EXHIBIT 4 

(CONTINUED)
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CHAPTER 5: WEIGHT OF EVIDENCE 

5.1 QUANTITATIVE CORROBORATIVE ANALYSIS 

5.1.1 Introduction 

The corroborative analysis presented in this chapter demonstrates the progress that the HoustonGalveston-Brazoria (HGB) area is making towards attainment of the 1997 eight-hour ozone National 

Ambient Air Quality Standard (NAAQS) of 0.08 parts per million (ppm). The United States 

Environmental Protection Agency’s (EPA) April 2007 “Guidance on the Use of Models and Other 

Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze” 

(EPA, 2007) states that all model attainment demonstrations should include supplemental evidence that 

the conclusions derived from the basic attainment modeling are supported by other independent sources 

of information. This document will present the supplemental evidence, i.e., the corroborative analyses, 

for the current modeling demonstration. The guidance also states that a weight of evidence demonstration 

is allowed when the future design value is at or below 87.9 parts per billion (ppb). 

The first section of the quantitative corroborative analysis will discuss photochemical grid modeling. 

Modeling is one of the most important tools available for evaluating progress toward meeting air quality 

standards, but it is not a perfect tool. The first section will also discuss known issues with photochemical 

grid modeling and how the Texas Commission on Environmental Quality (TCEQ) has dealt with them. It 

also discusses overall model performance. Finally, it discusses the diagnostic analyses performed by the 

TCEQ, and the implications of those analyses on the projected attainment status. The second section of 

the quantitative corroborative analysis will discuss trends in ozone and ozone precursors observed in the 

HGB area, and examines the possible causes for those trends. The third section describes air quality 

control measures that cannot yet be adequately quantified but are nonetheless expected to yield tangible 

air quality benefits. 

5.2 Corroborative Analysis: Modeling 

Photochemical grid modeling of the HGB area is challenging, due to complex coastal wind circulation, 

complex petrochemical point sources of emissions in Brazoria, Chambers, Galveston, and Harris 

Counties, and the challenges associated with modeling a metropolitan area of over five million 

inhabitants. 

One purpose of the Texas Air Quality Study 2000 (TexAQS 2000) and the Texas Air Quality Study 2006 

(TexAQS II) field studies was to address the uncertainties that affect photochemical grid modeling and 

their regulatory applications. Insights gleaned from the TexAQS 2000 and subsequent studies have 

helped resolve some of these uncertainties. 

Several studies have tried to identify and reduce uncertainties in the HGB photochemical grid modeling. 

Foremost among these efforts are the studies that have sought to quantify underreported industrial highly 

reactive volatile organic compounds (HRVOC) emissions (Wert et al., 2003; Xie and Berkowitz, 2007; 

Yarwood et al., 2004; TCEQ, 2002, 2004, 2006; Smith and Jarvie, 2008) and to assess the sensitivities of 

ozone simulations to underreporting these emissions (TCEQ, 2002, 2004, 2006; Byun et al., 2007; Jiang 

and Fast, 2004). Other modeling efforts have tested different chemical mechanisms in the HGB area’s 

photochemical grid modeling, to study the effects of using different mechanisms on ozone model 

performance and control strategy effectiveness (Byun et al., 2005b; Faraji et al., 2008; Czader et al., 

2008). Modeling sensitivity studies have also been performed to guide selection of model parameters 

such as vertical mixing schemes, number and depth of model layers, and horizontal grid resolution 

(Kemball-Cook et al., 2005; Byun et al., 2005b; Byun et al., 2007; Bao et al., 2005). 

 
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Some of the most important findings of these studies include the following. 

• Emissions inventories must be reconciled to some extent with observational data before the 

model can accurately depict the ozone formation processes in the HGB area, especially for 

HRVOC. 

• Adding HRVOC to modeling emissions inventories generally increases ozone concentrations and 

alleviates a portion of the ozone and HRVOC under-prediction problems found by every 

modeling group who has attempted to model the HGB area. 

• Reactivities of the TCEQ-defined HRVOC are high regardless of which chemical mechanism is 

used to evaluate their effects. In addition to the TCEQ list of HRVOC, formaldehyde also 

displays high reactivity. 

Mesoscale meteorological modeling is used to drive photochemical grid models, and many studies have 

examined and reduced uncertainties in these models as well. One of the most successful efforts improved 

meteorological simulations of ozone episodes by using radar profiler and other upper level wind data to 

“nudge” the meteorological modeling (Nielsen-Gammon et al., 2007; Zhang et al. 2007; Stuart et al., 

2007; Bao et al., 2005; Fast et al., 2006). Other efforts improved land cover data and land surface 

modeling (Byun et al., 2005a; Cheng et al., 2008a, 2008b) and studied the sensitivity of ozone simulations 

to solar irradiance and photolysis rates (Zamora et al., 2005; Fast et al., 2006; Pour-Biazar et al., 2007; 

Byun et al., 2007; Koo et al., 2008). 

Some of the most important findings of these meteorological modeling studies include the following. 

• Assimilation of radar profiler and other upper air wind data is essential to good meteorological 

modeling performance in the HGB area. 

• Modeling parameterizations need to be chosen carefully to alleviate the common problem of 

spurious thunderstorms and clouds. 

• Accurate simulation of cloud cover is crucial to getting photolysis rates correct in the 

photochemical grid model, and ozone predictions are very sensitive to photolysis rates. 

• An ensemble approach to meteorological and photochemical grid modeling may be warranted, 

given the sensitivity of ozone modeling to relatively small changes in meteorology. The 

ensemble approach will allow probabilistic attainment demonstrations to be produced. 

In the remainder of this section, modeling issues identified by the studies described above will be 

discussed, as well as issues raised by TexAQS 2000 research, by TexAQS II research, and by TCEQsponsored investigations. Overall performance of the photochemical grid modeling and the implications 

of the model’s ability to accurately simulate ozone episodes will also be discussed. Finally, additional 

metrics that show the effects of the proposed control strategies on ozone in the HGB area will be 

presented. 

5.2.1 Solving Modeling Problems 

For the HGB area, there are several aspects of ozone modeling that require special attention, due to their 

role in current or historical shortcomings in model performance. This section discusses some of these 

issues, and how TCEQ has attempted to resolve them in this round of modeling. 

5.2.1.1 Industrial Point Source Emission Inventory Issues 

High concentrations of light alkenes such as propylene, ethylene, 1,3-butadiene, and butenes have been 

observed in the HGB metropolitan area, and are closely associated with petrochemical industry facilities 

in eastern Harris, Galveston, Chambers, and Brazoria Counties (Ryerson et al., 2003; Daum et al., 2003; 

Daum et al., 2004; Berkowitz et al., 2004; Berkowitz et al., 2005; Kleinman et al., 2002; Kleinman et al., 

2005; Jobson et al., 2004; Karl et al., 2003; Buzcu and Fraser, 2006; Xie and Berkowitz, 2006, 2007; Kim 

et al., 2005). These compounds have been identified as highly reactive, and they play a major role in 

forming the highest concentrations of ozone observed in the HGB area (Ryerson et al., 2003; Daum et al., 

2003, 2004; Kleinman et al., 2002, 2005; Wert et al., 2003; Czader et al., 2008). Historical analyses of 

routinely collected volatile organic compounds (VOC) data indicate that these compounds are present in 
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high concentrations on a routine basis in the HGB area (Hafner Main et al., 2001; Estes et al., 2002; 

Brown and Hafner Main, 2002; Brown et al., 2002; Hafner and Brown, 2003; Jolly et al., 2003; Fang and 

McDowell, 2003; Jolly, 2003; Kim et al., 2005; Buzcu and Fraser, 2006; Xie and Berkowitz, 2006, 2007). 

Consequently, the high HRVOC concentrations observed during the two field study periods in 2000 and 

2006 are not anomalously large, and the conclusions drawn from those data should be generally 

applicable to the HGB area. 

Both field studies sponsored by the TCEQ, TexAQS 2000 and TexAQS II, have indicated that there are 

substantial discrepancies in the reported emissions of HRVOC, especially ethene and propylene (Ryerson 

et al., 2003; Daum et al., 2003; Daum et al., 2004; Wert et al., 2003; Gilman et al., 2009; de Gouw et al., 

2009). The TCEQ remote sensing studies of flares, storage tanks, cooling towers, and other sources have 

shown that large quantities of VOC emissions have gone unreported (Robinson et al., 2008; Smylie et al., 

2004). In addition, solar occultation flux measurements have shown that 30-minute variations in 

industrial HRVOC emissions can be an order of magnitude or more (Mellqvist et al., 2007, 2008). 

In an attempt to better quantify underreported HRVOC for purposes of photochemical grid modeling, the 

TCEQ commissioned a study by researchers at the Pacific Northwest National Laboratory (Xie and 

Berkowitz, 2006, 2007). The researchers used historical HRVOC measurements from the extensive 

automated gas chromatograph network currently in place in the industrial areas of the HGB area. Most of 

the sites in this network went into operation during 2003. Using trajectories to link the source areas to the 

observations, the researchers were able to estimate which areas had the greatest emissions relative to other 

areas. 

For the current round of modeling, TCEQ researchers extended the methods developed by Pacific 

Northwest National Laboratory to quantitatively estimate underreported HRVOC emissions in the HGB 

area. The Potential Source Contribution Function method has measurably improved model performance 

for ozone and its precursors by reconciling the industrial point source emissions inventory with observed 

HRVOC concentrations during 2005-2006 (Smith and Jarvie, 2008). This method does not attempt to 

reproduce the temporal variations in emissions, but instead calculates a median rate of emission for each 

square kilometer of the HGB area. Since two years of data are used to estimate the medians, the metric is 

statistically robust. 

5.2.1.2 Modeling of Emissions Events

Attempts have been made to quantify temporal variations in industrial point source emissions by 

accessing emission event reports that are delivered by industry to the TCEQ (Murphy and Allen, 2005). 

Problems with the event report data include the following. 

• Emission events were self-reported by industry, and the quantities of emissions reported were not 

independently observed or verified. Facilities are allowed, by rule, to estimate emissions during 

emergency releases due to safety concerns. 

• Emission events were only reported if estimated emissions were greater than a certain threshold 

above the permitted emission level. Some facilities have very large permitted emissions levels, and 

therefore large fluctuations in emissions may occur under an authorized emission rate that are not 

included in the data set. Consequently, the frequency and magnitude of emission events in this data 

set does not reflect the actual magnitudes or frequency of emission events. 

• Emission event data for the Murphy and Allen study were collected before industry was required to 

monitor HRVOC. Therefore, most of the emission estimates are not based upon measurements of 

the events. 

• The TCEQ infrared camera studies have found numerous instances where emissions were 

emanating from locations that were not included in any emissions inventory. 

• The TCEQ flare investigations have found that flares are typically managed to reduce noise, smoke, 

and glare. Optimizing the flare to keep destruction efficiency at a maximum is a secondary 

consideration. In particular, flares used as both emergency flares and process flares have been 

observed to operate with poor combustion efficiency when operating in process flare mode 

(Robinson et al., 2008). 
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• In addition, flare monitoring records only the chemicals flowing to the flare, not which species are 

actually being emitted. Combustion efficiencies are estimates of how much of the original material 

has been destroyed, and no effort is made to estimate the composition or reactivity of the 

combustion products. Circumstantial evidence from the TexAQS II and from the Study of Houston 

Atmospheric Radical Precursors (SHARP) suggests that formaldehyde may be produced during 

flare combustion, though the absolute quantity of emissions may only constitute a small part of the 

observed ambient formaldehyde (Gilman et al., 2009; De Gouw et al., 2009). The SHARP field 

campaign in April-May 2009 is investigating this hypothesis in greater depth. 

• Field studies (Mellqvist et al., 2007, 2008; de Gouw et al., 2009) and recent infrared camera and 

differential absorption lidar (DIAL) results (Robinson et al., 2008) show that the techniques used by 

industry to estimate HRVOC point source emissions are still inadequate to quantify them properly, 

because these experiments measured much higher emission fluxes than were reported. 

A number of recent modeling studies have attempted to investigate the frequency, magnitude, and impact 

of emission events upon ozone in Houston (Webster et al., 2007; Nam et al., 2006, 2008). Since these 

studies are based upon the emission event reports, they have not properly quantified the frequency or 

magnitude of the emission events, due to the problems discussed above. Therefore, the modeled impact 

of emission events described in the Webster et al. and Nam et al. studies are unlikely to accurately reflect 

the complete impact of emission events in the HGB area. Since the acquisition of properly quantified 

emissions for all industrial emission events that occur in the HGB area appears to be far in the future, the 

TCEQ has not attempted to speculate on the exact frequency or magnitude of sporadic emission events in 

this modeling exercise. 

5.2.1.3 Resolution of Photochemical Modeling Grids 

Numerous studies have investigated the effects of grid size on model behavior (Cohan et al., 2006; Esler, 

2003; Gego et al., 2005; Valari and Menut, 2008). The main interest in finer grid resolution is that higher 

resolution can increase concentrations of ozone precursors in narrow plumes, which can affect ozone 

production rate and sensitivity to VOC or nitrogen oxides (NOX) within the plumes. In a city such as 

Houston, using a higher resolution grid is sensible, given the abundance of industrial point sources, which 

can generate narrow plumes. Researchers during TexAQS 2000 determined that rapid ozone formation 

occurring within narrow industrial plumes are responsible for the highest observed ozone in the HGB 

area, and for the strong ozone gradients that can form. Strong ozone gradients can cause large increases 

in ozone concentration at monitoring sites as the plume is carried across town by winds that have shifted 

direction and are no longer parallel to the plumes. To resolve these atmospheric features, the TCEQ is 

using smaller-sized grid cells than previous modeling exercises (2 kilometer (km) × 2 km instead of 4 km 

× 4 km). In general, the TCEQ has found that smaller grid sizes can yield higher ozone production and 

can alleviate, in part, the commonly observed low bias for ozone within industrial plumes. There are 

limits to this solution, however; it is inappropriate to decrease grid size indefinitely. Parameterizations in 

both the meteorological modeling and the photochemical grid modeling are based upon the assumption 

that turbulence features within the planetary boundary layer (PBL) are much smaller than the grid size. If 

the grid size is decreased to 1 km × 1km or lower, the assumption probably no longer holds, and more 

uncertainty can be added to the modeling as a result of the finer resolution. If smaller grid sizes are 

desired, large eddy simulation modeling should be considered rather than photochemical grid modeling. 

Also, note that if the spatial resolution of the photochemical grid modeling is reduced, then the temporal 

resolution of the meteorological and chemical processes within the model ought to be reduced, to match 

the shorter residence time of precursors in each grid cell. In other words, as the size of the box shrinks, 

the amount of time that a mass of air resides in the box also shrinks, affecting how the ozone chemistry 

plays out. While the Comprehensive Air Model with Extensions (CAMx) automatically adjusts the time 

step for chemical processes, the meteorological process time step is fixed, based upon the input data from 

the Fifth Generation Meteorological Model (MM5). While it is possible to extract meteorological output 

with higher temporal resolution, reduction of the time steps seems likely to cause unusual model 

behavior. The reduction of time steps in regulatory photochemical grid modeling has not been well 

studied. In the future, it may be desirable to use grid sizes smaller than 2 km, and shorter time steps, but 

for now, TCEQ will refrain from experimenting with finer resolutions. For this round of modeling, the 
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TCEQ has reduced the size of the CAMx modeling grid cells from 4 km to 2 km through flexi-nesting, 

but has kept the size of the MM5 modeling grid cells at 4 km. 

5.2.1.4 Incommensurability and Model Performance Evaluation 

Swall and Foley (2009) discuss the problems inherent in comparing point measurements to grid cell 

values. In statistical parlance, this problem is known as incommensurability. A portion of the difference 

between point measurements and grid cell values is due solely to the fact that measurements made at a 

monitoring station do not generally represent an average of the conditions for the 2 km × 2 km grid cell in 

which it resides. The ability of a point measurement to represent the average of the entire grid cell area is 

related to how much sub-grid variation is observed in the area. If sub-grid variation is small, then the 

point measurement and the grid cell value are commensurate. If the spatial gradients of the variables of 

interest are large, the point measurements are less able to reflect the average conditions of the entire grid 

cell, and therefore they are incommensurate with the grid cell value. 

HGB area ozone often has strong spatial gradients due to the rapid ozone formation within industrial 

source plumes. In the HGB area, the worst ozone model performance is sometimes found in areas with 

the steepest ozone gradients, and the best ozone model performance is often found in areas further 

downwind, where the ozone gradients have lessened. Swall and Foley demonstrated that 

incommensurability alone is capable of degrading model performance in areas of steep gradients. They 

state in their discussion: “This means that, even if the model is performing perfectly and there is no 

observational error, we cannot expect that in a scatterplot, points representing paired modeled and 

observed values will lie on a one-to-one line. Our comparison of Gaussian and exponential correlation 

structures with the same effective range shows that this concern looms larger for correlation structures in 

which there is a rapid decrease in correlation for small distances relative to grid cell size (like the 

exponential).” While there are other causes of poor model performance as well, note that 

incommensurability is likely to be responsible for some of the differences between model output and 

point measurements. 

5.2.1.5 Ensemble Modeling 

A number of researchers have discussed the benefits of using ensembles of models to create more 

accurate forecasts (Pinder et al., 2009; Zhang et al., 2007). Pinder et al. and Zhang et al. have noted that 

probabilistic attainment demonstrations could be made using ensemble modeling and have argued that 

this approach can be more scientifically sound than a deterministic attainment demonstration. The TCEQ 

acknowledges the potential soundness of the ensemble approach but notes that the current regulatory 

framework does not easily allow for a probabilistic attainment demonstration. 

5.2.1.6 Vertical Distribution of Ozone 

Ozonesonde measurements have been made each summer in the HGB area since 2003 (Morris et al., 

2006). Findings from this study indicate that elevated free tropospheric ozone (i.e., above the PBL) in the 

HGB area is usually underestimated, and it often does not appear to mix down to the ground. Ozone in 

the lowest layers of the atmosphere often shows much more structure than the model simulates. The 

implication is that the model is mixing the lowest layers of the atmosphere more efficiently than they are 

actually mixing. The TCEQ has attempted to address these two issues. For the free tropospheric ozone, 

the TCEQ has obtained global model output for the appropriate time periods so that boundary conditions 

of free tropospheric ozone are more appropriate. Some of the discrepancies still persist; they appear to be 

related to phenomena that occur between the outermost domain boundaries and the HGB area. . For the 

PBL mixing issue, the TCEQ has improved the land cover data and sea surface temperature data in its 

latest round of modeling, in an attempt to improve the simulations of surface energy balance. In addition, 

the TCEQ has chosen the Eta PBL scheme (i.e., the Mellor-Yamada-Janjic scheme), which appears to be 

more effective at simulating PBL dynamics in the coastal regions than other available schemes. The 

TCEQ continues to investigate potential improvements for vertical mixing in the modeling. 

5.2.1.7 Photolysis Discrepancies Due to Improper Placement of Clouds 

Researchers at the University of Alabama-Huntsville performed a modeling study that examined the 

effects of modeled cloud cover on ozone performance in the HGB area, and found that some of the 
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shortcomings in model performance could be corrected with better depiction of clouds (Pour-Biazar et al., 

2007). University of Houston researchers also found that their forecasts were occasionally biased due to 

poor depiction of cloud cover (Byun et al., 2007). TCEQ-funded research found that higher-order 

decoupled direct method analysis of modeling sensitivities indicated substantial sensitivity to photolysis 

rates (Koo et al., 2008). 

The TCEQ has found similar cloud cover effects in the photochemical modeling for this state 

implementation plan (SIP). The greatest discrepancies tend to involve the model under-predicting cloud 

cover, and hence, greatly over-predicting ozone on low ozone days. Modeled episode days for which 

cloud cover problems exist include: May 28, 2005; June 17, 2005; July 31, 2005; Aug 5, 2005; May 31-

June 1, 2006; Aug 15, 2006; Aug 19, 2006; Aug 22, 2006; September 12, 2006; October 10, 2006. The 

average mean normalized bias for these days is +34.6 percent, compared to an average mean normalized 

bias on exceedance days of +9.7 percent. TCEQ process analysis shows that most of the radical 

initiation, propagation and termination steps are very sensitive to photolysis rates. Hence, improvements 

in cloud placement could greatly improve ozone and precursor performance, though the greatest 

improvements will likely occur on low ozone days. 

To improve the cloud distribution, the TCEQ has followed the guidance of Texas A&M University 

(TAMU) researcher and state climatologist John Nielsen-Gammon and has utilized the Grell cumulus 

parameterization, which reduces the amount of spurious thunderstorm formation in the HGB area. 

5.2.1.8 Radical Shortage 

A number of researchers studying urban photochemistry in the HGB area and other cities have found that 

available mechanisms for simulating radical production are unable to replicate the observed radical 

formation and propagation rates (Mao et al., 2007, 2009; Chen et al., 2009). The process analysis section 

of Appendix I: Corroborative Analysis for the HGB Attainment Demonstration SIP discusses this issue in 

detail and compares TCEQ process analyses to the Mao et al. and Chen et al. work. The TCEQ modeling 

is consistent with the Mao et al. and Chen et al. findings that there is apparently something missing in the 

current mechanisms. The atmospheric chemistry community as a whole has not yet resolved the problem 

or problems with the current mechanisms. Several hypotheses for the missing radical formation 

mechanism exist, including daytime nitrous acid (HONO) production from nitric acid-aerosol interactions 

and photolysis (Ziemba et al., 2009); isoprene production of hydroxyl radical (OH) (Lelieveld et al., 

2008; North and Ghosh, 2009); formation and decomposition of electronically excited nitrogen dioxide 

(NO2

*

) (Li et al., 2008); nitryl chloride (ClNO2) chemistry (Osthoff et al., 2008; Simon et al., 2008); 

improved aromatic chemistry (Faraji et al., 2008; Hu et al., 2007); and molecular chlorine reactions 

(Chang et al., 2002; Tanaka et al., 2003; Chang and Allen, 2006; Sarwar and Bhave, 2007). Given the 

manifold hypotheses and the current lack of a definitive explanation, the TCEQ has not incorporated 

modified chemical mechanisms into its base case modeling at this time. However, the TCEQ continues to 

support investigations for improving chemical mechanisms, and is prepared to adopt an improved 

mechanism when it becomes sufficiently mature. 

5.2.2 Model Performance Evaluations: Implications of the Model Performance of the Current SIP 

Modeling 

Model performance evaluation is presented in Chapter 3, Photochemical Modeling and in its associated 

appendices. Appendix I: Corroborative Analysis for the HGB Attainment Demonstration SIP includes 

two discussions of model performance in the Chemical Process Analysis and Intensive Model 

Performance sections. In addition, Appendix I: Corroborative Analysis for the HGB Attainment 

Demonstration SIP includes a discussion of using 2005 baseline modeling to estimate future 2018 design 

values. Based upon these evaluations, the following overall conclusions can be reached. 

Ozone performance 

• The model simulates the location, spatial extent, and relative intensity of ozone relatively well on 

most of the high-ozone days. 

