Emissions Calculations
Yorke CEQA evaluates emissions from construction and operations—including criteria pollutants, toxic air contaminants (TACs), and greenhouse gases (GHGs)—to determine potential impacts on air quality and climate. Our CEQA-focused approach goes beyond permitting, covering direct, indirect, and construction-related sources.
Emissions Calculations
Yorke CEQA evaluates emissions from construction and operations—including criteria pollutants, toxic air contaminants (TACs), and greenhouse gases (GHGs)—to determine potential impacts on air quality and climate. Our CEQA-focused approach goes beyond permitting, covering direct, indirect, and construction-related sources.
Emissions Calculations for CEQA Projects
Construction Emissions
Yorke staff perform construction emissions analyses using the California Emissions Estimator Model® (CalEEMod®®), the official statewide land use computer model designed to provide a uniform platform for estimating potential criteria pollutant and GHG emissions associated with both construction and operation of land use projects under CEQA.
CalEEMod®® was developed by the California Air Pollution Control Officers Association (CAPCOA) in collaboration with the 35 California air districts, which provided default data to account for local requirements and conditions.
CalEEMod®® quantifies mobile source emissions from on-road vehicles and off-road construction equipment by incorporating the California Air Resources Board (CARB) EMission FACtors (EMFAC) and OFFROAD models, respectively.
On-road vehicles are characterized using project-specific information or default data for emission factors, trip frequencies and lengths, meteorology, vehicle fleet mix (type and age), and the Pavley and Low Carbon Fuel standards. Off-road (non-road) equipment is characterized by type, age, horsepower rating, daily running hours, and average load factor.
In addition to engine exhaust, CalEEMod®® estimates fugitive dust generated by earthmoving activities and road traffic for both paved and unpaved surfaces using methodologies developed by the Environmental Protection Agency (EPA). The model also contains mitigation measures to reduce fugitive dust, criteria pollutant, and GHG emissions, along with calculating the benefits achieved from the selected measures.
Operational Emissions
Yorke staff calculate operational emissions from common stationary sources, such as boilers, heaters, gas turbines, firewater pumps, and emergency generators, using source-specific emission factors published by the EPA, CARB, or local air districts. Alternatively, rule-based emissions standards or manufacturer data are used to derive emission factors for particular equipment. Emissions of criteria air pollutants, TACs, and GHGs can be calculated with a high degree of confidence using emission factors.
For non-standard stationary sources where emission factors are not available, mass emissions are estimated using appropriate emission estimation techniques such as source tests, material balance, or engineering calculations.
Yorke staff can also estimate direct operational emissions from mobile sources (on-road vehicles and non-road equipment, as described above) and area sources (natural gas combustion, painting, consumer products, and landscape maintenance) using CalEEMod®. Furthermore, the model can be used to estimate indirect emissions, such as GHG impacts from energy use (electric power generation), solid waste disposal (collection and landfilling), vegetation planting and/or removal (sequestration), and water use (pumping energy and wastewater treatment). Plus, the model identifies mitigation measures to reduce criteria pollutant and GHG emissions, along with calculating the benefits achieved from the selected measures.
Relation to Health Risk Assessment
For projects where CalEEMod® is used to estimate construction emissions, off-road engine exhaust PM10 is usually treated as diesel particulate matter (DPM) for on-site risk assessment purposes, particularly for the site preparation and grading phases, which involve the use of heavy earthmoving equipment in a defined area relative to receptors. DPM is a composite TAC as defined by the California Office of Environmental Health Hazard Assessment (OEHHA), comprising several organic and inorganic contaminants expressed as a single value.
Operational stationary source emissions may include diesel-powered emergency generators and firewater pumps required for safety, or gas-fired commercial/industrial utility boilers. As applicable, TAC emissions from stationary equipment are quantified using source-specific emission factors and operating data. Emissions from emergency engines are estimated based on tier rating, nameplate horsepower, and annual operating hours allowed under the statewide Airborne Toxic Control Measures (ATCM) regulation and other operational restrictions, such as proposed permit conditions.
I Have a Project. Let’s Get Started!