Reply to Attn of: AWT-107 

MEMORANDUM 

DATE: February 19, 2010 

SUBJECT: Technical Support Document for: 

1. The Portland Portion of the Portland-Vancouver (Pdx/Van) Air Quality 

Maintenance Area, 8-hour ozone Section 110(a)(1) Maintenance Plan, and the 

Salem-Keizer Air 8-hour ozone Section 110(a)(1) Maintenance Plan, and 

2. Oregon’s phase out of the Vehicle Inspection Program's (VIP) enhanced 

BAR-31 test by January 1, 2007 for 1981-95 model year vehicles and 

elimination of the Gas Cap Pressure Test and the Evaporative Purge Test. 

FROM: Krishna Viswanathan, Environmental Scientist 

TO: Docket EPA-R10-OAR-2008-0155 

TABLE OF CONTENTS

1. The Portland Portion of the Portland-Vancouver (Pdx/Van) Air Quality Maintenance 

Area, 8-hour ozone Section 110(a)(1) Maintenance Plan, and the Salem-Keizer Air 8-

hour ozone Section 110(a)(1) Maintenance Plan. 

I. Purpose 

II. Background 

III. Review of the Maintenance Plan 

IV. Evaluation 

V. Conclusion 

VI. Recommended Agency Action 

2. Oregon’s phase out of the Vehicle Inspection Program's (VIP) enhanced BAR-31 test by 

January 1, 2007 for 1981-95 model year vehicles and elimination of the Gas Cap Pressure 

Test and the Evaporative Purge Test. 

I. Purpose 

II. Background 

III. Review of the Proposed Revisions 

IV. Evaluation 

V. Conclusion 
2

VI. Recommended Agency Action 

The Portland Portion of the Portland-Vancouver (Pdx/Van) Air Quality Maintenance 

Area, 8-hour ozone Section 110(a)(1) Maintenance Plan, and the Salem-Keizer Air 8-hour 

ozone Section 110(a)(1) Maintenance Plan. 

I. Purpose 

This technical support document (TSD) provides information supporting EPA’s proposed action 

to approve the State of Oregon’s May 22, 2007 request to approve the Section 110(a)(1) Ozone 

Maintenance Plans for the Portland portion of the Pdx/Van AQMA, the Salem-Keizer Area 

Transportation Study Air Quality Area (SKATS), and supporting New Source Review and 

Vehicle Inspection Program rules. The Section 110(a)(1) maintenance plans for these areas 

demonstrated how the State of Oregon will maintain compliance the 1997 8 hour Ozone National 

Ambient Air Quality Standards (NAAQS). The 110(a)(1) Maintenance Plans for both these areas 

meets the Clean Air Act (CAA) requirements and demonstrates that the Portland portion of the 

Pdx/Van AQMQ and the SKATS Air Quality Area will be able to remain in attainment for 1997 

Ozone NAAQS through 2015. Based on my review, I am recommending full approval of the 

maintenance plan and supporting rules. 

On January 17, 2007, EPA received a request from the Washington State Department of Ecology 

(Ecology) to approve under section 110 of the CAA, a SIP revision pertaining to the 

Maintenance Plan for the Vancouver Portion of the Pdx/Van AQMA. EPA intends to propose a 

corollary action on Ecology’s submission concurrently with this action as they both pertain to the 

Pdx/Van Air Quality Maintenance Area. 

II. Background 

The CAA establishes a process for air quality management through the attainment and 

maintenance of the NAAQS. Ground-level ozone is not emitted directly by sources. Rather, 

emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) react in the 

presence of sunlight to form ground-level ozone. The air pollutants, VOCs and NOx, are referred 

to as precursors of ozone. 

A. Pdx/Van AQMA

On March 3, 1978 (43 FR 8961), the Pdx/Van Interstate Area consisting of the southern 

portions of Clark County, Washington and portions of Multnomah, Clackamas, and 

Washington Counties in Oregon, was designated an Ozone nonattainment area under the 

1977 Clean Air Act. The Interstate designation was warranted as the Portland, OregonVancouver, Washington Interstate Urban Area shares a common air shed and common air 

quality problems1

. On November 15, 1990, the CAA was amended (42 U.S.C 7401-

7671(q) and Section 107(d)(1)(C) provided that designations occurred by operation of 

 

1

 Letter from Clark L. Gaulding, Chief Air Programs Branch, US EPA Region 10 to Peter Hildebrandt, Assistant Director, Office 

of Air Programs, State of Washington, dated June 12, 1978.
3

law for areas that had been designated nonattainment before enactment of the 

amendments. In 1990, the Pdx/Van Interstate nonattainment area was classified as a 

marginal 1-hour ozone nonattainment area (Section 181(a)(1) of the CAA). 

In May 1997, EPA redesignated the Pdx/Van Interstate Nonattainment Area to attainment 

for the 1-hour ozone NAAQS and approved a Maintenance Plan (62 FR 27204). In July 

1997, EPA revised the Ozone NAAQS and established a new standard of 0.08 ppm 

averaged over eight hours and temporarily vacated the 1-hour standard. No violations of 

the 1997 8-hour ozone standards have been reported in this nonattainment area. 

In 2002, EPA began the process to designate areas under the 1997 8-hour ozone standard. 

On April 30, 2004 (69 FR 23858), EPA designated and classified areas for the 8-hour 

ozone NAAQS. The PDX/Van Interstate Nonattainment Area was designated as an 

attainment area for the 1997 8 hour ozone NAAQS. Since then and through December 

31, 2008, the highest ozone reading in the area has been at the Carus Site, with a 2005 

design value of 0.069 ppm. This value is below the 1997 and 2008 ozone NAAQS. 

Therefore, the area remains in attainment with the 1997 and 2008 8-hour ozone NAAQS. 

B. Salem-Keizer Area Transportation Study Air Quality Area (SKATS)

The SKATS air quality area marginally violated the federal air quality standard for ozone 

in the 1970s and was designated an ozone nonattainment area on March 3, 1978, under 

the 1977 Clean Air Act Amendments (43 FR 8961). The Mid-Willamette Valley Council 

of Governments recommended the nonattainment area as the area within the SalemKeizer Area Transportation Study boundary (SKATS) (see Figure 2 in Section 4.50.1.2 

of the Oregon State Implementation Plan). This includes portions of Marion and Polk 

County, including the cities of Salem and Keizer. With the 1990 amendments to the 

CAA, the SKATS air quality area was designated “nonattainment/insufficient data.” 