• The model consistently underestimates peak ozone within the highest concentration plumes. 

• Simulated ozone depicts rapid morning ozone increases (30-50 ppb) relatively well, but tends to 
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miss afternoon peak concentrations. 

• Radical and ozone precursor budgets were calculated directly from observations by Mao et al. 

(2009) at the Moody Tower during TexAQS II. They observed that ozone formation in the HGB 

area is both VOC- and NOX-sensitive, with VOC-sensitive ozone formation usually occurring in 

the morning and NOX-sensitive formation occurring in the afternoon. Based upon the TCEQ’s 

process analysis, the TCEQ modeling appears to be simulating the VOC- and NOX-sensitivity of 

ozone formation at Moody Tower relatively well, because the relative radical termination rates 

generally agree with the Mao et al. data. 

• Process analysis and modeling sensitivity analyses show that peak eight-hour ozone is primarily 

NOX-sensitive in much of the domain, but can be VOC-sensitive downwind of the urban core and 

the HGB industrial areas. 

• According to TCEQ process analyses, VOC-sensitive conditions occur more often and more 

strongly in the industrial and urban core plumes. When ozone production is VOC-sensitive, 

usually more ozone is created than in NOX-sensitive conditions. 

• Chen et al. (2009) used the Moody Tower TexAQS II observations to constrain a steady-state 

photochemical box model. They used the Carbon Bond 05 chemical mechanism and several 

other chemical mechanisms to simulate the chemistry with the box model. They found that all of 

the chemical mechanisms underestimated peak daytime radical concentrations. The Carbon Bond 

05 mechanism used by the TCEQ in this modeling exercise is one of the better performing 

mechanisms, but it still doesn’t make enough radicals. The shortfall in radical production may be 

related to the shortfall in ozone production rates observed in the photochemical grid modeling. 

Note, however, that the results from Chen et al. are based upon a constrained steady-state box 

model, which assumes that the chemical system is in a photochemical steady state. It isn’t clear 

whether this assumption is valid all of the time in the HGB area. 

• Decreases in ozone production rates and other reaction rates correlate with decreases in NO2

photolysis, implying that most of the ozone formation chemistry is highly sensitive to photolysis, 

and hence, highly sensitive to cloud-cover errors. 

• Background ozone concentrations are important in accurately simulating the modeling for the 

HGB area. For most of the modeled days, the background ozone is unlikely to bias the modeling 

results in the HGB area, but during the July-August 2005 episode, excessively high background 

concentrations seem to compromise the model performance. 

• In rural areas, the model routinely over-predicts nighttime ozone and under-predicts NOX. The 

cause of this issue is unknown, but it could involve unreported NOX sources or problems with 

vertical mixing in rural areas. 

• Above the planetary boundary layer, the model sometimes underestimated ozone concentrations, 

especially in the springtime. Usually the high ozone above the PBL was not being mixed 

downward, so that this error usually did not have much effect upon the ozone concentrations in 

the HGB area. 

• Transport and mixing of urban and industrial emissions within the HGB area can apparently 

affect the ozone chemistry substantially, especially when the urban core plume and the industrial 

plumes mix together. Ozone behavior, including VOC- and NOX-sensitivity, appears to change 

when these plumes mix. The implication is that the VOC- and NOX-sensitivity of ozone 

formation in the HGB area depend somewhat on the wind direction. 

• Since ozone was sometimes overestimated during the evening hours, the model did not display 

the amount of dynamic range present in the observations. 

Ozone precursor performance

• In general, the modeling simulated ozone precursors relatively well, albeit with a large degree of 

scatter, and the peak concentrations for some species were underestimated. 

• NO2 was usually simulated in an unbiased manner, but nitric oxide (NO) was often 

underestimated for the peak concentrations, which were usually observed in the pre-dawn hours, 

i.e., during morning rush hour. 

• The highly reactive Carbon Bond 05 species ETH and OLE, which represent ethylene, propylene, 

and other alkenes, were well simulated much of the time, but the model tended to underestimate 
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the peak concentrations. Concentrations of these two species were routinely overestimated at the 

Wallisville Road (CAMS 617) monitoring site. 

• The performance of isoprene, represented by the Carbon Bond 05 species ISOP, was mixed, with 

some areas showing no bias, others showing high bias, and others showing low bias. 

• Formaldehyde data were available during the TexAQS II study at three sites. For the Moody 

Tower site, the concentrations were usually well simulated, but the peak concentrations were 

underestimated. For the Lynchburg Ferry (CAMS 1015) and HRM-3 Haden Road (CAMS 603) 

sites, the performance was mediocre. The HRM-3 Haden Road (CAMS 603) observations were 

consistent with secondary formaldehyde formation as the main source of formaldehyde, but the 

diurnal patterns of the modeled concentrations were more consistent with a primary source: 

concentrations peaked in the pre-dawn hours, like NO. The aircraft data generally show that the 

model underestimated formaldehyde peaks, though the location, extent, and relative magnitude 

were well simulated, much like the ozone data. 

Meteorological performance evaluation

• The meteorological modeling was able to successfully replicate the major features of ozone 

episodes in the HGB area much of the time, including the typical veering pattern of local winds, 

stagnation and flow reversal, and the coastal oscillations associated with the Galveston Bay 

breeze and Gulf breeze. 

• Trajectory analyses and vertical wind profiles in the HGB area show that much of the time on 

high ozone days, the model transported ozone and precursors to approximately the correct areas 

at approximately the correct times. 

• The model occasionally did not generate enough cloud cover, resulting in high ozone on days 

when low ozone was observed. While the addition of the Grell cumulus parameterization and 

improved land surface characteristics data appeared to reduce the common problem of spurious 

thunderstorms, the problem has not been completely eliminated. 

• Episode days with strong stagnation were more difficult to model precisely than days for which 

the winds did not stagnate. The model sometimes simulated nighttime winds that were too brisk, 

resulting in more dilution of emissions than was actually observed. 

• Ozonesonde and radar profiler data indicate that for most episode days, the PBL over land 

appeared to be modeled with good accuracy. Over water, however, planetary boundary layer 

depth was consistently modeled less accurately. 

Model response to emission changes

• The base case modeling has been challenged with different emissions inventories in order to 

evaluate its dynamic response to emission changes (Gilliland et al., 2009). 

• Adding more VOC to the flare emissions increases peak ozone concentrations, though the 

emission changes do not completely correct the ozone underestimations. Addition of 

formaldehyde emissions to HRVOC flares increases peak ozone concentrations further. 

• Substitution of flare emissions for the standard emission reconciliation tends to improve the 

model performance by increasing ozone production close to the industrial emission sources and 

by increasing the peak ozone concentrations, without adversely affecting ozone performance at 

other times and places. 

• Modeled ozone appears to decrease slightly in response to NOX emission decreases typical of the 

changes that occur on weekends. The observed weekend effect is a slightly stronger response to 

NOX emission decreases, implying that the model may be slightly less NOX-sensitive than it 

should be. 

• Modeled ozone increases substantially in response to VOC and NOX emission increases 

commensurate with the difference between 2006 emissions and 2000 emissions in the HGB area. 

When relative response factors are calculated using 2000 as the baseline year and 2006 as the 

future year, the modeled response to emission reductions is less vigorous than the observed 

response. This finding implies that the current modeling appears to underestimate the response to 

emission controls. If the atmosphere responds to the emission reductions from 2006 to 2018 in a 

manner similar to its response to the emission reductions between 2000 and 2006, the actual 

decrease in ozone design value will be greater than the model predicts. 
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• Some of the strongest model responses to emission changes occur outside the boundaries of the 

current ozone monitoring network, and sometimes outside the current nonattainment area. This 

finding suggests that the proposed controls may have a greater impact on ozone than the 

responses registered at the different monitoring sites would indicate. 

5.2.3 Model Response to Proposed Controls: Additional Ways to Measure Progress 

Table 5-1: Changes in the Area and Population Affected by an Eight-Hour Ozone Design Value Greater 

than or Equal to 85 ppb in Response to Growth and Controls shows how the area affected by high ozone 

is expected to shrink dramatically in response to the emission changes projected to occur between 2006 

and 2018. Even though peak ozone drops by only 8 percent, the area with an estimated ozone design 

value greater than the 85 ppb standard shrinks by 96 percent. The population living in those areas and 

how the changes might reduce the number of people that encounter high ozone were considered. The 

estimated number of people residing in the high ozone areas decreases by 92 percent. Note that the 

population data is from the 2000 Census and has not been grown to reflect changes in population in those 

areas in 2006 or 2018. Also note that the numbers reflect areas where people reside, i.e., their home 

addresses, not necessarily where they might be during the hours of highest ozone during the ozone season. 

However, the dramatic decrease in the area with high ozone suggests that ozone decreases arising from 

the proposed control strategies are likely to benefit many residents of the HGB area. 

Table 5-1: Changes in the Area and Population Affected by an Eight-Hour Ozone Design Value 

Greater than or Equal to 85 ppb in Response to Growth and Controls 

Run name 

Peak 

Ozone, 

ppb 

Area with 

design 

value > 85 

ppb, km2

2000 

population 

in area 

with 

design 

value > 85 

Area ×

Concentration 

(km2 × ppb) 

Population ×

ppb 

Ozone design value > 

85 ppb 

 baseline 2006.reg2 95 7,236 2,680,249 19,864 11,024,868

 future year 2018.cs05 87 296 219,285 291 197,713

Percentage decrease 

from 2006 to 2018 8% 96% 92% 99% 98%

5.2.4 Conclusion 

The photochemical grid model performed by the TCEQ for this SIP revision has been rigorously 

evaluated against observational data. While there are a number of shortcomings that this modeling has in 

common with other modeling exercises in the HGB area as discussed in Sections 5.2.1, Solving Modeling 

Problems, and 5.2.2, , Model Performance Evaluations: Implications of the Model Performance of the 

Current SIP Modeling, modeling for many of the simulated ozone days appears to behave in a manner 

consistent with most of the atmospheric phenomena of interest. Evaluation of the modeling response to 

emission changes appears to show that the modeled ozone is slightly less responsive to emission changes 

than the observed ozone. Thus, modeling of 2018 emissions with the proposed control package in place 

may overpredict the future ozone concentrations. 

 

5.3 AIR QUALITY TRENDS IN THE HGB AREA 

This section describes analyses of air quality observational data in the HGB area. Trends in ozone and its 

precursors demonstrate not only the substantial progress the HGB area has made in improving air quality 

but also the magnitude of the future challenge in attaining the ozone NAAQS. Trends are also useful to 

show how ozone is related to its precursors. Decreases in NOX and VOC demonstrate the effectiveness of 

policies to reduce emissions; however, due to its dependence on meteorological variables, ozone may not 

always exhibit trends identical to its precursors. Separating variations in meteorological factors from 

trends in ozone and its precursors can highlight whether ozone reductions are due to decreases in 
5-10

precursor emissions or are due to year-to-year variability in local meteorology (Sullivan, 2009; Camalier, 

et al., 2007). 

5.3.1 Ozone Trends 

This section examines the frequency at which the NAAQS for ozone are exceeded, with the 

understanding that the 1997 eight-hour standard of 0.08 ppm is the subject of interest for this SIP revision 

and that the one-hour standard is no longer in effect, but still a useful benchmark for understanding ozone 

behavior in the HGB area. While the NAAQS is expressed in units of ppm, this section will use the 

familiar convention of expressing concentrations in ppb. 

The trend in design values for the HGB area is seen clearly in Figure 5-1: Ozone Design Values for the 

HGB Area. While the HGB area continues to exceed both the one-hour and eight-hour ozone standards, 

one-hour ozone design values have generally decreased over the past 17 years, and eight-hour ozone 

design values have decreased over at least the past nine years. The eight-hour ozone design value in 2008 

was 91 ppb, a 24 percent decrease from the 1991 design value of 119 ppb. The 2008 value is approaching 

the 1997 eight-hour ozone NAAQS of 85 ppb. A regression analysis of design value on year estimates 

that eight-hour ozone design values decreased at the rate of 1.2 ppb per year, which is statistically 

significant at the 5 percent level (α = 0.05). If this trend were to continue at that rate, attainment of the 

1997 eight-hour standard could be reached in five years, though if the pace of recent years were 

maintained, it could occur even sooner. 

Ozone Design Values for the HGB Area

104 110 114 116 117 116 118 112 110 107 102 101 103 103

96

210

200 202

189 188

199 196

203 199

185

175 175 170 169

153 153

91

116 119

147

220

0

50

100

150

200

250

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Design Value

(ppb)

1-Hour NAAQS: 125 ppb

8-Hour NAAQS: 85 ppb

1-Hour DV

8-Hour DV

Figure 5-1: Ozone Design Values for the HGB Area 

The one-hour ozone design value in 2008 was 147 ppb, a 33 percent decrease from the 1991 design value 

of 220 ppb. Regression of one-hour design values on year shows they decreased at the rate of 3.6 ppb per 

year, which is faster than the decrease for eight-hour ozone design values; the slope is also statistically 

significant at the 5 percent level.
Table 5-2: Eight-Hour Ozone Design Values (in ppb) for Each Regulatory Monitor in the HGB Area

Monitor/CAMS # 

1991 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

2004 

Houston Bayland Park C53 111 110 100 102 101 Houston Westhollow C410 95 101 95 102 102 104 95 87 87 Park Place C416 Hous.DeerPrk2 C35/235/1001/  AFH139FP239 108 112 108 103 102 101 Manvel Croix Park C84 91 97 Northwest Harris Co. C26/A110/  X154 98 101 100 110 113 110 106 106 109 108 105 101 100 94 Houston Aldine C8/AF108/F150 119 116 104 102 103 114 116 116 108 111 108 107 100 95 Houston Monroe C406 105 102 96 93 97 102 109 112 113 106 93 90 90 95 Houston Croquet C409 117 112 103 96 104 104 117 115 118 110 104 102 99 99 Conroe Relocated C78 85 Channelview C15/C115 87 90 Houston East C1 104 103 88 86 108 106 102 103 101 100 95 Seabrook Friendship Park C45 85 94 Houston Texas Avenue C411 88 89 Lang C408 105 103 93 95 98 99 100 96 96 96 91 83 78 79 Lake Jackson C1016 Houston North Wayside C405 114 102 94 91 91 91 96 99 104 105 98 89 86 85 Lynchburg Ferry C1015 Houston Regional Office C81 95 94 88 Clinton C403/C113/C304 115 109 100 100 106 106 107 100 103 101 97 93 96 96 Galveston Airport C34/C109/C154 90 112 108 98 89 89 91 Clute C11 96 93 91 96 92 92 84 95 93 91 86 87 Texas City C10 93 82 90 89 114 102 105 91 100 98 91 83 80 Conroe C65 91 Houston Crawford C407 105 98 89 89 95 91 97 96 100 100 Houston Manchester C22 103 104 104 103 106 102 103 Houston Deer Park C18 107 96 85 89 107 116 

Note: Missing values indicate a monitor was not operating during that year or did not produce a valid year of data. Three years of valid data are required to calculate an eight-hour o

5-11
5-12

The design value in a metropolitan area is the highest design value of all of the area’s monitors’ 

individual design values. Because ozone varies spatially, it is also prudent to investigate trends at 

all monitors in an area. Table 5-2: Eight-Hour Ozone Design Values (in ppb) for Each 

Regulatory Monitor in the HGB Area and Table 5-3: One-Hour Ozone Design Values (in ppb) 

for Each Regulatory Monitor in the HGB Area contain the eight-hour and one-hour ozone design 

values at all regulatory monitors in the HGB area from 1991 to 2008. More monitors than these 

operate in the HGB area, but because the data at those monitors do not meet the EPA’s quality 

control standards, the design values at those additional monitors are not displayed here. These 

non-regulatory monitors are discussed in Section 5.2.2: Model Performance Evaluations: 

Implications of the Model Performance of the Current SIP Modeling. 
5-13

Table 5-3: One-Hour Ozone Design Values (in ppb) for Each Regulatory Monitor in the HGB Area 

Monitor/CAMS # 

1991 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

2004 

Houston Bayland Park C53 189 185 173 154 163 148 1Houston Westhollow C410 164 155 164 155 165 150 150 141 141 128 1Park Place C416 Hous.DeerPrk2 C35/235/1001/  AFH139FP239 147 164 203 185 182 168 161 157 1Manvel Croix Park C84 143 132 142 1Northwest Harris Co. C26/A110/  X154 160 160 166 173 172 172 165 164 163 161 157 154 156 148 1Houston Aldine C8/AF108/X150 220 190 197 197 189 173 189 187 187 180 166 166 143 136 1Houston Monroe C406 170 170 155 147 154 161 174 196 196 170 143 151 141 141 1Houston Croquet C409 200 200 178 152 167 167 168 168 167 167 160 157 150 141 1Conroe Relocated C78 119 137 128 1Channelview C15/C115 154 141 140 1Houston East C1 210 200 200 202 177 182 182 198 180 180 171 171 165 1Seabrook Friendship Park C45 132 135 135 1Houston Texas Avenue C411 146 172 157 1Lang C408 200 183 158 159 159 159 158 155 155 175 175 149 128 128 1Lake Jackson C1016 119 1Houston North Wayside C405 210 190 173 173 155 143 155 158 189 190 168 153 131 138 1Lynchburg Ferry C1015 157 1Houston Regional Office C81 185 178 175 170 1Clinton C403/C113/C304 210 210 176 158 173 173 173 161 183 199 176 157 175 158 1Galveston Airport C34/C109/C154 170 170 176 168 164 133 123 129 1Galveston 99th St. C1034 Clute C11 150 150 132 129 144 144 148 134 154 161 154 136 133 136 Texas City C10 150 150 163 163 184 182 182 146 175 172 139 121 116 116 1Conroe C65 145 145 140 Houston Crawford C407 220 190 165 165 165 166 172 172 164 173 173 194 Houston Manchester C22 190 190 180 160 172 170 175 173 176 Houston Deer Park C18 160 160 150 157 188 188 199 163 San Jacinto Monument C166/C245 143 124 124 Note: Missing values indicate a monitor was not operating during that year or did not produce a valid year of data. Only one year of valid data is required to calculate a one-hour oz

that have a one-hour ozone design value may not have an eight-hour ozone design value. 
5-14

Figure 5-2: Eight-Hour Ozone Design Value Statistics for All Monitors in the HGB Area and 

Figure 5-3: One-Hour Ozone Design Value Statistics for All Monitors in the HGB Area display 

three summary statistics for the eight-hour and one-hour design values, respectively: the 

maximum, median, and minimum design values computed across all monitors in the HGB area. 

These figures facilitate assessment of the range of design values observed within a year, as well 

as how these distributions change over time. From these figures, it appears that neither eighthour nor one-hour design values exhibited a noticeable trend until about 1999, after which both 

began falling steadily. Before 2002, no monitors in the HGB area met either standard; since then, 

the area has seen a steady increase in the number of monitors attaining both standards. By 2008, 

over half of the monitors in the area had attained both standards, as median ozone design values 

fell below the NAAQS that year. 

Eight-Hour Ozone Design Value Statistics in the HGB Area

0

20

40

60

80

100

120

140

199119921993199419951996199719981999200020012002200320042005200620072008

Design Value 

(ppb)

8-Hour NAAQS: 85 ppb

MAX

Median

MIN 

Figure 5-2: Eight-Hour Ozone Design Value Statistics for All Monitors in the HGB Area 
5-15

One-Hour Ozone Design Value Statistics in the HGB Area

0

50

100

150

200

250

199119921993199419951996199719981999200020012002200320042005200620072008

Design Value 

(ppb)

1-Hour NAAQS: 125 ppb

MAX

Median

MIN 

Figure 5-3: One-Hour Ozone Design Value Statistics for All Monitors in the HGB Area 

Ozone trends can also be investigated by looking at the number of days an exceedance of the 

ozone NAAQS was recorded, termed an exceedance day. An exceedance day for the 1997 eighthour ozone NAAQS is any day that any monitor in the area measures an eight-hour average 

ozone concentration greater than or equal to 85 ppb over any eight-hour period. An exceedance 

day for the one-hour ozone NAAQS is any day that any monitor in the area measures a one-hour 

average ozone concentration greater than or equal to 125 ppb for at least one hour. Previous 

research (Savanich, unpublished, 2006) by the TCEQ has shown that, until 2006, the number of 

exceedance days was positively correlated with the number of monitors in a particular area. As 

the number of monitors increases, so does the number of exceedance days recorded, at least until 

the area has been saturated with monitors or until ozone concentrations truly decrease. Because 

of this correlation, when examining exceedance-day trends, the number of monitors must always 

be considered. Thus, it is especially noteworthy that Figure 5-4: Number of Monitors and Ozone 

Exceedance Days in the HGB Area shows that, despite an increase in the number of monitors, the 

number of exceedance days for both one-hour and 1997 eight-hour ozone NAAQS has decreased, 

a decrease that is especially pronounced over the past three years. Since 1999, the number of 

1997 eight-hour and one-hour ozone exceedance days occurring in the HGB area has fallen 83 

percent and 96 percent, respectively. In just the last three years, the number of 1997 eight-hour 

and one-hour ozone exceedance days has fallen 76 percent and 92 percent, respectively. 
5-16

Number of Monitors and Ozone Exceedance Days 

in the HGB Area

39

34

52 54

48

54

45

36

41

44 45

32

20

11

28 28 30

26

35

49

34

28

23

27

30

26

17

6

39

73

64

32

45

56

2

37

0

20

40

60

80

100

199119921993199419951996199719981999200020012002200320042005200620072008

Days

0

5

10

15

20

25

Monitors

One-Hour Exceedances

Eight-Hour Exceedances

number of monitors

Figure 5-4: Number of Monitors and Ozone Exceedance Days in the HGB Area 

Results for individual monitors, displayed in Figure 5-5: Number of 1997 Eight-Hour Ozone 

Exceedance Days by Monitor and Figure 5-6: Number of One-Hour Ozone Exceedance Days by 

Monitor support the conclusion that the number of exceedance days at individual monitors also 

appears to be decreasing. Figure 5-5: Number of 1997 Eight-Hour Ozone Exceedance Days by 

Monitor highlights two monitors, Houston Aldine (CAMS 8) (red line) and Houston Bayland 

Park (CAMS 53) (blue line), that recorded the most 1997 eight-hour ozone NAAQS exceedances 

in the past. Since recent peaks in 1999 (at Houston Bayland Park (CAMS 53)) and in 2000 

(Houston Aldine (CAMS 8)), neither monitor, in any year, has come within 60 percent of these 

peaks; in 2008 both monitors experienced at least an 85 percent reduction from the recent peaks. 

While results for other monitors are less impressive, overall, the trend in ozone exceedance days 

at monitors throughout the HGB area is clearly downward. Due to the large number of monitors 

in the HGB area, data from Figure 5-5: Number of 1997 Eight-Hour Ozone Exceedance Days by 

Monitor and Figure 5-6: Number of One-Hour Ozone Exceedance Days by Monitor are 

presented in Table 5-4: Number of Days with a 1997 Eight-Hour Ozone Exceedance and Table 5-

5: Number of Days with a One-Hour Ozone Exceedance for detailed inspection. 
5-17

Eight-Hour Ozone Exceedance Days in the HGB Area 

0

5

10

15

20

25

30

35

40

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Days

Manvel Croix Park Lake Jackson

Galveston Airport Galveston 99th St.

