Anchorage CO Maintenance Plan (SIP) Revisions Presentation to the AMATS Air Quality Advisory Committee February 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 NAAQS11/01/07 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 compliance2/19/08 Status report to AMATS TAC2/28/08 Status report to AMATS Policy Committee3/13/08 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 revisions4/11/08 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 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 Used recommended models from EPA or FAA to estimate CO emission rates –Motor vehicles MOBILE6 –Aircraft EDMS –NonroadNONROAD –Area sourcesAP-42 –Point sourceADEC 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

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

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.

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

Projected CO Emissions Turnagain Area ( )

Estimate Probability of Compliance with CO Air Quality Standard

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 2 nd highest 8-hour concentration measured each year Second maximum 8-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

90th Percentile Prediction Interval Computed from Turnagain 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 % % % % % % % % % % % % % % % % %

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 % increase between 2007 and 2023 Fireplace and Woodstove Use No change in wood burning rates per household between % growth in wood heating per year

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” analysis % %98.7% %99.1% %97.8% %94.7% %95.3% %95.8% %96.2% %96.5% %96.8% %97.1% %97.5% %97.7% %97.8% %98.0% %98.0% %98.1% Even using “worst case” assumptions in sensitivity analysis, the probability of complying with the CO standard is well above 90% every year.