential transportation
impacts. Therefore, other transportation
thresholds— gauging crowding on Muni
vehicles or delays to delivery vehicles, for
example— may be useful alongside an ATG
threshold. For this reason, it would be
advisable for the City— if its goal is to
discontinue the use of auto LOS as a
threshold— to determine separately and in
advance that automobile congestion does not
by itself constitute an environmental impact,
and that the relevant transportation impact in a
dense, multimodal urban area such as San
Francisco is the generation of new auto trips,
and not congestion. ( The last section of this
memorandum discusses that issue in much
greater detail.) Given the legal complexities of
this topic, we encourage the SFCTA to seek the
advice of the City Attorney’s Office for more
conclusive opinions.
CONCLUSIONS
One of the two main objectives of this task was
to communicate to the SFCTA a solid
understanding of the requirements governing
the development of thresholds of significance
under CEQA. ( The other main objective is the
subject of the next section: to present a series of
case studies illustrating the establishment of
Ms. Rachel Hiatt January 10, 2007
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thresholds.) The information presented in this
section should provide such an understanding
to the SFCTA or any other public agency with a
similar interest.
To make the large amount of information in
this section easier to use, we have distilled it
into the list below of eight steps recommended
for public agencies to follow when establishing
thresholds of significance. ( The steps do not
address the adoption or implementation of
thresholds as those issues will be examined in
more detail as part of Task 5 of our study.)
Eight Steps for Establishing Thresholds of
Significance
􀁮 Begin by isolating the specific physical or
environmental impact( s) for which
thresholds are to be established. Be as
precise as possible in identifying the
impact( s) of interest.
􀁯 Gather information relative to the impact( s)
isolated in Step 􀁣 . Such information should
include technical studies, policy documents,
plans and environmental review reports,
whether prepared internally or by others.
􀁰 Review the information gathered in Step 􀁤 ,
looking for any quantitative or qualitative
criteria, regulations, standards, measures,
circumstances, situations or conditions
which make it possible to differentiate
between a significant impact and one that is
less than significant.
􀁱 Using the material compiled in Step 􀁥 ,
identify potential thresholds of significance
for the impact( s) chosen. Candidate
thresholds— whether quantitative standards
or qualitative descriptions— must be based
on facts, data, evidence, adopted policy or
enforceable standards or regulations which
identify the point at which a given impact
acquires significance in the public agency’s
judgment. ( If the agency believes that the
existing information is inadequate for the
purpose of establishing thresholds, it may
develop the factual basis for itself.)
􀁲 From among the candidate thresholds
identified in Step 􀁦 , select the threshold( s)
that best meet CEQA’s intent and the
agency’s purposes. Ideally, a threshold
should:
􀂃 reflect the agency’s policies ( especially as
expressed in adopted plans) and the
values of its constituents;
􀂃 be consistent with, though not
necessarily the same as, those of other
agencies ( particularly regulatory ones);
􀂃 be quantitative rather than qualitative, to
the extent that this is reasonable and
appropriate;
􀂃 be as objective as possible so that it can
be applied consistently; and
􀂃 be simple to interpret and implement.
􀁳 In certain instances, the significance of an
impact varies depending on the project’s
setting or locale. To address such cases,
consider establishing more than one
threshold of significance for a given impact,
or establishing a flexible threshold ( such as
a sliding scale) that recognizes differences in
setting.
􀁞 Certain impacts are not easily described, or
might not be suitable for translation into
clear, specific, fact‐ based thresholds. For
impacts that do not lend themselves readily
to the application of thresholds, it is better
to not establish thresholds than to “ force”
thresholds. Public agencies still maintain
responsibility for determining the
environmental significance of such impacts
but have the option of making
determinations on a case‐ by‐ case basis by
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examining the whole record before them of
the proposed project and the potential
impact.
􀁵 Lastly, formalize the selected threshold( s) in
writing. Ideally, a written threshold should
reference the impact to which it applies;
state the criteria for significance ( clearly and
succinctly, to avoid misinterpretation);
reference the factual basis for the criteria;
and explain why the threshold constitutes
environmental significance. If applicable,
thresholds should reference the settings,
locations or other physical scope to which
they apply. Also, thresholds may contain a
menu of mitigation or control measures to
underscore the boundary between
significance and insignificance.
II. Case studies
It should not be surprising, given the staff or
consultant resources necessary to do so, that
few agencies have developed thresholds of
significance. In 2001, two professors at
California State University, Northridge,
surveyed 500 agencies on their practices
concerning CEQA thresholds of significance for
a research paper (“ The Determination of
Thresholds of Environmental Significance in
the Application of CEQA,” by Owen Seiver
and Thomas Hatfield, March 2001). Of 185
agencies that replied to the survey, only 20 said
that they had developed thresholds ( and only
seven that they had done so within the
previous two years). Of those 20, only six were
able or willing to provide documents
containing an identifiable threshold as
requested by the survey ( which, of course,
raises questions about the validity of the
answers to this question by the other 14
agencies).
Nevertheless, we were able to find a
sufficiently large number of agencies that have
established thresholds of significance for us to
develop a series of informative case studies.
We have organized the case studies, presented
below, into three categories: ( i) agencies that
have developed thresholds of significance for a
comprehensive range of environmental impact
areas; ( ii) thresholds that have been developed
for issue‐ specific, non‐ transportation impacts;
and, ( iii) thresholds that have been developed
for transportation impacts. The case studies
cover a range of agencies, environmental
impact areas and approaches to the
development of thresholds.
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I. COMPREHENSIVE THRESHOLDS
􀁮 City of Los Angeles
Information obtained from “ L. A. CEQA Thresholds
Guide: Your Resource for Preparing CEQA
Analyses in Los Angeles” ( June 2003) and from
Jimmy Lau, environmental review planner at the
Los Angeles Department of City Planning.
The City of Los Angeles has developed
thresholds of significance for 46 impacts under
13 environmental impact areas. Table 1, shown
below, lists the thresholds established by the
City for a representative sample of 12 impacts
under a number of impact areas. The middle
column lists the significance threshold( s) for
each impact ( the wording of the thresholds has
been edited for the sake of brevity) while the
right‐ hand column provides the basis for each
threshold or the methodology to be used for
determining significance in case‐ by‐ case
situations.
According to the City, each threshold had to
meet several goals. These goals were:
objectivity and applicability, defensibility,
practicality, legal liability, and the presence of a
nexus between impacts and mitigation. The
City’s thresholds fall under three types:
quantitative, qualitative and case‐ by‐ case. The
first two types are self‐ explanatory while the
third type was developed, according to the
City, for impacts that are site‐ or project‐specific
or for which there was no “ consistent
technical guidance available.” The table lists
several examples of each type of threshold.
