Section 309 Mobile Source Significance Test Modeling Results WRAP Regional Modeling Center (RMC) University of California at Riverside, CE-CERT ENVIRON International Corporation for Conference Call with WRAP Mobile Source Forum October 18,

Section 309 SIP Modeling Elements Demonstrate that the SO 2 Annex Milestone strategy is “better than” Command and Controls with Uncertainty in 2018 Show visibility progress from 1996 to 2018 Evaluate the “significance” of Mobile Sources and Road Dust on visibility – Topic of today’s conference call 2

Mobile Source Significance Test Metric (Draft Memo from Mobile Source Forum, 06/10/02) Change in extinction due to Mobile Sources over the EPA Natural Conditions (Worst 20% Days) – Based on 10/09/02 IOC meeting, added looking at impacts over the 2018 WRAP Projected Base Case Conditions (Worst 20% Days) Applied to 13 urban areas and California to estimate “significance” at 16 Class I Areas on Colorado Plateau No On-Road and Off-Road Mobile Source Emissions (“Zero-Out”) modeling priorities: – 9 Grand Canyon (GC) States (Cumulative) – California – Phoenix, Arizona (Maricopa County) – Las Vegas, Nevada (Clark County) 3

Estimate 2018 Visibility using Model Scaling of 1996 Observations Scale observed 1996 concentrations using Relative Reduction Factors (RRFs) that are ratios of 2018 to 1996 modeling results Separate for each Class I Area Separate for each species (SO 4, NO 3, OC, EC, Soil, and CM) Calculate based on the mean of the Worst 20% observed visibility days during 1996 – e.g., SO = SO4 Obs_1996 x (SO4 Model _2018 /SO4 Model_1996 ) 4

Mobile Source Significance Test -- Accounting for Missing Fugitive Dust Emissions No Wind Blown Dust in emissions inventory Model results for Fine Soil and Coarse Matter (CM) are missing major sources Cannot use relative changes in modeling results for Soil and CM Set RRF(Soil) = RRF(CM) = 1.0 – i.e., 2018 CM&Soil = 1996 CM&Soil Not a big issue for Mobile Source Significance Test as Mobile Source Soil and CM are fairly small 5

Summary of 2018 Anthropogenic Emissions in 9 Grand Canyon (GC) States (No Biogenic, Geogenic, Fire, or Wind Blown Dust Emissions) 6

Comments on Emissions in 9 GC States 47% NO X due to Mobile Sources – (64% Off-Road vs. 36% On-Road) 21% SO 2 due to Mobile Sources – Almost all (97%) due to Off-Road Sources – Off-Road gas engines use low sulfur gasoline – Off-Road Rules for some Off-Road equipment expected before 2018 that would significantly reduce diesel sulfur content (~4000 ppm to 15 ppm) Mobile PM 2.5 is 12% of total but consists of EC & OC with high light extinction efficiencies New soon to be released EPA NONROAD model results in substantial reductions in emissions 7

Mobile Source Draft Significance Thresholds (Draft Memo from Mobile Source Forum, 06/10/02) Draft Cumulative Approach due to Mobile Sources in 9 GC States – If 5% shall be used – If >= 10%, then individual area significant thresholds of > 1% shall be used Excludes area if it is in lowest 20% of contributions to the cumulative impact Draft Individual Area Approach Significance – Approach#1: > 10% – Approach#2: > 1% 8

Cumulative Mobile Source Significance Test 9 GC States, EPA Natural Conditions, & 2018 WRAP Base Case 9

Individual Area Mobile Significance Test EPA Natural Conditions (Worst 20% Days) 10

Individual Area Mobile Significance Test 2018 WRAP Base Case Visibility for Worst 20% Days 11

Details Mobile Source Significance Test 9 GC States, Phoenix, and Las Vegas (EPA Natural Conditions) 12

Estimate On-Road & Off-Road Contributions 9 GC States for Petrified Forest, Capitol Reef, and Grand Canyon 13

Comments on Mobile Significance Calculations Effects of High Sulfur Diesel in Off-Road – If eliminate SO 2 effects, Mobile Source significance reduced but still > 10%/1% Effects of New NONROAD Model – Substantially lower, no numbers available If Applied Sig Test to On-Road Mobile Only – Estimate a factor of 3-5 reduction (20% in examples) – WRAP July Workshop presented On-Road Mobile Significance Test for entire domain (WUSA) of 3-8 percent 14

Postprocessing of Modeling Results If perform either a 9 GC States On-Road only or Off-Road only run then obtain separate Mobile Source contributions and can postprocess modeling results to estimate effects of: – Use of lower sulfur diesel in off-road engines – Effects of EPA’s new NONROAD model – Effects of potential new off-road engine standards/fuels 15

Road Dust Significance Results Road Dust mainly in Soil and CM components so cannot use scaled modeling results – Currently Road Dust is 20% of PM 10 emissions in 9 GC States (w/o wind blown dust) Use Absolute Modeling Results Results presented at Denver 07/10/02 WRAP Workshop No Road Dust in the Entire Domain – Will be conservative (overestimate) of Road Dust emission impacts for 9 GC States Cumulative impact from 0.80% to 3.13% 16

Road Dust Emissions Significance Test Using W20 Absolute Model Results (No RRFs) 17