Houston Aldine Channelview

NW Harris Co. North Wayside

Lang Croquet

Bayland Park Monroe

Westhollow Hou. Reg. Office

Texas Avenue Park Place

Lynchburg Ferry Houston East

Clinton Deer Park 2

Seabrook Conroe Relocated

Figure 5-5: Number of 1997 Eight-Hour Ozone Exceedance Days by Monitor 

One-Hour Ozone Exceedance Days in the HGB Area

0

5

10

15

20

25

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Days

Manvel Croix Park Lake Jackson

Galveston Airport Galveston 99th St.

Houston Aldine Channelview

NW Harris Co. North Wayside

Lang Croquet

Bayland Park Monroe

Westhollow Hou. Reg. Office

Texas Avenue Park Place

Lynchburg Ferry Houston East

Clinton Deer Park 2

Seabrook Conroe Relocated

Figure 5-6: Number of One-Hour Ozone Exceedance Days by Monitor 

The progress achieved in recent years in reducing eight-hour and one-hour ozone concentrations 

in the HGB area is evident in Table 5-4: Number of Days with a 1997 Eight-Hour Ozone 

Exceedance and Table 5-5: Number of Days with a One-Hour Ozone Exceedance. The number of 

times the monitors in the HGB area registered daily peak eight-hour ozone ≥ 85 ppb fell from a 
5-18

high of 340 occurrences in 1995, to 39 occurrences in 2007, to 19 occurrences in 2008. Prior to 

2007, that number was never below 90. The number of monitors recording at least one 

exceedance of the 1997 eight-hour ozone standard has fallen by half, from a maximum of 23 

monitors in 2003 to only 12 in 2008. 

A similar pattern is apparent with the number of exceedances of the one-hour ozone NAAQS 

presented in Table 5-5: Number of Days with a One-Hour Ozone Exceedance. The table shows 

that the total number of one-hour ozone NAAQS exceedance occurrences fell from a high of 165 

in 1995 to just three in 2008. Prior to 2005, the number of one-hour exceedances was never 

below 50. The three exceedances in 2008 occurred at only two monitors. As recently as 2006, a 

total of 15 monitors recorded at least one exceedance. This significant progress has occurred in a 

fairly short amount of time in an area well known for its air quality challenges. 
5-19

Table 5-4: Number of Days with a 1997 Eight-Hour Ozone Exceedance Monitor 

1991 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

Houston Bayland Park C53 17 31 19 17 11 16 Houston Westhollow C410 4 36 8 16 11 17 11 8 3 3 Park Place C416 Hou.DeerPrk2 C35/235/1001/AFHP139FP239 18 9 26 20 10 8 18 Manvel Croix Park C84 5 8 14 Northwest Harris Co. C26/A110/X154 3 14 12 21 34 13 12 23 25 7 11 9 11 Houston Aldine C8/AF108/X150 15 17 11 19 38 16 25 23 22 29 15 7 11 Houston Monroe C406 13 10 7 7 22 5 28 12 21 12 3 7 8 Houston Croquet C409 23 9 9 8 36 8 28 19 31 15 9 10 10 Conroe Relocated C78 1 3 7 Channelview C15/C115 1 5 10 Houston East C1 9 10 2 0 0 13 16 12 13 15 10 6 15 Seabrook Friendship Park C45 2 4 8 Houston Texas Avenue C411 5 2 9 Lang C408 5 10 8 10 18 8 5 11 5 8 2 3 1 Lake Jackson C1016 3 Houston North Wayside C405 9 8 5 5 26 8 9 12 24 14 5 2 9 Lynchburg Ferry C1015 14 Houston Regional Office C81 11 11 5 9 Clinton C403/C113/C304 16 11 7 6 21 7 14 11 22 11 6 7 10 Galveston Airport C34/C109/C154 18 13 23 5 3 4 12 Clute C11 8 10 6 5 15 3 4 5 9 2 3 6 3 Conroe C65 4 17 6 Houston Crawford C407 5 6 7 4 15 3 16 10 11 8 0 Houston Manchester C22 19 10 8 10 27 5 18 Houston Deer Park C18 8 4 3 18 27 12 Texas City C10 6 1 9 7 25 1 10 10 11 6 1 3 3 San Jacinto Monument C166/C245 0 5 1 Galveston 99th St. C10 34 Number of Monitors in Operation 13 13 13 14 14 14 15 15 16 17 23 21 23 2Note: Monitors with exceedance days do not necessarily have a complete year of ozone data; therefore, there may be years where a monitor has ozone exceedance days but no ozon
5-20

Table 5-5: Number of Days with a One-Hour Ozone Exceedance Monitor 

1991 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

Houston Bayland Park C53 12 18 8 10 3 6 Houston Westhollow C410 3 20 3 8 5 12 5 6 2 2 Park Place C416 Hou.DeerPrk2 C35/C235/1001/AFH139/FP239 13 7 14 13 6 5 7 Manvel Croix Park C84 1 2 1 Northwest Harris Co. C26/A110/C154 1 9 10 14 9 7 4 9 9 5 6 4 2 Houston Aldine C8/AF108/X150 9 8 7 12 11 15 12 12 8 16 8 1 6 Houston Monroe C406 8 6 3 3 11 2 15 8 10 5 5 5 3 Houston Croquet C409 16 5 5 4 21 3 14 12 14 6 4 5 4 Conroe Relocated C78 0 1 2 Channelview C15/C115 1 5 6 Houston East C1 6 6 2 0 0 12 13 8 10 11 7 4 7 Seabrook Friendship Park C45 3 4 5 Houston Texas Avenue C411 5 0 8 Lang C408 5 6 6 6 9 4 6 8 4 6 3 2 2 Lake Jackson C1016 1 Houston North Wayside C405 5 6 3 4 4 5 5 8 7 11 1 1 5 Lynchburg Ferry C1015 9 Houston Regional Office C81 6 7 3 5 Clinton C403/C113/C304 13 8 7 4 15 6 8 7 13 8 7 3 6 Galveston Airport C34/C109/C154 5 7 7 4 0 0 3 Galveston 99th St. C1034 Clute C11 3 3 2 0 6 1 3 1 4 2 0 2 1 Texas City C10 4 1 7 2 14 0 3 3 7 3 0 0 1 Conroe C65 1 5 2 Houston Crawford C407 5 4 5 3 9 4 11 12 5 8 0 Houston Manchester C1029 11 7 7 7 18 4 10 Houston Deer Park C18 6 2 1 6 18 4 San Jacinto Monument C166/C245 0 2 0 Number of Monitors in Operation 13 13 13 14 14 14 15 15 16 17 23 21 23 
5-21

The ozone season spans the entire year in the HGB area; the period of elevated ozone 

concentrations, however, varies from year to year. Figure 5-7: 1997 Eight-Hour Ozone 

Exceedance Days in the HGB Area shows the frequency of, and variation in, the number of 1997 

eight-hour ozone NAAQS exceedance days in the HGB area by month and year. While the 

duration and intensity of the ozone season does vary from year to year, in the past few years the 

HGB area has experienced fewer ozone exceedance days over fewer months. The darker areas in 

the figure show that peak ozone season in the HGB area typically occurs from August to 

September, with a smaller, secondary peak occurring earlier, roughly in June. 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

200620072008

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Eight-Hour Ozone Exceedance Days in the HGB Area

1 - 3

15 - 17 17 - 19 13 - 15

11 - 13

9 - 11

7 - 9

5 - 7

3 - 5

Figure 5-7: 1997 Eight-Hour Ozone Exceedance Days in the HGB Area 

In summary, the number and intensity of ozone exceedances in the HGB area has been dropping, 

especially since 2000, with 2007 and 2008 demonstrating the largest of these decreases. 

5.3.2 Ozone Trends at Regulatory and Non-Regulatory Monitors 

Twenty-three monitors in the HGB area, listed in Table 5-6: Eight-Hour Ozone Design Values at 

Regulatory and Non-Regulatory Monitors and Table 5-7: One-Hour Ozone Design Values at 

Regulatory and Non-Regulatory Monitors report ozone concentrations following EPA 

certification protocols and are used for attainment determinations for regulatory purposes. 

However, since 2003, over 20 additional monitors have become operational in the HGB area that 

measure ozone concentrations following protocols that have not been certified to EPA standards. 

Usually, this means fewer calibrations and/or zero and span checks. These non-regulatory 

monitors are located throughout the HGB area. The locations were chosen with the aim of 

ensuring that all episodes of elevated ozone and precursors are observed. The additional 

monitoring sites also help to describe the spatial extent and distribution of high ozone more fully 

than the regulatory monitors alone. While the non-regulatory monitors are not acceptable for 

making regulatory determinations, they help describe the spatial patterns of ozone more 

completely and thus provide a broader perspective on trends in ozone concentrations across the 

HGB area. 
5-22

Table 5-6: Eight-Hour Ozone Design Values at Regulatory and Non-Regulatory Monitors 

AIRS Site Name 2003 2004 2005 2006 2007 2008

ppb ppb ppb ppb ppb ppb 

Regulatory Monitors 

 482010055 Houston Bayland Park C53 102 101 103 103 96 91

 482010066 Houston Westhollow C410 87 87 89 96 92 89 

 482010416 Park Place C416 89 

 482011039 Houston Deer Park 2 C35/139 102 101 100 96 93 87 

 480391004 Manvel Croix Park C84 91 97 97 96 91 85 

 482010029 Northwest Harris Co. C26/A110/C154 100 94 93 91 91 85 

 482010024 Houston Aldine C8/AF108/X150 100 95 92 88 84 83 

 482010062 Houston Monroe C406 90 95 97 99 91 81 

 482010051 Houston Croquet C409 99 99 98 94 87 80 

 483390078 Conroe Relocated C78 85 86 85 84 80 

 482010026 Channelview C15/C115 87 90 89 85 83 80 

 482011034 Houston East C1 100 95 87 83 78 80 

 482011050 Seabrook Friendship Park C45 85 94 92 90 86 79 

 482010075 Houston Texas Avenue C411 88 89 88 84 78 76 

 482010047 Lang C408 78 79 79 80 77 76 

 480391016 Lake Jackson C1016 79 79 76 76 

 482010046 Houston North Wayside C405 86 85 82 78 76 75 

 482011015 Lynchburg Ferry C1015 96 89 82 74 

 482010070 Houston Regional Office C81 94 88 88 84 81 74 

 482011035 Clinton C403/C113/C304 96 96 95 85 79 73 

 481670014 Galveston Airport C34/C109/C154 89 91 87 83 71 

 480391003 Clute C11 87 

 481671002 Texas City C10 80 

Non-Regulatory Monitors 

 482010554 West Houston C554 102 99 94 

 482010558 Tom Bass C558 104 100 93 

 482010559 Katy Park C559 98 96 92 

 482010562 Bunker Hill Village C652 81 96 91 

 482010617 Wallisville Road C617 96 93 93 90 

 482010561 Meyer Park C561 90 89 84 

 482010557 Mercer Arboretum C557 88 88 84 

 482010560 Atascocita C560 88 86 83 

 482010556 La Porte Sylvan Beach C556 90 87 82 

 482010552 Baytown Wetlands Center C552 87 89 86 81 

 480390619 Mustang Bayou C619 93 89 84 81 

 482010572 Clear Lake High School C572 83 88 84 81 

 482010803 HRM-3 Haden Road C603 92 88 84 80 

 482010553 Crosby Library C553 87 86 84 80 

 481670056 Texas City 34th St, C620 89 90 84 79 

 482010570 Clear Brook High School C570 89 92 84 78 

 480390618 Danciger C618 80 83 80 78 

 482010555 Kingwood Library C555 82 81 77 

 482010551 Sheldon C551 92 85 80 76 

 481670571 Clear Creek High School C571 83 84 

Source: Leading Environmental Analysis and Display System (LEADS). 

Monitors are sorted in descending order of 2008 design values, then 2007, 2006, etc. The annual maximum of each series is noted in 

boldface type. Because of the way design values are computed, some monitors in some years may have one-hour but not eight-hour

design values. 

Table 5-7: One-Hour Ozone Design Values at Regulatory and Non-Regulatory Monitors 
5-23

AIRS Site Name 2003 2004 2005 2006 2007 2008

ppb ppb ppb ppb ppb ppb

Regulatory Monitors 

 482010055 Houston Bayland Park C53 163 148 148 143 142 139

 482010066 Houston Westhollow C410 141 128 126 131 127 126

 482010416 Park Place C416 136 136 136

 482011039 Houston Deer Park 2 C35/C139 161 157 153 150 150 147

 480391004 Manvel Croix Park C84 132 142 134 138 128 128

 482010029 Northwest Harris Co. C26/A110/C154 156 148 131 127 127 126

 482010024 Houston Aldine C8/AF108/X150 143 136 139 125 122 122

 482010062 Houston Monroe C406 141 141 131 133 131 117

 482010051 Houston Croquet C409 150 141 136 131 126 117

 483390078 Conroe Relocated C78 137 128 128 128 124 116

 482010026 Channelview C15/C115 141 140 135 134 128 120

 482011034 Houston East C1 171 165 154 137 119 119

 482011050 Seabrook Friendship Park C45 135 135 153 153 153 119

 482010075 Houston Texas Avenue C411 172 157 157 127 110 110

 482010047 Lang C408 128 128 127 126 108 108

 480391016 Lake Jackson C1016 119 113 105 99 101

 482010046 Houston North Wayside C405 131 138 138 118 100 102

 482011015 Lynchburg Ferry C1015 157 157 152 149 117

 482010070 Houston Regional Office C81 175 170 169 135 131 119

 482011035 Clinton C403/C113/C304 175 158 158 124 121 111

 481670014 Galveston Airport C34/C109/C154 123 129 129 117 104 97

 481671034 Galveston 99th St. C1034 115 115

 480391003 Clute C11 133 136

 481671002 Texas City C10 116 116 124 

Non-Regulatory Monitors 

 482010554 West Houston C554 141 141 146 145 131

 482010558 Tom Bass C558 145 145 146 146 138

 482010559 Katy Park C559 127 143 143 135 129

 482010562 Bunker Hill Village C562 135 137 135 132

 482010617 Wallisville Road C617 147 145 138 139 134

 482010561 Meyer Park C561 139 133 127 111

 482010557 Mercer Arboretum C557 108 118 121 121 121

 482010560 Atascosita C560 137 137 125 120

 482010556 La Porte Sylvan Beach C556 148 149 149 133

 482010552 Baytown Wetlands Center C552 138 138 133 129 129

 480390619 Mustang Bayou C619 134 130 127 112 107

 482010572 Clear Lake High School C572 145 141 140 119 114

 482010803 HRM-3 Haden Road C603 161 161 144 135 127 122

 482010553 Crosby Library C553 141 147 141 126 123

 481670056 Texas City 34th St C620 143 139 136 119 114

 482010570 Clear Brook High School C570 140 140 135 117 109

 480390618 Danciger C618 121 120 111 108 108

 482010555 Kingwood Library C555 130 123 122 108

 482010551 Sheldon C551 153 153 150 130 125 123

 481670571 Clear Creek High School C571 138 138 138 119 99

 480710013 Smith Point Hawkins Camp C96 143 143 133

 482010808 HRM-8 LaPorte C608 149

 482010804 HRM-4 Sheldon Rd. C604 128

480710900 HRM-10 Mont Belvieu C610 119
5-24

 482010807 HRM-7 W Baytown C607 113

Source: LEADS (Leading Environmental Analysis and Display System). 

The annual maximum of each series is noted in boldface type. Because of the way design values are computed, some monitors in 

some years may have one-hour but not eight-hour design values 

Figure 5-8: Distributions of Eight-Hour Ozone Design Values at Regulatory and Non-Regulatory 

Monitors in the HGB Area compares eight-hour ozone design values at regulatory and nonregulatory monitors in the HGB area from 2003 to 2008. This period was chosen because many 

non-regulatory monitors only became operational, or had complete data, in 2003 and later years. 

The distributions of eight-hour ozone design values dropped for both types of monitors over the 

six-year period, though the interquartile range, a measure of spread between high and low values, 

did not narrow noticeably for either. Annual median fourth high eight-hour ozone design values 

fell from 90 ppb in 2003 to 80 ppb in 2008 at regulatory monitors, a drop of 11.1 percent. The 

median at non-regulatory monitors fell from 89 ppb to 81 ppb over the period, a 9.0 percent drop. 

While medians and other moments from the distributions all dropped over the period, the annual 

maximum eight-hour ozone design value is most relevant, as this value is the current standard 

used for regulatory attainment determinations. The annual maximum eight-hour ozone design 

value measured at regulatory monitors fell from 102 ppb in 2003 to 91 ppb in 2008, a drop of 

10.4 percent. The annual maximum at non-regulatory monitors fell from 96 ppb in 2005, when 

three-year design values were first computable, to 94 ppb in 2008, a drop of 2.1 percent. Note, 

however, that maximum eight-hour design values at non-regulatory monitors in 2006 and 2007 

were higher than in 2008, 104 ppb and 100 ppb respectively, presumably because those years are 

strongly influenced by the fourth high value observed at Wallisville Road (CAMS 617) in 2006 

(111 ppb). Even though this 2006 fourth high value continued to influence the 2008 design value, 

when averaged with the 2008 fourth high value of 85 ppb, the three-year average dropped to 94 

ppb, a 6 percent decline in a single year. 

81

86

89 89

80

84

87

91

94

90

94

100

104

96

91

96

103 103

101 102

70

75

80

85

90

95

100

105

110

2003 2004 2005 2006 2007 2008 2003 2004 2005 2006 2007 2008

90th percentile

regulatory monitors non-regulatory monitors

maximum

75th percentile

median

25th percentile

10th percentile

ppb

no data no data

Figure 5-8: Distributions of Eight-Hour Ozone Design Values at Regulatory and NonRegulatory Monitors in the HGB Area 
5-25

The ozone design values computed for the non-regulatory monitors are within the range of design 

values computed for the regulatory monitors. This finding suggests that both sets of monitors 

observe the same ozone behavior. 

Figure 5-9: Distributions of One-Hour Ozone Design Values at Regulatory and Non-Regulatory 

Monitors in the HGB Area compares one-hour ozone design values at regulatory and nonregulatory monitors in the HGB area from 2003 to 2008. This period was chosen because many 

non-regulatory monitors became operational or had complete data in 2003 and later years. The 

one-hour design value is computed as the fourth highest one-hour value observed among all 

values during each rolling three calendar-year period. The distributions of one-hour ozone design 

values dropped for both types of monitors over the six-year period and the spread between high 

and low values narrowed for both. Annual median fourth high one-hour ozone design values fell 

from 141 ppb in 2003 to 118 ppb in 2008 at regulatory monitors, a drop of 16.3 percent. The 

median at non-regulatory monitors fell from 149 ppb to 122 ppb over the period, an 18.1 percent 

drop. 

While medians and other moments from the distributions all dropped over the period, the annual 

maximum one-hour ozone design value is most relevant, as this design value would be compared 

to the one-hour ozone NAAQS to determine attainment, were the one-hour standard still in force. 

The annual maximum one-hour ozone design value measured at regulatory monitors fell from 

175 ppb in 2003 to 147 ppb in 2008, a drop of 16.0 percent. The annual maximum at nonregulatory monitors fell from 161 ppb to 138 ppb over the period, or 14.3 percent. Note that the 

eight-hour design value does not change when the data from the non-regulatory monitors are 

added to the calculation. 

122

126

137

140 141

149

118

127

131

136

141 141

138

150 149 149

161 161

147

153 153

170 169

175

100

110

120

130

140

150

160

170

180

2003 2004 2005 2006 2007 2008 2003 2004 2005 2006 2007 2008

90th percentile

regulatory monitors non-regulatory monitors

75th percentile

median

25th percentile

10th percentile

maximum

ppb

# of monitors: 

 21 22 21 21 22 22 5 15 20 21 21 21 

Figure 5-9: Distributions of One-Hour Ozone Design Values at Regulatory and NonRegulatory Monitors in the HGB Area 
5-26

Figure 5-10: 1997 Eight-Hour Ozone Exceedance Days at Regulatory and Non-Regulatory 

Monitors, 2003 through 2008 presents the number of days per year from 2003 through 2008 that 

the 1997 eight-hour ozone NAAQS was exceeded in the HGB area at regulatory monitors and at 

all monitors, both regulatory and non-regulatory. Since 2005, the combined network has 

recorded a total of 19 additional exceedances of the 1997 eight-hour ozone standard that would 

not have been captured by the regulatory network, i.e., about four to five per year. This result 

confirms earlier findings that suggest as the monitoring network has expanded, fewer episodes of 

elevated ozone concentrations are likely to elude detection. 

54

48

37

26

12

43

50

41

31

16

51

44

0

10

20

30

40

50

60

2003 2004 2005 2006 2007 2008

Number of regulatory monitors operating: 

 21 22 21 21 22 22 

Number of non-regulatory monitors operating: 

 5 15 20 21 21 21 

Figure 5-10: 1997 Eight-Hour Ozone Exceedance Days at Regulatory and Non-Regulatory 

Monitors, 2003 through 2008 

Figure 5-11: One-Hour Ozone Exceedance Days at Regulatory and Non-Regulatory Monitors, 

2003 through 2008 presents the number of days per year from 2003 through 2008 that the onehour ozone NAAQS was exceeded in the HGB area at regulatory monitors and at all monitors, 

both regulatory and non-regulatory. Both series initially increased, then fell at similar rates 

throughout the period, suggesting that the two sets of monitors measure broadly similar 

phenomena. During the first half of the period, non-regulatory monitors measured from five to 

nine additional exceedance days that were not detected by regulatory monitors. However, in the 

second half of the period, that gap dropped to only two to three additional days, indicating that 

non-regulatory monitors are detecting fewer and fewer events not detected by regulatory 

monitors. This result confirms earlier findings that suggest that, as the monitoring network has 

expanded, fewer episodes of elevated ozone concentrations are likely to elude detection. 
5-27

37

31 32

28

18

34

9

3

33

20

6

10

0

10

20

30

40

2003 2004 2005 2006 2007 2008

exceedance days at regulatory

and unique non-regulatory 

monitors

exceedance days at

regulatory monitors

Number of regulatory monitors operating: 

 21 22 21 21 22 22 

Number of non-regulatory monitors operating: 

 5 15 20 21 21 21 

Figure 5-11: One-Hour Ozone Exceedance Days at Regulatory and Non-Regulatory 

Monitors, 2003 through 2008 

Table 5-8: Exceedance Days at Regulatory and Non-Regulatory Monitors, 2003 through 

2008 

 One-Hour Ozone 

 Exceedance days Number of monitors

 regulatory non-regulatory regulatory non-regulatory 

Year monitors monitors total monitors monitors total

 # # # # # # 

2003 31 2 33 21 5 35 

2004 32 5 37 22 15 37 

2005 28 6 34 21 20 41 

2006 18 2 20 21 21 42 

2007 9 1 10 22 21 43 

2008 3 3 6 22 21 43

Source: Leading Environmental Analysis and Display System (LEADS). 
5-28

Table 5-9: Monitors Recording the Annual Maximum One-Hour Ozone Design Value 

Regulatory monitors Non-regulatory monitors

year site name value site name value

 ppb ppb 

2003 Houston Bayland Park C53 163 HRM-3 Haden Road C603 161 

2004 Houston Deer Park 2 C35/139 157 HRM-3 Haden Road C603 161 

2005 Houston Deer Park 2 C35/139 153 Sheldon C551 150 

2006 Houston Deer Park 2 C35/139 150 La Porte Sylvan Beach C556 149 

2007 Houston Deer Park 2 C35/139 150 La Porte Sylvan Beach C556 149 

2008 Houston Deer Park 2 C35/139 147 Tom Bass C558 138

Source: Leading Environmental Analysis and Display System (LEADS). 