As the table shows, quantitative thresholds are
based primarily on numerical standards found
in relevant statutes or adopted by regulatory or
other agencies with authority over the impact
area in question. One note‐ worthy exception is
the threshold for traffic intrusion into
residential neighborhoods. This threshold was
determined by several traffic engineers at
LADOT and is based on their collective
professional experience with residents’
complaints about traffic intrusion into
residential neighborhoods. The engineers had
conducted research into the “ environmental
capacity” of streets, particularly residential
streets, but ultimately settled on specific traffic
volumes and percentage increases for the
threshold using their own judgment. ( The
concept of environmental capacity is discussed
at greater length under the case study for the
City of Palo Alto.)
The qualitative thresholds in the table are
based on a few sections of CEQA law and
implementing guidelines that suggest ways to
assess the significance of effects on specific
impact areas. These sections include:
􀂃 Section 21083.2 of the California Public
Resources Code, which discusses impacts
on archaeological resources;
􀂃 Section 15064.5 of the guidelines,
“ Determining the Significance of Impacts to
Archeological and Historical Resources;”
􀂃 Section 15065 of the guidelines, “ Mandatory
Thresholds of Significance;” and
􀂃 Appendix G of the guidelines,
“ Environmental Checklist Form.”
Lastly, for each impact that calls for case‐ by‐case
determinations of significance, staff at the
Department of City Planning prepared a list of
factors that, in their professional judgment,
were most relevant for determining
significance.
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Table 1: Thresholds of Significance Used by the City of Los Angeles
IMPACT
SIGNIFICANCE THRESHOLD( S)
( A project would normally have a
significant impact if it would…)
BASIS FOR THRESHOLD( S) OR
METHODOLOGY FOR DETERMINING SIGNIFICANCE
POPULATION AND
HOUSING
DISPLACEMENT
Determination of significance made on a
case- by- case basis
Determination based on such factors as the net
change in the number of habitable and of affordable
housing units; current and anticipated housing
demand and supply in the area; the character, land
use and zoning designations in the area; and the
appropriateness of housing at the site with regard to
applicable plans and policies
SEDIMENTATION AND
EROSION
Constitute a hazard to other properties
by causing instability from erosion or
result in sediment runoff or deposition
which would not be controlled on site
Adapted from Appendix G (“ Environmental Checklist
Form”) of the State’s CEQA guidelines
􀂃 Create pollution, contamination or
nuisance as defined in Section 13050 of
the California Water Code
The California Water Code is one of the main sources
of regulations for statewide surface water quality
SURFACE WATER
QUALITY 􀂃 Cause regulatory standards to be
violated, as defined in the applicable
NPDES storm water permit or regional
water quality control plan for the
receiving water body
The locally applicable NPDES storm water permit and
regional water quality control plan are the most
relevant sources of standards for the surface water
quality of local water bodies
TOTAL OPERATIONAL
AIR EMISSIONS
􀂃 Cause emissions exceeding 10 tons per
year of volatile organic gases; 55
lb/ day of ROG or NOx; 550 lb/ day of
CO; or 150 lb/ day of PM10 or SOx
Thresholds recommended by SCAQMD
INTERSECTION
CAPACITY
Cause an increase in the vehicle/ capacity
( V/ C) ratio on the intersection operating
condition of at least: 0.04 if post- project
level of service ( LOS) is C; 0.02 if LOS is
D; and 0.01 if LOS is E or F
Based on V/ C standards found in the “ Traffic Study
Policies and Procedures Manual” of the City of Los
Angeles Department of Transportation ( LADOT)
FREEWAY CAPACITY
Cause, or contribute to, a
demand/ capacity ( D/ C) ratio greater than
1.00 on a freeway segment or ramp by
increasing the D/ C ratio by at least 0.02
Based on a D/ C standard found in both LADOT’s
“ Traffic Study Policies and Procedures Manual” and
Los Angeles County’s congestion management plan
TRAFFIC INTRUSION
Cause the average daily traffic ( ADT)
volume on a local residential street to
increase by at least: 120 trips if post-project
ADT is under 1,000; 12% if ADT is
1,000– 1,999; 10% if ADT is 2,000– 2,999;
and 8% if ADT is 3,000 or more
Based on the collective professional judgment of
traffic engineering staff at LADOT, particularly their
experience with residents’ complaints about traffic
intrusion into residential neighborhoods, and
informed by research into the emerging field of
“ environmental capacity” of streets
SENSITIVE SPECIES
Diminish the chances for long- term
survival of a species designated by the
state or federal government as
endangered, threatened, protected, rare
or of special concern, by causing the loss
of species individuals or habitat,
interfering with species movement, or
disturbing species behavior
Adapted from Section 15065 of the state’s CEQA
guidelines (“ Mandatory Findings of Significance”)
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 12
IMPACT
SIGNIFICANCE THRESHOLD( S)
( A project would normally have a
significant impact if it would…)
BASIS FOR THRESHOLD( S) OR
METHODOLOGY FOR DETERMINING SIGNIFICANCE
OPERATIONAL NOISE
Cause the ambient noise level measured
at the property line of affected uses to
increase by 5 dB or more; or to increase
by 3 dB to, or within, “ normally
unacceptable” or “ clearly unacceptable”
ranges of noise- exposure levels for a
variety of specified land uses
􀂃 Three decibels is generally accepted by noise
professionals to be the threshold noise level
detectable by the normal human ear
􀂃 Planning staff settled on 5 dB as a mid- way level
between 3 dB ( see above) and 10 dB, which is the
level at which most people perceive a doubling of
the sound level
􀂃 “ Normally unacceptable” and “ clearly
unacceptable” ranges of noise- exposure levels
have been defined by the California Department of
Health Services’ Office of Noise Control for a
variety of common land uses
PUBLIC SCHOOL
CAPACITY
Determination of significance made on a
case- by- case basis
Determination based on such factors as the
population increase resulting from the project; the
anticipated demand ( including the project’s
contribution) for school services compared to the
expected level of service available; and the extent
to which increased demand would necessitate
construction of new facilities
OBSTRUCTION OF
VIEWS
Determination of significance made on a
case- by- case basis
Determination based on such factors as the effect on
views from a scenic highway, parkway or corridor;
the nature and quality of the affected or obstructed
views; and the degree of obstruction
ARCHAEOLOGICAL
RESOURCES
Damage or degrade an archaeological
resource or its setting which could
provide information that is scientifically
useful and of interest to the public;
possesses a unique quality or attribute; is
associated with an event of recognized
importance; or is at least 100 years old
and possesses substantial integrity
Derived from Section 21083.2 of the California Public
Resources Code ( concerning significant impacts to
archaeological resources) and Section 15064.5 of the
state’s CEQA guidelines (“ Determining the
Significance of Impacts to Archeological and
Historical Resources”)
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 13
􀁯 City of San Diego
Information obtained from “ Significance
Determination Thresholds” ( November 2004) and
from Martha Blake, environmental analysis planner
at the San Diego Development Services
Department.
