Victoria County Eight-Hour Ozone Maintenance Plan 

Technical Support Document

I. Background 

On March 3, 1978, under the 1977 Clean Air Act (CAA) amendments, Victoria County, 

Texas, was designated a nonattainment area because it did not meet the National Ambient Air 

Quality Standards (NAAQS) for 1-hour ozone (43 FR 8962). As required by the CAA, the state 

of Texas submitted a State Implementation Plan (SIP) to the EPA in 1979. This SIP outlined 

control measures to bring the area into attainment for the 1-hour ozone NAAQS. This SIP was 

approved by EPA in two actions, one in 1980 and another in 1984. An additional SIP revision 

for Victoria County was submitted to EPA on November 12, 1992. This submission revised the 

air monitoring, reporting and record keeping requirements for VOC sources and was approved 

by EPA on March 7, 1995 (60 FR 12348). 

On July 27, 1994, Texas submitted a request to redesignate Victoria County to attainment 

for the 1-hour standard. At the same time, Texas submitted the required ozone monitoring data 

and a maintenance plan to ensure the area would remain in attainment for ozone for a period of 

10 years. The maintenance plan submitted by Texas followed EPA guidance for limited 

maintenance areas, which provides relief for ozone areas that have design values less than 85% 

of the applicable standard. In this case, the applicable standard was the 1-hour ozone standard of 

0.12 parts per million (ppm). At the time of the redesignation request, the design value for 

Victoria County was 0.100 ppm, well below the 85% threshold of 0.106 ppm. EPA approved 

Texas’s request, and Victoria County was redesignated to attainment for the 1-hour ozone 

NAAQS and the maintenance plan was approved, on March 7, 1995, with an effective date of 

May 8, 1995 (60 FR 12453). 

 On April 30, 2004, EPA designated and classified areas for the 1997 8-hour ozone 

NAAQS (69 FR 23858), and published the final Phase 1 rule for implementation of the 1997 8-

hour ozone NAAQS (69 FR 23951). Victoria County, Texas was designated as 

unclassifiable/attainment for the 1997 8-hour ozone standard, effective June 15, 2004. The area 

is consequently required to submit a 10-year maintenance plan under section 110(a)(1) of the 

CAA and the phase 1 rule. On May 20, 2005, EPA issued guidance providing information 

regarding how a state might fulfill the maintenance plan obligation established by the Act and 

the Rule (Memorandum from Lydia N. Wegman to Air Division Directors, Maintenance Plan 

Guidance Document for Certain 8-hour Ozone Areas Under Section 110(a)(1) of Clean Air Act, 

May 20, 2005). This SIP revision satisfies the section 110(a)(1) CAA requirements for a plan 

that provides for implementation, maintenance, and enforcement of the 1997 8-hour ozone 

NAAQS in the Victoria County, Texas 1997 8-hour ozone unclassifiable/attainment area. 

 The above information is consistent with Designation Scenario C in the May 20, 2005, 

Guidance Document: “Areas that are designated unclassifiable / attainment for the 1997 8-hour 

ozone NAAQS and are designated attainment for the 1-hour ozone NAAQS with an approved 

maintenance plan (8UA/1M).” 
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 On December 22, 2006, the United States Court of Appeals for the District of Columbia 

Circuit issued an opinion that vacated EPA's Phase 1 Implementation Rule for the 1997 8-hour 

Ozone Standard. (South Coast Air Quality Management District. v. EPA, 472 F.3d 882 (D.C. 

Cir. 2006). Petitions for rehearing were filed with the Court, and on June 8, 2007, the Court 

modified the scope of the vacatur of the Phase I rule. See 489 F.3d 1245 (D.C. Cir. 2007), cert. 

denied, 128 S.Ct. 1065 (2008). The Court vacated those portions of the Rule that provide for 

regulation of 1997 8-hour ozone nonattainment areas under Subpart 1 in lieu of Subpart 2 and 

that allow backsliding with respect to new source review, penalties, milestones, contingency 

plans, and motor vehicle emission budgets. Consequently, the Court’s modified ruling does not 

alter any requirements under the phase 1 1997 8-hour ozone implementation rule for 

maintenance plans. 

 

On March 7, 2007, the Texas Commission on Environmental Quality (TCEQ), adopted 

a revision to the SIP to incorporate a plan for maintenance of the 1997 eight-hour ozone NAAQS 

in Victoria County. a The revision incorporating the ozone maintenance plan contained an 

updated attainment emissions inventory and technical analyses in support of the projections 

demonstrating maintenance of the eight-hour ozone NAAQS through 2014. 