Salem’s ozone concentrations are influenced by emissions of ozone precursors in the 

Portland area. In 1979, the Salem area was designated under EPA guidelines as a “rural” 

ozone nonattainment area and an Attainment Plan was approved by EPA on April 12, 

1982 (47 FR 15587). Salem’s attainment plan under the rural ozone policy consists of 

three elements: 

I. Controls on major existing sources of volatile organic compounds under 

Reasonably Available Control Technology (RACT) rules; 

II. Controls on major new VOC sources under Lowest Achievable Emission Rate 

(LAER) rules, and 

III. An approved plan for the Portland-Vancouver AQMA, which is the major 

urban area upwind of Salem. 

All of these program elements remain in place. Although the Salem/Turner ozone 

monitoring site has no reported violations of the 1 hour standard since 1996, Oregon 

Department of Environmental Quality (ODEQ) did not submit a redesignation request or 
4

a maintenance plan for this area. Therefore, SKATS remains a nonattainment area for the 

1 hour Ozone standard. 

In 2002, EPA began the process to designate areas under the 1997 8-hour ozone standard. 

On April 30, 2004 (69 FR 23858), the EPA designated and classified areas for the 8-hour 

ozone NAAQS. The Salem area was designated as an attainment area for the 8-hour 

ozone NAAQS. The Salem/Turner ozone monitor shows a 2005 design value of 0.065 

ppm. Based on ozone data since 1998, the area remains in remains in attainment with the 

1997 8-hour ozone NAAQS. 

C. All Areas

As of April 30, 2004 (69 FR 23951), EPA specified that even though the 1-hour ozone 

standard had been revoked, the 1-hour ozone NAAQS designations and classification 

statuses were retained as of the effective date of designation for the 8-hour NAAQS for 

purposes of anti-backsliding regulations (40 CFR 51.905). Consequently, antibacksliding regulations apply even after revocation of the 1-hour ozone NAAQS. 

EPA’s Phase 1 Implementation Rule for the 8-hour ozone standard was published on 

April 30, 2004 (69 FR 23951, 23998). 40 CFR 51.905 sets forth requirements for antibacksliding purposes for areas designated attainment for the 8-hour standard. These 

provisions require such areas to submit a 10 year maintenance plan under section 

110(a)(1) of the CAA if they were also a nonattainment or an attainment/unclassifiable 

area with a section 175A maintenance plan under the ozone standard. The maintenance 

plan needs to demonstrate that the area will maintain the standard for 10 years after 

designation in accordance with section 110(a)(1) of the CAA. 

On December 22, 2006, the U.S. Court of Appeals for the District of Columbia Circuit 

vacated EPA’s Phase 1 Implementation Rule for the 8-hour Ozone Standard (69 FR 

23951, April 30, 2004). On June 8, 2007, in South Coast Air Quality Management Dist. v. 

EPA, Docket No. 04-1201, in response to several petitions for rehearing, the DC Circuit 

clarified that the Phase 1 Rule was vacated only with regard to those parts of the rule that 

had been successfully challenged – the Phase 1 Rule provisions related to classifications 

for areas currently classified under subpart 2 of Title I, Part D of the CAA. The June 8 

decision reaffirmed the December 22, 2006, decision that EPA had improperly failed to 

retain measures required for areas that were previously designated nonattainment for the 

1-hour standard and the anti-backsliding provisions of the regulations. That decision does 

not affect EPA’s ability to take this action. 

On May 22, 2007, EPA received a request from the ODEQ to approve a SIP revision 

pertaining to the Maintenance Plan for the Portland Portion of the Portland-Vancouver 

Interstate Maintenance Area and a Maintenance Plan for the SKATS air quality area, 

under section 110 of the CAA. This plan demonstrates how the ODEQ intends to 

maintain the 8-hour ozone NAAQS. This maintenance plan contains a base-year 

inventory for 2002, projected emissions to 2015, and results of computer modeling that 

demonstrates that the 8-hour Ozone standards will not be violated in 2015. The plan also 
5

indicates how maintenance plan progress will be tracked and identifies measures that 

would be available to promptly correct any NAAQS violation. ODEQ’s SIP submittal 

meets the CAA requirements for SIP submittals under Section 110(a)(1), Section 110(l) 

and Section 193. 

III. Review of the Maintenance Plan 

A. What are the components of a section 110(a)(1) 8-hour ozone maintenance plan? 

CAA Section 110(a)(1) requires states to submit plans to EPA which provide for the 

implementation, maintenance and enforcement of NAAQS standards in each air quality control 

region with the state. On May 20, 2005, EPA issued guidance that applies to areas that are 

designated as unclassifiable/attainment for the 8-hour ozone standard. The purpose of that 

document is to address the maintenance requirements in section 110(a)(1) of the CAA, and 

provide guidance to the states in the development of a SIP. 

Both the Pdx/Van AQMA and the SKATS AQA are eligible to submit maintenance plans under 

section 110(a)(1) according to this guidance. The Pdx/Van AQMA qualifies as an area that is 

designated unclassifiable/attainment for the 8 hour ozone NAAQS and is designated attainment 

for the 1-hour ozone NAAQS with an approved maintenance plan. SKATS qualifies as an area 

that is designated unclassifiable/attainment for the 8 hour ozone NAAQS and is designated 

nonattainment for the 1-hour ozone NAAQS. The maintenance plan for these areas should 

include the following five components: 

1. Attainment Inventory – The attainment inventory should be based on actual “typical summer 

day” emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) for a 10-year 

maintenance period. For purposes of an attainment emissions inventory, the state must choose 

any of the three years on which the 8-hour ozone attainment designation was based. As many 

areas are already required to develop an inventory for the 2002 under EPA’s Consolidated 

Emissions Reporting Rule (CERR; 40 CFR Part 51, Subpart A, 67 FR 39602, June 10, 2002), 

EPA recommends that areas use that year as the attainment emission inventory base year for the 

section 110(a)(1) maintenance plan. 

2. Maintenance Demonstration – The area must demonstrate how it will remain in compliance 

with the 8-hour ozone standard for a period of 10 years following the effective date of 

designation as unclassifiable/attainment. If the effective date of the areas’ designation for the 8-

hour NAAQS was June 15, 2004, the maintenance plan must project attainment for 2014 or 

beyond. 

A typical method that areas have used to demonstrate that an area will maintain the 1-hour 

standard has been to use the attainment inventory and to show that future emissions of ozone 

precursors will not exceed those levels. However, in areas where transport of precursor 

emissions from an area outside a jurisdiction is a factor to ozone levels, more sophisticated 

analysis using air quality models may be required to demonstrate maintenance of the standard. 
6

3. Ambient Air Quality Monitoring - The state should continue to operate air quality monitors 

in accordance with 40 CFR Part 58 to verify maintenance of the 8-hour ozone standard. 

4. Contingency Plan – The state must develop measures so that in the event of a violation of the 

8-hour ozone NAAQS, the measures can be implemented as expeditiously as practicable after the 

violation. 

