What CalEEMod is and how to read its report
The California Emissions Estimator Model, CalEEMod, is the statewide land use emissions model, and the guidance of each of the five largest districts names it for CEQA construction and operational emissions. It takes a description of a development project, its land uses, construction schedule, equipment, trips, and utilities, and produces criteria pollutant emissions in pounds per day and tons per year and greenhouse gas emissions in metric tons of CO2 equivalent. The consultant's model run is the evidence behind every number in an air quality technical report, and the report is only as good as the inputs and the reading of the output.
Versions
| Version | Status | Note |
|---|---|---|
| 2022.1 (2022.1.1 and later) | Current | Web-based. The Bay Area's Appendix D is written to 2022.1 and its screenshots to 2022.1.1.0. Detailed Report is the standard export. |
| 2020.4.0 | Superseded | Still appears in existing-use baseline runs and older appendices filed alongside 2022 runs. |
| 2016.3.2 | Superseded | The version behind San Joaquin Valley's 2020 Small Project Analysis Levels. |
A report whose proposed project and existing-use baseline were run in different versions is comparing two emission factor sets. Districts ask for the current version; a run in an older version needs a stated reason.
What goes in
CalEEMod fills every field with a default from the project's location, size, and land use type, and the Bay Area's guidance says plainly that defaults should be replaced whenever project-specific information exists. Every changed default must carry a note in the Justification for Changes box, and the model will not advance without one. Reviewers read those notes first.
- Land uses. Type, subtype, size and unit (dwelling units, thousand square feet, acres, rooms), lot acreage, building square footage, landscape area, population. Mixed use projects list each use.
- Construction. Phases (demolition, site preparation, grading, trenching, paving, building construction, architectural coating), each with start and end dates, days per week (default five), and the off-road equipment list with horsepower, load factor, hours per day, and engine tier. Trips for workers, vendors, and haul trucks. Demolition tonnage and soil import and export volumes. Days per week changes the working days, and working days are what the Bay Area divides by.
- Operations. Vehicle trips from the traffic study or model defaults, trip lengths, fleet mix, energy use, water and wastewater, solid waste, and area sources such as hearths and landscaping. Equipment that needs a district permit, such as standby generators, boilers, and fire pumps, is not run in CalEEMod in the Bay Area; its emissions are calculated by the district's permit method and added to the project total.
- Measures. Construction dust controls and operational reductions. In the Bay Area the required twice-daily watering is entered in the construction module, so it is inside the unmitigated results; additional controls go in the measures module and appear as the mitigated run. Which side of that line a measure sits on decides whether a table row is labeled unmitigated or mitigated.
What comes out
The Detailed Report is what districts ask consultants to attach. It prints every input, every default that was changed with its justification, and emissions in three time bases for each construction year and for operations:
- Maximum daily, summer and winter. The highest single day. South Coast compares this.
- Average daily. Annual tons converted to a daily rate by the model's own divisor. The Bay Area's construction value is not this row: the guidance computes it from the annual row and that year's working days, so the report must show the divisor it used. Operational average daily is annual tons over 365 for uses that operate most days, and over the actual operating days for a school, arena, or other intermittent use.
- Annual. Tons per year of criteria pollutants and metric tons CO2e of greenhouse gases. San Joaquin Valley compares this; the Bay Area uses it for the operational annual test and Sacramento for its PM tons per year values in both phases.
Criteria pollutants are printed as ROG, NOx, CO, SO2, PM10 exhaust, PM10 fugitive dust, PM10 total, and the same for PM2.5. GHGs are printed by gas and as CO2e, by source (mobile, area, energy, water, waste, refrigerants, stationary) for operations and by year for construction. The construction section prints CO2e by calendar year without a total across years; reports sum the years themselves.
Where reports go wrong
- Comparing the wrong time basis. Reading maximum daily against an average daily threshold, or the model's own average daily row against the Bay Area's working-day rate. The threshold's basis is on the district page; the report must say which row it used.
- Mixed versions. A baseline in 2020.4.0 and a project in 2022.1, then netting one against the other.
- Operational year drift. The model run assumes one first year of operation, the project description another. Emission factors fall every year, so the year matters.
- Project changes after the run. Parking counts, floor areas, and site acreage revised at approval without a rerun; the report then analyzes a project that no longer exists.
- Carrying the wrong total. A baseline or existing-use total printed as the project's operational total, or the net figure presented without the gross.
- Unstated overrides. Equipment tiers, trip lengths, or fleet mix changed from default without the justification note, so the reviewer cannot tell a real project fact from an assumption.
- Permitted equipment. A generator or boiler calculated by the permit method and then left out of the project total, or counted both there and in the model's stationary source module.
- Watering counted twice. Twice-daily watering already in the unmitigated Bay Area run, then claimed again as mitigation.
Where CalEEMod is published
California Air Pollution Control Officers Association, California Emissions Estimator Model, current version 2022.1, with its User's Guide and appendices; hosted by the South Coast Air Quality Management District. Bay Area Air Quality Management District, 2022 CEQA Air Quality Guidelines, Appendix D, Using CalEEMod for Bay Area Projects. San Joaquin Valley APCD, Small Project Analysis Levels, November 13, 2020.