The City of San Diego recently updated their
thresholds of significance, which cover
numerous impacts under 19 environmental
impact areas. Of particular interest about San
Diego’s thresholds is that they were updated in
large part to address the Communities for a
Better Environment ruling in 2002. As
mentioned in a previous section, the court in
that case indicated that a project that did not
exceed a threshold for a particular impact
could still be found to have significant effects
upon that impact if substantial evidence
existed to demonstrate significance. 3
No doubt in response to that ruling, San
Diego’s guidelines on significance thresholds
state that the thresholds “ are not intended to be
stand‐ alone policies and are to be used in
conjunction with commonly accepted
professional standards, judgments, and
practices.” Also no doubt in response, the
City’s updated threshold are the most detailed
we found. To illustrate San Diego’s approach
to thresholds in the wake of the Communities for
a Better Environment ruling, below are
summaries of the City’s thresholds for six
impacts ( or impact areas) as well as the
accompanying guidance for those thresholds.
􀂃 Air quality: The thresholds for air quality
impacts are based primarily on standards
3 However, several important points remain about the
usefulness of thresholds, including: ( 1) a comprehensive, well‐designed
threshold is much more defensible than a poorly
designed one; and ( 2) thresholds shift the burden of proof to
the challengers for coming up with another way of gauging
the significance of an environmental impact.
promulgated by the San Diego Air Pollution
Control District ( SDAPCD). The guidelines
acknowledge the impact of the Communities
for a Better Environment ruling by stating:
“ use of regulatory standards as the sole
threshold for significance was struck from
CEQA pursuant to Communities For A Better
Environment v. California Resources
Agency… . Given the… ruling, reliance on the
SDAPCD regulatory standards… can no longer
be used as the sole determinant of
significance. The SDAPCD thresholds are
provided… as a guideline to be considered on
a case- by- case basis with other substantial
evidence in light of the whole record to
determine if the project may have a
significant air quality impact. ‘ Other
substantial evidence’ may include factors
such as the proximity of sensitive
receptors… . Use of these [ thresholds]
should be applied as a screening tool to see
where the project aligns along a sliding
scale of potential significance. If sensitive
receptors are involved, the more restrictive
of the guidelines should be applied.
To account for sensitive receptors and other
variables, the City’s thresholds for air
quality impacts have been arranged into
three “ tiers,” from broadest ( or least
restrictive) to most specific ( or most
restrictive). This arrangement supports the
advice given in the guidelines that the
thresholds be used as a screening tool and
also as a gauge for determining where a
project lies on a continuum of potential
significance. The rationale behind the
thresholds is not substantially different
from that used by the Bay Area Air Quality
Management District ( BAAQMD) for its
thresholds, which are examined in the
following section.
􀂃 Odor: For odor impacts, the City has
established thresholds that are very similar
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 14
to the BAAQMD’s. In addition, the
guidelines provide a table for estimating the
concentrations at which different chemical
odors might become detectable. The table
provides the levels of odor recognition
established by three different organizations:
the U. S. Coast Guard, the American
Association of Railroads and the American
Industrial Hygiene Association. Since the
levels vary greatly for any chemical, the
guidelines advise that a project’s reviewer
determine which standard to apply based
on project‐ specific conditions. For
additional assistance to project reviewers,
the guidelines cite the experience of the
City’s Metropolitan Wastewater
Department that odor complaints are not
typically generated if ambient
concentrations of chemicals are less than 5
“ odor units,” or five times the odor
recognition threshold.
􀂃 Land use: The threshold for land use
impacts is based on seven factors that, in the
experience of planning staff at the City,
have in the past often been seen by City
residents as significant. These factors
include:
□ Conflict, incompatibility or inconsistency
with the general plan or with a
community, environmental or airport
land use plan;
□ Conflict, incompatibility or inconsistency
with an adopted land use or zoning
designation or with the prevailing land
use in the vicinity;
□ Development or conversion of
designated open space or prime
farmland to a more intensive land use;
and
□ Construction in a “ special flood hazard
area,” in a floodplain/ wetland buffer
zone, or which would significantly
increase the base flood elevation for
upstream properties.
􀂃 Traffic noise: The noise section of San
Diego’s CEQA guidelines consider several
different sources of noise impacts, including
traffic noise, airport noise, noise from
stationary sources and construction noise. 4
Rather than thresholds, standards of
“ general indication of potential
significance” from traffic‐ generated noise
impacts have been developed for both
interior and useable exterior spaces. The
thresholds are provided in a matrix and are
a function of the structure or use that would
be impacted by the noise and of the distance
from the center of the closest lane on a street
meeting certain existing or future ADT
volumes. The specific decibel levels,
distances and ADT volumes were based on
standards in the transportation and noise
elements of the City’s general plan and in
the City’s guidelines for the preparation of
acoustical reports. The standards were
themselves based on guidance from the
Office of Noise Control at the state’s
Department of Health Services and from a
review of literature concerning the human
impacts of traffic‐ generated noise.
􀂃 Transportation: The City has established
seven thresholds for transportation impacts.
Of these, two— regarding the creation of
traffic hazards and the addition of “ a
substantial amount of traffic to a congested
[ facility]”— are adapted from the state’s
4 By contrast, San Francisco’s analyses of noise impacts look at
the nature— rather than the source— of the noise impact ( eg,
ambient noise, groundborne noise). San Francisco’s approach
is more consistent with appendix G of the State’s CEQA
guidelines ( the environmental checklist form) and, more
generally, with CEQA’s emphasis on the nature of the impact
rather than the specific source of the impact. San Francisco’s
approach is also analogous to the BAAQMD’s approach to
analyzing air quality impact, which focuses on pollutants
rather than the sources of the pollutants.
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 15
“ Environmental Checklist Form.” Another
two— dealing with construction of a
roadway that is inconsistent with the
general plan or a community plan, and
substantial restriction in access— are
impacts that, in the experience of the City’s
planners, have the potential to be significant
based on past reactions by the community.