5. Verification of Continued Attainment – The state must indicate how it intends to track the 

progress of the maintenance plan. This is necessary because emissions projections for the 

maintenance demonstration depend on assumptions of point, area, and mobile source growth. 

B. How has the state addressed the components of a section 110(a)(1) 8-hour ozone 

maintenance plan? 

1. Attainment Inventory - This maintenance plan contains a base-year inventory for 2002 and 

projects emissions to 2015. The effective year of the 8-hour ozone initial designation was 2004; 

ODEQ projected emissions for 10 years or beyond from the effective date of the initial 

designation. Consequently, ODEQ developed an emissions inventory for ozone precursors for 

the year 2002 and 2015. In this projection is a built-in growth allowance for point sources of 

5000 tons of VOC and 5000 tons of NOx. Section 4.50.4.1.2 Industrial Emission Management 

Rules and Growth Allowance Program Procedures explain how the 5000 tons will be allocated to 

industrial facilities. 

ODEQ used a comprehensive emissions inventory for VOCs, NOx and CO for the 2002 BaseYear in order to project emissions. DEQ developed an attainment emission inventory for the year 

2002. The emission inventory reflects detailed estimates of emissions from all sources, grouped 

into four major categories: 

۞ Industrial Point Sources (sources with a DEQ air quality permit), 

۞ On-Road Mobile Sources (e.g. motor vehicles and trucks), 

۞ Non-Road Mobile Sources (e.g. lawnmowers, construction equipment and other engines), 

and 

۞ Area Sources (e.g. household products, print shops, degreasing and surface coating 

operations, pesticide application, open burning and wildfires). 

The 2002 Consolidated Emissions Reporting Rule (CERR) emissions data submitted by DEQ 

and SWCAA to EPA’s National Emission Inventory (NEI) were used as the basis for the 2002 

attainment year inventory. This 2002 county-by-county annual inventory was developed 

following the currently accepted methodologies for the National Emission Inventory. The 

Technical Appendices submitted with ODEQ’s maintenance plan contain more detailed 

information for each sector of the emission inventories. 
7

Table 1 

Figure 1 

Table 2 
8

Figure 2 

Emissions for all source categories were calculated following EPA guidance and are properly 

documented in the Appendix D of the Maintenance Plans. This component of the Maintenance 

Plans meets the requirements for attainment inventories under Section 110(a)(1) and EPA 

guidance. 

2. Maintenance Demonstration – Since 2004 is the effective date of designations for this area 

for the 8 hour NAAQS, the maintenance plan must demonstrate maintenance to 2014 or beyond. 

This maintenance plan projects emissions to 2015. The ODEQ developed two different growth 

scenarios for major industrial (point) sources. The first growth scenario (called “2015 

Projection”) reflects the 2002 estimate of actual industrial emissions, increased by regional 

employment projections for that sector. The second growth scenario (called “2015 Maintenance 

Demonstration”) represents a very conservative estimate of possible future year emissions and is 

used in maintenance demonstration for the maintenance plan. The 2015 Maintenance 

Demonstration reflects maximum “legally allowable” emission levels currently permitted for 

existing industry, plus the emissions growth allowance reestablished for new industry growth. 

For the Portland, OR side of the Pdx/Van AQMA the growth allowance is 5,000 tons per year 

each of NOx and VOCs. 

Portland Area 2105 Emissions projections used for Maintenance Demonstration in lbs/day
9

Table 3 

The submission from ODEQ depicts on-road emissions decreasing significantly (61% less VOC 

emissions and 68% less NOX emissions) due to the implementation of federal motor vehicle 

emission and fuel standards and continuing implementation of the vehicle inspection program. 

Non-road emissions also show a 30% decrease in NOX emissions due to the phase-in of federal 

emission and fuel standards. Area source emissions are expected to increase due to increases in 

population that affect categories such as architectural surface coating and consumer solvent use. 

Point source “actual” emissions are inflated by the growth allowance to derive the 2015 

Maintenance Demonstration amount. 

For the Portland area, this summarizes to 2015 VOCs increasing by about 5% from 2002 actual 

emissions, and 2015 NOX emissions decreasing by about 30% with point sources showing the 

greatest increase and on-road mobiles sources showing the greatest decrease. 

Figure 4 
10

Table 4 

ODEQ submitted information to verify that on-road emissions for the Salem area decrease 

significantly (71% less VOC emissions and 69% less NOX emissions) due to the implementation 

of federal motor vehicle emission and fuel standards. The Salem area will also benefit from the 

phase in of on-board canister systems in motor vehicles that control gasoline vapors while 

refueling. Non-road emissions also show a 42% decrease in NOx emissions due to the phase-in 

of federal emission and fuel standards. Area sources in the Salem area are projected to increase 

slightly due to increases in population. 

Point source “actual” emissions are not expected to change significantly although the table above 

describes the difference between “actual” emissions in the 2002 attainment inventory and the 

“allowable” emissions and growth allowance in the 2015 Maintenance Demonstration. The 2015 

Maintenance Demonstration includes one proposed energy facility that has withdrawn its permit 

application making the inventory very conservative. 

For the Salem area, this summarizes to 2015 VOCs decreasing by about 8% from 2002 actual 

emissions, and 2015 NOX emissions decreasing by about 51% with point sources showing the 

greatest increase and on-road mobiles sources showing the greatest decrease. 

As the tables above indicate, 2015 emissions show an overall decrease for both the Pdx/Van and 

the SKATS areas during the 10-year maintenance period. However, it is important to note that 

the formation of ozone is dependent on a number of variables, which cannot be estimated by 

emissions projections alone. As the Pdx/Van Interstate Urban Area shares a common airshed and 

common air quality problems2

, examining the effects of transport of ozone precursors from the 

Vancouver, WA side of the AQMA is necessary. Other variables include, weather and the 

transport of ozone precursors from areas outside of the State of Oregon. In order to demonstrate 

continued maintenance, a state may utilize more sophisticated tools such as air quality or 

dispersion modeling. 

 

2

 Letter from Clark L. Gaulding, Chief Air Programs Branch, US EPA Region 10 to Peter Hildebrandt, Assistant 

Director, Office of Air Programs, State of Washington, dated June 12, 1978. 
11

In section 4.40.5.4 of their maintenance plan, ODEQ summarizes the results of dispersion 

modeling study performed for the Pdx/Van Maintenance Area in 2004 by the Washington State 

University (WSU) (see table and chart below). For further details of the study see Appendix D – 

of the ODEQ SIP submittal. 

