August 10, 2011 

MEMORANDUM

SUBJECT: Technical Support Document (TSD): Technical Review of 2010 and 2009 

submittals to Alaska Statewide SIP and the Anchorage Carbon Monoxide 

Maintenance Plan 

FROM: Krishna Viswanathan 

 Environmental Engineer 

 Claudia Vaupel 

 Environmental Protection Specialist 

TO: EPA Docket EPA-R10-OAR-2010-0917 

I. PURPOSE 

This TSD presents our review of the revisions to the Alaska State Carbon Monoxide (CO) State 

Implementation Plan (SIP) submitted to EPA in 2010 and 2009. It documents our conclusion that 

the 2010 revision meets the requirements of the Clean Air Act (CAA or the Act). Although we 

reviewed the 2009 submittal in support of our technical analysis, we are not taking action to 

approve its provisions because the 2010 submittal supersedes the 2009 revision. 

II. BACKGROUND 

A. Anchorage maintenance area planning history 

Anchorage, Alaska, was first declared a nonattainment area for CO and classified as moderate on 

January 27, 1978. The Municipality of Anchorage (MOA) prepared a plan to attain the CO 

National Ambient Air Quality Standard (NAAQS)1

 by December 31, 1987; however, Anchorage 

failed to achieve attainment by December 31, 1987. The CAA was amended in November 1990, 

and EPA designated Anchorage as a moderate nonattainment area for CO and required 

submission of a revised air quality plan to bring Anchorage into attainment by December 31, 

1995. EPA approved the plan in 1995, however, two violations of the NAAQS in 1996 resulted 

in EPA reclassifying Anchorage to serious nonattainment on July 13, 1998, with an attainment 

date of December 31, 2000. 

 

1 The national 8-hour CO ambient standard is attained when the highest 8-hour CO concentration of 9 parts per 

million (ppm) is exceeded no more than one time in a calendar year. EPA has proposed to retain the current standard 

of 9 ppm, based on the latest review of the CO NAAQS (76 FR 8158, February 11, 2011).
2 

The Alaska Department of Environmental conservation (ADEC or the State) submitted a new 

plan on January 4, 2002, and EPA proposed approval of the plan (67 FR 38218) on June 3, 2002. 

On September 18, 2002, EPA approved the Anchorage CO attainment plan (67 FR 58711). 

The State submitted a maintenance plan and a redesignation request for the Anchorage CO 

nonattainment area on February 18, 2004. EPA proposed approval of the Anchorage CO 

maintenance plan on May 10, 2004 (69 FR 25869) and approved the plan on June 23, 2004 (69 

FR 34935). The maintenance plan relied on control strategies needed to assure maintenance of 

the CO NAAQS. The strategy focused on the Federal Motor Vehicle Emission Control Program, 

an I/M program, expanded wintertime transit service and promotion of engine pre-heaters. 

On March 29, 2002, and December 11, 2006, the State submitted revisions to the CO SIP. The 

2002 submittal revised the statewide I/M regulations to provide for electronic vehicle inspection 

renewal and to remove the requirement for a paper certificate to be maintained in the vehicle. 

The 2006 submittal revised the statewide I/M regulations to lengthen the time period before 

which new vehicles are required to obtain their first certificate of inspection from two years to 

four years. Each of the submittals also contained minor revisions that were administrative in 

nature. On September 15, 2009, EPA proposed to approve the State’s submittals (74 FR 47154) 

and finalized the approval on April 21, 2010 (75 FR 13436). 

B. What changes to the Alaska SIP were submitted for EPA approval? 

The State has submitted two revisions to the Anchorage CO maintenance plan. The contents of 

the submittals are listed below and described in more detail with analysis in the sections of this 

TSD that follow. 

November 13, 2009 Submittal (2009 submittal): 

1) Alaska Administrative Code, Title 18, Chapter 50 Air Quality Control, and Chapter 52 

Emissions Inspection and Maintenance Requirements for Motor Vehicles, with an 

effective date of November 4, 2009. 

2) Amended sections of the State Air Quality Control Plan, adopted by reference under 18 

AAC 50.030, August 5, 2009, including: 

a. Volume II. Section II: Air Quality Control Program 

b. Volume II. Section III.A: Statewide Carbon Monoxide Control Program 

c. Volume II. Section III.B: Anchorage Transportation Control Program 

d. Volume III. Appendices to Volume II (includes 18 AAC 50 regulations, 

Anchorage emission inventory, Anchorage analysis for complying with the 

NAAQS for CO, and Anchorage I/M ordinances and code) 

The 2009 submittal contains a significant revision to the Anchorage CO maintenance plan that 

lengthens the grace period for new vehicles to obtain the first certificate of inspection from four 

years to six years and exempts certain types of vehicles from the I/M program. The 2009 
3 

submittal updates the CO contingency measures and includes an updated 2007-2023 emissions 

inventory and motor vehicle emission budget. 

