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

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.