Table 5 

2015 Maintenance Demonstration for the Pdx/Van/SKATS 

Maintenance Area (ppm)

1997 8-hour ozone standard = 0.08 ppm 

Exceedance ≥ 0.085 ppm maximum 

Violation >0.085 ppm Predicted Design Value 

Monitoring Site 1998 Predicted 

Maximum 

2015 Predicted 

Maximum 

2015 Predicted Design Value*, ppm 

Portland/Carus 0.098 0.094 0.072 

Portland/Milwaukie 0.092 0.096 0.062 

Portland/Sauvie Island 0.082 0.076 0.054 

Vancouver/Mountain View 0.083 0.081 0.061 

Salem/Turner 0.088 0.075 0.060 

*Predicted Design Value is calculated using the EPA statistical procedure called the Relative Reduction 

Factor described in Appendix 6 of the ODEQ’s submittal and in EPA’s 8-hour ozone modeling guidance. 

Predicted design value is compared to the 8-hour ozone standard to determine compliance. 

Figure 5 
12

These results in Table 5 and Figure 5 illustrate that the Pdx/Van AQMA and the SKATS will 

maintain compliance with the 8-hour ozone standard through 2015. The Carus monitoring site, 

downwind of Portland, has historically been the site with the highest ozone readings in the 

region. The model predicted that the Milwaukie site would produce a slightly higher maximum 

value under worst case meteorological conditions, and the maximum values at both Milwaukie 

and Carus would exceed but not violate the standard. However, the Carus site is expected to 

remain the highest and most important site for determining compliance with the ozone standard. 

The design value at Carus and all other sites demonstrate continued compliance with the 1997 

and 2008 ozone NAAQS. 

Supplemental Review for Compliance with section 110(l) of the CAA 

Does ODEQ’s Section 110(a)(1) 8-hour ozone maintenance plan comply with all aspects of the 

Clean Air Act?

Before a modification to the Portland Ozone Maintenance Plan can be approved by EPA, the 

Agency must determine that the submission meets the requirements of CAA Section 110(l) of the 

CAA which states “....The Administrator shall not approve a revision of a plan if the revision 

would interfere with any applicable requirement concerning attainment and reasonable further 

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

The Ozone NAAQS has changed from 1997 to 2008. The 2008 8-hour Ozone NAAQS was 

promulgated in March 2008 with primary and secondary standards at 0.075 ppm or 75 ppb. 

These are the currently applicable NAAQS and the attainment demonstration has to show that 

the 2008 NAAQS is also not being violated into the future due to the changes proposed by the 

State of Oregon. As seen from the table and chart above the 2015 predicted design values are 

below the 2008 NAAQS. Therefore this plan demonstrates compliance with all applicable Ozone 

NAAQS, from 1997 and 2008. 

We applied the same standard of review for all criteria pollutant NAAQS. The Portland area is 

currently designated as an attainment area for all criteria pollutants, and historical monitoring 

data affirms that this area is in compliance with other criteria air pollutants NAAQS3

. 

Additionally, EPA’s evaluation of the impacts of the changes proposed in this Plan has 

determined that these changes will not cause an increase in direct or precursor emissions that will 

interfere with the attainment or maintenance of any other NAAQS. 

Therefore the proposed approval of this plan will not interfere with any applicable requirement 

concerning attainment or maintenance of any applicable NAAQS in the Portland area. 

Based on monitoring in the area, SKATS is in compliance with the remaining NAAQS4

. 

Additionally, the actions proposed for approval in this Plan will not cause an increase of direct or 

precursor emissions of any criteria pollutant such as to interfere with the attainment or 

maintenance of any other criteria pollutant NAAQS. 

 

3

 EPA’s AirData database at http://www.epa.gov/oar/data/reports.html 4 EPA’s AirData Database - http://www.epa.gov/oar/data/reports.html
13

Therefore, this plan demonstrates compliance with all applicable ozone NAAQS in Pdx/Van and 

SKATS and the proposed approval of this plan will not interfere with the attainment or 

maintenance of any other NAAQS for these areas. 

Control Strategies for the Portland and Salem Area, Applicable Rules and Changes:

The following strategies are supported by the rules that are in the currently approved SIP and 

will continue to will remain in the Portland Ozone Maintenance Plan as they currently apply to 

sources in the Portland area: 

۞ Motor Vehicle Inspection Program (OAR 340-256-0300 through 0470); 

۞ Emission Standards for VOC Point Sources (Reasonably Available Control Technology) 

for existing major industrial facilities (OAR 340-232-0010 through 0230); 

۞ New Source Review Program for new and expanding major industrial facilities (OAR 

340-224-0010 through 0100 and 340-225-0010 through 0090); 

۞ Voluntary Parking Ratio Rules (OAR 340-242-0300 through 0390); 

۞ Barge Loading Rules and Stage I vapor recovery systems that control VOCs from 

gasoline delivery operations (included within OAR 340-232); 

۞ Aerosol Paint Rules that lower VOC content from spray paints sold in the Portland area 

(OAR 340-242-0700 through 0750); 

۞ Motor Vehicle Refinishing Rules that require low-emitting painting methods at auto body 

shops (OAR 340-242-0600 through 0630); and 

۞ Public education and outreach that encourages people to voluntarily reduce emissions, 

such as not mowing lawns and driving less on Clean Air Action Days (now called Air 

Pollution Advisories). 

The following strategies in the Portland-Vancouver Ozone Maintenance Plan (Oregon portion) 

have been modified and were submitted for approval by EPA. More details are discussed with 

each rule submitted for approval, as needed. Based on EPA review and determination that these 

modifications are acceptable under the CAA, these modifications are proposed for approval and 

incorporation in the federally approved SIP for Oregon. 

۞ General Air Pollution Procedures and Definition: OAR 340-200; 

۞ Ambient Air Quality Standards and PSD Increments: OAR 340-202 

o OAR 340-202-0090 Ozone: OAR 340-202 includes Oregon’s ambient air quality 

standards and section 202-0090 was revised to update the ozone standard to 

reflect revisions to the national ambient air quality standards (NAAQS). 

Specifically, this revision replaces the 1-hour standard of 0.12 ppm with the new 

8-hour standard of 0.08 ppm and adopts by reference 40 CFR 50, Appendix I as 

the appropriate method for determining compliance with the standard. This 

revision is consistent with EPA revisions to the ozone NAAQS and should be 

approved. 

۞ Designation of Air Quality Areas: OAR 340-204 

۞ Major New Source Review: OAR 340-224 

o OAR-340-224-050: OAR-340-224 includes ODEQ’s Major New Source Review 

regulations for both nonattainment areas (section 224-0050) and maintenance 
14

areas (section 224-0060). Since Salem is being re-designated from nonattainment 

to maintenance, the special exemption provisions for the Salem Ozone 

Nonattainment Area included in paragraph 224-0050(4) of the nonattainment area 

provisions are being moved to the maintenance area provisions in a new 

paragraph 224-0060(2)(e). The proposed revision is consistent with the redesignation of the Salem nonattainment area to maintenance and should be 

approved. 