Another way to see the ozone trend in the HGB area is to examine how the spatial distributions of 

ozone have changed over the years. Figure 5-12: Eight-Hour Ozone Design Values for 2000, 

2005, and 2008 shows the spatial distribution of eight-hour ozone design values in the HGB area, 

for regulatory monitors only, and the changes that have occurred from 2000 to 2005 to 2008. In 

2000, local peaks in design value were at Houston Aldine (CAMS 8), Houston Bayland Park 

(CAMS 53), and Deer Park (CAMS 35/139), and all three peaks were 110 ppb or higher. 

By 2005, eight-hour ozone design values had dropped across the region. While the highest 

concentrations still occurred at Houston Bayland Park (CAMS 53) and Deer Park (CAMS 

35/139), they were no longer observed in the Houston Aldine (CAMS 8) area. Further, the 2005 

peaks are much lower, between 100 and 103 ppb. The lowest eight-hour ozone concentration is 

still observed at Lang (CAMS 408), but low ozone also occurs to the northeast at Houston North 

Wayside (CAMS 405), to the north at Conroe (CAMS 65) or Conroe Relocated (CAMS 78), and 

to the south at Galveston Airport (CAMS 34/CAMS 109/CAMS 154). The minimum eight-hour 

ozone concentration in 2005 is below the 1997 NAAQS. 

In 2008, eight-hour ozone design values dropped even further. Ozone concentrations are 

substantially lower across a large part of the HGB area, with the kriging model predicting design 

values below the 1997 eight-hour ozone NAAQS at many locations. Maximum eight-hour ozone 

concentrations are now considerably lower, between 89 ppb and 91 ppb. The highest 

measurements occurred at Houston Bayland Park (CAMS 53) and Deer Park (CAMS 35/139), 

and also at a new monitor, Park Place (CAMS 416), which measured ozone in the same range as 

Houston Bayland Park (CAMS 53) and Deer Park (CAMS 35/139). The eight-hour ozone 

concentrations in 2008 are lower throughout the HGB area, with a local ozone minimum located 

in the urban core area surrounding the Lang (CAMS 408), Houston North Wayside (CAMS 405), 

Houston Texas Avenue (CAMS 411), Clinton (CAMS 403/CAMS 113/CAMS 304), and the 

TCEQ Houston Regional Office (CAMS 81) monitors. 

Notice that while the overall concentrations of eight-hour ozone are lower, the areas that 

experience the highest and lowest ozone remain the same. Spatial interpolation shows that high 

ozone concentrations continue to occur south of downtown Houston, and stretch from the 

Houston Ship Channel in the east to west Houston, near Houston Bayland Park (CAMS 53). The 

lowest ozone values are found to the south along the coast, at the northern edge of the 

nonattainment area towards Conroe (CAMS 65), and to the northwest of downtown Houston, at 

Lang (CAMS 408). 
5-29

Figure 5-12: Eight-Hour Ozone Design Values for 2000, 2005, and 2008 
5-30

The kriging method can also be employed to investigate the geographic origins of high ozone 

concentrations. Studies during the TexAQS 2000 field study reported that the highest ozone in 

the HGB area occurs in plumes emanating from industrial areas (Daum et al., 2004; Kleinman et 

al., 2005; Ryerson et al., 2003; Berkowitz et al., 2005; Banta et al., 2005). As these plumes are 

transported across the region, they can be tracked by the high ozone concentrations recorded at 

successive downwind monitors as the day progresses. An analysis of the time of day of 

maximum ozone at each monitoring site can confirm or challenge conclusions of the field study 

about these origins by revealing spatial patterns of ozone formation and movement. 

Yet another way to examine the ozone behavior in the HGB area is to investigate the time of day 

that ozone peaks, on average, in each part of the monitoring network. Daily maximum ozone 

concentrations were divided into two groups: days with values exceeding the 1997 eight-hour 

ozone NAAQS, and days not exceeding the 1997 eight-hour ozone NAAQS. The time of day 

when peak ozone was recorded at each monitor was determined for each day, then averaged 

across the two groupings of days. Only monitors that report data to the EPA were included. 

Days were restricted to March through November to exclude months when few or no exceedance 

days occur in the HGB area. 

Maps of the time of peak ozone in the HGB area, averaged from March through November 1998-

2008, are found in Figure 5-13: Time of Day of Peak Hourly Ozone on Low and High Ozone 

Days. The left map shows that on days with low eight-hour ozone values, daily maximum values 

are recorded in the Galveston area early in the day, between 11:30 a.m. and 11:45 a.m. Inland 

monitors record their highest daily values at progressively later times of day, as monitors are 

located farther inland from the Gulf Coast. On low ozone days, the earliest ozone maxima occur 

near the coast, and the latest occur in the Conroe area between 2:00 p.m. and 2:15 p.m. This 

pattern of ozone concentrations is consistent with the occurrence of the sea breeze, which often 

dominates local weather during the summer in the absence of strong synoptic-scale weather 

influences. After the plume is carried past a monitor, ozone levels often drop, reflecting the 

cleaner maritime air behind the sea breeze front. 

By contrast, the right map of the daily pattern on high eight-hour ozone days looks quite different. 

Daily maximum ozone concentrations are observed earliest in the industrial areas, and 

successively later at sites that are progressively farther away from these areas. This pattern 

indicates that high ozone forms first in the industrial areas, and is transported outward to urban, 

suburban, and rural sites later in the day. Maximum ozone occurs latest at Lake Jackson (CAMS 

1016), Clute (CAMS 11), Northwest Harris Co. (CAMS 26), Conroe (CAMS 65) and Conroe 

Relocated (CAMS 78), the sites at the greatest distance from the industrial area. 

The time of day of maximum ozone on high eight-hour ozone days represents a composite 

pattern: high ozone formed in industrial areas is carried by winds to Conroe (CAMS 65) and 

Conroe Relocated (CAMS 78) on some days, to Lake Jackson (CAMS 1016) on other days, and 

to western Houston on other days. Combined with the earlier spatial design value analysis, the 

patterns of peak ozone appear to show that the highest ozone concentrations are formed in the 

vicinity of the heavily industrialized areas of metropolitan Houston and are then transported 

throughout the area. 
5-31

Figure 5-13: Time of Day of Peak Hourly Ozone on Low and High Ozone Days 
5-32

5.3.3 Trends in the Strength of Observed Ozone Gradients in the HGB Area 

Rapid ozone increases have been observed at HGB area monitoring sites for many years, but the 

phenomenon was not sufficiently explained until the TexAQS 2000 study. Researchers from 

Brookhaven National Laboratory and National Oceanic and Atmospheric Administration 

(NOAA) Aeronomy Laboratory were able to establish that the rapid ozone increases were due to 

strong spatial ozone gradients that arose when ozone formed very rapidly in industrial plumes. 

The rapid ozone formation observed by Daum et al. (2003, 2004) allowed ozone to build up in the 

plumes before ozone and its precursors could disperse. Shifting winds due to the coastal 

oscillation or bay/Gulf breeze phenomena pushed the strong ozone gradients over the monitoring 

sites, resulting in observations of rapid ozone increases (Banta et al., 2005). The rapid ozone 

formation occurs when industrial HRVOC reacts with co-emitted NOX (Ryerson et al., 2003; 

Wert et al., 2003). The following analysis examines whether the strength of these ozone 

gradients has lessened, as measured by the magnitude of one-hour changes in ozone observed at 

monitoring sites. 

One-hour changes in ozone concentrations examined for each hour during the ozone season (May 

through October) at each site for each year. The maximum daily peak change in ozone 

concentration was chosen for each day, and various statistical measures were calculated from 

those values. Not all sites were included in this analysis: only those with long operating histories 

were included. 

Figure 5-14: Trends in the Strength of Ozone Gradients Measured in the HGB Area from 1995 

through 2008 shows how the daily maximum one-hour change in ozone has changed since 1995 

in the HGB area. While at the mean and median levels the change is slight, the steepest observed 

ozone gradients have been reduced dramatically since 1995, decreasing by about 40 percent. 
5-33

32

27

30

28

32

27 28

26

30

27 28

25 24

21 29

22

26

23

29

22

24

21

26

23

25 25

22 20

62

57

65 66

62 63

55

62

58

53 52

44

48

38

0

10

20

30

40

50

60

70

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Peak 1-hr delta ozone, ppb/hr

Mean

Median

95th percentile

32

27

30

28

32

62

57

65 66

62 63

55

62

58

53 52

44

48

38

27 28

26

30

27 28

25 24

21 29

22

26

23

29

22

24

21

26

23

25 25

22 20

0

10

20

30

40

50

60

70

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Peak 1-hr delta ozone, ppb/hr

95th percentile

Mean

Median

Figure 5-14: Trends in the Strength of Ozone Gradients Measured in the HGB Area from 

1995 through 2008 

Figure 5-15: The Number of Occurrences of One-Hour Increases in Ozone Greater Than 40 

ppb/hr in the HGB Area for the Subset of Monitors with Long Historical Records shows that the 

number of strong ozone gradients observed by monitoring sites in the HGB area has also 

decreased substantially since the 1990s, matching the general trends in decreasing ozone 

concentrations. The intensity of ozone gradients has decreased, and the frequency of strong ozone 

gradient observations has also decreased, which strongly suggests that ozone is forming less 

rapidly in the HGB area than in previous years. This change in ozone behavior is consistent with 

decreasing reactivity of VOC emitted in the HGB area. Note that the intensity of ozone gradients 

can depend upon meteorological factors as well as chemical factors. This analysis has not 

examined the importance of meteorological factors upon the observed trends. Subsequent 

sections will discuss trends in HRVOC concentrations. 
5-34

y = -5.6593x + 92.659

R2 = 0.6093

0

20

40

60

80

100

120

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Number of observed strong ozone gradients

Figure 5-15: The Number of Occurrences of One-Hour Increases in Ozone Greater Than 

40 ppb/hr in the HGB Area for the Subset of Monitors with Long Historical Records 

5.3.4 The Impact of Hurricane Ike on Ozone Observations in the HGB Area 

The HGB area typically records high ozone values each year in September. Sometimes, these 

values help determine the area-wide design value for that year. The HGB eight-hour ozone 

design value has been declining recently and was particularly low in 2008 (91 ppb). September 

2008 was not typical for the HGB area. Hurricane Ike, a strong Category 2 hurricane, struck the 

Texas coast near Galveston Bay on September 13, 2008. Most monitors in the area were shut 

down and emissions patterns were substantially altered. 

Hurricane Ike struck the Texas coast near Galveston Bay on September 13, 2008. Before the 

hurricane struck, the evacuation of Galveston Island and the surrounding areas created enormous 

traffic jams. After the storm passed, there was far less automobile traffic than normal for several 

weeks. In preparation for the storm, many of the local petrochemical facilities shut down their 

operations, generating unknown quantities of emissions in the process, and after the storm, their 

operations were atypical for an extended period. Rescue operations, tree cutting and burning, 

lack of electrical power, unusual traffic patterns, and abnormal industrial operations were among 

the atypical conditions that occurred before, during, and after the hurricane. The exact effect of 

the emission changes on ozone concentrations is unknown, due to the number of ozone 

monitoring sites disabled indirectly or directly by Hurricane Ike. Monitors in the HGB area 

ceased operations for as little as one day, and as long as 69 days at a site that was severely 

damaged by storm surge. Key monitors that typically record the area design values were down 

for as much as 16 days, e.g., Houston Bayland Park (CAMS 53) (see Table 5-10: List of the 

Number of Days HGB Ozone Regulatory and Non-Regulatory Monitors were Not Operating 

Before and After the Landfall of Hurricane Ike). 
5-35

Table 5-10: List of the Number of Days HGB Ozone Regulatory and Non-Regulatory 

Monitors were Not Operating Before and After the Landfall of Hurricane Ike 

Monitor 

First Date 

Monitor Did Not 

Report Data 

Restart 

Date 

Days 

Down 

Houston Bayland Park C53/A146 9/13/2008 9/29/2008 16 

Houston Westhollow C410 9/12/2008 9/30/2008 18 

Park Place C416 9/12/2008 9/15/2008 3 

Houston Deer Park 2 C35/C139 9/12/2008 9/22/2008 10 

Manvel Croix Park C84 9/12/2008 9/21/2008 9 

Northwest Harris Co. C26/A110/X150 9/13/2008 9/14/2008 1 

Houston Aldine C8/AF108/X150 9/13/2008 9/15/2008 2 

Houston Monroe C406 9/12/2008 9/19/2008 7 

Houston Croquet C409 9/12/2008 9/26/2008 14 

Conroe Relocated C78/A321 9/13/2008 9/17/2008 4 

Channelview C15/AH115 9/13/2008 9/16/2008 3 

Houston East C1/G316 9/13/2008 9/29/2008 16 

Seabrook Friendship Park C45 9/13/2008 9/16/2008 3 

Houston Texas Avenue C411 9/12/2008 9/16/2008 4 

Lake Jackson C1016 9/12/2008 9/16/2008 4 

Lang C408 9/12/2008 9/18/2008 6 

Houston North Wayside C405 9/12/2008 9/15/2008 3 

Lynchburg Ferry C1015/A165 9/12/2008 10/16/2008 34 

Houston Regional Office C81 9/13/2008 9/20/2008 7 

Clinton C403/C304/AH113 9/12/2008 9/30/2008 18 

West Houston C554 9/13/2008 9/14/2008 1 

Tom Bass C558 9/13/2008 9/18/2008 5 

Wallisville Road C617 9/12/2008 9/17/2008 5 

Meyer Park C561 9/13/2008 9/15/2008 2 

Atascocita C560 9/14/2008 9/23/2008 9 

La Porte Sylvan Beach C556 9/12/2008 11/6/2008 55 

Baytown Wetlands Center C552 9/12/2008 10/31/2008 48 

Mustang Bayou C619 9/12/2008 9/26/2008 14 

Clear Lake High School C572 9/13/2008 9/14/2008 1 

HRM-3 Haden Road C617 9/12/2008 9/22/2008 10 

Crosby Library C553 9/13/2008 9/20/2008 7 

Texas City 34th St. C620 9/12/2008 9/18/2008 6 

Dacinger C618 9/12/2008 9/19/2008 7 

Kingwood Library C555 9/13/2008 9/14/2008 1 

Mercer Arboretum C557 9/22/2008 10/8/2008 16 

Sheldon C551 9/12/2008 9/22/2008 10 

Clear Creek High School C571 9/13/2008 9/15/2008 2 

Galveston 99th St. C1034/A320/X183 9/12/2008 11/20/2008 69 

Pasadena AAMS C672 9/12/2008 9/22/2008 10 

Hurricane Ike’s greatest impact occurred during the second half of September and the first half of 

October. August and September are typically the months when the HGB area records the most 

number of days that exceed the ozone standard. For 2000 through 2008, 21 percent of the 266 

observed 85 ppb exceedance days in the HGB area were recorded in September (Figure 5-16: 

Number of Days that Exceeded the 1997 Eight-Hour Ozone NAAQS by Month from 2000 through 

2008). 
5-36

3

20

26

49

32

54 55

22

5

0

10

20

30

40

50

60

Mar Apr May Jun Jul Aug Sep Oct Nov

Number 

of Days

Figure 5-16: Number of Days that Exceeded the 1997 Eight-Hour Ozone NAAQS by Month 

from 2000 through 2008 

Figure 5-17: Frequency of Daily Peak Eight-Hour Ozone Values for All Ozone Monitoring Sites 

in Texas, September 2006 and Figure 5-18: Frequency of Daily Peak Eight-Hour Ozone Values 

for All Ozone Monitoring Sites in Texas, September 2008 show peak eight-hour ozone at all 

Texas monitoring sites in September 2006, which was unaffected by tropical systems and in 

September 2008, the month in which Hurricane Ike struck. In 2008, the number of monitors in 

operation dropped substantially just before the hurricane made landfall, as they were shut down 

by the TCEQ. The monitors came back on-line gradually, as electrical power was restored, and 

storm damage was repaired. Ozone concentrations immediately before and after Ike were fairly 

low. 

The purpose of this analysis is to examine how the ozone behavior in September and October 

2008 deviated from the 2000 through 2007 average, and thus to ascertain whether the lower 

design value observed in 2008 was due primarily to the effects of Hurricane Ike. 
5-37

0

20

40

60

80

100

120

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Sept 2006 date

Site Count

below 15 ppb

15 to 29 ppb

30 to 44 ppb

45 to 59 ppb

60 to 74 ppb

75 to 84 ppb

85 ppb or above

Figure 5-17: Frequency of Daily Peak Eight-Hour Ozone Values for All Ozone Monitoring 

Sites in Texas, September 2006 

0

20

40

60

80

100

120

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Sept 2008 date

Site Count

below 15 ppb

15 to 29 ppb

30 to 44 ppb

45 to 59 ppb

60 to 74 ppb

75 to 84 ppb

85 ppb or above

Figure 5-18: Frequency of Daily Peak Eight-Hour Ozone Values for All Ozone Monitoring 

Sites in Texas, September 2008 

5.3.4.1 Approach

One approach to estimate the influence of Hurricane Ike on the HGB area’s ozone design value is 

to estimate what the eight-hour ozone design value might have been in 2008 if Hurricane Ike had 

not occurred. This estimate is derived from historical data collected during 2000-2007. 

Removing calendar days affected by Hurricane Ike and replacing them with averages derived 

from historical data yields a re-calculated fourth-highest eight-hour ozone concentration for each 

monitor. The actual fourth-high is then divided by the re-calculated fourth-high to obtain an 
5-38

adjustment ratio or an Ike Adjustment Factor (IAF). This ratio is expected to be greater than one, 

and can be used to adjust 2008 ozone data to non-hurricane conditions. The IAF can be 

calculated as an area-wide average IAF or as a monitor-specific IAF. An area-wide average IAF 

is computed as the average of all IAFs from all monitors in the region, applied to all 2008 data. 

The monitor-specific IAF was applied only to the monitor in question. After the data were 

adjusted with IAFs, an IAF-corrected design value was calculated and compared to the current 

unadjusted ozone design value to determine the influence of Hurricane Ike. 

The days affected by Hurricane Ike are not easy to identify. As stated before, many unusual 

activities occurred in the HGB area before the arrival of Hurricane Ike, and many others occurred 

in the aftermath. For example, many industrial facilities shut down operations before the storm 

arrived, releasing emissions that they usually would not release. After the hurricane, electrical 

power was not available in parts of the HGB area for two or more weeks. Given the difficulties 

in establishing the exact period of Hurricane Ike’s influence, alternative IAFs were calculated by 

removing three different time periods from the historical ozone data. The first period considered 

for exclusion was a two-week period from September 11 through September 25, 2008, which 

includes days immediately before and after the hurricane. Two other periods considered for 

exclusion were a one-month period from September 6 through October 5, 2008, and a one-month 

period after the storm (September 13 through October 12, 2008). All data used in this analysis 

were obtained from the TCEQ-LEADS system, and are eight-hour ozone averages. The HGB 

area eight-hour ozone design value was obtained from the EPA. 

5.3.4.2 Results

Table 5-11: Alternative Fourth-High Daily Peak Eight-Hour Ozone Concentration Calculations 

Using Different Ike Adjustment Factors (IAFs) shows results of the six different methods for 

estimating the fourth-high daily peak eight-hour ozone concentration for each monitoring site. 

The table shows that the expected fourth high is greater than the observed at most sites, regardless 

of which method is used to calculate the expected fourth high. This indicates that the atypical 

conditions experienced during and after Hurricane Ike during September and October in 2008 did 

have an effect on the monitored values, but the effect was no greater than 4 ppb on the fourthhigh daily maximum ozone concentration. 
5-39

Table 5-11: Alternative Fourth-High Daily Peak Eight-Hour Ozone Concentration 

Calculations Using Different Ike Adjustment Factors (IAFs) 

Monitoring site 

2008 

observed 

fourth 

high 

9/11-

9/26 

average 

IAF 

9/11-

9/26 

monitorspecific 

IAF 

9/6-

10/5 

average 

IAF 

9/6-10/5 

monitorspecific 

IAF 

9/13-

10/12 

average 

IAF 

9/13-

10/12 

monitorspecific 

IAF 

ppb ppb ppb ppb ppb ppb ppb 

Houston Aldine C8 /AF108/X150 83 85 86 87 86 86 86 

Houston Bayland Park C53 83 85 84 87 86 86 85 

Channelview C15/C115 76 78 77 79 78 79 78 

Houston Croquet C409 76 78 78 79 80 79 79 

Houston Deer Park C18 76 78 78 79 79 79 78 

Lake Jackson C1016 76 78 77 79 80 79 78 

Northwest Harris Co. C26/A110/C154 76 78 78 79 81 79 80 

Manvel Croix Park C84 75 77 77 78 81 78 78 

Conroe C65 73 75 74 76 75 76 75 

Houston East C1 73 75 74 76 76 76 76 

Houston Monroe C406 71 73 73 74 75 74 74 

Seabrook Friendship Park C45 71 73 75 74 75 74 75 

Houston North Wayside C405 70 72 70 73 71 73 71 

Houston Texas Avenue C411 70 72 71 73 73 73 73 

Lang C408 70 72 73 73 75 73 74 

Clinton C403/C113/C304 69 71 70 72 72 71 72 

Houston Westhollow C410 69 71 70 72 71 71 71 

Houston Regional Office C81 68 70 69 71 71 70 70 

Lynchburg Ferry C1015 65 66 65 68 66 67 66 

This table compares the observed 2008 fourth-high at each monitor to the expected fourth high, as 

calculated by six different methods. 

The attainment status of an area is not based upon fourth-high ozone concentrations, but upon 

design values. Table 5-12: Observed and Expected Design Values, Recalculated to Account for 

Hurricane Ike shows the observed 2008 design value, and the expected design values, as 

calculated with the six different methods described above. As Table 5-12: Observed and 

Expected Design Values, Recalculated to Account for Hurricane Ike shows, the effect upon the 

design value for the HGB area is at most 1 ppb, and for two of the alternatives there is no effect. 

