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Anchorage CO Maintenance Plan
(SIP) RevisionsPresentation to the
AMATS Air Quality Advisory CommitteeFebruary 19, 2008
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.
Anchorage CO Maintenance Plan / SIP
Development Schedule
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
Steps in preparation of a revised CO Maintenance Plan (SIP)1. Prepare new CO emission inventory and
emission projections thru 20232. Estimate probability of continued compliance with
CO air quality standards given expected changes in emission rates
3. Decide which CO control measures should be included in the plan.
4. Identify contingency measures should a violation of the air quality standard occur
5. Prepare a “CO emission budget” for determining conformity between future transportation plans and air quality goals outlined in the SIP
Anchorage CO Emission Inventory
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
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.
Assume that I/M will end December 2009
CO Emission Inventory for Anchorage
Bowl
motor vehicles66.5%
natural gas heating3.8%
aircraft13.0%
point sources1.3%
miscellaneous9.0%
fireplaces & woodstoves
6.2%
rail & marine0.2%
Estimated Anchorage Bowl CO Emissions in 2007
Total CO Emissions = 100.7 tpd
Projected Area-wide CO Emissions in Anchorage (2007-2023)
0.0
20.0
40.0
60.0
80.0
100.0
120.0
2007 2009 2011 2013 2015 2017 2019 2021 2023
CO
Em
issi
on
s (t
on
s p
er d
ay)
other (nonroad, rail, marine)
point sources
space heating
fireplaces and woodstoves
aircraft
motor vehicles
CO emission inventory for the area surrounding the Turnagain monitoring Station.
The Turnagain station measures the highest CO concentrations in Anchorage
CO emissions in the Turnagain area are among the highest in the bowl.
motor vehicles 73%
fireplaces and wood stoves
10%
miscellaneous 12%
Space heating – natural gas
5%
CO emissions in Turnagain area = 5.99 tpd
Estimated CO Emissions in Turnagain Area (2007)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
2007 2009 2011 2013 2015 2017 2019 2021 2023
CO
em
issi
on
s (t
on
s p
er d
ay)
miscellaneous
natural gas heating
fireplaces & wood stoves
motor vehicles
Projected CO Emissions Turnagain Area (2007-2023)
Estimate Probability of Compliance with CO Air Quality Standard
2007-2023
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
Compliance is determined by the magnitude of the 2nd highest
8-hour concentration measured each year
Second maximum8-hour average concentration < 9 ppm
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
yp = yh + t(; n-2) . s{pred}
90th Percentile Prediction Interval Computed fromTurnagain 2nd Maximum
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.
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 98.8%
2013 5.62 99.1%
2014 5.54 99.1%
2015 5.45 99.2%
2016 5.38 99.2%
2017 5.30 99.3%
2018 5.21 99.4%
2019 5.11 99.4%
2020 5.05 99.5%
2021 4.98 99.5%
2022 4.93 99.6%
2023 4.89 99.6%
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 ?
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 2007-2023
2% growth in wood heating per year
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
2007 2009 2011 2013 2015 2017 2019 2021 2023
CO
em
iss
ion
s (
tpd
)
extra emissions due to increased wood heating
extra emissions from growth in vehicle travel
extra emissions assumed from termination of I/M
original CO emission projection
"extra" emissions assumed in sensitivity analysis
In this sensitivity analysis, by 2023, assumed CO emissions are 23% higher than the original projections
Comparison of Sensitivity Analysis Assumptions with Original Emission Projections
Original emission projections “Worst Case” analysis2007 98.1% 98.1%2008 98.8% 98.7%2009 99.2% 99.1%2010 99.0% 97.8%2011 98.4% 94.7%2012 98.8% 95.3%2013 99.1% 95.8%2014 99.1% 96.2%2015 99.2% 96.5%2016 99.2% 96.8%2017 99.3% 97.1%2018 99.4% 97.5%2019 99.4% 97.7%2020 99.5% 97.8%2021 99.5% 98.0%2022 99.6% 98.0%2023 99.6% 98.1%
Even using “worst case” assumptions in sensitivity analysis, the probability of complying with the CO standard is well above 90% every year.