The remaining three thresholds concern
allowable changes in traffic delays, speeds
and vehicle/ capacity ratios by projects that
would cause automobile LOS to degrade to
levels E or F at any intersection, roadway
segment, or freeway segment or ramp‐ meter
location. The specific allowable changes are
based on guidelines provided by Caltrans
and the San Diego Association of
Governments— in its capacity as the
congestion management agency for the
county— for the preparation of traffic
impact studies, deficiency plans and other
similar reports. It should be noted that in
this case, the actual thresholds are
incremental changes to the transportation
system, not changes in the LOS level. The
logic for this is that a single project causes
only incremental impacts to conditions that
have been created over many years by all
the projects that have come before it.
􀂃 Water quality: Compliance with the City’s
storm water standards constitutes the
threshold for water quality impacts.
According to the guidelines, “[ a] dherence to
the City’s Stormwater Standards is
considered to preclude water quality
impacts unless a fair argument is made that
a significant impact will still occur.” The
storm water standards are derived from
requirements in the 2001 permit issued to
the City by the San Diego Regional Water
Quality Control Board under the National
Pollutant Discharge Elimination System.
The permit requires the implementation of
control measures to reduce to the maximum
extent practicable storm water pollutants
discharged from a project site, both during
construction and use of a project.
II. THRESHOLDS FOR ISSUE- SPECIFIC, NON-TRANSPORTATION
IMPACTS
􀁰 Bay Area Air Quality Management
District ( BAAQMD)
Information obtained from “ BAAQMD CEQA
Guidelines: Assessing the Air Quality Impacts of
Projects and Plans” ( December 1999) and from
Henry Hilken, principal co‐ author of the guidelines
and now planning director at the BAAQMD.
The BAAQMD has thresholds of significance
for several air quality impacts which it
recommends be used by public agencies within
its jurisdiction when determining significance.
The BAAQMD’s thresholds are particularly
instructive because, even though they fall
under a single environmental impact area ( air
quality), the agency used a wide range of
approaches for establishing them. The
thresholds for operational air emissions and
toxic air contaminants, for example, were based
on existing BAAQMD regulations and policies;
the thresholds for local carbon monoxide
concentrations and accidental releases of
acutely hazardous materials were based on the
existing standards and guidelines of state
agencies; and the thresholds for construction
emissions and local plan impacts were based
on project design and incorporation of
mitigation measures. This variety of
approaches should be of interest to the SFCTA
as it considers alternatives for the threshold to
replace automobile LOS.
Below is a list of the BAAQMD’s thresholds
and the basis or rationale for each one.
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 16
􀂃 Construction emissions: The determination of
significance should be based on the
implementation of control measures, rather
than on the quantification of emissions.
This reflects the BAAQMD’s experience that
there are feasible control measures that can
greatly reduce the air quality emissions
from construction activities. Such emissions
would be considered significant if not all of
the control measures that the BAAQMD has
identified for projects based on the size of
their construction site will be implemented.
( Exceptions would be made if a measure is
shown to be unnecessary or infeasible.)
􀂃 Airborne asbestos fibers: The demolition or
removal of asbestos‐ containing building
materials in the Bay Area is subject to the
BAAQMD’s Regulation 11, Rule 2,
“ Asbestos Demolition, Renovation and
Manufacturing.” Any subject activity that
does not comply with the requirements
under that regulation would be considered
to have a significant impact.
􀂃 Local carbon monoxide ( CO) concentrations:
Projects would be considered to have a
significant impact if they contribute to CO
concentrations exceeding nine parts per
million ( ppm) averaged over eight hours or
20 ppm for one hour. Those figures are the
“ state ambient air quality standards” for
CO, adopted by the California Air
Resources Board.
􀂃 Operational emissions: The thresholds for
total emissions from project operations of
reactive organic gases ( ROG), nitrogen
oxides ( NOx) and PM10 are 15 tons/ year and
80 lb/ day. For ROG and NOx, those
thresholds are equivalent to the BAAQMD’s
offset requirement threshold for stationary
sources under its Regulation 2‐ 2‐ 302, and
for PM10, they are based on the BAAQMD’s
definition of a major modification to a major
facility, per Regulation 2‐ 2‐ 221.
􀂃 Odors: Any project with the potential to
frequently expose members of the public to
objectionable odors would be deemed to
have a significant impact. This
determination should be based on the
distance between a proposed project and an
odor source or between a proposed odor
source and sensitive receptors; and on the
number of odor‐ related complaints lodged
with the district for existing odor sources or
for facilities similar to proposed odor
sources. The specific distances and
numbers of complaints cited in the
threshold were ultimately based on the
judgment of planning staff at the BAAQMD,
in consultation with permitting and
enforcement staff.
􀂃 Toxic air contaminants ( TAC’s): The
thresholds for TAC’s are, ( i) a probability of
contracting cancer for the “ maximally
exposed individual” ( MEI) that exceeds 10
per million; and, ( ii) ground‐ level
concentrations of non‐ carcinogenic TAC’s
would result in a hazard index greater than
one for the MEI. These thresholds are
derived directly from the BAAQMD’s risk
management policy.
􀂃 Accidental releases of acutely hazardous
materials ( AHM’s): At a minimum, a project
would be found to have a significant impact
if it results in receptors being within
exposure level 2 of the “ emergency response
planning guidelines” ( ERPG) for a facility.
The source is the “ State of California
Guidance for the Preparation of a Risk
Management and Prevention Program”
( California Office of Emergency Services,
November 1989), which defines ERPG
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 17
exposure level 2 as the “ maximum airborne
concentration below which it is believed
that nearly all individuals could be exposed
for up to one hour without experiencing or
developing irreversible or other serious
health effects or symptoms which could
impair an individual’s ability to take
protective action.”
􀂃 Cumulative impacts: The determination of
significant cumulative impact should be
based on a multi‐ step evaluation, using
several criteria, of the consistency of the
project with the local general plan and of the
local general plan with the Bay Area’s most
recently adopted “ clean air plan.” The
evaluation process is elaborate, so we do not
provide details of it here; however, a flow
chart of the process is included in the
BAAQMD’s guidelines.
􀂃 Local plan impacts associated with odors and
toxics: For local plans to have a less‐ than‐significant
impact with respect to potential
odors or TAC’s, buffer zones should be
established around existing and proposed
land uses that would emit these air
pollutants. Such buffer zones should be
reflected in local plan policies, land use
maps and implementing ordinances.
􀁱 South Coast Air Quality Management
District ( SCAQMD)
Information obtained from “ Final Localized
Significance Threshold Methodology” report ( June
2003) and from James Koizumi, air quality
specialist at SCAQMD and co‐ author of the report.
Like the BAAQMD, SCAQMD has long‐established
recommended thresholds of
significance, both quantitative as well as some
qualitative, for common air quality impacts.