This analysis is robust, because six different methods of estimating the effect of the hurricane on 

ozone design value have given substantially the same answer: the 2008 eight-hour ozone design 

value was not different from the expected design value, based upon comparisons with historical 

data. Therefore, based upon the historical analysis, the effect of Hurricane Ike upon the eighthour ozone design value in the HGB area was apparently minimal. 

Table 5-12: Observed and Expected Design Values, Recalculated to Account for Hurricane 

Ike 

Observed Design Value: 91 ppb 2-weeks 

9/11-9/25 

1-month 

9/13-10/12 

1-month 

9/6-10/5 

Estimated Design Value after applying area-wide 

average Ike Adjustment Factor 91 ppb 92 ppb 92 ppb 

Estimated Design Value after applying monitorspecific Ike Adjustment Factor 92 ppb 91 ppb 92 ppb 
5-40

5.3.5 NOX Trends 

Nitrogen oxides, or NOX, are a variable mixture of NO and NO2 and are critical precursors to 

ozone formation. NOX is primarily created by fossil fuel combustion, lightning, biomass burning, 

and microbial action in the soil. 

Previous analyses performed using aircraft measurements and emission inventories obtained 

during TexAQS 2000 and TexAQS II indicate that NOX emissions in the Houston Ship Channel 

area have decreased between 2000 and 2006 (Cowling et al., 2007). Furthermore, aircraft data 

obtained during the two field studies were in agreement with data measured by continuous 

emission monitoring systems (CEMS) located at the facilities. Analyses done by the Rapid 

Science Synthesis Team of the 2005-2006 Texas Air Quality Study (TexAQS II) indicate that 

NOX emissions at several electric generating units (EGUs) have decreased by factors ranging 

from two to four between 2000 and 2006 (Cowling et al., 2007). These reductions were seen at 

EGUs that implemented NOX control features, such as selective catalytic reduction (SCR), 

between 2000 and 2006, which suggests these control strategies are working. The two field 

studies effectively describe the emissions during two short time windows, six years apart. To 

complement these analyses, the TCEQ has performed a more comprehensive investigation of 

long-term trends in NOX concentrations. 

Daily peak one-hour NOX from all monitors in the HGB area from 1991 through 2008 is plotted 

in Figure 5-19: Daily Peak Hourly NOX in the HGB Area. The increasing density of NOX data 

points shows that the number of NOX monitors in the HGB area has greatly increased since 1991. 

Annual 90th percentile and annual average NOX values are also plotted in the figure. Both of 

these measures have decreased markedly over the 1991 to 2008 period, falling 64 percent and 68 

percent, respectively. Even more remarkable may be the 53 percent and 48 percent declines since 

1999. 
5-41

 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 20Date of 90th percentile: 

 Oct Dec Dec Oct Nov Dec Nov Feb Nov Sep Apr Dec Dec Apr D

 22 15 25 30 22 12 19 24 12 5 27 15 19 28 Figure 5-19: Daily Peak Hourly NOX in the HGB Area 
5-42

Table 5-13: NOX Values in the HGB Area by Year shows the degree of decrease in NOX 

concentrations from 1991 through 2008 and 1999 through 2008. 

Table 5-13: NOX Values in the HGB Area by Year 

 annual annual 

 maximum average 

year NOX NOX

 ppb ppb 

1991 880 110 

1992 780 110 

1993 622 103 

1994 523 99 

1995 524 99 

1996 773 98 

1997 521 75 

1998 520 67 

1999 696 75 

2000 641 57 

2001 629 66 

2002 678 52 

2003 809 53 

2004 509 49 

2005 609 49 

2006 593 49 

2007 461 48 

2008 409 35 

overall decrease through 2008 since: 

1991 -53.5% -67.7% 

1999 -41.2% -53.0% 

annual decrease through 2008 since: 

1991 -4.4% -6.4% 

1999 -5.7% -8.0% 

Annual decreases are computed as compound annual rates. 

Though highly variable from season to season, daily peak hourly NOX also shows a general 

decreasing trend since 1991. Maximum NOX concentrations have decreased overall by 41 

percent since 1999, an average of roughly 32 ppb per year, or nearly 6 percent per year. The 

drop since the 1991 high of 880 ppb is 54 percent or greater than 4 percent annually. 

Average daily peak hourly NOX has dropped even more precipitously, falling 53 percent, or 8 

percent per year, from 75 ppb to 35 ppb, since 1999. Since 1991, average hourly NOX has 

dropped 68 percent, or over 6 percent per year, from the series high of 110 ppb. Notice that in 

2008, both the NO2 design value and maximum daily peak NOX recorded the lowest values of any 

previous year back to 1991. 
5-43

While the highest NOX values occur in the winter, the NOX values during the summer months, 

when ozone production is the highest, are of particular interest. Trends in median hourly NOX

concentrations at individual monitors in the HGB area from May through October, 1998 to 2008, 

are shown in Figure 5-20: Median NOX Concentrations in the HGB Area. Four monitors of 

particular interest, Houston Texas Avenue (CAMS 411), Lang (CAMS 408), Clinton (CAMS 

403/CAMS 113/CAMS 304), and Houston Bayland Park (CAMS 53), are highlighted. Sites with 

less than 75 percent complete data for a year were not plotted for that year; for example, Clinton 

(CAMS 403/CAMS 113/CAMS 304) had less than 75 percent complete data in 2008 and 

therefore was not plotted. 

Median NOX Concentrations in the HGB Area 

(May through October)

0

5

10

15

20

25

19981999200020012002200320042005200620072008

NOX

(ppb) Conroe

Deer Park

Lynchburg Ferry

Manvel Croix

NW Harris Co.

Park Place

Texas Ave

Houston East Clinton

Lang

Galveston Airport Lake Jackson

Aldine

Seabrook

Channelview

Bayland Park

Figure 5-20: Median NOX Concentrations in the HGB Area 

Median NOX values tend to vary from year to year, but most monitors show overall decreases in 

median NOX since 1998. Monitors that show the smallest decreases or show no change are at 

sites that have traditionally had lower NOX concentrations. Some of the largest median NOX

concentrations were measured at the Lang (CAMS 408) monitor (in close proximity to Highway 

290), and at the Houston Texas Avenue (CAMS 411) monitor (in downtown Houston). These 

monitors are both near major roadways; their similar trends suggest they may be measuring 

decreases in NOX emissions from mobile sources. Monitors at Galveston Airport (CAMS 

34/C109/C154), Seabrook Friendship Park (CAMS 45), and Lake Jackson (CAMS 1016) 

measured the lowest median NOX concentrations. 

Sites recording among the highest ozone design values, for example, Houston Bayland Park 

(CAMS 53) and Park Place (CAMS 416), are not necessarily the sites with the highest median 

NOX concentrations. The previous section showed that Houston Bayland Park (CAMS 53) has 

the highest eight-hour ozone design value in the HGB area of 91 ppb, yet it has a lower median 

NOX concentration than many other sites in the area. This observation is consistent with the 

behavior expected from ozone chemistry; in addition to being an ozone precursor, NO also reacts 

directly with ozone and in areas with high NO emissions, can destroy more ozone than it creates. 
5-44

Downwind from the high emission areas, however, ozone destroyed by reaction with NO can reform. 

The largest decreases since 1998 (Table 5-14: Median and 90th Percentile Hourly NOX Values) 

were observed at monitors primarily influenced by mobile source emissions, rather than industrial 

sources. Clinton (CAMS 403/CAMS 113/CAMS 304) and Houston East (CAMS 1), which are 

located near both industrial sources and highways, have seen larger decreases in median NOX

values than in 90th percentile values since 1998. At Houston East (CAMS 1), the 90th percentile 

value decreased 34 percent, while the median decreased 42 percent between 1998 and 2008. The 

Clinton (CAMS 403/CAMS 113/CAMS 304) monitor experienced a drop of 16 percent in the 90th

percentile, with a 21 percent decrease in the median between 1998 and 2007 (2008 was not used 

due to incomplete data), though these measures have increased in recent years. 

Table 5-14: Median and 90th Percentile Hourly NOX Values 

 median 90th percentile 

% change % change 

monitor 1998 2007 2008 1998-2008* 1998 2007 2008 1998-2008*

ppb ppb ppb % ppb ppb ppb % 

monitors with decreasing trends

 Houston Bayland Park C53 8 8 3 -63 33 30 19 -42 

 Northwest Harris Co. C26/ 10 5 4 -60 21 12 12 -43 

 A110/C154 

 Lang C408 21 16 11 -48 65 48 35 -46 

 Houston East C1 19 15 11 -42 56 46 37 -34 

 Clinton C403/C113/C304*

 24 19 - -21 56 47 - -16 

monitors with increasing trends

 Houston Aldine C8/AF108/X150 3 10 9 200 30 32 30 0 

 Houston Deer Park C18 3 5 5 67 25 21 18 -28 

monitors with indeterminate trends

 Channelview C15/C115 - 9 8 - 24 20 

 Conroe C65 - 4 4 - 10 10 

 Galveston Airport 

 C34/C109/C154 0 - - 1 - - 

 Houston Texas Avenue C411 - 17 14 - 53 37 

 Lake Jackson C1016 - 2 2 - 7 6 

 Lynchburg Ferry C1015 - 11 - - 33 - 

 Manvel Croix Park C84 - 5 4 - 17 15 

 Park Place C416 - 11 8 - 47 32 

 Seabrook Friendship Park C45 - 4 3 - 12 12 

* Percentage changes computed from 1998 to 2007 for years missing 2008 data, due to 

incomplete data. 

Monitors are sorted in increasing order by percentage change in median values. Monitors with 

indeterminate trends began operating after 1998. 

While several monitors recorded large decreases from 2007 to 2008, most others observed only 

minimal changes over that same period. These large disparities in patterns of ambient NOX

concentrations across the region are appropriate for further investigation, suggesting that larger 

decreases are not due solely to variations in meteorological conditions, which would be expected 
5-45

to influence all monitors similarly, though not identically. The differences seem to be related to 

the relative magnitudes of the overall concentrations. Sites with the highest concentrations, 

which tend to be urban sites, showed the greatest decrease. More rural sites like Lake Jackson 

(CAMS 1016), Conroe (CAMS 65), and Conroe Relocated (CAMS 78) may reflect slight 

changes in background values, while more urban sites may reflect actual emission changes. 

Similar to ozone, NOX concentrations in the HGB area appear to be decreasing over time, in large 

measure the result of the comprehensive suite of NOX-targeted controls implemented since 2000. 

Stringent point source NOX standards have been adopted along with numerous factors affecting 

mobile source NOX emissions. 

5.3.6 Ambient VOC Concentrations 

The other major class of compounds that are ozone precursors are VOC. TexAQS 2000 

researchers identified a specific subset of VOC that were closely associated with rapid and 

efficient ozone formation, i.e., light alkenes (Ryerson et al., 2003; Daum et al., 2003, 2004; 

Jobson et al., 2004). The TCEQ examined the historical data for these compounds, and decided 

to regulate several light alkenes emitted by industry that were particularly reactive, and that often 

had particularly high concentrations: ethylene, propylene, 1,3-butadiene, and butenes. 

Since the mid-1990s, the TCEQ has collected 40-minute measurements, on an hourly basis, of 45 

VOC compounds using automated gas chromatograph (auto-GC) instruments. Initially, 

measurements were collected at just one site (Clinton (CAMS 403/CAMS 113/CAMS 304)), but 

in subsequent years, auto-GC monitors have been added to new sites (see Figure 5-21: Houston 

Ship Channel Auto-GC Monitors and 2006 Reported Point Source HRVOC Emissions Points and 

Plant Boundaries). Currently, eight sites, listed in Table 5-15: Auto-GC Monitors in the Houston 

Ship Channel Area, along or near the Houston Ship Channel, along with three in Brazoria County 

and one in Texas City, are collecting VOC measurements with auto-GCs. 
5-46

Figure 5-21: Houston Ship Channel Auto-GC Monitors and 2006 Reported Point Source 

HRVOC Emissions Points and Plant Boundaries 

Ambient concentrations of the TCEQ-defined HRVOC (ethylene, propylene, 1,3-butadiene, 1-

butene, c-2-butene, and t-2-butene) were analyzed from 1995 to 2008. 

Table 5-15: Auto-GC Monitors in the Houston Ship Channel Area 

 start 

site name CAMS AIRS code latitude longitude city date 

Channelview C15/C115 482010026 29.8025 -95.1256 Channelview 8/3/2001 

Houston Milby Park A169 482010069 29.7062 -95.2611 Houston 2/19/2005 

HRM-3 Haden Road C603 482010803 29.7483 -95.1811 Houston 8/20/2001 

Lynchburg Ferry C1015 482011015 29.7646 -95.0780 Houston 5/24/2003 

Clinton C403/113/304 482011035 29.7337 -95.2576 Houston 7/1/1995 

HousDeerPrk2 C35/139 482011039 29.6700 -95.1285 Deer Park 1/5/1997 

Cesar Chavez C1020/175 482016000 29.6844 -95.2536 Houston 4/13/2004 

Wallisville Road C617 482010617 29.8214 -94.99 Baytown 6/5/2003 

Trends at each of the eight Houston Ship Channel monitors were examined. Data from the four 

other auto-GC monitors were analyzed only for trend slope and possible statistical significance of 

trends. Daily geometric means were computed from valid ambient hourly measurements for days 

with at least 18 valid hours of data. A geometric mean was calculated by taking the natural 

logarithm of each of the measurements, averaging these logs, then calculating the antilog of this 

mean log value. The geometric mean is a preferable statistic to median or arithmetic (ordinary) 

mean for evaluating the central tendency of data when the data are skewed, that is, when the data 

are not symmetrically, or normally, distributed, but clustered around extreme high or low values. 

It is more robust than an ordinary average, meaning its value is not greatly influenced by one or a 

few very high or very low values. Many distributions of pollutant measurements in the HGB area 

are skewed. Monthly geometric means were also computed with a 75 percent data completeness 

criterion for valid days in a month. 

Figure 5-22: Monthly Geometric Mean Ethylene Concentrations at the Eight Houston Ship 

Channel Monitors, July 1995 through December 2008 shows monthly geometric mean ethylene 

concentrations, ordered according to the monitor location from west to east. Grey bars denote the 

range of values from the 25th through 75th percentile concentrations, for all monitors. Noteworthy 

in this figure is the frequency of extremely high values recorded during the 1990s at Clinton 

(CAMS 403/CAMS 113/CAMS 304), at the western end of the Houston Ship Channel, and Deer 

Park (CAMS 35/139), in south central Houston Ship Channel. These were the only monitors 

operating during the early years of this period; this pattern suggests that high ethylene 

concentrations were not restricted to certain areas of the Houston Ship Channel, but were 

somewhat geographically widespread. 
5-47

Figure 5-22: Monthly Geometric Mean Ethylene Concentrations at the Eight Houston Ship 

Channel Monitors, July 1995 through December 2008 

For four consecutive years, July 1995 through July 1999, valid monthly geometric mean 

concentrations at Clinton (CAMS 403/CAMS 113/CAMS 304) exceeded the 75th percentile of the 

multi-decade series. Deer Park (CAMS 35/139) also exhibited high concentrations in the first 

several years, including the highest mean value for any complete month, 10.2 parts per billion, 

carbon (ppbC) in March 2001. By contrast, few monthly mean concentrations exceeded the 75th

percentile in the most recent four years, 2005 through 2008. 

Though measured ethylene and propylene concentrations show a large degree of variability at all 

auto-GC monitors, downward trends are apparent at seven of the eight; only Wallisville Road 
5-48

(CAMS 617) appears to show no decrease. A statistical trend analysis, described below, provides 

further insight into this. 

Peak monthly geometric mean ethylene concentrations at all monitors, 6.9 ppbC and 8.4 ppbC in 

2003 and 2004 respectively, decreased to 5.6 ppbC in 2005, 4.9 ppbC in 2006, and 4.5 ppbC in 

2007, before climbing to 5.1 ppbC in 2008. This decline in ambient ethylene concentrations 

suggests that ethylene emissions in the Houston Ship Channel are declining, though meteorology 

could be responsible for some or all of the decline in geometric mean concentrations. 

Similar to Figure 5-22: Monthly Geometric Mean Ethylene Concentrations at the Eight Houston 

Ship Channel Monitors, July 1995 through December 2008, Figure 5-23: Monthly Geometric 

Mean Propylene Concentrations at the Eight Houston Ship Channel Monitors, July 1995 through 

December 2008 displays monthly geometric mean concentrations of propylene for the eight 

Houston Ship Channel area auto-GC monitors. Again, Clinton (CAMS 403/CAMS 113/CAMS 

304) and Deer Park (CAMS 35/139) show higher concentrations in earlier years compared to 

recent ones; however, the magnitude of concentrations at the two monitors are dissimilar, unlike 

ethylene, suggesting elevated propylene concentrations are more geographically limited than 

elevated ethylene concentrations. Two other eastern Houston Ship Channel monitors, 

Channelview (CAMS 15/CAMS 115) and Lynchburg Ferry (CAMS 1015), report concentrations 

well above the 75th percentile in 2003, and to a lesser extent in 2004 and subsequent years, 

suggesting there are greater propylene emissions in the eastern Houston Ship Channel than the 

western Houston Ship Channel. However, the relatively fast reactivity of propylene, compared to 

ethylene, may explain part or all of the low concentrations seen in the western Houston Ship 

Channel. 

Similar analyses were performed for 1, 3-butadiene and the isomers of butene; however, trends in 

these pollutants can be difficult to interpret, as their relatively low concentrations are frequently 

within accepted measurement uncertainty. Further work is needed before trend estimation for 

these compounds can be considered accurate. 

Though still variable from month to month, pervasive decreases in the ambient concentrations of 

ethylene and propylene suggest that overall industrial emissions of these compounds have 

decreased considerably since 1995. This finding agrees with early reports from TexAQS II that 

ethylene emissions along the Houston Ship Channel have decreased approximately 40 percent 

from 2000 to 2006. 
5-49

Figure 5-23: Monthly Geometric Mean Propylene Concentrations at the Eight Houston 

Ship Channel Monitors, July 1995 through December 2008 

A preliminary analysis was performed to verify whether decreases observed were statistically 

significant. Ordinary least squares regression lines were fit to the monthly geometric mean 

ethylene and propylene concentrations, using an index of month, where the first recorded month 

was given a value of zero. Results of these fits are reported in Table 5-16: Parameter Estimates 

of Monthly Geometric Mean Concentrations Trends. In 23 of the 24 regressions, concentrations 

decreased across the respective study periods, with correlation coefficient (R2

) values ranging 

from 0.045 to 0.549. Eight of 12 monitors recorded statistically significant decreases for 

ethylene, including six of eight Houston Ship Channel monitors. All 12 monitors recorded 

statistically significant decreases for propylene. However, caution must be exercised when 
5-50

interpreting these results. First, some of the computed R2 values are very low, confirming there is 

a substantial degree of variation in the measured values, with only a portion of it explained by a 

simple linear model. Further statistical testing and verification, such as testing for and correcting 

possible autocorrelation, is necessary to fully validate these models. 

Table 5-16: Parameter Estimates of Monthly Geometric Mean Concentrations Trends 

 ethylene propylene 

monitoring site N slope intercept R2

 N slope intercept R2

Houston Ship Channel-area auto-GC monitors: 

 Cesar Chavez C1020/175 52 -0.019*

 2.74 0.09 52 -0.025* 2.86 0.16 

 Channelview C15/C115 62 -0.017*

 3.85 0.22 62 -0.039* 4.64 0.49 

 Clinton C403/C113/C304 60 -0.032*

 4.75 0.44 62 -0.018* 3.85 0.36 

 Deer Park C35/139 54 -0.033*

 4.12 0.25 65 -0.026* 4.09 0.22 

 HRM-3 Haden Road C603 56 -0.051*

 5.37 0.55 55 -0.026* 3.82 0.42 

 Houston Milby Park A169 39 -0.011 1.88 0.06 39 -0.021*

 2.05 0.20 

 Lynchburg Ferry C1015 56 -0.029*

 3.41 0.24 56 -0.059* 4.89 0.42 

 Wallisville Road C617 55 -0.002 1.79 0.00 55 -0.017*

 2.08 0.17 

Non-Houston Ship Channel-area auto-GC monitors: 

 Mustang Bayou C619 53 -0.008*

 0.72 0.20 53 -0.006* 0.83 0.13 

 Danciger C618 56 -0.003 0.57 0.05 56 -0.006*

 0.78 0.16 

 Lake Jackson C1016 50 -0.006 1.00 0.05 50 -0.007*

 0.77 0.18 

 Texas City 34th St. C620 59 -0.027*

 2.43 0.50 59 -0.020* 2.19 0.37

*Significant at the 5 percent (0.05) level. Significance levels for intercepts are not reported. 

Parameter estimates from ordinary least squares fits of monthly geometric mean concentrations of 

ethylene and propylene on an index of month, by monitoring site and compound. 

5.3.7 Geographic Patterns in Ambient HRVOC Concentrations Near the Houston Ship 

Channel 

The next analysis showed that, for some HRVOC, geographic patterns are apparent. Wind speed 

and wind direction measurements, collected in tandem with HRVOC concentrations at the 

Houston Ship Channel auto-GC monitors, were used not only to identify these patterns, but to 

track their changes over time. Radar plots of geometric mean concentrations of ethylene and 

propylene, by wind direction, were plotted, superimposed on maps of the Houston Ship Channel, 

and displayed in Figure 5-24: Geometric Mean Ethylene Concentration at Western Houston Ship 

Channel Monitors through Figure 5-27: Geometric Mean Propylene Concentration at Western 

Houston Ship Channel Monitors. 

These plots consist of jagged rings encircling a monitor. Each ring around a particular monitor 

represents the geometric mean concentration of the subject HRVOC at each of the 360 degrees 

surrounding the monitor, for a particular year. The distance from the origin to any point on the 

ring is proportional to the concentration of HRVOC arriving at the monitor from that direction. 

For example, Figure 5-25: Geometric Mean Ethylene Concentrations at Eastern Houston Ship 

Channel Monitors shows that in 2003 at Deer Park (CAMS 35/139), the highest mean ethylene 

concentration, 16 ppbC, occurred when winds were blowing from the northeast, suggesting there 

may be large ethylene emissions sources upwind of Deer Park (CAMS 35/139) in that direction. 

To help interpret these graphs, it is useful to describe a couple of hypothetical scenarios. In the 

first one, if HRVOC did not vary when winds arrived from different directions, i.e., the same 

concentrations were observed regardless of the wind direction, the ring would be a smooth circle. 
5-51

Conversely, in the second scenario, if HRVOC were detected only when winds arrived from a 

single direction, the ring would simply be an elongated spike pointing in that direction. 

In Figures 5-24: Geometric Mean Ethylene Concentration at Western Houston Ship Channel 

Monitors through 5-27: Geometric Mean Propylene Concentration at Western Houston Ship 

Channel Monitors, for the Houston Ship Channel monitors, a strong directional association with 

mean concentration is typical. The directional spikes seen in these rings are referred to as “lobes” 

in this section. 

