This page answers some common questions asked by planners and consultants on assessment of air quality impacts of land-use projects. If you have additional questions you would like to see posted here, please e-mail

What land uses require APCD permits?

Any stationary sources (e.g., businesses, utilities, government agencies, and universities) need an APCD permit before constructing, changing, replacing, or operating any equipment or process that may cause air pollution. This includes equipment designed to reduce air pollution. Permits are also required if an existing business that causes air pollution transfers ownership, relocates, or otherwise changes its operations. In these cases, the APCD is a responsible agency under CEQA and the APCD permit cannot be issued until the lead agency (usually a City or the County) has approved the project.

Examples of land uses that need APCD permits are oil and gas facilities, gas stations, dry cleaners, auto body shops, refinishing operations, printing facilities, large wineries, and operators of certain gas engines or diesel-powered engines over 50 bhp. A more detailed list is provided in the Engineering Division’s description of The APCD Permit Process.

What standards are in non-attainment currently?

Santa Barbara County was designated unclassifiable/attainment for the 2008 federal 8-hour ozone standard on April 30, 2012. (The 1-hour federal ozone standard was revoked for Santa Barbara County). The California 8-hour ozone standard was implemented in May, 2006. The County violates the state 8-hour ozone standard and the state standard for PM10. The County is unclassifiable/attainment for the federal PM2.5 standard and unclassified for the state PM2.5 standard (based on monitored data from 2007 – 2009). For more information, see this page.

What are the APCD’s thresholds of significance for environmental review?

Thresholds of significance are intended to supplement provisions in the state CEQA guidelines for determining significant effects. Thresholds of significance provide general guidance for determining significant impacts, but are not ironclad definitions of significant impacts. Each project must be judged individually for its potential for significant impacts based on specific circumstances and evidence. When the APCD is lead agency under CEQA, the air quality thresholds of significance are described in the APCD Environmental Review Guidelines adopted by the APCD Board of Directors in October 1995. Lead agencies may use these or more stringent thresholds to determine the significance of air quality impacts in their jurisdictions. The following are the APCD’s thresholds of significance:

A proposed project will not have a significant air quality effect on the environment if the project will:

  • emit (from all project sources, both stationary and mobile) less than the daily trigger for offsets or Air Quality Impact Analysis set in the APCD New Source Review Rule, for any pollutant ( i.e., 240 pounds/day for ROC or NOx; and 80 lbs/day for PM10. There is no daily operational threshold for CO ; it is an attainment pollutant) ; and
  • emit less than 25 pounds per day of NOx or ROC from motor vehicle trips only; and
  • not cause or contribute to a violation of any California or National Ambient Air Quality Standard (except ozone); and
  • not exceed the APCD health risk public notification thresholds adopted by the APCD Board (10 excess cancer cases in a million for cancer risk and a Hazard Index of more than one, or 1.0, for non-cancer risk ; and
  • be consistent with the latest adopted federal and state air quality plans for Santa Barbara County.

A proposed stationary source project will not have a significant GHG impact if operation of the project will:

  • emit less than the screening significance level of 10,000 metric tons per year (MT/yr) CO2e, or
  • show compliance with an approved GHG emission reduction plan or GHG mitigation program which avoids or substantially reduces GHG emissions (sources subject to the AB 32 Cap-and-Trade requirements pursuant to Title 17, Article 5 (California Cap on Greenhouse Gas Emissions and Market-based Compliance Mechanisms) would meet the criteria), or
  • show consistency with the AB 32 Scoping Plan GHG emission reduction goals by reducing project emissions 15.3 percent below Business As Usual (BAU).

Cumulative impacts and consistency with the policies and measures in the Air Quality Supplement of the County’s Comprehensive Plan (for projects located in the unincorporated areas of the County), general plans, and the current air quality plans, should be discussed for all projects (i.e., whether the project exceeds the growth assumptions in the air quality plan). Quantitative thresholds of significance are not currently in place for short-term (construction) emissions.

What analysis/thresholds are appropriate for short-term construction emissions for large-scale grading operations?

The APCD has no adopted short-term thresholds in place. For fugitive dust associated with construction, the APCD’s standard dust control measures must be applied to all projects. The County’s adopted thresholds state that all construction equipment exhaust emissions of NOx and ROG are insignificant. However, if the grading and construction emissions are associated with a stationary source for which an APCD permit is required, then APCD Rules and Regulations will apply.

The APCD uses 25 tons per year of ROC or NOx as a general rule of thumb for determining significance of construction exhaust emissions. Also, because diesel particulate matter is the number one airborne carcinogen in the State, if the activity involves the use of diesel powered equipment within a quarter-mile of a sensitive receptor such as a school, residence, daycare or eldercare facility, the APCD may consider the impact significant.

How do the APCD’s quantitative emission thresholds of significance differ from other agencies’ thresholds?

The APCD does not regulate land use projects. Air quality impacts for land use projects should be evaluated using the thresholds of significance adopted or used by the jurisdiction in which the project is located. Santa Barbara County’s adopted thresholds of significance may be found here.

Both the APCD and the County use the same thresholds for motor vehicle-related, long-term emissions (25 pounds per day of ROC or NOx ). The difference lies in the significance threshold for total project emissions because the types of projects considered by the APCD as the lead agency differ from the land-use projects. The County Board of Supervisors also considers construction equipment emissions to be insignificant (as adopted in the County Environmental Thresholds and Guidelines Manual in April 1994) while the APCD Board deferred the adoption construction thresholds.

How are a project’s motor vehicle emissions estimated?

The APCD recommends the use of CalEEMod, a computer program approved for use in California. The program uses trip generation rates published in the Institute of Transportation Engineers 8th edition manual for common land uses; the Air Resources Board EMFAC2011 emission factors for on-road emissions and OFFROAD 2011 for off road equipment emissions. Project-specific trip-generation rates, if available, must be substituted. For more details see APCD’s Scope and Content of Air Quality Sections in Environmental Documents.

What mitigation measures does the APCD recommend when a project’s motor vehicle related emissions exceed the threshold of significance?

In general, the APCD emphasizes sustainable development projects that incorporate land-use designs and ways to get people out of their cars and encourage them to carpool, walk, bicycle, or use public transit. The CalEEMod program includes a quantifiable mitigation component based on Sustainable Development principles. In addition, the APCD may recommend project-specific educational or public outreach measures to encourage people to use alternative transportation modes. For more details see APCD’s Scope and Content of Air Quality Sections in Environmental Documents.

Information on sustainable land use principles may be found at a number of web sites including:

See also Building Stronger Communities, and Chapter 9 of the 2001 Clean Air Plan on this website.