The BAAQMD’s and SCAQMD’s thresholds,
and the rationale used to establish them, are
similar. To avoid redundancy with the
previous section, here we examine only
SCAQMD’s recently adopted thresholds for
localized air quality impacts ( an impact for
which the BAAQMD has not developed
thresholds).
Assessing localized air quality impacts requires
complex analysis. To assist public agencies
that do not have the resources for such
analysis, SCAQMD developed simple
“ localized significance thresholds” ( LST’s) for
three pollutants— NOx, CO and PM10— based
on the amount of daily emissions of these
pollutants that would be generated by
construction and operational activities from
proposed projects. The LST’s were derived
using an air quality dispersion model to back‐calculate
the emissions per day that would:
􀂃 for CO and NO2 ( which converts gradually
from NOx): cause, or contribute to, a
violation of the state or federal ambient air
quality standard;
􀂃 for PM10 from construction activities: exceed
a concentration equivalent to the control
requirement in SCAQMD’s Rule 403
(“ Fugitive Dust”); and
􀂃 for PM10 from operational activities: worsen
an existing PM10 violation, using the
allowable change in concentration
thresholds under SCAQMD’s Rule 1303
(“ New Source Review— Requirements”).
Allowable amounts of emissions can be
estimated by using look‐ up tables developed
by SCAQMD for each of the three pollutants.
( The amounts are given as a function of several
variables.) The detailed methodology used to
develop the tables is presented in SCAQMD’s
“ Final Localized Significance Threshold
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 18
Methodology” report. It is worth noting that
this report was characterized by SCAQMD as
providing the “ substantial evidence relative to
the methodology for developing LST’s.”
􀁲 County of Santa Barbara
Information obtained from John Day, environmental
planner at the County’s Planning and Development
Department and manager of the oil spill thresholds
update project, and from written staff reports on the
project.
In 2002, Santa Barbara County received grant
funding from the state and federal
governments to update their thresholds of
significance for impacts associated with the
risk of onshore and offshore oil spills from
facilities and activities related to oil and gas
development. Spill‐ related thresholds have
been prepared for four environmental impact
areas: biological resources, water quality,
recreation, and tourism.
The thresholds are not cited here as they are
not yet available for public review.
Nonetheless, we use this project as a case study
because it is useful to consider the thorough
methodology that has been used by the County
to establish the thresholds. As part of this
project, County planners have examined local,
state and federal legislation and policies related
to coastal development and protection;
reviewed environmental impact reviews and
statements ( EIR’s and EIS’s) for past practices
in evaluating significance for oil spill impacts;
analyzed oil spill statistics; investigated the
effectiveness of responses to spills and of
cleanups; and synthesized current knowledge
about the impacts of spills and substantiated
the local resources at risk.
The updated thresholds take into account not
only the size, volume and probability of spills
but also their location and projected trajectory,
and any potential impediments— such as
inclement weather— to timely response. The
thresholds have been developed with the input
of state and federal agencies concerned with
coastal resources, and incorporate both
qualitative and quantitative factors, including
consideration of the National Oceanic and
Atmospheric Administration’s “ environmental
sensitivity index” and the use of spill trajectory
analysis.
It is unrealistic to expect public agencies that
do not have the benefit of grant funding for
establishing thresholds of significance to
replicate the level of effort devoted by the
County of Santa Barbara. Nevertheless, the
County’s experience might serve as a “ best
practice” for other public agencies when
developing substantial evidence for the
establishment of thresholds.
􀁳 City and County of San Francisco
Information obtained from Bill Wycko, planner at
the San Francisco Planning Department, and from
project EIR’s.
The City and County of San Francisco uses
thresholds of significance for all major impact
areas. The thresholds in use are those that
have gained acceptance over years of practice
by staff at the City’s planning department;
however, the thresholds have not been adopted
by the City and County’s Planning
Commission or Board of Supervisors.
The majority of the City’s thresholds are
relatively minor adaptations of the Appendix G
checklist questions and, as such, are not of
particular interest to this study. Below we
discuss three thresholds that have been
developed using other approaches. ( The City’s
treatment of parking deficits as social impacts
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 19
is another interesting deviation; that issue is
discussed in detail in the last section of this
memorandum.)
􀂃 Shadow: The Appendix G checklist does not
include shadow impacts and few other
jurisdictions, if any, have established
thresholds for this impact area. The City
would consider a project to have a
significant effect if it violated Section 295 of
the San Francisco Planning Code. Section
295 generally prohibits new buildings that
would cause significant new shadow on
open space under the jurisdiction of the
Recreation and Park Commission between
one hour after sunrise and one hour before
sunset, at any time of the year ( suggesting a
qualitative threshold).
􀂃 Wind: Similarly to the above, the Appendix
G checklist does not cover wind impacts
and few other jurisdictions, if any, have
established thresholds under this impact
area. A project would have a potentially
significant wind impact if it resulted in
construction of a building whose exposure,
orientation or massing would cause
violations of the wind hazard criterion of 26
mph for a single hour of the year as
established in Section 148 of the Planning
Code. ( Such analysis is conducted by wind
modeling. It is not clear, however, how the
City determined that 26 mph was the
threshold of significance.) A project that
would cause violations of the comfort
criteria ( also as established in the Planning
Code) but not the wind hazard criterion,
would not be considered to have a
significant impact.
􀂃 Intersection LOS: A project would be
considered to have an impact on the
operation of signalized intersections if it
caused intersection LOS to degrade to, or
within, LOS E– F. ( The threshold for
unsignalized intersections uses a similar
standard.) The rationale for this threshold is
similar to that used by San Jose for its
equivalent threshold and is explained in
detail under the following case study.
III. THRESHOLDS FOR TRANSPORTATION
IMPACTS
􀁴 City of San Jose
Information obtained from Akoni Danielsen,
environmental review manager at the San Jose
Department of Planning, Building and Code
Enforcement, and from written staff reports on the
topic.
We have chosen the City of San Jose’s
intersection LOS thresholds as a case study
both because they are highly representative of
such thresholds and because of the innovative
way in which they are applied to what the City
calls “ protected intersections.” ( Protected
intersections are those located, ( i) within the
downtown core area, as defined by the general
plan; and, ( ii) along transit‐ oriented
development corridors, transit station areas,
planned communities and neighborhood
business districts, all as identified in the
general plan.)