Figure 5-24: Geometric Mean Ethylene Concentration at Western Houston Ship Channel 

Monitors 

Sources of ethylene (blue circles) and propylene (brown circles) are also depicted on the map of 

the respective compound, with sizes proportional to values reported in the 2006 TCEQ point 

source emissions inventory. Valid hourly measurements from 2002 through 2008 were used; 

hours with hourly wind speed measurements less than two miles per hour (mph) were discarded, 

due to considerable error in wind direction measurements at low wind speeds. 

While a compound’s concentration for a particular wind direction at a particular monitor is 

proportional to the distance from the monitor to the ring at that direction, the scale differs across 

monitors. For example, peak 2003 ethylene concentration (see Figure 5-25: Geometric Mean 

Ethylene Concentrations at Eastern Houston Ship Channel Monitors) at Lynchburg Ferry 

(CAMS 1015) is 24 ppbC, and 15 ppbC at Wallisville Road (CAMS 617), yet the length from 

each monitor to its respective peak (tip of sharp “point”) is approximately the same. For this 

reason, peak concentration at each monitor, for each pollutant, is labeled. 
5-52

Figure 5-25: Geometric Mean Ethylene Concentrations at Eastern Houston Ship Channel 

Monitors 

Figure 5-24: Geometric Mean Ethylene Concentration at Western Houston Ship Channel 

Monitors shows mean ethylene concentrations at the three western-most Houston Ship Channel 

auto-GC monitors. Sources of ethylene having the greatest impact on these monitors are all 

located east of the monitors, because the greatest peaks for each monitor point in this direction for 

all the years. The plot also shows trends across time at each monitor. At Clinton (CAMS 

403/CAMS 113/CAMS 304), peak ethylene occurred in 2003 from almost due east, as seen in the 

lobe labeled “14 ppbC.” Following 2003 and 2004, peak concentrations from that direction have 

been somewhat lower. Also, the lobes pointing south observed in 2003 and 2004 are markedly 

smaller in 2005 and subsequent years. An olefins production plant located in the Houston Milby 

Park (A169) area shut down in 2005; its emissions may have been responsible for those lobes. 

The plot shows mean ethylene concentrations for the Cesar Chavez (CAMS 1020/175) and 

Houston Milby Park (A169) monitors, which started operation in 2004 and 2005, respectively. 

While these monitors measured peak concentrations in different years, both monitors have peaks 

pointing in the direction of the Houston Milby Park (A169) olefins plant while it was in 

operation; Houston Milby Park (A169) observed a large lobe to the southeast in 2005, and Cesar 

Chavez (CAMS 1020/175) observed a notable lobe to the north in 2004 and 2005. This provides 

a stronger indication, when combined with the Clinton (CAMS 403/CAMS 113/CAMS 304) peak 

to the south, of the influence of emissions from that plant on local concentrations. 

Figure 5-25: Geometric Mean Ethylene Concentrations at Eastern Houston Ship Channel 

Monitors shows mean ethylene concentrations at the five auto-GC monitors located in the eastern 

part of the Houston Ship Channel. Variation in mean concentrations by direction is even more 

pronounced here than in the western portion of the Houston Ship Channel. The pattern in mean 

concentrations at Lynchburg Ferry (CAMS 1015) suggests there is a large source of ethylene 

emissions south-southeast of the monitor, near Battleground Road and Highway 225, and that 

emissions from this area have decreased. 
5-53

Table 5-17: Geometric Mean Ethylene for Key Wind Direction Lobes at Eastern Houston Ship 

Channel Monitors shows that this lobe’s mean 2003 concentration of 24.3 ppbC has halved in 

recent years. 

Table 5-17: Geometric Mean Ethylene for Key Wind Direction Lobes at Eastern Houston 

Ship Channel Monitors 

 principal 

Monitor direction(s) 2003 2004 2005 2006 2007 2008

 ppbC ppbC ppbC ppbC ppbC ppbC 

lobes pointing to the same sources in the central Houston Ship Channel area: 

HRM 3 ESE 24.8 18.0 15.6 5.0 4.7 5.2 

Channelview C15/C115 SW 8.9 8.9 5.6 4.3 3.6 4.1 

lobes pointing to the same sources in the eastern Houston Ship Channel area: 

Hous.DeerPrk2 C35/139 NE 16.6 missing 12.1 10.7 11.1 13.0

Lynchburg Ferry C1015 SSE 24.3 17.7 14.5 10.8 14.0 12.6 

Channelview C15/C115 SE 12.5 11.9 6.6 6.9 7.1 6.8 

Wallisville Road C617 SW 15.0 9.8 8.4 11.1 9.9 12.8 

lobes pointing in other directions: 

Channelview C15/C115 N 10.5 9.0 3.7 6.3 7.9 6.9 

Wallisville Road C617 ENE 9.7 11.5 9.6 10.8 9.2 11.6

Annual maxima are noted in boldface type. 

The pattern observed at Deer Park (CAMS 35/139) may provide additional evidence of suspected 

emission decreases in the same source area. The northeast lobe in Table 5-17: Geometric Mean 

Ethylene for Key Wind Direction Lobes at Eastern Houston Ship Channel Monitors has dropped 

from a high of 16.6 ppbC in 2003 to a range of about 11 to 13 ppbC in recent years. Similarly, 

the southeast lobe at Channelview (CAMS 15/CAMS 115), which points yet again to the same 

source area, peaked at 12.5 ppbC in 2003, dropped to 11.9 ppbC in 2004, and has not exceeded 

7.1 ppbC since. While this monitor is farther from this source region than are the other two 

monitors, and therefore is more likely to be impacted by other emissions sources, consistent 

decreases observed at these three monitors across the six-year span of available data suggest 

ethylene emissions have decreased in the subject source region. 

HRM-3 Haden Road (CAMS 603) shows a peak of 24.8 ppbC to the southeast in 2003, which fell 

to 18 ppbC in 2004, then further to 15.6 ppbC in 2005. The mean concentration has dropped 

since then, not exceeding 5.2 ppbC. The magnitude of the decrease over 2006 to 2008, as 

compared to 2005 and earlier years, suggests a shut down of one or more major process units, or 

even entire plants, somewhere southeast of this monitor, or implementation of HRVOC rules. 

Peaks at the Wallisville Road (CAMS 617) monitor point southwest, toward the east Houston 

Ship Channel, and east-northeast, in the direction of the Mont Belvieu industrial area, where there 

is considerable ethylene and propylene storage in underground salt caverns. Table 5-17: 

Geometric Mean Ethylene for Key Wind Direction Lobes at Eastern Houston Ship Channel 

Monitors shows that ethylene originating to the southwest decreased from the six-year peak in 

2003 (15 ppbC), to a range from 9.9 to 11.1 ppbC, before rising slightly to 12.8 ppbC in 2008. In 

contrast, the east-northeast lobe at this monitor shows relatively unvarying mean concentrations 
5-54

across the entire six-year period, ranging from 9.2 to 11.6 ppbC, with the six-year peak occurring 

in 2008. 

These conclusions for five monitors and eight directional lobes show a nearly consistent pattern 

across these monitors. Seven of eight lobes witnessed their highest mean concentration in 2003. 

Within one or two years of this peak, concentrations at all seven had dropped, from 27 to 65 

percent, and have leveled off since; mean concentrations have not varied appreciably from 2006 

to 2008. These findings suggest ethylene emissions from source areas close to these monitors, 

especially Battleground Road, Highway 225 in La Porte, and the petrochemical complex north of 

the Channelview (CAMS 15/CAMS 115) monitor, have decreased considerably in recent years. 

These observations suggest that the new TCEQ regulations specifically targeting HRVOC 

emissions and requiring full compliance by 2006 are proving effective in controlling point source 

HRVOC emissions. However, the trends shown here have not been corrected for meteorological 

variations. 

Results for the lobe pointing east-northeast from the Wallisville Road (CAMS 617) monitor 

disagree with some key findings at other lobes. The Wallisville Road (CAMS 617) east-northeast 

lobe, unique among the eight, experienced an increase in mean concentration from 2003 (9.7 

ppbC) to 2004 (11.5 ppbC). While 2006 to 2008 mean concentrations at Wallisville Road (CAMS 

617), like those of other monitors and lobes, changed relatively little, mean concentrations of the 

east-northeast Wallisville Road (CAMS 617) lobe changed relatively little across the entire sixyear period. The absence of recent decreases at this lobe compared to earlier years suggests that 

meteorology may not have caused high concentrations seen at most other lobes in earlier years. 

Figure 5-26: Geometric Mean Propylene Concentration at Eastern Houston Ship Channel 

Monitors displays monthly geometric mean concentrations of propylene in the same area of the 

eastern Houston Ship Channel. Table 5-18: Geometric Mean Propylene Concentrations for Key 

Wind Directions at Eastern Houston Ship Channel Monitors lists mean propylene concentrations 

across the study period, for each monitor and lobe. Similarities with ethylene are evident. For 

propylene, all seven lobes measured their highest concentrations in 2003 or 2004; five of the 

seven had their two lowest annual concentrations in 2007 and 2008. All seven lobes had 

concentrations in 2007 and 2008 that were 40 percent or more lower than their respective six-year 

peaks. 
5-55

Figure 5-26: Geometric Mean Propylene Concentration at Eastern Houston Ship Channel 

Monitors 

These results suggest that the propylene emissions in the source regions near the monitors have 

dropped considerably in the six-year study period, and that the HRVOC regulations may be 

responsible for the decreases. As seen with ethylene, patterns in geometric mean propylene 

concentrations at the east-northeast Wallisville Road (CAMS 617) lobe differed considerably 

from the other seven. Propylene concentrations varied relatively little across the six-year period, 

suggesting that, like ethylene, Mont Belvieu propylene emissions have changed little or not at all, 

on average, across the study period. 

Figure 5-27: Geometric Mean Propylene Concentration at Western Houston Ship Channel 

Monitors shows mean propylene concentrations by wind direction at the three western Houston 

Ship Channel monitors. Patterns depicted here exhibit strong similarities to those seen with 

ethylene in this area: the largest propylene source areas are to the east, and judging from the 

disappearance of strong peaks from 2006 onward, emissions from the now-defunct olefins plant 

located in the Houston Milby Park (A169) area were probably affecting these monitors. 
5-56

Figure 5-27: Geometric Mean Propylene Concentration at Western Houston Ship Channel 

Monitors 

Table 5-18: Geometric Mean Propylene Concentrations for Key Wind Directions at Eastern 

Houston Ship Channel Monitors lists mean propylene concentrations across the study period, for 

each monitor and lobe. 

Table 5-18: Geometric Mean Propylene Concentrations for Key Wind Directions at 

Eastern Houston Ship Channel Monitors 

 principal 

Monitor direction(s) 2003 2004 2005 2006 2007 2008

 ppbC ppbC ppbC ppbC ppbC ppbC 

lobes pointing to the same source in the eastern Houston Ship Channel area: 

HRM-3 Haden Road C603 SE 17.1 20.5 15.2 12.4 7.8 7.0 

Hous.DeerPrk2 C35/139 NE 50.0 30.3 25.4 21.2 19.6 18.6 

Lynchburg Ferry C1015 S 82.8 75.4 51.5 46.2 31.5 26.3

Channelview C15/C115 SE 30.1 19.0 11.7 13.8 11.7 8.2 

Wallisville Road C617 SW 35.6 27.3 22.3 18.4 14.5 21.3 

lobes pointing to other sources: 

Lynchburg Ferry C1015 SW 68.7 33.9 13.7 18.8 9.9 6.8 

Channelview C15/C115 N 11.3 7.7 3.0 5.5 8.1 5.2 

Wallisville Road C617 ENE 9.0 12.2 9.7 12.3 9.7 11.2

Annual maxima are noted in boldface type. 
5-57

5.3.8 Ambient Total VOC Concentrations 

Considerable research has focused on patterns and trends in HRVOC concentrations in the HGB 

area (Hafner Main et al. 2001; Brown and Hafner Main, 2002; Jolly et al., 2003; Fang and 

McDowell, 2003). Less examined are patterns for other, less-reactive VOC. This section 

presents a detailed examination of patterns in total VOC concentrations in the HGB area, using 

concentrations of total nonmethane hydrocarbons (TNMHC) as a measure of total VOC. Each 

TNMHC measurement corresponds to the sum of all chromatogram peaks (identified and 

unidentified) from the start to the end of sample collection. TNMHC is a useful measure of total 

VOC because it has been calculated in a consistent manner over the entire study period, unlike 

other parameters, such as the sum of Photochemical Assessment Monitoring Stations (PAMS) 

target compounds, whose constituents have changed periodically. 

Similar to the first HRVOC analysis presented in this section, geometric mean TNMHC 

concentrations, by monitor, year, and month, were calculated for valid months for all available 

data from each of the 12 HGB monitors. Further analysis of the four non-Houston Ship Channelarea monitors has not been completed at this time. 

Figure 5-28: Monthly Geometric Mean TNMHC Concentrations, July 1995 through December 

2008 shows, for each of the eight Houston Ship Channel monitors, monthly geometric mean 

TNMHC concentration for all months with complete data, between the start of monitoring and 

December 2008. Monitors are sorted according to their location from west (top) to east (bottom); 

the grey bars denote the 25th through 75th percentile concentrations (85 ppbC and 149 ppbC 

respectively) of all valid months across all monitors. 

As with ethylene and propylene, the two monitors with data before 2001, Clinton (CAMS 

403/CAMS 113/CAMS 304) and Deer Park (CAMS 35/139), recorded their highest monthly 

geometric mean values before 2001. Both monitors exhibited overall decreases across their 

respective data collection periods. A statistical analysis of possible trends, using ordinary least 

squares regression, is presented in Table 5-19: Parameter Estimates of Monthly Geometric Mean 

TNMHC Concentration Trends Houston Ship Channel Area Auto-GC Monitors. This statistical 

model indicates that all 12 monitors had decreasing monthly mean concentrations, from the 

beginning to the end of each monitor’s respective data range. As well, this model indicates that 

eight of the 12 monitors’ decreases were statistically significant at the 95 percent confidence 

level. 
5-58

Figure 5-28: Monthly Geometric Mean TNMHC Concentrations, July 1995 through 

December 2008 
5-59

Table 5-19: Parameter Estimates of Monthly Geometric Mean TNMHC Concentration 

Trends Houston Ship Channel Area Auto-GC Monitors 

Sitename 

Slope of 

Trend Intercept 

Degrees of 

Freedom R squared 

Cesar Chavez C1020/175 -0.61 132 47 0.07 

Channelview C15/C115 -0.37* 153 49 0.10 

Clinton C403/C113/C304 -0.63* 225 78 0.46 

Hous.DeerPrk2 C35/139 -0.55* 148 80 0.31 

Houston Milby Park A169 -0.33 99 33 0.03 

HRM-3 Haden Road 

C603 -1.22* 173 47 0.52 

Lynchburg Ferry C1015 -1.14* 156 47 0.27 

Wallisville Road C617 -0.31* 79 49 0.11 

Non-Houston Ship Channel-area auto-GC monitors 

Sitename 

Slope of 

Trend Intercept 

Degrees of 

Freedom R squared 

Danciger C618 -0.22* 44 47 0.12 

Lake Jackson C1016 -0.18 34 43 0.04 

Mustang Bayou C619 -0.11 61 43 0.01 

Texas City 34th St. C620 -0.95* 102 57 0.46 

*Significant at the 5 percent (0.05) level. Significance levels for intercepts are not reported. 

Parameter estimates from ordinary least squares fits of monthly geometric mean concentrations of 

TNMHC on an index of month, by monitoring site. 

Figure 5-29: 90th Percentile TNMHC Concentration in the HGB Area presents 90th percentile 

TNMHC concentrations at each auto-GC monitor. The area-wide 90th percentile TNMHC 

concentrations and the 90th percentile TNMHC at most of the individual monitors are decreasing. 

Smaller decreases are evident at Wallisville Road (CAMS 617), Channelview (CAMS 15/CAMS 

115), Lake Jackson (CAMS 1016), Mustang Bayou (CAMS 619), and Danciger (CAMS 618), 

while larger decreases are observed primarily at monitors closer to the Houston Ship Channel. 

Monitors in Brazoria County (Danciger (CAMS 618), Lake Jackson (CAMS 1016), and Mustang 

Bayou (CAMS 619)) and Galveston County (Texas City 34th St. (CAMS 620)) tend to report 

lower 90th percentile TNMHC than monitors located in Harris County. In the past, Clinton 

(CAMS 403/CAMS 113/CAMS 304) has recorded the highest TNMHC concentrations, but since 

2006 Clinton has decreased at a faster rate and Channelview (CAMS 15/CAMS 115) has 

recorded the highest concentrations. 
5-60

90th Percentile TNMHC Concentration in the HGB Area

0

100

200

300

400

500

600

700

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Concentration 

(ppbC)

Mustang

Milby Park

HRM-3

Cesar Chavez

Clinton

Channelview

Deer Park

Lynchburg

Danciger

Lake Jackson

Texas City

Wallisville

Figure 5-29: 90th Percentile TNMHC Concentration in the HGB Area 

5.3.9 Meteorologically Adjusted Ozone Trends 

Ozone formation is dependent not only on its precursors (NOX and VOC), but also on 

meteorological variables. While trends in ozone design values have been decreasing, design 

value trends must be examined to determine if the values are decreasing due to emission controls 

or if they are decreasing simply because of meteorological conditions in the area in the past 

several years. To determine whether control strategies have been effective, meteorological 

influences must be removed from ozone trends. Analysis done by Sullivan (2009) used a 

generalized linear model to account for meteorological influences in ozone trends. The following 

discussion is based upon Sullivan (2009), who used a modified version of the Camalier et al. 

(2007) technique for removing the meteorological influences from the ozone trends. 

Before meteorological influences can be removed from ozone trends, the meteorological factors 

that are most important to ozone formation must first be identified. Various correlations and 

factor analyses were used to identify the most important meteorological variables for ozone 

formation in the HGB area. Data from the Omnibus Meteorological Database (METDAT) 

maintained by the EPA was compared to ozone data obtained from surface monitors in the HGB 

area. Because the set of observed ozone levels can be influenced by the number of monitors in an 

area, Sullivan (2009) used a consistent set of ozone monitors in the HGB area. These monitors 

are listed in Table 5-20: Area Ozone Monitoring Sites with Long-Term Data. Most contain a 

consistent set of data from 1990 to 2007. Data from monitors that were moved a short distance 

during the period from 1990 to 2007 were combined with data from monitors in nearby locations, 

for example, data at Clute (CAMS 11) were combined with data from Lake Jackson (CAMS 

1016). 
5-61

Table 5-20: Area Ozone Monitoring Sites with Long-Term Data 

AQS Number Site Name 

482011039 Hous.DeerPrk2 C35/139 

482011035 Clinton C403/C113/C304 

482011034 Houston East C1 

482010075 Houston Texas Avenue C411 

482010062 Houston Monroe C406 

482010051 Houston Croquet C409 

482010047 Lang C408 

482010046 Houston North Wayside C405 

482010029 Northwest Harris Co. C26/A110/C154 

482010024 Houston Aldine C8/AF108/X150 

480391016 Lake Jackson C1016 (and Clute C11) 

Source: Sullivan, 2009. 

Figure 5-30: Actual Mean Eight-Hour Ozone Concentrations (Blue Line) and Mean Eight-Hour 

Predicted Concentrations with the Non-Meteorological Trend Removed (Red Line), which was 

reproduced from Sullivan (2009), displays two time series. The values in blue represent the 

observed mean daily maximum eight-hour ozone concentrations; values in red represent the daily 

peak ozone based purely on the meteorological variations, with the non-meteorological factors 

removed. In other words, the statistical model described above has been used to re-create the 

ozone time series with only the meteorology taken into account. 

For 2006 and 2007, the statistical model predicts that the observed mean daily peak eight-hour 

ozone should have been higher than observed, based upon the conduciveness of the meteorology 

toward ozone formation. In other words, based on the weather, ozone concentrations should have 

been higher in 2006 and 2007. Subtracting the meteorologically-based eight-hour ozone 

estimates from the actual eight-hour ozone results in a trend with the meteorological effects 

removed (Figure 5-31: Residual Meteorologically Adjusted Eight-Hour Ozone Concentrations 

Trend). This trend represents how the sum of anthropogenic factors, model error, and 

undiagnosed meteorological factors have changed from 1996 to 2007. Figure 5-31: Residual 

Meteorologically Adjusted Eight-Hour Ozone Concentrations Trend, which was reproduced from 

Sullivan et al., 2009, represents the trend in peak daily maximum ozone with the meteorological 

factors removed. The meteorologically-adjusted ozone trend is clearly downward. Since the 

meteorological variations have been removed, this downward trend shows the effect of emission 

reductions in the HGB area. Statistical results of this analysis are listed in Table 5-21: Summary 

Statistics for Meteorologically Adjusted Ozone Trends from 1996 to 2007. The slope of -0.86 

shows that eight-hour ozone trends in the HGB area are decreasing and that they are significant 

(p-value = 0.00). 
5-62

Figure 5-30: Actual Mean Eight-Hour Ozone Concentrations (Blue Line) and Mean EightHour Predicted Concentrations with the Non-Meteorological Trend Removed (Red Line) 

Figure 5-31: Residual Meteorologically Adjusted Eight-Hour Ozone Concentrations Trend 
5-63

Table 5-21: Summary Statistics for Meteorologically Adjusted Ozone Trends from 1996 to 

2007 

Parameter Value 

Intercept 6.438 

Slope -0.86*

 t-statistic -4.20 

p-value 0.00 

Lag 1 Coefficient -0.20 

 t-statistic -0.63 

* Value is statistically significant. (Sullivan et al., 2009) 

The analysis from Sullivan (2009) shows that, after adjusting for meteorology, concentrations of 

ozone has declined substantially in the HGB area. All else held equal, daily maximum eight-hour 

ozone concentrations in the HGB area should be around 9 ppb lower in 2007 compared to 1996. 

5.3.10 Background Ozone Concentrations: Transport of Ozone into the HGB Area 

Estimating the levels of ozone transported into the HGB area is important in order to identify so 

that the amount of locally produced ozone. Several researchers have previously investigated the 

background ozone concentrations in Texas and the transport winds that are associated with them. 

Nielsen-Gammon et al. (2005) investigated background ozone from 1998-2003 in the HGB area 

and obtained the following insights (paraphrased from Nielsen-Gammon et al., 2005): 

• The seasonal variability in eight-hour maximum ozone in eastern Texas is primarily 

associated with background ozone. Local contributions tend to be highest during the 

summer when background ozone reaches a minimum. 

• The late spring peak in eight-hour maximum ozone in eastern Texas is primarily 

associated with “tropospheric background” ozone. This ozone maximum has been 

observed at rural sites elsewhere and is associated with variations in the lifetime of 

ozone, the concentrations of NOx, and enhanced transport from the stratosphere. 