 On July 28, 2010, the TCEQ adopted a Contingency Plan Revision to the 1997 8-hour 

Ozone Maintenance Plan for the Victoria County Ozone Attainment Area SIP. This SIP revision 

is an amendment as required by the CAA and no new control strategies have been incorporated 

into this revision. The revision includes three voluntary contingency measures that are triggered 

prior to a violation of the 1997 8-hour ozone NAAQS, and a fourth contingency measure 

triggered upon violation of the 1997 8-hour ozone NAAQS. This fourth contingency measure 

provides a list of potential rules the TCEQ may adopt and implement: the rules considered 

include but are not limited to: 30 Texas Administrative Code (TAC) Chapter 114 rule for Texas 

Low Emission Diesel; Chapter 115 volatile organic compound rules; and Chapter 117 nitrogen 

oxides rule. 

 This SIP revision satisfies the CAA requirements for the Victoria County O3 maintenance 

areas. 

II. Analysis of the State’s Submittals

A. General Requirements of 8-hour O3 Maintenance Plans 

Section 110 of the Clean Air Act provides the general framework for Implementation 

Plans. The EPA document entitled “Maintenance Plan Guidance Document for Certain 8-hour 

Ozone Areas Under Section 110(a)(1) of Clean Air Act” dated May 20, 2005, provides more 

detailed information about maintenance plan requirements. 
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The maintenance plan submitted by Texas meets CAA requirements, and follows EPA 

guidance. 

B. Specific Requirements of 8-hour O3 Maintenance Plans 

The 8-hour ozone 110(a)(1) maintenance plan constitutes a SIP revision and must provide 

for continued maintenance of the 8-hour ozone NAAQS in the area for 10 years from the 

effective date of the area’s designation as unclassifiable/attainment for the 8-hour ozone 

NAAQS. The Victoria County maintenance plan includes the following components: 

 Attainment Inventory (Chapter 2) 

 Maintenance Demonstration (Chapter 3) 

 Ambient Air Quality Monitoring (Chapter 4) 

 Contingency Plan (Chapter 5). 

1. Attainment inventory. The State must include an emissions attainment inventory to 

identify a level of emissions in the area which is sufficient to attain the NAAQS. According to 

the EPA Guidance, May 20, 2005, the attainment inventory should be based on actual “typical 

summer day” emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx). The 

Phase I Implementation Rule provides that the 10-year maintenance period begins as of the 

effective date of designation for the 8-hour NAAQS for the area and indicates that the State may 

use one of any of the three years on which the 8-hour attainment designation was based (i.e., 

2001, 2002, and 2003) for an attainment inventory. 

 For the emissions attainment inventory for the Victoria County maintenance plan, 

Texas is using actual “typical summer day” emissions of VOCs and NOx for the base year 2002. 

As recommended by the EPA, the TCEQ selected 2002 as the attainment emission inventory 

base year because it is one of the three years on which the 8-hour ozone designation was based. 

The 2002 VOC and NOx emissions for the Victoria County area were developed consistent with 

EPA guidance. This information is provided in Chapter 2 of the plan. 

 

2. Maintenance Demonstration. In this section, the State must demonstrate how the 

area will remain in compliance with the 8-hour ozone standard for the applicable 10 year period, 

which in this case begins with an effective date of designation of June 15, 2004, and extends to 

June 15, 2014. The typical method that areas have used in the past to demonstrate that an area 

will maintain the 1-hour standard has been to identify the level of ozone precursor emissions in 

the area which is sufficient to attain the NAAQS and to show that future emissions of ozone 

precursors will not exceed the attainment levels. To perform this analysis for the 8-hour 

maintenance plan, the State could develop emission inventories for one of the three years used to 

establish the area’s attainment status and for the projection year. Maintenance may also be 

demonstrated using other methods, such as modeling. 

 

In Chapter 3: Maintenance Demonstration of the updated plans, the State is using 2002 

base year inventory data, and emission projections for 2004, 2010, and 2014. The State has 
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identified the level of precursor emissions in Victoria County that are sufficient to attain the 

NAAQS, i.e., the 2002 attainment inventory, and established interim emission projections of 

ozone precursors for the years 2004, 2010, and 2014. The below summary tables for NOx and 

VOC emissions in Victoria County by source type depict the emission inventories that will be 

used to compare against 2002. 