The City’s intersection LOS thresholds are: ( i)
degradation of a signalized intersection below
LOS D; and, ( ii) an increase of 1% or more to
the traffic volume at an intersection already
operating at LOS E or F. Intersection LOS
standards have, over time, been refined into
average seconds of delay or vehicle/ capacity
ratios. Fundamentally, however, LOS
standards measure an intersection’s
throughput capacity. Specifically, LOS D, E
and F represent intersections operating near, at
or over capacity, respectively. At LOS E, when
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 20
an intersection nears its capacity, queues begin
to form and do not to dissipate during peak
hours. At that point, many drivers choose to
arrive at the intersection earlier or later than at
the peak or to choose another route. This
results in “ spreading” of the peak or diversion
to other streets.
Most cities have selected either LOS C or D as
the lowest generally acceptable service level at
intersections, with levels below that being
considered unacceptable. The City of San
Jose’s policy, as set out in its general plan, is a
minimum LOS D for signalized intersections,
in order to avoid the undesirable effects of
traffic spreading and diversion. Regarding the
second threshold, there is little uniformity
among jurisdictions in the increase in
automobile traffic, average delay or
vehicle/ capacity ratio that constitutes an
unacceptable level. San Jose’s standard of 1%
increase in traffic reflects the City’s attitude
that when an intersection is already operating
at an unacceptable LOS ( that is, LOS E or F),
even the smallest practicable increase in delay
is unacceptable.
Proposed projects that cause the City’s
intersection LOS thresholds to be exceeded are
required to implement all improvements
identified as necessary to mitigate the LOS
impacts. ( The City makes an exception for
improvements that would have “ an
unacceptable impact on other transportation
facilities.”) Protected intersections, on the
other hand, are subject to different
requirements, explained below. Such
intersections are treated differently because,
according to the City,
To continue to expand local intersections in
order to increase their vehicular capacity may,
under certain circumstances, result in a
deterioration of the local environmental
conditions near those intersections, and an
erosion of the City’s ability to both encourage
infill in designated Special Strategy Areas, and
to support a variety of multi- modal
transportation systems.
The City of San Jose has identified certain local
intersections [ that have been built to their
planned maximum capacity and] for which no
further physical improvement is planned.
These specific intersections, because of the
presence of substantial transit improvements,
adjacent private development, or a
combination of both circumstances, cannot be
modified to accommodate additional traffic and
operate at LOS D or better.
Proposed projects causing a significant LOS
impact at a protected intersection are required
to implement improvements not to the
impacted intersection but to other parts of the
City’s transportation system. Highest priority
is given to improvements for neighborhoods
impacted by the project traffic, followed by
areas in the vicinity of the project site.
It is important to note that the City does not
consider such improvements to be mitigation
measures for the purposes of CEQA, since they
would not reduce or avoid the significance of
the impact to intersection LOS. An LOS impact
to a protected intersection would still be
considered a significant impact under CEQA.
However, the sponsor of a project whose only
significant impact was to the LOS of a
protected intersection would not be required to
prepare an EIR for the project. Instead, the
environmental review for the project would be
able to “ tier” off the EIR that was certified by
the City when it created its list of protected
intersections. ( That EIR acknowledged that
traffic at protected intersections will eventually
exceed the City’s LOS standard. In certifying
the EIR, the San Jose City council adopted a
statement of overriding consideration for LOS
impacts to those intersections.) Lastly, if the
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 21
project sponsor chooses not to implement the
other transportation improvements or not to
downsize the project sufficiently, the project
would be found to have a significant
unavoidable impact under CEQA.
􀁵 City of Palo Alto
Information obtained from Gail Likens, interim
transportation manager, and from written staff
reports on the topic.
We have chosen Palo Alto as an additional case
study because the City has proposed
thresholds in two innovative transportation
impact areas: traffic intrusion on residential
streets and cycling LOS. Below is a discussion
of these two thresholds.
􀂃 Traffic intrusion: The threshold for this
impact would be an increase in vehicles per
day ( vpd) of 25 percent or more on a
residential local, collector or arterial street.
An increase of up to 150 vpd would be
acceptable regardless of the percentage
increase or street type; and no increase
would be allowed on a local street beyond a
total volume of 2500 vpd.
The threshold is based on staff’s experience
using the TIRE ( Traffic Infusion on
Residential Environments) Index, which is a
quantitative representation of people’s
perception of traffic increases on a
residential street. ( The index has been used
for many years by the City for
transportation analysis purposes.) The
threshold is also based on additional staff
research into the “ environmental capacity”
of residential streets. A loosely used
definition of environmental capacity is the
maximum daily traffic volume at which
residential activities become difficult or
unpleasant, and safety hazards can be
expected.
The threshold’s 25 percent level for traffic
increases corresponds to a 0.1 increase in the
TIRE Index. According to the research
behind the index, the 0.1 figure is the point
at which changes in traffic volume start to
be noticeable to residents. An increase of
150 vpd was deemed to be acceptable as it
represents— under staff’s interpretation of
the research behind the TIRE Index— a
change that is not noticeable under any
practical circumstance. An increase of that
magnitude would be lost in the random
daily fluctuations in traffic volume
measurements even on minor streets.
Lastly, the ceiling of 2500 vpd is the
maximum acceptable volume on a local
residential street as defined by Palo Alto’s
neighborhood traffic calming program. The
traffic calming program adopted that
standard as a reasonable compromise—
given Palo Alto’s existing traffic volumes—
between the needs of the traffic calming
program and the desires of people living on
residential streets. According to the City, a
lower ceiling for local residential streets
would make it more difficult to implement
traffic calming measures on adjacent streets
since the calming measures would divert
traffic to side streets.
􀂃 Cycling LOS: The threshold being considered
for this impact is degradation of conditions
for bicyclists below a cycling LOS C on
certain types of streets. City staff have
evaluated alternative cycling LOS
methodologies and settled on the Bicycle
Compatibility Index ( BCI). The BCI,
developed for the U. S. Federal Highway
Administration, is considered the most
comprehensive and best‐ validated analysis
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 22
of cycling LOS determinants on urban and
suburban streets. Unlike auto LOS
standards, the BCI emphasizes qualitative
criteria such as cyclist comfort, convenience
and freedom to maneuver.
The BCI scores cycling LOS on a six‐ level
scale, ranging from A to F. The threshold of
LOS C has been chosen by City staff as the
level that, in the judgment of planning and
transportation staff, best corresponds to
declared City policy on the maintenance of
bicycling routes. The threshold would
apply only to those street types that carry
the bulk of bicycle traffic in the City, namely
local, collector and residential arterial
streets, and school commute corridors.
CONCLUSIONS
As mentioned previously, the second main
objective of this task was to present to the
SFCTA a series of case studies that illustrate
the range of approaches used by public
agencies in California to establish thresholds of
significance for a variety of impact areas. The
case studies discussed above cover a range of
agencies, environmental impact areas and,
most importantly, approaches to the
development of thresholds.