September 29, 2010 Submittal (2010 submittal): 

1) Alaska Administrative Code, Title 18, Chapter 50 Air Quality Control with an effective 

date of October 29, 2010. 

2) Sections of the State Air Quality Control Plan, adopted by reference under 18 AAC 

50.030 as amended August 20, 2010, including: 

a. Volume II. Section II: Air Quality Control Program 

b. Volume II. Section III.A: Statewide Carbon Monoxide Control Program 

c. Volume II. Section III.B: Anchorage Transportation Control Program 

d. Volume III. Appendices to Volume II (includes 18 AAC 50 regulations) 

The 2010 submittal supersedes the 2009 submittal with a significant revision to the Anchorage 

CO maintenance plan that will remove the I/M program as an active control measure in the SIP 

upon final approval of this revision by EPA. The 2010 submittal updates the 2007-2023 

emissions inventory to account for the removal of the I/M program after 2011 and includes a 

revised the motor vehicle emissions budget. The submittal moves the I/M program as an active 

control measure in the SIP and shifts it to a contingency measure that can be implemented should 

a violation of the CO standard occur. The 2010 submittal also includes the contingency measures 

that were updated in the 2009 submittal. 

III. REVIEW OF SUBMITTALS 

 A. What SIP revisions is EPA reviewing in this TSD? 

This TSD evaluates the 2010 submittal. Technical information from the 2009 submittal was used 

only to substantiate the review of the 2010 submittal. 

B. Clean Air Act basis for review 

EPA proposed approval of the Anchorage CO maintenance plan on May 10, 2004 (69 FR 25869) 

and approved the plan on June 23, 2004 (69 FR 34935). The maintenance plan relies on control 

strategies needed to assure maintenance of the NAAQS for CO. As stated earlier in this 

document, one of the primary control measures is an I/M program. The I/M program may be 

revised or removed as an active control measure in the SIP, provided the State can satisfy the 

requirements of CAA section 110(l), which states: 

Each revision to an implementation plan submitted by a State under this Act shall 

be adopted by such State after reasonable notice and public hearing. The 

Administrator shall not approve a revision to a plan if the revision would interfere 

with any applicable requirement concerning attainment and reasonable further 
4 

progress (as defined in section 171), or any other applicable requirement of this 

Act. 

A demonstration is necessary to show that the State’s proposed revisions will not interfere with 

attainment or maintenance of any NAAQS, and any other applicable requirement of the Act. In 

addition, although EPA may approve removal of a control measure with such a demonstration, 

any measure that is removed from the active portion of a SIP must be retained as a contingency 

measure under section 175A(d) of the Act.2

 

C. EPA’s review of the State’s analysis demonstrating continued maintenance of the 

carbon monoxide standard 

Because the 2010 submittal supersedes the 2009 submittal, EPA’s review focuses on evaluating 

the removal of the I/M program as an active control measure in the 2010 submittal. However, we 

reviewed the maintenance demonstration in the 2009 submittal and considered it in our analysis. 

The 2009 review provided technical information that enabled comparability of the two I/M 

options, the 6 year new car exemption and removal of the I/M program. This supporting 

technical comparison provided EPA with additional confidence that the State submission was 

technically robust. 

All of the technical work contained in the State’s submittal was performed using similar 

methodology that the State used to demonstrate maintenance in the Anchorage maintenance plan 

that EPA approved in 2004. Where data was available, emissions inventory and modeling inputs 

were updated with more recent information. This is explained further in our review and analysis 

of the State’s submittal below. 

1. Emissions inventory: area-wide and Turnagain micro-inventory 

The State submitted an updated emissions inventory for the period 2007-2023. The inventory 

was prepared in accordance with EPA’s CO emissions inventory guidance.3

 The inventory 

included emissions for stationary sources, area sources, non-road mobile sources and on-road 

mobile sources on a typical 24-hour winter day. The State prepared an area-wide inventory of the 

Anchorage maintenance area and a micro-inventory of the area surrounding the Turnagain 

monitoring station in west Anchorage. The Turnagain station exhibits the highest CO 

concentrations of the current monitoring network; it has been shown to be approximately 20% 

higher than the next highest site. The Turnagain micro-inventory provides added insight into the 

sources of CO surrounding the monitor and guided the state in developing control strategies for 

the Anchorage maintenance area. The complete inventory is included in the Appendix to Section 

III.B.3 of the State’s submittal. 