Table 1: Total VOC Emissions for 2002-2014 (tpd)

Source 

Category 

2002 VOC 

Emissions 

2004 VOC 

 Emissions 

2010 VOC 

Emissions 

2014 VOC 

Emissions 

Nonroad 

Mobile 

1.21 1.00 0.64 0.57 

Area 6.28 6.31 6.85 7.23 

Point 2.60 3.10 3.30 3.60 

Onroad 

Mobile 

3.29 2.71 1.78 1.40 

Total 13.38 13.12 12.57 12.8 

Table 2: Total NOx Emissions for 2002-2014 (tpd)

Source 

Category 

2002 NOx 

Emissions 

2004 NOx 

 Emissions 

2010 NOx 

Emissions 

2014 NOx 

Emissions 

Nonroad 

Mobile 

2.23 2.02 1.77 1.51 

Area 2.56 2.65 2.90 3.07 

Point 13.00 15.00 16.00 17.00 

Onroad 

Mobile 

11.26 9.72 4.86 2.90 

Total 29.05 29.39 25.53 24.48 

The trend analysis shows an overall decrease in NOx and VOC emissions for Victoria County 

and thus shows continued attainment through the end of the 10-year period following designation 

under the eight-hour standard. 

3. Ambient Air Quality Monitoring. To verify the attainment status of the area over the 

ten-year maintenance period, the maintenance plan should contain provisions for continued 

operation of an appropriate, EPA-approved air quality monitoring network in accordance with 40 

CFR Part 58. 
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In Chapter 4 of the plan, the State of Texas has provided data indicating that the Victoria County 

area will remain in compliance with the 8-hour ozone standard for the 10-year period following 

the effective date of designation for the 8-hour NAAQS of June 15, 2004, and has projected 

attainment for 2014. This data will be quality controlled and submitted to EPA AQS on a 

monthly basis. A set of indicators and trigger levels, based on monitoring data, is specified in 

Section VI.B.10a.7(e), Contingency Plan. The Victoria County monitoring network is located in 

the City of Victoria (CAMS 87) and is the monitor driving the area’s design value. The monitor 

is managed in accordance with 40 CFR Part 58, to verify the attainment status of the county. 

The monitor will be used to detect if and when appropriate levels have been exceeded for 

contingency measure triggering purposes. As per the current minimum ozone monitoring 

requirements in 40 CFR Part 58, Appendix D, Table D-2, only one monitor is required for the 

Victoria MSA. That monitor (AQS #48-469-0003, or CAMS 87) has a 2005-2007 8-hour ozone 

design value of 69 ppb (72 ppb for 2004-2006).

 

The eight-hour ozone design value based upon data collected from 2003-2005 at the 

CAMS 87 monitor is 76 parts per billion (ppb). Since that time, the 8-hour ozone design values, 

which are based on a three-year average of the fourth-highest daily maximum average ozone 

concentration, were as follows in parts per billion: 

 2000 2001 2002 2003 2004 2005 

 79 ppb 79 ppb 76 ppb 78 ppb 79 ppb 76 ppb 

 2006 2007 2008 2009 2010 2011 2012 

 72 ppb 69 ppb 66 ppb 65ppb 66 ppb 70 ppb 69 ppb 

These design values are well below the current 8-hour ozone NAAQS level of 75 ppb. (Allowed 

up to .084 ppm) 

4. Contingency Plan. EPA guidance requiring Section 110(a)(1) maintenance plan areas to 

include in the contingency plan an enforceable commitment to adopt and implement the 

contingency measures once triggered, and identify measures to be adopted. The current 

contingency plan includes six 30 Texas Administrative Code (TAC) rules the TCEQ may choose 

to amend should Victoria County monitoring data indicate the area has violated the 1997 eighthour ozone NAAQS. 

 The rules listed are included in the Chapter 114 Texas Low Emission Diesel (TxLED) 

compliant marine diesel rule, Chapter 115 volatile organic compounds (VOC) emission controls 

for storage tanks, and Chapter 117 nitrogen oxides (NOX) controls for combustion engines. 
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Those to be considered include but are not limited to the control measures identified, as the most 

appropriate contingency measures may be significantly different from the measures mentioned. 

 If Victoria County monitors a three-year eight-hour ozone average at or above 82 parts 

per billion (ppb), the City of Victoria will institute a voluntary program with industry to 

reschedule, revise, or curtail activities during Ozone Advisory Days, which are EPA’s AIRNow 

Air Quality Index “Orange Days,” and are at or above 76 ppb. This program will be developed 

and available within 30 days after notification by the TCEQ that the contingency measure will be 

required. This program will be implemented as expeditiously as practicable, but no later than 24 

months after the Texas Commission on Environmental Quality’s (TCEQ) notification that the 

contingency measure is needed. 

