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GHG Impacts Analysis

The California Global Warming Solutions Act of 2006 (Assembly Bill 32) requires the California Air Resources Board (CARB) to facilitate substantial greenhouse gas (GHG) emissions reductions, both from within the State and from imported electric power generated in other states. The goal of AB 32 is to reduce statewide GHG emissions to 1990 levels by 2020. This will be achieved by cutting about 30% from “business as usual” emission levels projected for 2020. In 2007, the state legislature passed Senate Bill 97, which required amendments to the California Environmental Quality Act (CEQA) Guidelines to incorporate analysis of and mitigation for GHG emissions from projects subject to CEQA.

The CEQA Guidelines do not contain statewide quantitative thresholds of significance for GHG impacts; establishing numeric thresholds has been delegated to each of California’s 35 air districts. However, in lieu of meeting a quantitative threshold, the Guidelines state that a project may be found to have a less than significant impact on climate change if it complies with an adopted plan – typically at the County or District level – that includes specific measures to limit future GHG emissions to substantially less than business as usual.

Most California air districts have adopted some form of GHG mass emissions threshold expressed in the international units of metric tons per year of carbon dioxide equivalents (MT/yr CO2e). These thresholds can vary from district to district and can comprise different thresholds for permitted stationary/industrial sources versus land use projects such as housing developments, office buildings, and shopping centers. Instead of stack emissions, land use projects generate direct and indirect GHG emissions, mainly via motor vehicle traffic and utilities consumption. This latter category is the focus of most CEQA GHG impact assessments conducted for the private sector.

Many California cities and counties have updated general plan conservation elements or have developed “climate action plans” to include goals and policies designed to address air pollution and GHGs. Typical goals and policies apply to land use projects – not stationary sources – and tend to focus on sustainability topics, including improvements to the transportation system, reducing long-distance commuting, encouraging and supporting non-auto transportation, and reducing future land use conflicts related to air pollution. While many goals and policies are geared toward criteria pollutants, such as ozone and particulate matter, implementation of such goals and policies also benefits efforts to reduce GHG emissions.

While required in CEQA analyses, the content and complexity of GHG evaluations are evolving continuously through agency actions and CEQA practice precedents. Yorke Engineering, LLC keeps abreast of current requirements in the major California air districts in order to conduct GHG impact analyses that are approvable by Lead Agencies consistent with AB 32 and SB 97. Pursuant to the current Guidelines, both direct and indirect project-related GHG emissions impacts must be estimated for short-term construction and long-term operation for a CEQA analysis to be approved.

  • For estimating the direct construction impacts of any project, Yorke uses the California Emissions Estimator Model™ (CalEEMod), a public domain software developed by the California Air Pollution Control Officers Association (CAPCOA) in collaboration with the 35 California air districts. Construction emissions can be based on either “default” criteria contained in CalEEMod or user-defined values that characterize and quantify construction activities, equipment specifications, and planned schedules.
  • CalEEMod is also used for estimating direct and indirect operational impacts of land use projects, including project-induced traffic, maintenance activities, consumer products usage, off-site electric power generation, water delivery, and waste disposal. Optional GHG mitigation measures include enhanced energy efficiency, water conservation, waste reduction/recycling, and carbon sequestration.
  • To ensure consistency and accuracy for stationary source projects that will require Air District permits, Yorke calculates direct GHG emissions in an integrated manner along with criteria pollutants and toxic air contaminants (TACs). For stationary sources, GHGs are emitted mainly from fossil fuel combustion in boilers, heaters, gas turbines, and internal combustion engines. Other types of sources include oil and gas production and refining facilities, electric power transmission equipment, small leaks from natural gas pipelines, municipal landfills, composting operations, and fermentation.

GHGs are also covered in the emissions calculations and the Air Quality Technical Report for CEQA.

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31726 Rancho Viejo Rd. Suite 218
San Juan Capistrano, CA 92675

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