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Page 42 Contributions to GHGs from on-road vehicles (commuting construction workers, dump trucks, semi-trucks) were based on estimated vehicle year, fuel usage, and miles traveled. Average mile per gallon values were selected based off the EPA’s Center for Climate Leadership, Simplified GHG Emission Calculator (from the U.S. Department of Transportation, Federal Highway Administration, Highway Statistics 2022) (46) for gasoline-powered passenger vehicles and diesel-powered dump/semi-trucks (47). Emission factors for gasoline-powered passenger vehicles were based on rates from 2012, as the average age of light vehicles in the U.S. reached 12.2 years as of a May 2022 Business Wire report (48) (49). The U.S. EPA’s Emission Factors for GHG inventories (Tables 2, 3, and 4; last modified June 5 th, 2024) was used to calculate emissions from ‘mobile sources’ during the construction phase (50) (Table 27). Table 27. Construction Emissions - On-Road Vehicles Vehicle Vehicle/ Day1 Days Miles/ Day Miles Miles/ Gal.2 Est. Gal Emission Factor3 CO2 CH4 N2O Passenger Cars 30 150 50 225,000 24.8 9,072 8.78 kg CO2/gal 0.0071 g CH4/ vehicle-mile 0.0046 g N2O/ vehicle-mile Dump Trucks 9 50 67,500 7.9 8,544 10.21 kg/CO2/ gal 0.0313 g CH4/ vehicle-mile 0.0015 g N2O/ vehicle-mile Semi- Trucks 6 50 45,000 6.9 6,522 Vehicle Metric Tons CO2eq Annual Emissions CO2 CH4 N2O Passenger Cars 79.6573 0.0447 0.2743 79.96 metric tons CO2eq Dump Trucks 87.2373 0.0592 0.0268 87.32 metric tons CO2eq Semi-Trucks 66.5870 0.0394 0.0179 66.64 metric tons CO2eq Construction Phase Emissions (9 years)4 2,105.50 metric tons CO2eq Lifecycle Annualized Emissions (50 years)5 42.84 metric tons CO2eq 1 The number of vehicles onsite during the construction phase will likely vary throughout the construction season. The number of vehicles on site per day was an estimate. 2 The miles/gallon values were from the U.S. EPA Simplified GHG Emission Calculator (U.S. Department of Transportation, Federal Highway Administration, Highway Statistics 2024). 3 The U.S. EPA’s Emission Factors for GHG inventories (Tables 2, 3, and 4; last modified June 5th, 2024). 4 Annualized emissions multiplied by the construction phase. 5 Construction phase emissions divided over the lifetime of the project. Contributions to GHGs from off-road vehicles (construction equipment) were also estimated. As previously stated, the phasing will be partially market driven, and the duration of equipment usage and type are estimates. It was assumed that eight diesel-powered off-road construction vehicles (three earth movers, three excavators, and two skid steers) would be in operation during the construction phase. The default diesel fuel consumption rate of 0.05 gallons per horsepower- hour was used to determine fuel usage for all equipment. The estimated construction season of 150 10-hour days (1,500 hours total). Emission factors were based on U.S. EPA’s Emission Factors for GHG inventories (Tables 2 and 5; last modified June 5th, 2024) (50) (Table 28).