۞ Air Quality Analysis Requirements: OAR 340-225 

o OAR 340-225-0090: OAR 340 225 includes ODEQ’s Air Quality Analysis 

Requirements and minor edits are made to paragraph 225.0090(2)(e) reflecting 

the re-designation of Salem from a nonattainment to maintenance area. 

۞ Emission Standards for VOC Point Sources: OAR 340-232 

۞ Rules Applicable to the Portland Area: OAR 340-242 

۞ Employee Commute Options Program (OAR 340-242-0010 through 0290): 

o Program requirements now focus on larger employers (100 or more employees) 

and reduce the survey requirements from annual to every two years. Section 

4.50.4.1.1 Changes to the Employee Commute Options Rule discusses the 

changes to the rule in detail. EPA reviewed this proposal and concludes that 90% 

of the trip and emission reductions are maintained by focusing on larger 

employers. Therefore, this change in focus retains substantial benefits of the ECO 

program making it easier to administer. 

۞ Industrial Emission Management Program (OAR 340-242-0400 through 0440): 

o Reestablish the industrial growth allowance for new and modified major industrial 

sources to ensure that the ozone standard will not be violated even under 

conservative growth assumptions. Section 4.50.4.1.2 Industrial Emission 

Management Rules of the maintenance plan describes this program in great detail. 

This maintenance plan reestablishes the existing growth allowance for new and 

expanding major VOC and NOX industrial sources, creates an administrative and 

public process for releasing the growth allowance in increments, and retains the 

emission offset requirement as a safeguard. The growth allowance has been 

included in the modeled 2015 ozone maintenance demonstration. 

Sections 4.50.4.1.3 ODEQ’s 110(a)(1) submission mentions that although according to EPA’s 

2004 ozone implementation rules (40 CFR 51.900), neither general conformity nor transportation 

conformity is required for areas attaining the 8-hour ozone standard, the ODEQ and the Portland 

Metropolitan Service District or Metro (Metro is a Portland metropolitan area elected regional 

government chartered as primarily responsible for regional land-use planning5

) will informally 

track VOC, NOx, air toxics and greenhouse gas emissions when Metro assesses conformity for 

the purposes of the Portland Carbon Monoxide Maintenance Plan as a voluntary program to 

assess impacts of transportation emissions on air quality over time. This will help the state 

understand and track the trends of these emissions with respect to the growth projections in this 

maintenance plan and its relation to air quality in the area. 

ODEQ commits to retaining strategies in the SKATS Attainment Plan that was adopted in 1980 

and revised in 1982, including Emission Standards for VOC Point Sources (OAR 340-232-0010 

 

5 http://www.oregonmetro.gov/index.cfm/go/by.web/id=211 – accessed on Sept, 04, 2009. 
15

through 0230) and continued reliance on the control strategies in the Portland-Vancouver AQMA 

Ozone Maintenance Plan. 

All these controls were incorporated in the maintenance demonstration inventory and modeling 

performed for the Pdx/Van AQMA and the SKATS area. Even with these policies represented by 

these rule incorporated in the technical analysis, the results indicate that both these areas will 

maintain the 1997 and the 2008 8 hour ozone standards through 2015. 

3. Ambient Air Quality Monitoring – ODEQ commits to operate an ozone air quality 

monitoring network in accordance with 40 CFR 58 to verify maintenance of the 8-hour ozone 

standard in Portland and Salem (see Appendix D10-1 of ODEQ’s submittal). The agency further 

commits that any modification to the ambient air monitoring network, such as removal of 

duplicative or unnecessary monitors, will be accomplished through close consultation with the 

EPA Regional office. Proposed network modifications would be accompanied by technical and 

statistical analysis sufficient to document that a given monitor may be removed because: 

a. it is unnecessary or duplicative in the case of network reductions, or 

b. to justify the value of investing in monitoring network enhancements. 

In accordance with 40 CFR 58, the final network design will be subject to the approval of the 

EPA Regional Administrator. 

4. Contingency Plan – Section 110(a)(1) of the CAA requires that the state develop a 

contingency plan which will ensure that any violation of a NAAQS is promptly corrected. The 

purpose of the contingency plan is to adopt measures, outlined in the maintenance plan, in order 

to assure continued attainment in the event of a violation of the 8-hour ozone NAAQS. The 

maintenance plan should identify the events that would “trigger” the adoption and 

implementation of a contingency measure(s), the contingency measure(s) that would be adopted 

and implemented, and the schedule indicating the time frame by which the state would adopt and 

implement the measure(s). 

The provisions specified under Part A of the Contingency Plan for the Portland-Vancouver 

AQMA are linked to ambient concentrations of ozone and would be triggered if measured ozone 

levels at any of the ozone monitoring sites (Mountain View, Sauvie Island, Milwaukie, or Carus) 

exceed the early-warning thresholds specified below, or if a violation of the 8-hour ozone 

standard occurs. 

The provisions specified under Part B of the Contingency Plan are linked to increases in the 

average amount of vehicle use per person in the Portland metropolitan area, and would only 

affect the Oregon portion of the Portland-Vancouver AQMA. The following are the specific 

steps that ODEQ will take the based on monitored values of ambient ozone: 

Part A of the Contingency Plan Based On Ambient Concentrations in Portland or 

Vancouver

PHASE 1: ELEVATED OZONE LEVELS 
16

If the air quality index (AQI) is forecast to be within the “orange” range for ozone air quality 

(unhealthy for sensitive populations), or 8-hour daily maximum ozone values approach 0.100 

ppm or greater, and meteorological conditions conducive to ozone formation are expected to 

persist, SWCAA will coordinate to issue an advisory to inform the public of air quality levels 

and voluntary actions they can take to limit exposure to unhealthy air pollution levels and reduce 

emissions. 

PHASE 2: RISK OF VIOLATION 

If monitored 8-hour ozone levels at any site within the Portland-Vancouver area registers an 

annual fourth highest monitored value of 0.085 ppm or greater within a single ozone season or 

0.080 ppm or greater averaged over two years, ODEQ and SWCAA and will assess the likely 

sources of emissions and meteorological events contributing to elevated ozone levels. ODEQ 

may form a planning group to assist ODEQ in its review. The ODEQ could recommend that no 

action be taken if it is determined that: 

1. elevated ozone levels were caused by an event that is unlikely to occur again, or 

2. high ozone levels were caused by an uncontrollable event, such as a severe wildfire, 

or 

3. federal regulations that will reduce ozone precursor emissions are scheduled to be 

implemented within two years. 

If it is determined that the event did not meet the criteria above, DEQ will evaluate options for 

appropriate action, including the option for additional emission reduction strategies to prevent 

future exceedances or a violation of the 8-hour ozone standard. 