• The midsummer minimum in background ozone in eastern Texas leads to a minimum in 

eight-hour peak ozone that is strongest in southeastern Texas and barely noticeable in 

northeastern Texas. The primary cause of the summertime minimum is a decline in the 

tropospheric background ozone. Although the relatively clean southerly flow is 

weakening during this period, most air parcel paths remain maritime in nature. 

• When easterly and northeasterly winds become more frequent in late summer, 

background ozone and total ozone in eastern Texas begin rising. Winds are also less 

steady than in the middle of summer, so continental transport becomes increasingly 

frequent. 

Langford et al. (2009) showed that the techniques used by Nielsen-Gammon et al. (2005) yielded 

results consistent with a different technique of estimating background, except on some occasions 

when the Galveston Airport (CAMS 34/CAMS 109/CAMS 154) site was chosen as the 

background site. Langford et al. showed that the Galveston site is the site most strongly affected 

by the Gulf breeze, and that on some days, the maritime air from the Gulf does not affect the 

Houston area, even though this air affects Galveston. Hardesty et al. (2007) have shown that 

during the TexAQS II study in August through September 2006, background ozone in southeast 

Texas averaged about 50 ppb, with background concentrations lower near the coast, and higher in 

northeast Texas. On one day, September 8, 2006, the background ozone entering Texas from east 

was 85-90 ppb. The results of these studies have shown that background ozone entering 

southeast Texas can have a large effect on the total observed eight-hour ozone concentrations. To 

investigate the role of background ozone for the most recent years, the TCEQ commissioned a 

study of background ozone and its relationship to larger-scale wind patterns. Below is a 

description of this work. 
5-64

Sullivan (2009) used 72-hour back trajectories calculated with the Hybrid Single Particle 

Lagrangian Integrated Trajectory (HYSPLIT) algorithm, using data from the Ecosystem 

Dynamics and the Atmosphere Section (EDAS) meteorological model to estimate the amount of 

ozone entering into the HGB area. A total of 1,456 backward trajectories were run starting at 

12:00 Central Standard Time in central Houston, at 300 meters above ground level, during the 

peak of ozone season in the HGB area (May 1 through October 31, 2000 to 2007). Analysis of 

multiple trajectories can distinguish between source areas, or paths, that lead to higher than 

average, or lower than average ozone concentrations (Sullivan et al., 2009). A clustering 

algorithm was used to group multiple trajectories based on trajectory size and shape. Six 

identified clusters appear in Figure 5-32: Six Clusters Found Using HYSPLIT Backward 

Trajectory Clustering Algorithm, which was reproduced from Sullivan, 2009. Forty backward 

trajectories that did not end up in any of the six clusters, illustrated in Figure 5-33: Cluster 0 

Backward Trajectories, reproduced from Sullivan (2009), were grouped and assigned a cluster 

number of zero. All but one of the back trajectories in cluster zero originate from the south and 

that these trajectories appear to extend beyond the EDAS modeling domain, which is the only 

difference between cluster zero and cluster two. 
5-65

Figure 5-32: Six Clusters Found Using HYSPLIT Backward Trajectory Clustering Algorithm 
5-66

Figure 5-32: Six Clusters Found Using HYSPLIT Backward Trajectory Clustering Algorithm

shows that cluster one and cluster two represent days in which winds originated from the Gulf of 

Mexico; these trajectories typically represent cleaner air coming from the Gulf of Mexico and 

hence lower observed ozone concentrations in the HGB area. Cluster three represents long 

trajectories, which come into the HGB area from the north as far away as Canada. This type of 

trajectory can also bring clean air from northern states and Canada into the HGB area. Cluster 

four represents stagnant air conditions, a frequent cause of ozone accumulation. Cluster five 

shows trajectories that originate from the northeast, in the Ohio River Valley, that bring polluted 

air from more populated areas into the HGB area. Cluster six illustrates trajectories from the east, 

some of which cross over Louisiana and the Beaumont-Port Arthur (BPA) area and some of 

which cross over the Gulf of Mexico. The mean centerline from each of the six clusters is shown 

in Figure 5-34: Means of Six 60-Hour Backward Trajectory Clusters. Trajectories were 

compared to ozone concentrations in the HGB area to quantify how these trajectories are related 

to ozone in the HGB area. 

Figure 5-33: Cluster 0 Backward Trajectories 
5-67

Figure 5-34: Means of Six 60-Hour Backward Trajectory Clusters 

Twelve ozone sites, shown in Figure 5-35: Sites Used in Ozone Area Maximum and Background 

Determination, that had near continuous operation from 2000 to 2007 in the HGB area were 

selected to compare with trajectory clusters. In an effort to use measurements from a consistent, 

long-term set of monitors, data from sites that were shut down were combined with data from 

sites that began collecting data near the sites that were taken off-line. Sites where data were 

combined are Lake Jackson (CAMS 1016) and Clute (CAMS 11), and Galveston Airport (CAMS 

34/CAMS 109/CAMS 154) and Galveston Airport 99th St. (CAMS 1034). Sites were selected 

based on locations as either a site upwind or downwind of the HGB area. Northwest Harris 

County (CAMS 26), the Lake Jackson (CAMS 1016) / Clute (CAMS 11) combined site pair, and 

the Galveston Airport (CAMS 34/CAMS 109/CAMS 154)/ Galveston 99th St. (CAMS 1034) 

combined site pair generally represent sites measuring background ozone concentrations. Sites 

on the downwind side of downtown Houston and the Houston Ship Channel generally represent 

sites measuring maximum ozone concentrations in the HGB area. Maximum peak and minimum 

peak eight-hour ozone concentrations from the twelve monitors were found for each day, then 

merged with the cluster classification from each day. Following Nielson-Gammon et al. (2005), 

that minimum peak eight-hour average ozone concentration was used to represent the 

“background” ozone level in the HGB Area. 
5-68

Figure 5-35: Sites Used in Ozone Area Maximum and Background Determination 

Table 5-22: Ozone Statistics for HYSPLIT Back Trajectory Clusters summarizes average 

maximum and average minimum, or background, ozone concentrations for each cluster. Average 

maximum peak daily eight-hour ozone among the clusters ranges from 40.6 ppb to 73.3 ppb, 

while average minimum peak daily eight-hour ozone, considered a proxy for background ozone 

concentrations, ranges from 21.4 ppb to 45.1 ppb. The difference between these two means can 

be used as a surrogate for locally produced ozone. Cluster four and cluster five, which represent 

the short fetch and the northeast fetch, have the highest average maximum ozone concentrations, 

71.6 ppb and 73.3 ppb, respectively, and the highest average background, 40.8 ppb and 45.1 ppb. 

These two clusters also exhibit some of the largest average differences or local contributions. 

Cluster zero, the far southeast cluster, cluster one, the east southeast cluster, and cluster two, the 

southeast cluster, exhibited some of the lowest average background and average peak ozone; 

these clusters are expected to have a lower background ozone due to their origins over the Gulf of 

Mexico. 
5-69

Table 5-22: Ozone Statistics for HYSPLIT Back Trajectory Clusters 

 Average Average Average 

 Number maximum minimum difference, 

 of back peak daily peak daily minimum 

 trajec- eight-hour eight-hour and maximum 

Cluster Fetch tories ozone ozone ozone*

 # ppb ppb ppb 

 5 NE 166 73.3 45.1 28.1 

 4 Short 312 71.6 40.8 30.8 

 6 East 151 61.1 35.6 25.5 

 3 North 49 59.1 37.2 21.9 

 2 SE 506 48.5 24.8 23.7 

 0 far SE 40 45.0 23.8 21.1 

 1 ESE 217 40.6 21.4 19.1

*

 May not sum due to rounding. Note: Data is May through October, 2000 to 2007. Fetch 

represents the main direction of the cluster, count is the number of back trajectories in each 

cluster, average minimum peak daily eight-hour ozone is taken as the background ozone 

concentration. Clusters are sorted in descending order by average maximum peak daily eight-hour 

ozone. 

The 95 percent confidence intervals for the mean eight-hour ozone maximum for each cluster are 

shown in Table 5-23: Average Maximum Ozone and 95 Percent Confidence Intervals. Two 

standard errors were used for the confidence intervals in each row. The confidence intervals in 

the table show that differences between means are statistically significant for most of the pairwise comparison. This is shown graphically in Figure 5-36: Average Maximum Ozone and 95 

Percent Confidence Intervals. Fetches originating from the northeast and east, as well as the 

“short” fetch, have the highest average peak daily ozone values, and they are tightly clustered. 

Clusters originating from the north and far southeast have noticeably wider confidence intervals, 

indicating more variability, but with lower average peak daily ozone concentrations than the 

northeast and east clusters. 

Table 5-23: Average Maximum Ozone and 95 Percent Confidence Intervals 

 Average Average Average 

 Cluster maximum maximum maximum 

 ranked by peak daily + 2 - 2 

 maximum eight-hour standard standard 

 average Fetch Count ozone errors errors 

 # ppb ppb ppb 

 5 NE 166 73.3 76.7 69.8 

 4 Short 312 71.6 74.3 68.9 

 6 East 151 61.1 64.5 57.8 

 3 North 49 59.1 65.2 53.0 

 2 SE 506 48.5 50.3 46.6 

 0 far SE 40 45.0 51.5 38.4 

 1 ESE 217 40.6 42.7 38.5 

Note: Confidence intervals were constructed using two standard errors. Clusters are sorted in 

descending order by average maximum peak daily eight-hour ozone. Confidence intervals for 

differences between the area ozone maximums generally do not overlap beyond one or two rows. 

Although many of the selected sites were intended to represent background and maximum ozone 

in the HGB area, note that on many days true background ozone concentrations may be observed 
5-70

farther away, in more rural areas, and the true maximum ozone concentration may also be 

underestimated. Despite uncertainty in estimates of true background and maximum ozone 

concentrations, the large number of observations used in this analysis, as well as evidence 

presented earlier, provide clear evidence that ozone in the HGB area is affected by transport of 

ozone from external sources. 

0

20

40

60

80

NE Short East North SE far SE ESE

ppb

average maximum peak ozone

upper bound of 95% confidence interval

lower bound of 95% confidence interval

Figure 5-36: Average Maximum Ozone and 95 Percent Confidence Intervals 

Figure 5-37: Relationship Between Minimum and Maximum Ozone Concentrations, recreated 

from Sullivan (2009), shows there is a significant linear relationship between mean HGB area 

minimum and maximum eight-hour average ozone concentrations by trajectory cluster (p-value < 

0.01). The dark red points and estimated regression line represent the relationship between mean 

maximum ozone and mean minimum (background) ozone concentrations by cluster. The olive 

points and estimated regression line represent the relationship between “local contribution” 

(difference between maximum and minimum) and mean minimum ozone concentrations by 

cluster. The relationship between maximum and minimum ozone by cluster suggests that 

trajectory direction is a factor determining severity of both HGB area maximum and background 

ozone concentrations (Sullivan, 2009). The estimated slope parameter (β = 1.36) of the ordinary 

least squares regression of average minimum ozone concentration against average maximum 

ozone concentration shows that maximum ozone concentration increases at a greater rate with 

trajectory direction when compared to minimum ozone. 
5-71

O3max = 1.36 O3min + 12.76

R2 = 0.96

O3(max-min) = 0.36 O3min + 12.67

R2 = 0.65

10

30

50

70

10 30 50 70

1

0

2

3

4 5

6

ppb

ppb

 ESE

far SE 

SE 

 north

short NE

east 

Figure 5-37: Relationship Between Minimum and Maximum Ozone Concentrations 

Figure 5-37: Relationship Between Minimum and Maximum Ozone Concentrations also shows 

that the difference between mean HGB area maximum and minimum ozone concentrations is also 

roughly linear with area minimum, but with a lower slope (β=0.36) and lesser statistical 

significance (p-value=0.03) (Sullivan, 2009). The linear relationship between the difference and 

mean HGB area minimum ozone suggests the transport direction also affects local ozone 

production. The slower air movement of cluster four, which is the “short” cluster, allows greater 

accumulation in the area under lower local surface wind speeds. Winds originating from the 

directions of cluster six, the “east” cluster, and cluster five, the “northeast” cluster, help to move 

surface air along the area around the Houston Ship Channel and across the downtown Houston 

area, which, as noted, contain large amounts of ozone precursors. Overall, this analysis shows 

that directions of back trajectories can account for up to 24 ppb of variation in background ozone 

concentrations, and up to 35 ppb of variation in maximum ozone concentrations. 

5.3.11 Transport and Surface Wind Trajectories 

While still incomplete, a preliminary analysis of upper level, or transport, wind trajectories was 

conducted to confirm and extend findings from the previously discussed directional analysis. 

Additional HYSPLIT modeling of 48-hour back trajectories at 1,500 meters altitude for May 

through August, 2000 to 2008, was used to detect difference in trajectories across years that may 

have influenced ozone concentrations in the HGB area. 

A simple visual inspection of the densities of distributions of trajectory end points presented in 

Figure 5-38: Distributions of End Points from HYSPLIT 48-Hour Back Trajectories shows that 

upper level wind patterns for 2008, a year which had relatively low ozone concentrations, do not 

noticeably differ from patterns in other years. Of the years analyzed, the pattern for 2000, a year 

with relatively high levels of ozone, is perhaps the most similar to 2008. The spatial distribution 

is similar among years and wind speeds are also similar. Higher wind speeds are evident in 2004 

and 2005, as implied by trajectories with longer fetches. The implication is that the wind patterns 
5-72

observed during 2008 were not responsible for the lower ozone concentrations observed, since 

high ozone was observed during other years that had wind patterns similar to 2008. 

Figure 5-38: Distributions of End Points from HYSPLIT 48-Hour Back Trajectories 

5.3.12 Background Ozone in Texas 

Research on the meteorology of the HGB area has found that the highest background ozone 

transported into the HGB area predominately originates from the north and northeast (NielsonGammon et al., 2005). In the present analysis, two techniques are used to examine background 

ozone concentrations in Texas since 2000. The first technique examines the trend in ozone 

concentrations at four sites that can be considered background sites under certain flow conditions. 

The second technique examines ozone concentrations associated with different patterns of longterm backward trajectories. 

Identifying appropriate background ozone monitoring sites from which to ascertain trends is 

complicated by local ozone, complex wind patterns, and natural variability in background ozone 

itself. To estimate background ozone, Nielson-Gammon et al. evaluated all monitors in the 

region to identify those that could be considered to be recording background ozone values. They 

proposed a modification of a TCEQ procedure to identify such sites. 

The TCEQ procedure involves determining the direction of transport winds, then selecting a rural 

monitor upwind of the area in that direction. Nielson-Gammon et al. simply select as the 

background value the lowest of the peak eight-hour ozone values from all monitors. Unlike the 
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Nielson-Gammon procedure, which used gridded output of a meteorological model, this analysis 

follows the TCEQ approach using direct measurements of surface winds and tracking background 

ozone concentrations over time at selected monitors. Modifying the Nielson-Gammon procedure, 

the approach presented here identifies the 90th percentile values recorded at the selected monitors 

and examines the distribution of daily maximum ozone concentrations over time to determine 

whether these supposed background concentrations have increased or decreased. Both the 

Nielson-Gammon method and the TCEQ method may not strictly estimate background ozone, as 

defined above, because they do not remove any potential recirculation of pollutants generated via 

local emissions. Also, background ozone alone may not tell the complete story, since ozone 

precursors, which can react with each other and with local emissions to produce ozone, may also 

be present in transported air. 

Four candidate monitors were selected for this analysis and are listed in Table 5-24: Monitors 

Selected for Background Transport Analysis. Two monitors, West Orange (CAMS 9) and 

Mauriceville (CAMS 642/CAMS 311/CAMS 665), are located east of the HGB area, adjacent to 

the Texas-Louisiana border, east of the BPA area; one, Karnack (CAMS 85), is located in 

northeast Texas near the Texas-Louisiana-Arkansas border and the Tyler-Longview-Marshall 

(TLM) area; and one, Hamshire (CAMS 64/CAMS 654), is located east of the HGB area, 

between the HGB area and the BPA area. Each of these monitors was selected for specific 

purposes. West Orange (CAMS 9) and Mauriceville (CAMS 642/CAMS 311/CAMS 665) were 

chosen because they are as close as possible to the Texas border and, thus, are useful for isolating 

background ozone being transported into the state from the east. Karnack (CAMS 85), in 

northeast Texas, is also very near the Texas border, and was selected to provide an assessment of 

background ozone transport from more northerly regions. The final site, Hamshire (CAMS 

64/CAMS 654), was selected to aid stratification of background ozone being transported into the 

HGB area into a component originating outside the state, and a component contributed by the 

BPA area. 

Table 5-24: Monitors Selected for Background Transport Analysis 

Monitor metro area location years CAMS code 

West Orange BPA TX-LA border 2000-2008 C9/A141 

Mauriceville BPA TX-LA border 2000-2008 C642/C311/C665 

Karnack TLM TX-LA-AR border 2001-2008 C85/AFHP303 

Hamshire HGB between BPA and HGB 2000-2008 C64/C654 

Source: TCEQ/LEADS database. Data with wind speeds less than 3 miles per hour were 

excluded to minimize influences from periods of stagnation which may result in over estimation 

of background concentrations. 

To isolate ozone being transported into the state, measurements at the selected monitors were 

restricted by wind direction. The West Orange (CAMS 9) monitor is located less than 3 miles 

from the Louisiana border but is near several industrial sites. Only ozone measurements taken 

when winds originated from directions ranging from 30° to 90° (Figure 5-39: Mauriceville 

C642/C311/C665) and West Orange (C9) Monitors) were considered, to minimize possible 

influence from these sources. Thirty degrees corresponds to a north-northeast direction and 90o

 is 

due east. The Mauriceville (CAMS 642/CAMS 311/CAMS 665) monitor is located ten miles 

from the Louisiana border, north of the West Orange (CAMS 9) monitor. This site may have 

some minor influence from relatively small NOX and VOC sources. Data from this monitor was 

restricted to wind directions originating from 30° to 90°, similarly to West Orange (CAMS 9), to 

minimize any possible influence of nearby point sources. 

The Karnack (CAMS 85) monitor in the TLM area is located eight miles from the TexasLouisiana border, and roughly 20 miles from Arkansas. Measurements from Karnack (CAMS 

85) were restricted to wind directions originating from 30° to 135° (Figure 5-40: Karnack 

C85Monitor), that is, from north-northeast clockwise to southeast. Though this site is not near 
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the HGB area, it records large influxes of continental air transported from the Midwestern United 

States into Texas, which ultimately may raise background ozone concentrations throughout the 

state. Also, estimates of background ozone concentrations from Karnack (CAMS 85) can be 

compared to background estimates from West Orange (CAMS 9) and Mauriceville (CAMS 

642/CAMS 311/CAMS 665), which is useful for corroborating estimates at these two sites, and 

determining the range of background ozone entering the state. 

The final site under consideration is Hamshire (CAMS 64/CAMS 654), located between the HGB 

area and the BPA area. Ozone measurements from this site can be used to estimate background 

ozone concentrations transported to the HGB area when winds are from the east. These 

background ozone measurements are a combination of pollution transported into Texas, as well as 

the contribution of pollution from the BPA area. To avoid undue influence of nearby industrial 

sites, similar to Karnack (CAMS 85), data from Hamshire (CAMS 64/CAMS 654) are restricted 

to measurements obtained when winds originate from directions ranging from 30° to 135°. For 

the four monitors, monthly 10th, 25th, 50th, 75th and 90th percentiles of hourly ozone 

concentrations were calculated for the spring and summer ozone season, May through September, 

2000 through 2008, except Karnack (CAMS 85) which only has data since 2001. These values 

are plotted in Figure 5-42: Selected Statistics for the West Orange C9 Monitor, Figure 5-43: 

Selected Statistics for the Mauriceville C642/C311/C665 Monitor, Figure 5-44: Selected 

Statistics for the Karnack C85 Monitor, and Figure 5-45: Selected Statistics for the Hamshire 

C64/C654 Monitor. Ninetieth percentile values are reported in Table 5-25: Range of Monthly 

90th Percentile Daily Peak Hourly Ozone Concentrations for Subject Wind Directions. 
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Figure 5-39: Mauriceville C642/C311/C65 and West Orange C9/A141 Monitors 

Figure 5-40: Karnack C85 Monitor 

Figure 5-41: Hamshire C64/C654 Monitor
West Orange

0

102030405060708090

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note: data shown is May - September only

median

90th

75th25th10th

 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 5-42: Selected Statistics for the West Orange C9 Monitor 

Mauriceville

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 2000 2001 2002 2003 2004 2005 2006 200

Figure 5-43: Selected Statistics for the MaurC642/C311/C665 Monitor 

Karnack

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median

th

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Figure 5-44: Selected Statistics for the Karnack C85 Monitor 

Hamshire

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 2000 2001 2002 2003 2004 2005 2006 2

Figure 5-45: Selected Statistics for the HamMonitor 

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Table 5-25: Range of Monthly 90th Percentile Daily Peak Hourly Ozone Concentrations for 

Subject Wind Directions 

 Hamshire Karnack Mauriceville West Orange 

C64/C654 C85 C642/C311/C665 C9 

year min max min max min max min max 

 ppb ppb ppb ppb ppb ppb ppb ppb 

2000 38 74 . . 56 81 43 83

2001 50 71 . 54 45 69 57 68 

2002 51 62 58 84 40 68 53 69 

2003 30 68 60 64 39 61 38 66 

2004 43 71 39 66 30 61 41 66 

2005 55 79 62 75 43 76 52 75 

2006 45 76 42 78 32 63 43 75 

2007 37 62 55 67 40 62 47 69

2008 40 62 . 65 47 70 50 60 

9-year period 30 79 39 84 30 81 38 83 

Note: Though data has been restricted by wind direction to mitigate influences 

from nearby pollution sources, there may be unknown influences that are 

unaccounted for. Maximum values for each year are highlighted in boldface 

type. 

To statistically verify whether a trend across time exists in the data, an index of date was fit to the 

daily peak values using ordinary least squares regression. Additional regressions were performed 

using an index of month against the selected percentiles of the monthly distributions. The 

resulting parameter estimates from these models revealed no statistically significant trend at the 5 

percent significance level; however, the data likely suffer from autocorrelation, a problem 

common to time series data. Time series data are often not independent, but correlated with 

themselves across time, which complicates formal statistical estimation by biasing parameter 

estimates. 

Rather than performing the procedures necessary to detect, measure, and correct for 

autocorrelation, a careful visual inspection of time series plots, presented in Figure 5-42: Selected 

Statistics for the West Orange C9 Monitor through Figure 5-45: Selected Statistics for the 

Hamshire C64/C654 Monitor, satisfies that no time trend is perceptible. These four figures plot 

the five selected percentiles of the monthly distributions at each monitor. While no trend is 

detectable, what is apparent is that ozone concentrations measured at these monitors, which have 

been restricted in such a way as to proxy background levels, vary substantially. Background 

ozone at these monitors varies as much as 35 ppb, due to meteorological effects and ozone 

dynamics occurring in upwind regions. 