The approaches used vary across several
dimensions. Some agencies established
thresholds for a comprehensive suite of impact
areas while others established them for a
limited number of impacts. Some agencies
appear to have devoted a not insignificant
amount of resources to develop thresholds
customized to their own needs while others
adopted generic thresholds derived from the
Appendix G checklist questions.
The methods used to arrive at specific
thresholds vary greatly. Common sources of
inspiration for thresholds include: CEQA law;
other environmental statutes; the state’s CEQA
guidelines ( especially the questions from the
Appendix G checklist); an agency’s own
policies; standards adopted by regulatory
agencies; commonly accepted professional
standards; academic research; the professional
judgment and experience of agency staff; and
past practice.
Correspondingly, the format of thresholds also
varies widely. Some thresholds are simple
numerical standards while others are elaborate
qualitative descriptions. The City of Los
Angeles’ case‐ by‐ case “ thresholds” are, in
effect, guidelines. The City of San Diego’s
noise thresholds are contained in a matrix
while its air quality thresholds lie along a
continuum. The BAAQMD’s thresholds for
construction emissions are a menu of
mitigation measures; its thresholds for asbestos
fibers require compliance with a set of
regulations; and its thresholds for cumulative
impacts incorporate a flowchart. Along with
the wide range in thresholds’ technical and
policy bases, this diversity in formats should be
a source of ideas for the SFCTA and the
consultant team during Task 3 of this study.
In addition, the case studies discussed above
raise several issues worth pointing out with
regard to the City’s efforts to develop a
replacement threshold for auto LOS. First, the
Authority’s Technical Working Group on LOS
considered the possibility of adopting mode‐specific
LOS thresholds ( as documented in the
LOS Methodologies SAR). The TWG
concluded that using LOS thresholds for
specific modes such as transit, biking and
walking could improve the evaluation of
impacts to those modes. However, it also
concluded that mode‐ specific LOS thresholds
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 23
would not resolve the unintended negative
consequences of auto LOS ( which are outlined
at the very beginning of this memorandum)
and, therefore, that developing an alternative
to auto LOS should be the main priority.
Another issue is that because of San Francisco’s
urban density and its resulting transportation
environment, the City’s LOS standards are
already lower ( that is, at a poorer grade) than
those in use by many other cities and counties.
In areas where LOS is already very poor ( or
“ low”), LOS becomes less useful as a measure
of transportation impact. Shifting towards an
incremental, relative measure of transportation
impact, such as ATG, becomes a more useful
way of understanding transportation impacts
in dense, congested cities such as San
Francisco.
Finally, these case studies suggest two
potential ATG thresholds that may be
considered in the next phase of this study. The
first is inspired by San Jose’s approach of a 1%
increase in vehicle trips per unit time at LOS E
and F intersections ( or potentially applied to all
intersections). The second alternative
threshold suggested by the case studies is
inspired by Palo Alto, and is defined as a 25%
increase in vehicles per day per unit time, with
both a minimum and a maximum allowable
increase ( 150 vehicles per day and 2500
vehicles per day, respectively). These
approaches might be considered for further
evaluation, along with other alternative
approaches to setting an ATG threshold.
III. Considerations in
discontinuing and replacing
the automobile LOS
threshold
The first section of this memorandum provided
general guidance to the SFCTA on developing
a replacement threshold of significance. This
section discusses potential consequences or
considerations involved with discontinuing
and replacing the threshold for automobile
LOS at intersections.
Appendix G of the state’s CEQA guidelines
provides a checklist, in the form of questions,
of potential environmental impacts that public
agencies should consider when reviewing
projects under CEQA. Regarding the checklist,
the form states that “ lead agencies are free to
use different formats; however, lead agencies
should normally address the questions from
this checklist that are relevant to a project’s
environmental effects in whatever format is
selected.”
Two of the questions on the checklist—
specifically the first and second questions
under Section XV (“ Transportation/ Traffic”)—
concern automobile traffic congestion. These
questions would seem to indicate that the City
must continue to consider the impacts of all
proposed projects on traffic congestion,
whether this is done with the assistance of
thresholds of significance or on a case‐ by‐ case
basis. The questions ask whether the proposed
project would:
􀂃 Cause an increase in traffic which is substantial
in relation to the existing traffic load and
capacity of the street system ( i. e., result in a
substantial increase in either the number of
vehicle trips, the volume to capacity ratio on
roads, or congestion at intersections)?
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 24
􀂃 Exceed, either individually or cumulatively, a
level of service standard established by the
county congestion management agency for
designated roads or highways?
While the City might be required to analyze
transportation impacts under CEQA, there is
no regulation or guideline that requires that
such analysis be based on LOS standards.
However, if the City discontinued its LOS
threshold, it might leave itself open to
challenges that it fails to analyze transportation
impacts adequately. A challenging party could
use LOS measurements as substantial evidence
that a project might have a significant
environmental impact. That argument would
be supported by the fact that LOS‐ based
analysis is longstanding practice under CEQA
and is indirectly suggested by the state’s
guidelines.
On the other hand, CEQA gives public
agencies certain latitude in establishing their
own procedures for the evaluation of
environmental impacts ( as evidenced partly by
the use of the word “ normally” in the
directions for the use of the Appendix G
checklist). San Francisco’s own CEQA
practices, discussed below, are as good an
illustration as any of the flexibility granted
public agencies, and might offer a way for the
City to discontinue the use of its auto LOS
threshold in a way that overcomes challenges
that congestion is an environmental impact.
SAN FRANCISCO’S TREATMENT OF PARKING
DEFICITS UNDER CEQA
The sixth question under Section XV of the
Appendix G checklist asks whether the
proposed project would “[ r] esult in inadequate
parking capacity?” Despite this, it has been
long‐ standing practice by the San Francisco
Planning Department to approach parking
deficits as social rather than physical or
environmental impacts and, therefore, to not
consider them as potentially significant
impacts under CEQA. ( Section 15131 of the
state’s CEQA guidelines states that
“[ e] conomic or social effects of a project shall
not be treated as significant effects on the
environment.”)
The Department’s rationale has been that,
because parking conditions are dynamic—
changing from hour to hour— parking supply
is not part of the permanent physical
environment. The Department argues that
parking conditions change over time as people
change their modes and patterns of travel:
In the experience of San Francisco
transportation planners…, the absence of a
ready supply of parking spaces, combined with
available alternatives to auto travel… and a
relatively dense pattern of urban development,
induces many drivers to seek and find
alternative parking facilities, shift to other
modes of travel, or change their overall travel
habits. Any such resulting shifts to transit
service in particular would be in keeping with
the city’s “ Transit First” policy.