PHASE 3: ACTUAL VIOLATION 

If a violation of the 8-hour ozone standard occurs, ODEQ SWCAA will determine the emissions 

and meteorological events contributing to the violation. If the violation is not due to an 

uncontrollable event or other criteria in Phase 2, ODEQ will identify new strategies necessary to 

ensure compliance with the 8-hour ozone standard within 18 months of the conclusion of the 

ozone season that prompted the contingency plan, and revise the maintenance plan as needed to 

correct the violation. A revised maintenance plan would be submitted to EPA for approval. 

Measures that would be considered for implementation include the following: 

o Reinstatement of applicable measures as defined in 40 CFR 51.900, which includes the 

Enhanced Inspection/Maintenance Test for certain model year vehicles; 

o Contingency Plan Requirements described in OAR 340-224-0060(5) that reinstate the 

LAER and offset requirements and eliminate the growth allowance until a revised 

maintenance plan is adopted by the EQC and approved by EPA; 

o Other measures as appropriate. 

Part B of the Contingency Plan Based on Significant Increase in Vehicle Miles Traveled in 

the Oregon portion of the Portland-Vancouver AQMA
17

Although EPA’s 8-hour ozone implementation rule (69 FR 23987-88, April 30, 2004) does not 

allow states to implement conformity for attainment areas as a matter of federal law, the rule 

states that states can work with their metropolitan planning organizations to develop a voluntary 

program to address motor vehicle emissions growth. Metro has agreed to informally track motor 

vehicle VOC and NOx emissions at the same time as they are demonstrating conformity with the 

Portland Carbon Monoxide Maintenance Plan emissions budget. In addition, Metro has agreed to 

the following contingency measures for the Portland Carbon Monoxide Maintenance Plan that 

are also appropriate as voluntary measures for addressing ozone precursor emissions within the 

Portland metropolitan area. Although transportation control measures cannot be enforced and are 

removed from the Portland AQMA Ozone Maintenance Plan, other measures to reduce vehicle 

miles traveled (VMT) such as the Employee Commute Option program and public education and 

outreach remain in the ozone maintenance plan. In addition, DEQ participates in Metro’s 

Regional Transportation Options program which includes many efforts in the Portland area 

designed to reduce single-occupancy vehicle trips. 

PHASE 1: 5% VMT INCREASE

Metro will review and verify the local average vehicle miles traveled per capita 

(VMT/capita) for the Oregon portion of the Portland-Vancouver Air Quality Maintenance 

Area derived from the most recent estimates of population and daily vehicle miles 

traveled from federal and state sources. 

If daily VMT/capita exceeds a 5 % increase above the 2002 rate for two successive years, 

the Standing Committee [TPAC, as defined at OAR 340-252-0060(2)(b)(A)(iii)] shall be 

convened to: 

1. determine whether there is a data problem with the trigger; 

2. if there is not a data problem with the trigger, identify and analyze the 

effectiveness of those local actions that could reduce air pollutant emissions; and, 

3. determine whether a recommendation should be made to JPACT to initiate local 

action to reduce VMT/capita until the 2002 level is once again attained. 

PHASE 2: 10% VMT INCREASE 

Metro will review and verify local VMT/capita values derived from the most recent 

estimates of population and daily vehicle miles traveled from federal and state sources. 

If average daily VMT/capita exceeds a 10 percent increase above the 2002 rate for the 

Oregon portion of the Portland-Vancouver Air Quality Maintenance Area for two 

successive years, the following measures will become required Transportation Control 

Measures for the region (as determined by the programming of funds for specified 

projects) under the Portland Carbon Monoxide Maintenance Plan: 

1. Washington County Commuter Rail within six years after exceeding the 10% 

increase above the 2002 VMT/capita rate, 
18

2. Interstate 205 Light Rail Transit (I-205 LRT) within six years after exceeding the 

10% increase above the 2002 VMT/capita rate; 

3. An increase of efforts for the Regional Travel Options Program sufficient to 

increase the number of employers reached by the program by at least 5 % per year 

the number of employers currently subject to the DEQ Employee Commute 

Options program. 

4. Alternatively, specific projects from the Regional Transportation Options 

program could be substituted. 

5. An increase of funding of at least 5% per year greater than current funding for 

Transit Oriented Development projects. 

6. Other programs or projects consistent with state and federal law as may be 

determined by the Metro Council after consultation with the Joint Policy 

Advisory Committee on Transportation. 

Salem SKATS 8-Hour Ozone Contingency Plan 

PHASE 1: ELEVATED OZONE LEVELS 

If the air quality index (AQI) is forecast to be within the “orange” range for ozone air 

quality (unhealthy for sensitive populations), or 8-hour daily maximum ozone values 

reach 0.100 ppm or greater, and meteorological conditions conducive to ozone formation 

are expected to persist, DEQ will issue an advisory to inform the public of air quality 

levels and actions they can take to limit exposure to unhealthy air pollution levels and 

reduce emissions. 

PHASE 2: RISK OF VIOLATION 

If monitored 8-hour ozone levels at any site within the Salem/Turner area registers an 

annual fourth high monitored value of 0.085 ppm or greater within a single ozone season, 

or 0.080 ppm or greater averaged over two years, DEQ will assess the likely emissions 

and meteorological events contributing to elevated ozone levels. DEQ may form a 

planning group to assist DEQ in its review. The DEQ could recommend that no action be 

taken if it is determined that: 

(a) elevated ozone levels were caused by an event that is unlikely to occur again, or 

(b) high ozone levels were caused by an uncontrollable event, such as a severe wildfire, 

or 

(c) federal regulations that will reduce ozone precursor emissions are scheduled to be 

implemented within two years. 

If it is determined that the event did not meet the criteria above, DEQ will evaluate 

options for appropriate action, including the option for additional emission reduction 

strategies to prevent future exceedances or a violation of the 8-hour ozone standard. 

PHASE 3: ACTUAL VIOLATION 
19

If a violation of the 8-hour ozone standard occurs, DEQ will determine the probable 

emissions and meteorological events contributing to the violation. If the violation is not 

due to an uncontrollable event or other criteria in Phase 2, DEQ will identify new 

strategies necessary to ensure compliance with the 8-hour ozone standard within 18 

months of the conclusion of the ozone season that prompted the contingency plan, and 

revise the maintenance plan as needed to correct the violation. Contingency plan 

requirements described in OAR 340-224-0060(5) that reinstate the LAER requirement 

would also apply until a revised maintenance plan is adopted by the EQC and approved 

by EPA. 

5. Verification of Continued Attainment – ODEQ will continue to monitor ambient air quality 

ozone levels in the Portland-Vancouver AQMA as described in Contingency Plan. ODEQ will 

update countywide emission inventories every three years as required by the Consolidated 

Emission and Reporting Rule (CERR) to update the National Emissions Inventory. If ambient 

ozone levels increase, ODEQ will compare CERR updates with the 2002 and 2015 emissions 

inventories and evaluate the assumptions used in the 2015 emissions projections to determine 

whether emissions are increasing at a rate not anticipated in the maintenance plan. 