Area-wide emissions inventory

 

2 See September 4, 1992 memorandum from John Calcagni to the EPA Air Division Directors (``Procedures for 

Processing Requests to Redesignate Areas to Attainment,'' Memorandum from John Calcagni, Director, Air Quality 

Management Division). 

3 Emissions Inventory Requirements for Carbon Monoxide State Implementation Plans EPA-450/4-91-011 
5 

The State projected the area-wide and Turnagain inventories from the 2007 base year inventory 

to the years 2008-2023. In the 2010 submittal, the area-wide inventory depicts elimination of the 

I/M program starting in 2011. EPA has reviewed these projections and summarized them in 

Table 1. 

Table 1. Anchorage Area Wide Projected CO Emissions: Tons per Day (tpd) 

2007 Base Year 

with I/M program 

in effect in 2007 

2023 Horizon Year 

with no I/M 

program 

Source Category CO 

Emitted 

% of 

total 

CO 

Emitted 

% of 

total 

Motor Vehicles 67.4 66.7% 55.7 57.1% 

Aircraft – Ted Stevens International and 

Merill Field Airport Operations 

13.1 12.9% 19.0 19.5% 

Woodburning-fireplaces and 

woodstoves 

6.2 6.2% 7.0 7.1% 

Space Heating-natural gas 3.8 3.7% 4.1 4.2% 

Miscellaneous-snowmobiles, snow 

removal, welding, rail, marine, etc) 

9.3 9.2% 10.2 10.4% 

Point Sources (power generators, 

sewage sludge, incineration) 

1.3 1.3% 1.4 1.4% 

Total 101 100% 97.5 100% 

Without an I/M program, total area-wide CO emissions are projected to decline by 3.5 tpd 

(3.5%) between the 2007 base year (101 tpd) and the 2023 horizon planning year (97.5 tpd). This 

is caused by a 16% reduction in on-road emissions (from 51.04 tpd to 42.85 tpd) during this 

timeframe. The primary driver of lower on-road emissions is a sustained reduction in average inuse emission rates, as newer, cleaner vehicles continue to replace older, higher emitting vehicles. 

Projections from the area-wide emissions inventory indicate that CO emissions reductions from 

2007-2023 are expected to occur in Anchorage either with or without the I/M program in place. 

If the I/M program is removed as an active control measure in the Anchorage SIP, it must be 

retained as one of the plan’s contingency measures that can be implemented should a violation of 

the CO standard occur. 

Turnagain micro-inventory

The Turnagain micro-inventory represents the area near the Turnagain monitoring station, 

located in the Spenard-area neighborhood, which the State has identified as having the highest 

CO concentrations of all the monitoring stations in Anchorage. Maximum 8-hour concentrations 

were typically 10 to 20% higher than the next highest site called Garden in east Anchorage. 

During the 1997-98 CO Saturation Study 8-hour CO concentrations at Turnagain were the 

highest among the 20 sites included in the study. The state provided support to establish that the 

probability of exceeding the national ambient air quality standard at Turnagain at current CO 

emission levels is about 1 in 100 while the probability of violating at the Garden station is less 

than 1 in 1,000. For this reason, the State prepared a micro-inventory of the area surrounding the 

Turnagain monitoring site for the maintenance demonstration. In order to perform this 
6 

demonstration, CO emissions were estimated from the 2007 base year and projected through 

2023. Table 2 shows the State’s emission inventory projections. Emissions are projected to 

decrease by about 12% in the Turnagain micro-inventory area without an I/M program. The 

micro-inventory trends are consistent with the area-wide trends. 