The Department’s rationale was upheld by a
court of appeals in a 2002 case concerning the
redevelopment of the former Emporium store
in downtown ( San Franciscans Upholding the
Downtown Plan v. City and County of San
Francisco). The court agreed closely with the
Department’s argument that parking deficits
have social consequences ( that is, they are
inconvenient or frustrating) but do not
constitute an environmental impact. Implicitly,
the court found that the City’s arguments were
supported by substantial evidence.
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 25
EXTENDING THE RATIONALE ON PARKING
DEFICITS TO TRAFFIC CONGESTION
It appears to us that the Department’s
reasoning concerning parking deficits applies
equally to traffic congestion. Extensive
research internationally over the past two
decades has shown that traffic congestion is, to
a large extent, a self‐ correcting problem since it
motivates drivers to change travel habits. San
Francisco’s own experience with the removal of
the Embarcadero and Central freeways are but
two local manifestations of this phenomenon.
As mentioned earlier, any system of thresholds
that ignores supportable environmental
impacts could be vulnerable to legal challenge.
Therefore, discontinuing the City’s auto LOS
threshold will require a determination by the
City that auto LOS does not measure an
environmental impact under CEQA. The San
Franciscans Upholding the Downtown Plan case is
an example of how an impact that has been
typically thought of as falling under the
umbrella of CEQA can be reinterpreted.
Consequently, it might be possible for the
Planning Department to discontinue and
replace the automobile LOS threshold while
protecting itself against legal challenges by
extending its treatment of parking deficits
under CEQA to traffic congestion. While such
a policy would be inconsistent with the
Department’s past CEQA practice on
congestion, it would be supported by the
recent research suggesting that drivers’
behavior— and, consequently, the volume of
traffic— adjusts to traffic conditions. Also, as
with modal shifts induced by parking deficits,
modal shifts induced by traffic congestion
would be supportive of the city’s “ Transit
First” policy.
The SFCTA’s main objective in replacing the
City’s LOS threshold is to prevent the
unintended negative consequences that LOS‐based
analysis has on the City’s ability to
implement the Transit First policy and thus, the
environment. One possibility for meeting that
objective would be to design a threshold that—
similarly to the BAAQMD’s threshold for
construction emissions discussed above— is
based not on the measurement of LOS but
rather on the implementation of measures or
projects that support the City’s Transit First
policy. This option would be defensible on the
grounds that transit‐ supportive projects reduce
automobile traffic volumes in the medium and
long terms.
A second, related option would be to continue
to define transportation impacts in a way that
includes congestion, as measured by LOS
impacts, while employing mitigated negative
declarations for projects that degrade
automobile LOS so long as those projects
support the Transit First policy. This option
would recognize that transit‐ supportive
projects are in themselves mitigation for traffic
impacts, at least in the medium and long terms.
Finally, a third option is to adopt an ATG
threshold to replace auto LOS, and incorporate
explicit reasoning into the new threshold that
auto congestion is a social and not an
environmental phenomenon in a dense,
multimodal, urban context such as San
Francisco’s, and that the number of auto trips
generated is a superior measure of
transportation impact in such a context.
INDIRECT PHYSICAL CHANGES CAUSED BY
SOCIAL EFFECTS
As mentioned earlier, CEQA does not treat
social effects as potentially significant effects
on the environment. It does, however, require
public agencies to address the secondary, or
indirect, physical impacts which might be
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 26
triggered by a social impact [ Section 15131( a) of
the CEQA guidelines]. In terms of parking
deficits, as explained by the Planning
Department, this means that having drivers
look for scarce parking spaces is in itself not an
environmental impact but could result in
physical impacts such as air or noise pollution
that would need to be considered under
CEQA. To address the indirect physical
impacts of parking deficits, the Department
generally assumes that the amount of project‐related
driving caused by people searching for
parking is offset by the number of people who
are discouraged from driving once they
become aware of constrained parking
conditions in a given area. Arguments similar
to the above could be made, again, regarding
traffic congestion.
It is worth pointing out that efforts to preserve
automobile LOS are sometimes based on the
idea that idling vehicles at intersections can
create high localized concentrations, or
“ hotspots,” of carbon monoxide ( CO).
However, this justification has lost much of its
validity over the past decade as improvements
in automotive engines, combined with the
introduction of reformulated fuel, have greatly
reduced CO emissions. BAAQMD records
dating back to 1993 show zero exceedances of
both the one‐ and eight‐ hour state and federal
CO standards at the district’s regional network
of air‐ quality monitoring stations. In addition,
based partly on their review of environmental
review documents from around the region,
BAAQMD staff believe that CO hotspots are a
rarity at other locations in the Bay Area.
In any event, automobile LOS thresholds are
not an appropriate way to address issues
related to air quality. Any outstanding
concerns over air quality impacts are best
addressed using the BAAQMD’s
recommended thresholds of significance. ( The
BAAQMD’s CEQA guidelines do contain a
screening criterion for CO hotspots based on
deficient automobile LOS at intersections.
However, this is not a threshold signaling
significance but simply a screening tool
indicating situations for which localized CO
concentrations should be estimated. Besides,
given the increasing rarity of CO hotspots in
the Bay Area since the BAAQMD’s guidelines
were first developed, that screening criterion
has become an outmoded tool.)
It should be mentioned that the BAAQMD has
become concerned more recently with localized
concentrations of diesel emissions. Because
this is a recent concern, however, the agency
has not yet developed recommended
thresholds of significance for that impact.
BAAQMD staff has indicated that the
geographic scope of such an impact would
likely be limited to areas of very heavy truck
traffic such as in and near ports and on and
along certain freeway segments.
CONCLUSIONS
The City and County of San Francisco
pioneered the treatment of parking deficits as
social effects, an approach that has been upheld
by a court of law. The City might have the
opportunity to be a pioneer again by extending
its rationale on parking deficits to traffic
congestion. The issue is not straightforward,
however, and deserves more extensive
consideration than has been possible under the
scope of this task. Specifically, given the
frequent contentiousness of decisions taken by
public agencies under CEQA, we suggest that
the SFCTA seek the opinion of the Office of the
San Francisco City Attorney on this issue.
On a related note, we also suggest that the
SFCTA seek the advice of the City Attorney’s
Ms. Rachel Hiatt January 10, 2007
San Francisco County Transportation Authority Page 27
Office during Task 3 of this study, when the
consultant team will be developing specific
alternatives for a replacement threshold of
significance. This is important because the
threshold that is ultimately selected will need
to be legally defensible. Attorneys’ advice will
also need to be sought during Task 5, when we
will formulate a strategy for the City for the
adoption and implementation of the
replacement threshold.