III. Evaluation

The State of Oregon has met the requirements to submit a Section 110(a)(1) Maintenance Plan 

that presents satisfactory information regarding the five elements of the Maintenance Plan and 

has satisfied Section 110(l) and 193 of the CAA. Therefore, approval of the State of Oregon’s 8-

hour Ozone Maintenance Plan is recommended. 

IV. Conclusion

This submission satisfies all requirements for an acceptable SIP revision. 

V. Recommended Agency Action 

The SIP revision request should be approved. 

Rules Approved With this Action

۞ General Air Pollution Procedures and definition: OAR 340-200; 

۞ Ambient Air Quality Standards and PSD Increments: OAR 340-202 

۞ Designation of Air Quality Areas: OAR 340-204 

۞ Major New Source Review: OAR 340-224 

۞ Air Quality Analysis Requirements: OAR 340-225 

۞ Emission Standards for VOC Point Sources: OAR 340-232 

۞ Rules Applicable to the Portland Area: OAR 340-242 

۞ Employee Commute Options Program (OAR 340-242-0010 through 0290) 

۞ Industrial Emission Management Program (OAR 340-242-0400 through 0440) 
20

Oregon’s phase out of the Vehicle Inspection Program's (VIP) enhanced BAR-31 test by 

January 1, 2007 for 1981-95 model year vehicles and elimination of the Gas Cap Pressure 

Test and the Evaporative Purge Test. 

I. Purpose 

This technical support document (TSD) provides information supporting EPA’s proposed action 

to approve the State of Oregon’s August 9, 2005 request to approve revisions to the Oregon State 

Implementation Plan: Volume 2 -Section 5.4.7 – Test Procedures and Standards. These pertain to 

phasing out the ODEQ’s Vehicle Inspection Program Enhanced Test, changing fleet testing 

frequency requirements and eliminating the gas cap and tank vapor recovery tests. The submitted 

revisions are supported by demonstration that these changes will not affect the ability of the State 

of Oregon to comply with all applicable NAAQS, especially CO and Ozone. For Ozone, the 

submittal refers to the Section 110 (a)(1) Maintenance plans for the Portland portion of the 

Pdx/Van AQMA and the SKATS submitted thereafter. The Section 110(a)(1) maintenance plans 

for these areas demonstrate how the State of Oregon will maintain compliance with the 1997 8 

hour Ozone National Ambient Air Quality Standards. The 110(a)(1) Maintenance Plans for both 

these areas meet the Clean Air Act (CAA) requirements and demonstrate that the Portland 

portion of the Pdx/Van AQMQ and the SKATS Air Quality Area will be able to remain in 

attainment with the 1997 Ozone NAAQS through 2015. EPA further analyzed that the revisions 

comply with the CAA, including Section 110(l). The applicable NAAQS for Ozone is the 2008 

8-hour standard and the 110(a)(1) Maintenance Plan includes technical information that shows 

the 2008 8-hour ozone NAAQS will not be violated with all the revisions and changes proposed. 

Based on our review, we are proposing full approval of the revisions to the Oregon State 

Implementation Plan: Volume 2 -Section 5.4.7 – Test Procedures and Standards and supporting 

rules. 

II. Background 

On August 9, 2005, the Oregon department of Environmental Quality (ODEQ) submitted 

revisions to the Oregon State Implementation Plan: Volume 2 -Section 5.4.7 – Test Procedures 

and Standards. These revisions pertain to: 

1. Phasing out the ODEQ Vehicle Inspection Program (VIP) Enhanced test and using only 

the Basic and On-Board Diagnostic (OBD) tests; 

2. Implementing HB2546 of the 2003 Oregon Legislative Session (fleet testing frequency 

requirements), and 

3. Eliminating the gas cap and gas tank vapor recovery tests (Cap and Purge). 

The ODEQ tests pollution from vehicles in both Medford and Portland as one of the ways to 

ensure that these areas meet and do not exceed the Clean Air Act based National Ambient Air 

Quality Standards (NAAQS). ODEQ uses the following three test methods: Basic, Enhanced, 

and Onboard Diagnostic (OBD). According to ODEQ, the Basic test is relatively inexpensive to 

operate and is the least effective in reducing pollution, the Enhanced test is very expensive to 

operate and is moderately effective in reducing vehicle emissions while the OBD test is the least 

expensive to operate, but the most effective in reducing emissions. However, the OBD test can 
21

only be used for 1996 and newer model year vehicles because it relies on technology that is 

present on these later model vehicles. In Portland, ODEQ currently performs all three tests: Basic 

for 1975-80 model year vehicles, Enhanced for 1981-95 model years, and OBD for 1996 and 

newer model years. In Medford, ODEQ conducts the Basic and OBD tests. 

OBD-ready vehicles represent a large and increasing percentage of the vehicle population with a 

corresponding decline in the percentage of vehicles that receive the Enhanced test. Therefore, 

ODEQ can replace the Enhanced test with the Basic test for 1981-1995 model year vehicles 

without significantly affecting Portland's air quality. This change has no effect on the Medford 

area vehicle inspection program as ODEQ does not conduct the Enhanced test in Medford. 

III. Review of the Proposed Revisions to the SIP 

Even though the Enhanced test will be phased out, ODEQ has submitted technical evidence to 

EPA that the air quality, specifically related to Ozone and CO will not be degraded in the 

Portland Air Quality Maintenance Area. This change will allow ODEQ to conduct the testing 

operations more quickly and with fewer employees. ODEQ is able to achieve this operational 

cost reduction without significantly impacting air quality due to the effectiveness of the OBD test 

method. The OBD system helps keep 1996 and newer vehicles clean by precisely controlling all 

aspects of the vehicle operation. When the proposed Enhanced test phase-out is expected to be 

complete in January 2007, ODEQ forecasts that over 75 percent of the fleet will be 1996 and 

newer and therefore will have OBD systems. 

In addition to the Enhanced test phase-out, ODEQ is proposing other rule changes that provide 

improved customer service at reduced costs. ODEQ has already implemented House Bill 2546, 

enacted by the 2003 Oregon Legislature. House Bill 2546 reduced the frequency of testing 

required for self-testing fleets from once a year to once every other year. 

Another proposed change is to eliminate the requirement for two elements of the vehicle 

inspection test operations that have been difficult to implement: gas cap and purge testing. 

The gas cap test is designed to reduce emissions by ensuring that the vehicle's gas cap has an 

adequate seal on the vehicle's fuel tank as part of the Basic and Enhanced tests. The device 

developed for this test had compatibility issues with some adapters in testing and has proved to 

be an impediment for the State of Oregon. 