 If Victoria County monitors an eight-hour ozone three-year average at or above 83 ppb, 

the TCEQ will work with the City of Victoria and the local Air Victoria Team to implement 

various voluntary control measures that may include: 

substantially increasing the number of businesses notified on Ozone Advisory Days; 

increasing the number of ozone public announcements; and 

other voluntary control measures as identified in a letter from the City of Victoria, dated 

September 8, 2009. 

 In the event that this contingency measure is triggered, Victoria County may also be 

expected to voluntarily implement further local control measures, and previous efforts to reduce 

ozone may need to be retained. This program will be developed and available within 30 days 

after notification by the TCEQ that the contingency measure will be required. This program will 

be implemented as expeditiously as practicable, but no later than 24 months after verified 

monitoring data indicate that the Victoria County three-year average of each annual fourthhighest daily maximum eight-hour ozone average is at or above 83 ppb. 

 If air quality monitoring data indicate three or more exceedances of the 1997 eight-hour 

ozone NAAQS (measured at 0.08 parts per million) within one calendar year, the TCEQ will 

analyze air quality data, meteorological conditions, transport, and related factors in Victoria 

County to determine the cause of the exceedances. The TCEQ will notify the EPA of its findings. 

 If air quality monitoring data indicate that Victoria County’s design value violates the 

1997 eight-hour ozone NAAQS with a monitored value of 85 ppb or above, the TCEQ will 

implement specific contingency measures to promptly correct the violation. Those to be 

considered include but are not limited to the control measures identified below. The most 

appropriate contingency measures may be significantly different from the measures mentioned 

below due to technological, societal, economic, and political factors that are impossible to 

predict. Contingency measures will be implemented as expeditiously as practicable, but no later 

than 24 months after verified air quality monitoring data indicate that the Victoria County three-
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year average of each annual fourth-highest daily maximum eight-hour ozone average violates the 

1997 eight-hour ozone NAAQS. 

 Revision to 30 Texas Administrative Code (TAC) Chapter 117 Subchapter E, Division 4, 

to control rich-burn, gas-fired, reciprocating internal combustion engines located in Victoria 

County to meet nitrogen oxides (NOX) emission specifications and other requirements to reduce 

NOX emissions and ozone air pollution. 

 Inclusion of Victoria County in 30 TAC Chapter 115 volatile organic compounds (VOC) 

rules for the control of crude and condensate storage tanks at upstream oil and gas exploration 

and production sites or midstream pipeline breakout stations with uncontrolled flash emissions 

greater than 25 tons per year. 

 Inclusion of Victoria County in 30 TAC Chapter 115 VOC rules for more stringent 

controls for tank fittings on floating roof tanks, such as slotted guidepoles and other openings in 

internal and external floating roofs. 

 Inclusion of Victoria County in 30 TAC Chapter 115 VOC rules limiting emissions from 

landings of floating roofs in floating roof tanks. 

 Inclusion of Victoria County in 30 TAC Chapter 115 VOC rules for control of VOC 

emissions from degassing operations for storage tanks with a nominal capacity of 75,000 gallons 

or more storing materials with a true vapor pressure greater than 2.6 pounds per square inch 

absolute (psia), or with a nominal capacity of 250,000 gallons or more storing materials with a 

true vapor pressure of 0.5 psia or greater. Degassing vapors from storage vessels, transport 

vessels, and marine vessels would be required to vent to a control device until the VOC 

concentration of the vapors is reduced to less than 34,000 parts per million by volume as 

methane. 

 Inclusion of Victoria County in 30 TAC Chapter 114 rule for Texas Low Emission Diesel 

(TxLED) compliant marine diesel. 

 The contingency measures and schedules for implementation included in the maintenance 

plan are consistent with EPA’s long-standing guidance on contingency measures, including the 

discussion of contingency measures in the General Preamble (57 FR 13498) (see docket). 

III. EPA Conclusion and Recommendation

 Based on the above discussion, I recommend approval of the submitted SIP revision 

incorporating the Victoria County Section 110(a)(1) 8-hr Ozone Maintenance Plan into the Texas 

SIP. 

 
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Attachments:

1. EPA Guidance Memorandum: Maintenance Plan Guidance Document for Certain 8-hour 

Ozone Areas Under Section 110(a)(1) of Clean Air Act (Lydia N. Wegman, Director, Air 

Quality Strategies and Standards Division, May 20, 2005). 

 

2. Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard – Phase 

1, 69 FR 23951, April 30, 2004. 

3. Consolidated Emissions Reporting Rule (CERR), Final Rule, 67 FR 39602, June 10, 2002. 

4. Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National 

Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations, August, 2005, 

revised November 2005.