EPA Comments on Utah's "Particulate Matter (PM) Exhaust Emissions Reductions from

Diesel Inspection and Maintenance 

### (liM) Programs in Utah (Davis, Salt Lake and Utah Counties)," January 20, 2005 1. General Comments In order for Utah to claim 2% PM10 emission reduction credit for their diesel I/M program, the technicaljustification must meet the requirements ofEPA's memorandum entitled, "Guidance on Incorporating Voluntary Mobile Source Emission Reduction Programs [(VMEP)] in State Implementation Plans (SIPs)," dated October 24, 1997

. This policy requires the state to submit a SIP which 1) identifies and describes a VMEP; 2) contains projections ofemission reductions attributable to the program, along with relevant technical support documentation; 3) commits to monitor, evaluate, and report the resulting emissions effect ofthe voluntary measure; and 4) commits to remedy in a timely manner any SIP credit shortfall ifthe VMEP program does not achieve projected emission reductions. In addition, as part ofthe SIP submittal, Utah must commit to monitor, evaluate, and report the resulting emissions effect ofthe voluntary measure. Ifthere is an emissions reduction shortfall, Utah must pursue appropriate follow-up, or
"backstop", actions in a timely fashion including, but not limited to: adjusting the voluntary measure, adopting a new measure, or revising the VMEP emission credits to reflect actual emission reductions. Under the VMEP policy, the total amount ofemissions reductions from voluntary measures shall not exceed 3% ofthe emissions determined necessary to demonstrate progress toward, attainment of, or, maintenance ofthe relevant National AmbientAir Quality Standards (NAAQS). Utah must committo conducting program evaluations within an appropriate timeframe and report the resulting information to EPA within an appropriate time-frame in order to document whether the program is being carried out, and emission reductions are being achieved

. The SIP submittal must contain a good faith estimate ofemission reductions, including technical support documentation for the conclusion that the measure will produce the anticipated emission reductions. The SIP must describe how the state plans to evaluate program implementation and report on program results in terms ofactual emission reductions. The procedures designed should compare projected emission reductions with actual emission reduction achieved

. Finally, Utahmust provide timely post-evaluation reports to EPA. UDAQ used EPA's PARTS emissions model to develop their mobile source inventories. We recommend using our more recent vehicle emissions model, MOBILE6.2, officially released on May 19,2004 (69 FR 28830). MOBILE6.2 is a significant improvement to its predecessor, PARTS. Please note though, MOBILE6.2 does not include degrading (increasing) levels of emissions for heavy-duty diesel vehicles

. That is, a vehicle is estimated to have the same emissions when it is brand new as it does when it is 1S years old. The goal ofany liM program is aimed at limiting the increased vehicle emissions over time by assessing the emissions and taking corrective actions to reduce them. This means, UDAQ and every other state are already getting a diesel I/M emission credit because engine degradation (over time) is not included in mobilesource inventories that are estimated with the MOBILE6.2 model. UDAQ's report references the "Heavy-Duty Vehicle Inspection and Maintenance Final Report," Radian Corporation, May 1988. Further review will be needed to determine ifthe correlation established between opacity and particulate emissions, used in this report, is va}id and can be used by UDAQ

. We ask the state to perform a current literature search to determine if more recent studies, other than those cited by EPA, relating opacity and particulate emissions are available. As with any innovative approach, we strongly suggest using the latest, most defensible data possible. For example, has Radian's position changed or do they still support their 1988 findings? EPA has cited more recent and possibly more reliable studies that find opacity is not a good predictor ofPM emissions

. In addition, it appears that the dTEMLs from the 1988 Radian study, are hard to identify in your report and may be mislabeled Please review this issue and also provide us with a copy ofthe full study from whichUDAQ obtained its methodology and multipliers

. The program evaluation section needs to analyze not only PM10 emission reductions, but any incidental increases in other pollutants, such as NOx(which is a secondary component of PM10). Opacity based liM programs seek to reduce the visible smoke exiting vehicle exhausts. Adjustments or repairs are then made to reduce the visible smoke. We are concerned with decreasing opacity leading to an increase in NOx. Utah currently acknowledges, in their approved PM10 SIP, that NOxis transformed into or is a precursor to PM

. Any decreased PM from a diesel I/M program should consider the offsetting impact ofincrease in PM precursors of NOx . We note that this tradeoffis not considered in Utah's draft report and must be included. UDAQ's report applies to repaired vehicles only, or only failed vehicles. UDAQ will need to apply the findings ofthis report to the entire fleet ofdiesel vehicles, both light-duty and heavy-duty. We also suggest verifying the failure rates and repair rates used in the report
. 2. Specific Comments 2.1 Program Description: 1s t and 3rd bullets contradict one another, with the 1s tbullet stating that all vehicles are tested annually, but the 3rd bullet states that vehicles less than six years old are tested biennially

. Does the biennial test apply to all counties,and notjustUtah County? Should the last bullet include Salt Lake County? Please clarify that the OBD tests are only for 1996 and newer model year vehicles. Are the counties running OBD-only or are they performing opacity tests on vehicles with the MIL on? Calculation 2: Please verify the values for" % targeted" and "a" as 100%

. The vehicle inspection is biennial for the first 6 years and the test is valid for 2 years ifthe vehicle passes. Should the 100% values be re-determined to reflect this? Also, please explain the value for "b" as 1 00%

. Does this mean all ofthe diesel vehicles fail the inspection and need repairs? Tables 1 and 2: Inventory Change in Salt Lake County, UT and Inventory Change in Utah County, UT: The values for the Heavy-Duty Control Factor appear to be incorrect. For Salt Lake County,we calculated them to be: 84

.66 for 1968- 1984, 86.87 for 1985-1987, and 297.18 for 1988-2002. For Utah County, we calculated them to be 82.43 for 1968- 1984, 81.52 for 1985- 1987, and 95.65 for 1988-2002. Would there be a significant impact to these values ifUDAQ used more recent data from 2003 and 2004? We need an explanation for the paragraph under Table 1 as we cannot understand this. Does the Heavy-Duty Control Factor apply to the heavy-duty vehicles only? Are the values for the number ofvehicles tested, and the number of vehicles failed for heavy-duty vehicles only? Should UDAQ subtract out the light-duty portion? Please provide a sample calculation for 0.612 tons-per-day (tpd) PM and 0.634 tpd PM for Salt Lake County and 0.220 tpd PM and 0.236 tpd PM for Utah County

. Appendix: We ask UDAQ to clarify ifthe calculation for the weighted average should be the weighted average ofthe failed vehicles or all vehicles? Also, the sentence which states "The diesel inventory is both heavy-duty diesel vehicle and light-duty diesel vehicle emissions so the reduction must be calculated for the whole diesel inventory" is worded awkwardly and needs to be clarified

. Finally, we are having difficulty understanding the calculation as presented Further clarification is necessary.

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