Table 2. Turnagain Micro-emissions inventory: Tons per Day (tpd) 

2007 Base Year 

with I/M program in 

effect in 2007 

2023 Horizon Year 

with no I/M 

Source Category CO 

Emitted 

% of total CO 

Estimated 

% of total 

Motor Vehicles 4.42 73.4% 3.59 67.8% 

Air Craft – Ted Stevens International 

and Merill Field Airport Operations 

-- --% -- --% 

Woodburning-fireplaces and 

woodstoves 

0.62 10.3% 0.67 12.6% 

Space Heating-natural gas 0.28 4.6% 0.29 5.5% 

Miscellaneous-snowmobiles, snow 

removal, welding, rail, marine, etc) 

0.70 11.7% 0.73 13.8% 

Point Sources (power generators, 

sewage sludge, incineration) 

-- -- -- -- 

Total 6.01 100% 5.29 100% 

2. Maintenance demonstration with probabilistic rollforward modeling 

Because the Turnagain monitoring site exhibits the highest CO concentrations in the monitoring 

network, the State used the micro-inventory from the Turnagain area in the maintenance 

demonstrations. After discussions with the EPA Regional Office, the State used a probabilistic 

roll-forward approach to demonstrate maintenance with the CO standard. A detailed discussion 

of this methodology and results can be found in the Appendix to Section III.B.6 of the State’s 

submittal. Below is a brief overview of the methodology and the results of the methodology 

which are largely comprised of excerpts from Vol. II Section III.B and the Appendix to Section 

III.B.6. 

The results of the probabilistic rollforward modeling in the submittals demonstrate that the 

Anchorage area will continue to attain the CO standard through the year 2023 without the I/M 

program in place. 

Rollforward modeling is a simple calculation that assumes that the percentage reduction in 

ambient CO design values (maximum regulatory values recorded during the period of interest) to 

the level of the ambient standard is directly proportional to the percentage reduction in emissions 

needed to demonstrate attainment of that standard or the increase in emissions that can occur and 

still demonstrate attainment (allowable emissions). The probabilistic roll-forward procedure is 
7 

described in detail in the Vol. II Section III.B.6 of the state’s submissions. The results are as 

follows: 

1. The computed 2007 Design Value from the Turnagain monitor is 7.23 ppm. 

2. Total 2007 CO emissions for the Turnagain micro-inventory area is 6.01 tpd. 

3. The allowable percentage emission increase from 2007 levels in the Turnagain area is 

24.5%. 

4. The allowable emissions increase is 7.48 tpd. 

5. The theoretical probability of maintaining compliance with the CO NAAQS is greater 

than 90% provided emissions remain below the allowable emissions level identified in 

step 4. 

Figure 1. Probability of Compliance with Allowable Emissions with no I/M program 

The composite modeling results as shown in the figure above indicate that the projected 

emissions remain consistently below the allowable emissions levels and show a decreasing trend 

through the projection horizon despite an increase in emissions in 2011 consistent with the 

termination of the I/M program. 

The State prepared an additional sensitivity analysis to verify the robustness of the method 

against assumptions that represented a worst-case scenario. The state re-estimated CO for the 

2008-2023 period with the assumptions that: 

1) the growth in vehicle travel in the Turnagain area will be three times greater than 

projected (vehicle travel would increase by 12% between 2007 and 2023 instead of the 

4% assumed); 

2) there will be a 2% per annum growth in wood heating among households in the 

Turnagain area resulting from high natural gas prices. 

The State’s sensitivity analysis shows that even with the assumed higher rates of growth in 

vehicle travel and wood burning, the probability of compliance remains at 99% or greater each 

year through 2023 with or without an I/M program. 
8 

EPA’s evaluation of the probabilistic rollforward modeling in the State’s 2010 submittal 

concludes that the Anchorage area will continue to attain and maintain the CO standard through 

the year 2023 without the I/M program in place. 

3. Contingency measures 

As a primary control strategy in the Alaska SIP, the I/M program for Anchorage must be retained 

as a contingency measure. In addition to this contingency measure, the previously approved 

contingency measures in the SIP continue to apply (69 FR 25872). 

As stated above, section 175A(d) of the Act requires that the State will implement all measures 

with respect to the control of the air pollutant concerned which were contained in the State 

implementation plan for the area before redesignation of the area as an attainment area. To 

satisfy this requirement, the State will be removing the Anchorage I/M program as a primary 

control measure in the SIP and shifting it to a contingency measure that will be available for 

implementation if needed to ensure continued maintenance of the CO NAAQS. As documented 

in Volume II, Section III.B.9 of the State’s 2010 submittal, Anchorage will retain the local legal 

authority necessary to implement the I/M program as a contingency measure. Similarly, the State 

will retain its authority to implement the I/M program under state regulation, 18 AAC 52 

(included in the State’s submittal in Section III.A.2), as specified in Alaska Statutes 46.14.400. 

