1. Anchorage CO Maintenance Plan (SIP) Revisions
Presentation to the AMATS Air Quality Advisory Committee
February 19, 2008

2. Anchorage Assembly voted discontinue I/M on or before December 31, 2009
Current SIP commits to continued operation of the I/M Program.
Before I/M can be lawfully discontinued, SIP must be revised to show that Anchorage will continue to comply with CO air quality standards without I/M.
EPA must approve changes to SIP.

3. Anchorage CO Maintenance Plan / SIP
Development Schedule

4. Begin preparation of CO emission inventory and analysis of probability of compliance with NAAQS
11/01/07
Complete preliminary review with EPA and ADEC of CO inventory and analysis of probability of compliance.
2/15/08
Meet with AMATS Air Quality Advisory Committee to review and discuss CO emission inventory and analysis of probability of compliance
2/19/08
Status report to AMATS TAC
2/28/08
Status report to AMATS Policy Committee
3/13/08
Meet with AMATS Air Quality Advisory Committee to present staff recommendations on CO control measures in Plan. Which primary and contingency measures should be included in the Plan?
3/17/08
Staff completes draft CO Maintenance Plan / SIP revisions
4/11/08
Meet with AMATS Air Quality Advisory Committee to review draft CO SIP/Maintenance Plan and prepare final recommendations for consideration by AMATS TAC and Policy Committees.
4/21/08
AMATS TAC meets to review draft CO SIP/Maintenance Plan and prepare recommendations for consideration by Policy Committee.
4/24/08
AMATS Policy Committee considers approval of CO SIP/Maintenance Plan. (If approved, Plan is forwarded to Anchorage Assembly.)
5/08/08

5. Steps in preparation of a revised CO Maintenance Plan (SIP)
Prepare new CO emission inventory and emission projections thru 2023
Estimate probability of continued compliance with CO air quality standards given expected changes in emission rates
Decide which CO control measures should be included in the plan.
Identify contingency measures should a violation of the air quality standard occur
Prepare a “CO emission budget” for determining conformity between future transportation plans and air quality goals outlined in the SIP 

6. Anchorage CO Emission Inventory

7. CO emission inventory and emission projections 2007-2023
Used recommended models from EPA or FAA to estimate CO emission rates
Motor vehicles MOBILE6
Aircraft EDMS
Nonroad NONROAD
Area sources AP-42
Point source ADEC permit info

8. Current and future CO emission estimates were based in part on:
Transportation model projections of vehicle travel activity (miles traveled per day, number of starts)
Current aircraft operations based on counts, future growth based on Airport Master Plan projections
Fireplace and wood stove use estimated with telephone survey data.
ISER forecasts of growth in population, households, and employment were used to help predict CO emissions through 2023.

9. Assume that I/M will end December 2009

10. CO Emission Inventory for Anchorage Bowl

11. Estimated Anchorage Bowl CO Emissions in 2007
Total CO Emissions = tpd

13. CO emission inventory for the area surrounding the Turnagain monitoring Station.

14. The Turnagain station measures the highest CO concentrations in Anchorage

15. CO emissions in the Turnagain area are among the highest in the bowl.

16. Estimated CO Emissions in Turnagain Area (2007)
CO emissions in Turnagain area = 5.99 tpd

17. Projected CO Emissions Turnagain Area (2007-2023)

18. Estimate Probability of Compliance with CO Air Quality Standard 2007-2023

19. The EPA has recommended using a probabilistic approach to assessing long term compliance with the federal CO standard.
Need 90% or greater probability of compliance
Use statistical techniques (linear regression and prediction interval) to analyze monitoring data and compute probability of compliance
Project probability of compliance in future years based on projected CO emission trend

20. Second maximum 8-hour average concentration < 9 ppm
Compliance is determined by the magnitude of the 2nd highest 8-hour concentration measured each year
Second maximum
8-hour average concentration < 9 ppm

21. Prediction Interval - In regression analysis, a range of values that estimate the value of the dependent variable for given values of one or more independent variables.
                                                     
where
                                                                                         
This is a one-sided prediction interval because we are interested only in the upper range of values for the dependent variable

22. 90th Percentile Prediction Interval Computed from
Turnagain 2nd Maximum

23. The probability of complying with the standard at 2007 emission levels is estimated to be 98.1%.
The probability of complying with the standard in a future year can be estimated based on whether emissions are projected to increase or decrease relative to 2007.

24. TOTAL CO EMISSIONS (tpd) Probability of Compliance
Year 
TOTAL CO EMISSIONS (tpd)
Probability of Compliance
2007
5.99
98.1%
2008
5.72
98.8%
2009
5.45
99.2%
2010
5.66
99.0%
2011
5.86
98.4%
2012
5.74
2013
5.62
99.1%
2014
5.54
2015
2016
5.38
2017
5.30
99.3%
2018
5.21
99.4%
2019
5.11
2020
5.05
99.5%
2021
4.98
2022
4.93
99.6%
2023
4.89

25. What if we have underestimated the impact of discontinuing I/M
What if we have underestimated the impact of discontinuing I/M? What if vehicle travel and wood heating grow faster than anticipated?
How sensitive are our projected probabilities of compliance to changes in initial assumptions about future CO emissions ?

26. Comparison of Original Assumptions used in Maintenance Demonstration with those used in Sensitivity Analysis
Original Assumptions used in Maintenance Demonstration and Probability Computations
Revised “Worst Case” Assumptions Used in Sensitivity Analysis
Discontinuation of I/M
Motor vehicle emissions increase by roughly 20%
Motor vehicle emissions increase by roughly 40%
Growth in VMT and Vehicle Starts and Idling
4% increase between 2007 and 2023
12% increase between 2007 and 2023
Fireplace and Woodstove Use
No change in wood burning rates per household between
2% growth in wood heating per year

27. Comparison of Sensitivity Analysis Assumptions with Original Emission Projections
In this sensitivity analysis, by 2023, assumed CO emissions are 23% higher than the original projections

28. Original emission projections
Even using “worst case” assumptions in sensitivity analysis, the probability of complying with the CO standard is well above 90% every year.
Original emission projections
“Worst Case” analysis
2007
98.1%
2008
98.8%
98.7%
2009
99.2%
99.1%
2010
99.0%
97.8%
2011
98.4%
94.7%
2012
95.3%
2013
95.8%
2014
96.2%
2015
96.5%
2016
96.8%
2017
99.3%
97.1%
2018
99.4%
97.5%
2019
97.7%
2020
99.5%
2021
98.0%
2022
99.6%
2023