The purge test is designed to ensure that gasoline fumes from the fuel tank are captured and 

subsequently burned by the vehicle's engine, as part of the Enhanced test. Available test methods 

did not cover all makes and models, was intrusive and required highly qualified personnel to 

correctly administer the test. These difficulties also tended to create bottle-necks in the testing 

lanes. However, presently installed OBD systems automatically monitor and ensure 

dependability of purge operations and evaporative control systems to prevent evaporative 

emissions from escaping in to the atmosphere. This accomplishes the goal of reducing 

evaporative emissions from venting to ambient air. Finally, additional rule changes were made to 

correct grammatical errors, citations and definitions. 
22

IV. Evaluation 

a. Compliance of the submitted changes to the CO and Ozone NAAQS 

ODEQ demonstrated to EPA that the changes proposed will not affect long term 

attainment of the Carbon Monoxide and Ozone clean air standards in the Portland 

area. NAAQS have been met for the last ten years in this area, and ODEQ has 

demonstrated that it will continue to meet standards in the future. 

For Carbon Monoxide, this requirement was addressed when the EQC adopted the 

renewal to the Carbon Monoxide maintenance plan in December 2004. This 

Portland CO 2nd 10-Year maintenance plan demonstrates continued maintenance 

attainment of the Carbon Monoxide standard through the year 2017, without the 

Enhanced test. The CO Maintenance Plan was approved by the EPA on January 

24, 2006 (71 FR 3768). 

For Ozone, this requirement was addressed by ODEQ when it submitted a Section 

110 Ozone Maintenance Plan for the Portland AQMA. (Can you reference the 

earlier analysis in this doc- that is the thing you’re referring to, correct?) The 

analysis in that plan confirmed that the area would not exceed the 1997 or the 

2008 8-hour Ozone NAAQS with the phasing out of the Enhanced Test and other 

changes mentioned above. The plan also demonstrated that the Ozone standards 

will be maintained through the year 2014 and is being acted on US EPA 

concurrently with this action. 

b. Compliance of submitted changes to section 110(l) of the CAA

A review of whether this plan revision meets all CAA requirements was done per 

Section 110(l) of the CAA which states “....The Administrator shall not approve a 

revision of a plan if the revision would interfere with any applicable requirement 

concerning attainment and reasonable further progress (as defined in section 171), 

or any other applicable requirement of this Act.” 

With respect to these specific tests, the only pollutants that are affected are 

Nitrogen Oxides, VOCs, and CO. Other criteria pollutants such as PM, Pb, and 

SO2, are not affected by these changes proposed by ODEQ. With respect to CO, 

the above section clarifies that the approved CO Maintenance Plan for Portland 

(71 FR 3768) serves to demonstrate that the applicable CO NAAQS will be 

maintained with the changes proposed because(?) these changes were 

incorporated into the maintenance demonstration. 

VOC’s and NOx are ozone precursors and any increases to those precursors must 

be analyzed to demonstrate that they do not interfere with the attainment and 

reasonable further progress of any applicable requirement of the CAA 

(specifically the Ozone NAAQS). The most significant change is that of the 
23

Ozone NAAQS from 1997 to 2008. The 2008 8-hour Ozone NAAQS were 

promulgated in March 2008 with primary and secondary standards at 0.075 ppm 

or 75 ppb. These are the currently applicable NAAQS and the attainment 

demonstration has to show that the 2008 NAAQS is also not being violated into 

the future due to the changes proposed by the State of Oregon. 

In section 4.40.5.4 of ODEQ’s 110 (a)(1) Maintenance Plan for the PortlandVancouver Air Quality Management Area (AQMA) and the Salem-Keizer Area 

Transportation Study Air Quality Area (SKATS AQA), ODEQ summarizes the 

results of dispersion modeling study performed for the Pdx/Van Maintenance 

Area in 2004 by the Washington State University (WSU) (see table and chart 

below). This 110(a)(1) maintenance plan is being concurrently processed with this 

SIP modification. 

2015 Maintenance Demonstration for the Pdx/Van/SKATS 

Maintenance Area (ppm) 

8-hour ozone standard = 0.08 ppm 

Exceedance ≥ 0.085 ppm maximum 

Violation >0.085 ppm Predicted Design Value 

Monitoring Site 1998 

Predicted 

Maximum 

2015 

Predicted 

Maximum 

2015 

Predicted 

Design 

Value*, ppm 

Portland/Carus 0.098 0.094 0.072 

Portland/Milwaukie 0.092 0.096 0.062 

Portland/Sauvie Island 0.082 0.076 0.054 

Vancouver/Mountain View 0.083 0.081 0.061 

Salem/Turner 0.088 0.075 0.060 

*Predicted Design Value is calculated using the EPA statistical procedure called the 

Relative Reduction Factor described in Appendix 6 of the ODEQ’s submittal and in 

EPA’s 8-hour ozone modeling guidance. Predicted design value is compared to the 8-

hour ozone standard to determine compliance. 
24

These results illustrate that the Pdx/Van AQMA and the SKATS will maintain compliance with 

the 1997 and the 2008 8-hour ozone standards of 0.08 and 0.075 ppm respectively, through 2015. 

The Carus monitoring site, downwind of Portland, has historically been the site with the highest 

ozone readings in the region. The model predicted that the Milwaukie site would produce a 

slightly higher maximum value under worst case meteorological conditions, and the maximum 

values at both Milwaukie and Carus would exceed but not violate the standards. However, the 

Carus site is expected to remain the highest and most important site for determining compliance 

with the ozone standard. The design values at Carus and all other sites demonstrate continued 

compliance with all applicable ozone NAAQS. 

IV. Conclusion 

Based on our review, this plan revision meets the requirements of Section 110(l) of the CAA. 

V. Recommended Agency Action 

The SIP revision request is proposed to be approved. 
25

Rules Approved with this Action

OREGON ADMINISTRATIVE RULES Chapter 340, Division 256 -Department of 

Environmental Quality: MOTOR VEHICLES 

° Definitions: 340-256-0010, 

° Visible Emissions: 340-256-0100, 

° Motor Vehicle Fleet Operation: 340-256-0130, 

° Emission Control System Inspection: 340-256-0300, 

° Government-Owned Vehicle, Permanent Fleet Vehicle and United States Government 

Vehicle Testing Requirements: 340-256-0310, 

° Light Duty Motor Vehicle and Heavy Duty Gasoline Motor Vehicle Emission Control 

Test Method for Basic Program: 340-2560340, 

° Light Duty Motor Vehicle Emission Control Test Method for Enhanced Program: 340-

256-0350, 

° Light Duty Motor Vehicle Emission Control Test Criteria for Basic Program: 340-256-

0380, 

° Heavy Duty Gasoline Motor Vehicle Emission Control Test Criteria: 340-256-0390