The 2009 submittal updated the contingency measures section of the Anchorage CO maintenance 

plan. The contingency measure identified as “transit service expansion through 2006” was 

removed from the list of contingency measures. Projected times for implementation of 

contingency measures were added for each measure. The implementation times range from 6 to 

24 months. The following contingency measures were added in the 2009 submittal and included 

in the 2010 submittal: 

 Increase public awareness and education, transit, carpool, and vanpool promotion 

efforts. 

 Curtail or limit the use of fireplaces, wood stoves and other wood burning 

appliances when high CO is predicted 

 Promote increase in transit ridership among commuters by offering reduced fares 

or free transit fares for employees of companies that contribute to subsidy. 

4. Conformity budget 

Under section 176 of the Act, transportation plans, programs and projects in nonattainment or 

maintenance areas that are funded or approved under 23 USC or the Federal Transit Act must 

conform to an approved SIP. In short, a transportation plan is deemed to conform to the 

applicable SIP if the emissions resulting from implementation of that transportation plan are less 

than or equal to the motor vehicle emission level established in the SIP for the maintenance year 

and other analysis years. A motor vehicle emissions budget applies as a ceiling on emissions in 

the year for which it is defined, and for all subsequent years until another year for which a 

budget is defined or until a SIP revision modifies the budget. The State’s submittal establishes a 
9 

new on-road motor vehicle emissions budget for the Anchorage area to be used for transportation 

conformity and regional conformity analyses. 

The budget is based on the emission inventories and attainment projections found in the State’s 

submittal in Volume III. Appendix to Volume II, Section III.B.3. The State used the most recent 

population, employment, and land use assumptions and forecasts to generate the 2007 base year 

CO inventory and forecasts through 2023. This motor vehicle emissions budget applies for each 

of the years listed in Table 3. The values presented are based upon the 90% confidence level 

target for maintenance plans. 

Table 3. Anchorage Motor Vehicle Emissions Budget: Tons per Day (tpd)

Calendar Year CO Emissions 

2007 92.1 

2008 91.7 

2009 91.2 

2010 90.8 

2011 90.3 

2012 89.9 

2013 89.4 

2014 89.0 

2015 88.5 

2016 88.0 

2017 87.6 

2018 87.0 

2019 86.4 

2020 85.8 

2021 85.2 

2022 84.6 

2023 84.0 

The motor vehicle emissions budget in the submitted SIP meets the criteria contained in the 

conformity rule (40 CFR 93.118(e)(4)). 

Once a motor vehicle emissions budget is approved by EPA, emissions modeled from the 

transportation network reflected in the Anchorage Long Range Transportation Plan (LRTP) and 

Transportation Improvement Program (TIP) must be less than or equal to the approved motor 

vehicle emissions budget. For projects not from a conforming TIP, the additional emissions from 

the project together with the TIP emission must be less than or equal to the budget. 
10 

Consistent with the previously approved maintenance plan, the on-road source budget is based 

on emissions inventories and attainment thresholds calculated using a hybrid method that 

combined measured idle test data and plug-in data with outputs from MOBILE6.2. The 

maintenance plan sets out a means for agencies to compute emissions for use in TIP and project 

conformity determinations.

EPA has found that the conformity budget in the 2010 submittal meets the purpose of section 

176(c)(2)(A) and meets the criteria contained in the conformity rule 40 CFR 93.118(e)(4). 

Accordingly, EPA is proposing to approve the conformity budget contained in the State’s 2010 

submittal. 

5. EPA’s review of the State’s analysis demonstrating continued attainment and 

maintenance of other criteria pollutants

As discussed above, section 110(l) of the Act states that a revision to a plan cannot interfere with 

any applicable requirement concerning attainment and reasonable further progress (as defined in 

section 171), or any other applicable requirement of the Act. Based on our review of EPA’s Air 

Quality System database, the Anchorage CO maintenance area is well within the attainment 

limits for all of the criteria pollutants that are monitored in the area.4

 Based on this information, 

EPA concludes that removing the I/M program will not interfere with attainment or maintenance 

of other NAAQS in the area. 

IV. CONCLUSION

The State’s forecast and analysis of motor vehicle pollutant emissions show that CO 

concentrations will decline substantially in Anchorage between 2008 and 2023 without the I/M 

program in place. The State’s 2010 submittal demonstrates that removal of the I/M program as 

an active control measure will not interfere with the maintenance of the CO or any other NAAQS 

in Anchorage. EPA finds that the 2010 submittal meets the requirements of section 110(l) of the 

Act and proposes to approve it. 

 

4 See air quality monitoring reports in the docket.