Notable in Figure 5-45: Selected Statistics for the Hamshire C64/C654 Monitor, hourly ozone 

concentrations at Hamshire (CAMS 64/CAMS 654) behave similarly to West Orange (CAMS 9) 

and Karnack (CAMS 85), in that there is no observable or statistically significant trend of the 

median or 90th percentile values. The 90th percentile value at Hamshire (CAMS 64/CAMS 654), 

considering directionally restricted data for May to September, 2000 through 2008, is 59 ppb. 

This value is in the range of values computed by Nielson-Gammon using different procedures; 

however, the 90th percentile can exceed 80 ppb at any of the sites, and even exceeded 90 ppb at 

Mauriceville (CAMS 642/CAMS 311/CAMS 665) in 2000. TexAQS II also found background 
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ozone concentrations that exceed the 1997 eight-hour ozone NAAQS (TexAQS II Rapid Science 

Synthesis Team 2006). 

Over the 2000 through 2008 period, the maximum 90th percentile one-hour ozone concentrations 

at West Orange (CAMS 9) and Mauriceville (CAMS 642/CAMS 311/CAMS 665) are 79 and 92, 

respectively. The maximum 90th percentile for Karnack (CAMS 85) over the 2001 through 2008 

period is 81. Karnack (CAMS 85) appears to consistently measure a higher background than 

either West Orange (CAMS 9) or Mauriceville (CAMS 642/CAMS 311/CAMS 665). These 

results are consistent with estimates reported by Nielson-Gammon, et al. (2005), which also 

found higher background ozone concentrations during the ozone season in northeast Texas than 

in the HGB area. 

Regression analysis was used to determine whether the 90th percentile values at West Orange 

(CAMS 9) and Mauriceville (CAMS 642/CAMS 311/CAMS 665) track one another, which 

suggests they are measuring roughly equivalent phenomena. The resulting R2

 of 0.78, which is 

significant at a probability level less than 0.1 percent (Table 5-26: Parameter Estimates for 

Regression of West Orange C9 on Mauriceville C642/C311/C665, indicates very strong 

correlation between measurements at the two sites. The scatter plot of the data is illustrated in 

Figure 5-46: Scatter-plot of 90th Percentile Hourly Values at West Orange C9 and Mauriceville 

C642/C311/C665. The values in the scatter plot are from May through September, 2000 to 2008. 

The scatter plot supports the contention that these two monitors are measuring roughly the same 

phenomena, under wind-restricted regimes. 

Table 5-26: Parameter Estimates for Regression of West Orange C9 on Mauriceville 

C642/C311/C665 

intercept slope 

β estimate 4.95706 1.01251 

Std. Error 0.55480 0.01421 

t-statistic 8.935 71.278 

 Pr(>|t|) <2e-16 <2e-16 

 R2

 0.78 
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Figure 5-46: Scatter-plot of 90th Percentile Hourly Values at West Orange C9 and 

Mauriceville C642/C311/C665 

In summary, none of the four sites used for estimating background ozone concentrations recorded 

a statistically significant trend. The Karnack (CAMS 85) monitoring site recorded the highest 

90th percentile measurement of the four background sites, with 90th percentile ozone 

concentrations reaching as high as 63 ppb. Since it is farthest from the HGB area, however, the 

HGB area may not be strongly affected by the ozone observed at this site, at least not on the same 

day. 

5.3.13 Air Quality Trends Conclusions 

Ozone concentrations have decreased dramatically in the HGB area since the 1990s. 

Examination of trends in one-hour ozone, eight-hour ozone, the number of exceedances, the 

spatial distribution of ozone, the seasonal distribution of ozone, and the strength of ozone 

gradients all show substantial downward trends. The causes of the trends were investigated by 

examining the meteorological variations that have occurred over the years, by evaluating the local 

changes in ozone precursor concentrations, and by examining trends in background ozone. The 

analyses found that the interannual meteorological variations cannot explain the observed 

decreases in ozone, and that the ozone precursors are on statistically significant downward trends. 

In addition, the analyses have found that background ozone has not dropped substantially since 

2000, suggesting that the significant ozone reductions in the HGB area are due to local emission 

controls, not due to background ozone decreases. 

5.4 QUALITATIVE CORROBORATIVE ANALYSIS 

5.4.1 Introduction 

Because photochemical modeling is an evaluation tool and not an absolute prediction of future 

ozone concentrations, additional data must be considered in order to draw conclusions about the 

validity of the final predicted design value and whether the attainment demonstration satisfies the 

requirements of the Federal Clean Air Act (FCAA). The EPA’s “Guidance on the Use of Models 
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and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and 

Regional Haze,” referenced as modeling guidance in Chapter 3, Photochemical Modeling

acknowledges that many issues cannot be accurately quantified and therefore cannot be properly 

included in the photochemical modeling demonstration. The qualitative corroborative analysis 

contains information regarding federal preemption issues and analysis of additional measures that 

were not included in the modeling. 

5.4.2 Federal Preemption Issues 

The TCEQ has limited authority to regulate certain components of the emissions inventory. The 

federal government has jurisdiction over on-road and non-road vehicles, ships, locomotives, and 

aircraft, among other sources. Since states cannot control sources that are under federal 

jurisdiction or located in other states, the state is limited in its ability to impose controls on all of 

the sources that contribute to ozone formation in a nonattainment area. 

5.4.2.1 Federal Assignment

While these categories have been addressed through expeditiously implemented state incentive 

programs such as the Low Income Vehicle Repair Assistance, Retrofit, and Accelerated Vehicle 

Retirement Program (LIRAP) and the Texas Emissions Reduction Plan (TERP), future reductions 

are dependent on the prompt implementation of new federal engine and fuel standards for on-road 

and non-road vehicles, ships, locomotives, and aircraft. 

5.4.3 Additional Measures 

5.4.3.1 New International Marine Diesel Engine and Marine Fuel Standards for Oceangoing 

Vessels and Emissions Control Areas

In October 2008, the United States ratified the International Maritime Organization's (IMO) 

adoption of the amendments to Annex VI of the International Convention for the Prevention of 

Pollution from Ships (MARPOL) for new international marine diesel engine and marine fuel 

standards for oceangoing vessels (OGV). The new Annex VI Tier II and Tier III emission 

standards will apply to diesel engines with a power rating above 130 kilowatts (kW) (i.e., 175 

horsepower) installed on marine vessels constructed on or after January 1, 2011 (Tier II), and 

January 1, 2016 (Tier III), or diesel engines above 130 kW that undergo a major conversion on or 

after those dates. The revised MARPOL Annex VI will become effective on July 1, 2010. 

In March 2009, the United States submitted a request to the IMO for the creation of an emissions 

control area (ECA) around the nation's coastlines. If the ECA is granted, all marine diesel fuels 

used by OGV in the ECA will be limited to a maximum sulfur content of 1,000 ppm beginning 

January 1, 2015, and all new engines on OGV operating in these areas must use emission controls 

that achieve an 80 percent reduction in NOX emissions beginning January 1, 2016. Table 5-27: 

New MARPOL Annex VI Emission Standards for Marine Diesel Engines lists the new emission 

standards for marine diesel engines with greater than 30 liter per cylinder displacement. 
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Table 5-27: New MARPOL Annex VI Emission Standards for Marine Diesel Engines 

New MARPOL Annex VI emission standards for marine diesel engines 

with >30 liter per cylinder displacement 

NOX Emission Standards (g/kW–hr) Engine Speed (n) Tier 1 Tier 2 Tier 3 

N < 130 revolutions 

per minute (rpm) 17.0 14.4 3.4 

2000 > n ≥ 130 rpm 45.0 × n-0.20 44.0 × n-0.23 9.0 × n-0.20

N ≥ 2000 rpm 9.8 7.7 2.0 

Applicable to engines 

installed in vessels 

constructed on: 

01/01/2000 – 

12/31/2010 

01/01/2011 - 

12/31/2015 

01/01/2016 and 

thereafter 

Note: NOX emission standards presented in grams per kilowatt hour. 

In the August 28, 2009, issue of the Federal Register (74 FR 44442), the EPA proposed 

rulemaking to adopt new federal Tier 2 and Tier 3 engine standards for new marine engines above 

30 liters per cylinder displacement (i.e., Category 3 marine diesel engines) that are consistent 

with the new MARPOL Annex VI NOX emission standards shown in Table 5-27: New MARPOL 

Annex VI Emission Standards for Marine Diesel Engines. The EPA's proposed new Category 3 

marine diesel engine standards also include new standards limiting the emissions of hydrocarbons 

and carbon monoxide from new Tier 2 and later Category 3 engines to 2.0 g/kW-hr and 5.0 

g/kW-hr, respectfully. 

The EPA regulations for marine diesel fuel and new marine engines less than 30 liters per 

cylinder displacement and the new MARPOL Annex VI standards for marine residual fuels and 

new marine diesel engines above 30 liters per cylinder displacement will apply to all OGV 

flagged and registered in the United States. The EPA's proposed new regulations for new 

Category 3 marine engines and new sulfur limits for marine diesel fuel will also apply to all OGV 

flagged and registered in the United States. In addition, the new MARPOL Annex VI standards 

will apply to all new marine diesel engines and fuels on foreign marine vessels that operate near 

United States coasts and ports. 

The new marine diesel engine and fuel standards will provide a 96 percent reduction in sulfur in 

marine diesel fuels, as well as an 85 percent reduction in particulate matter emissions and an 80 

percent reduction in NOX emissions, when compared to current standards (EPA, 2009a, 

http://www.epa.gov/otaq/oceanvessels.htm#emissioncontrol). The cumulative effects of these 

new marine diesel engine and fuels standards will result in a 0.5 to 1.0 ppb reduction of ozone in 

the ambient air of the HGB ozone nonattainment area by 2020 (EPA, 2009b). 

5.4.3.2 SmartWay Transport Partnership and the Blue Skyways Collaborative

Among its various efforts to improve air quality in Texas, the TCEQ is currently promoting two 

voluntary programs in cooperation with the EPA: the SmartWay Transport Partnership and the 

Blue Skyways Collaborative. 

The SmartWay Transport Partnership is a voluntary EPA program for the freight transport 

industry that promotes strategies and technologies to help improve fleet efficiency while also 

reducing air emissions. Fleets participating in the SmartWay Transport Partnership commit to 

implementing voluntary measures over three years, providing the EPA with annual updates of 

their progress throughout that period. 

SmartWay carriers typically commit to integrating fuel-saving strategies and technologies into 

their fleet including: improved aerodynamics, single-wide tires, lighter wheels and rims, idle 

reduction, automatic tire inflation systems, driver training, and advanced powertrain technologies. 
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Rolling resistance is estimated by the EPA to account for as much as 13 percent of a heavy-duty 

vehicle’s fuel consumption. By reducing rolling resistance, as well as vehicle weight, the EPA 

believes that single-wide tires will help to improve fuel economy and reduce NOX emissions by 

an average of 5 percent. Aerodynamic drag accounts for most of a long-haul truck’s energy 

losses at highway speeds. As a result, the EPA estimates that improving the aerodynamics of 

both a long-haul truck and its trailer can help to improve fuel economy and reduce NOX

emissions by another 5 percent. 

The extended periods of idling typically associated with long-haul trucks consume an average of 

one gallon of fuel per hour, while generating associated emissions. New technologies such as 

auxiliary power units (APU) and truck stop electrification (TSE) systems reduce vehicle idling by 

providing power for air conditioning, heating, and onboard electrical accessories, even when the 

vehicle is not in operation. The EPA estimates that, assuming typical idling levels, idling 

reduction technologies such as APU and TSE can reduce NOX emissions by approximately 10 

percent. 

The transient nature of freight transportation makes it difficult to isolate emissions reductions to a 

certain region or even a certain state. As a result, any estimates of the impact of these 

technologies will largely rely on estimates of accumulated reductions based on estimated levels of 

overall fleet integration. These estimates are possible through ongoing research, and in 

conjunction with the more than 2,000 companies nationwide already committed as SmartWay 

partners, the EPA has identified a variety of technologies and the potential fuel savings and 

emissions reductions from those technologies. There are 87 Texas companies that are currently 

SmartWay partners. 

The Blue Skyways Collaborative is a related effort, spearheaded by the EPA Region 6 office in 

Dallas, Texas and the Region 7 office in Kansas City, Missouri. 

Partnering with the EPA Region 6 and Region 7 through this effort are the environmental and 

energy agencies from the 10 states along the Interstate Highway 35 (IH-35) corridor, including 

Texas, New Mexico, Louisiana, Arkansas, Oklahoma, Kansas, Missouri, Nebraska, Iowa, and 

Minnesota. In implementing the Blue Skyways Collaborative, the EPA and the participating 

states recognize that because air quality is often a regional concern, greater reductions are 

possible through cooperative efforts as opposed to individual efforts initiated independently in 

each state. 

The primary objective of the Blue Skyways Collaborative is to improve air quality in these states 

by promoting innovative technologies in a variety of sectors. In addition to promoting reduction 

strategies through the SmartWay Partnership for freight transportation via air, water, and rail, 

Blue Skyways also focuses on promoting emissions reduction strategies for other on-road 

sources, non-road sources, and highway fueling and idling reduction infrastructure, while also 

promoting renewable, efficient, and alternative energy sources. 

To achieve these objectives, the collaborative develops partnerships among international, federal, 

state, and local governments, as well as non-profit organizations, environmental groups, and 

private industries. These partnerships work together in projects along the key transportation 

corridors by sharing emission reduction technologies and leveraging financial resources from a 

variety of sources. 
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5.4.3.3 Control of VOC Emissions from Flash Emissions

When the TCEQ and its research partners began the second Texas air quality study, TexAQS II, 

in May 2005, one of the study’s primary goals was to identify VOC emission sources that have 

been historically underestimated, unreported, or underreported in the TCEQ emissions inventory 

and could potentially be contributing to a discrepancy between measured and reported emissions. 

TexAQS II remote sensing VOC project results indicate that certain types of storage tank 

emissions, including flash, generally have been underestimated, unreported, or underreported in 

the emission inventory. Flash emissions occur when a liquid with entrained gases goes from a 

high pressure to a low pressure. As the pressure on the liquid drops, some of the lighter VOC 

dissolved in the liquid are released or flashed. Compounds that are liquids at the initial pressure 

may transform from a liquid into a vapor and are also released from the liquid. As these gases are 

released, some of the heavier compounds in the liquids may become entrained in these gases and 

are emitted with the lighter VOC. 

In May 2007, the commission adopted rule amendments to 30 Texas Administrative Code (TAC) 

Chapter 115, Subchapter B, Division 1 that revised the requirements for VOC storage tanks 

located in the HGB ozone nonattainment area. The revised requirements were developed to 

reduce VOC emissions that result from uncontrolled flash emissions at upstream oil and gas 

exploration and production sites and other sources of tank emissions. At the time of the rule 

proposal, the amount of flash emissions from minor sources was unknown. 

A method for quantifying flash emissions became available around the same time. Houston 

Advanced Research Center Project 51C, conducted in 2006, quantified emission rates from 

heater-treaters (separators) and storage tank batteries, including flash and condensate tanks, 

associated with the upstream oil and gas industry in the Dallas-Fort Worth and HGB ozone 

nonattainment areas, and Jefferson County. In April 2007, the TCEQ used the results of this 

study to determine the flash emissions from the oil and gas production industry. However, the 

flash emissions were not included in the 2005 area source periodic emissions inventory (PEI) 

because there was not sufficient time to incorporate the emissions before the 2005 area source 

PEI was submitted to the EPA in May 2007. However, the updated 2005 area source emissions 

inventory is being used for this SIP revision. More information on this study can be found at: 

http://www.harc.edu/Projects/AirQuality/Projects/Projects/H051C. 

The rule amendments adopted in May 2007 resulted in actual reductions to flash emissions but no 

credit is claimed in this SIP revision. 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 (tpy) are controlled under the rule. Since the method of 

calculating the emissions was based on county-level production, it is unknown at this time how 

many sites were over 25 tpy and were required to put on controls. Also unknown is how much 

flash emissions were already controlled due to economic reasons. Because of the unknown total 

effect of this rule, the reduction in flash emissions cannot be quantified at this time and is not 

included in the modeling for this SIP revision. These amendments to Chapter 115 are described 

in more detail in the preamble of the adopted rule (Project Number 2006-038-115-EN). 

5.4.3.4 Energy Efficiency and Renewable Energy (EE/RE) Measures

Energy efficiency efforts are typically programs that reduce the amount of electricity and natural 

gas consumed by residential, commercial, industrial, and municipal energy consumers. Examples 

of energy efficiency include increasing insulation in homes, installing compact fluorescent light 

bulbs, and replacing motors and pumps with high efficiency units. Renewable energy efforts 

include programs that generate energy from resources that are replenished or are otherwise not 

consumed as with traditional fuel-based energy production. Examples of renewable energy 

include wind energy and solar energy projects. 
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The Texas Legislature has enacted a number of EE/RE measures and programs. The following is 

a summary of Texas EE/RE legislation since 1999. 

• 76th Texas Legislature, 1999 

o Senate Bill (SB) 7 (Regular Session) 

o House Bill (HB) 2492 (Regular Session) 

o HB 2960 (Regular Session) 

• 77th Texas Legislature, 2001 

o SB 5 (Regular Session) 

o HB 2277 (Regular Session) 

o HB 2278 (Regular Session) 

o HB 2845 (Regular Session) 

• 78th Texas Legislature, 2003 

o HB1365 (Regular Session) 

• 79th Texas Legislature, 2005 

o SB 20 (First Call Session) 

o HB 2129 (Regular Session) 

o HB 2481 (Regular Session) 

• 80th Texas Legislature, 2007 

o HB 66 (Regular Session) 

o HB 3070 (Regular Session) 

o HB 3693 (Regular Session) 

o SB 12 (Regular Session) 

SB 5, 77th Texas Legislature, 2001, set goals for political subdivisions in affected counties to 

implement measures to reduce energy consumption from existing facilities by 5 percent each year 

for five years from January 1, 2002 through January 1, 2006. In 2007, the 80th Texas Legislature 

passed SB 12, which extended the timeline set in SB 5 through 2007 and made the 5 percent each 

year a goal instead of a requirement. The State Energy Conservation Office (SECO) is charged 

with tracking the implementation of SB 5 and SB 12. Also during the 77th Texas Legislature, the 

Energy Systems Laboratory (ESL), part of the Texas Engineering Experiment Station, Texas 

A&M University System, was mandated to provide an annual report on EE/RE efforts in the state 

as part of the Texas Emissions Reduction Plan (TERP) under Texas Health and Safety Code 

(THSC), § 388.003(e). HB 2129, 79th Texas Legislature, 2005, directed the ESL to collaborate 

with the TCEQ to develop a methodology for computing emission reductions attributable to use 

of renewable energy and for the ESL to quantify annually such emission reductions. HB 2129 

directed the Texas Environmental Research Consortium to use the Texas Engineering Experiment 

Station to develop this methodology. With the TCEQ’s guidance, the ESL produces an annual 

report detailing these efforts (Statewide Air Emissions Calculations from Energy Efficiency, Wind 

and Renewables). The report: 

• analyzes power production from wind and other renewable energy sources; 

• provides quantification of energy savings and NOX reductions resulting from the 

installation of wind and other renewable energy sources; 

• describes methodologies developed to quantify energy savings and NOX reductions from 

energy efficiency, wind and other renewable energy initiatives; and 

• provides degradation analysis for future predictions of power production of wind farms. 

The ESL documents methods used to develop estimates of energy savings and NOX emissions 

reductions resulting from reductions in natural gas consumption and displaced power from 

conventional electric generation facilities. The ESL used the EPA’s Emissions and Generation 

Resource Integrated Database to spatially allocate energy use and emission reductions among 

electric generation facilities. The THSC, § 389.002 and § 389.003 contain requirements that the 

Public Utility Commission of Texas (PUCT), SECO, and the ESL report to the TCEQ all 
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emission reductions resulting from EE/RE projects in Texas. The ESL analyzed the following 

areas/programs: 

Renewable Energies 

The 79th Texas Legislature, 2005, amended SB 5 through SB 20, HB 2129, and HB 2481 to add, 

among other initiatives, the following renewable energy initiatives, which require: 5,880 

megawatts of generating capacity from renewable energy by 2015; the TCEQ to develop a 

methodology for calculating emission reductions from renewable energy initiatives and 

associated credits; the ESL to assist the TCEQ in quantifying emissions reductions from EE/RE 

programs; and the PUCT to establish a target of 10,000 megawatts of installed renewable 

technologies by 2025. 

Residential Building Codes and Programs 

The THSC, Chapter 388, Texas Building Energy Performance Standards, as adopted by the 77th 

Texas Legislature, 2001, states in § 388.003(a) that single-family residential construction must 

meet the energy efficiency performance standards established in the energy efficiency chapter of 

the International Residential Code. The Furnace Pilot Light Program includes energy savings 

accomplished by retrofitting existing furnaces. Also included are Seasonal Energy Efficiency 

Ratio (SEER) 13 upgrades to single-family and multi-family buildings. In January 2006, federal 

regulations mandated that the minimum efficiency for residential air conditioners be increased 

from SEER 10 to SEER 13. 

Commercial Building Codes 

The THSC, Chapter 388, Texas Building Energy Performance Standards, as adopted by the 77th 

Texas Legislature, 2001, states in § 388.003(b) that all other residential, commercial, and 

industrial construction must meet the energy efficiency performance standards established in the 

energy efficiency chapter of the International Energy Conservation Code. 

Federal Facilities EE/RE Projects 

Federal facilities are required to reduce energy use by Presidential Executive Order 13123 and the 

Energy Policy Act of 2005 (Public Law 109-58 EPACT20065). The ESL compiled energy 

reductions data for the federal EE/RE projects in Texas. 

Political Subdivisions Projects 

SECO funds loans for energy-efficiency projects for state agencies, institutions of higher 

education, school districts, county hospitals, and local governments. Political subdivisions in 

nonattainment and affected counties are required by SB 5 to report EE/RE projects to SECO. 

These projects are typically building systems retrofits, nonbuilding lighting projects, and other 

mechanical and electrical systems retrofits such as municipal water and waste water treatment 

systems. 

Electric Utility Sponsored Programs 

Utilities are required by SB 7, 76th Texas Legislature, 1999, and SB 5, 77th Texas Legislature, 

2001, to report these projects to the PUCT. See THSC, § 386.205 and Texas Utilities Code, 

§ 39.905. These projects are typically air conditioner replacements, ventilation duct tightening, 

and commercial and industrial equipment replacement. 

In addition to the programs discussed and analyzed in the ESL report, local governments may 

have enacted measures beyond what has been reported to SECO and the PUCT. The TCEQ 

encourages local political subdivisions to promote EE/RE measures in their respective 

communities and to ensure these measures are fully reported to SECO and the PUCT. 

HB 3693, 80th Texas Legislature, 2007, amended the Texas Education Code, Texas Government 

Code, THSC, and Texas Utilities Code. The bill: 
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• requires state agencies, universities and local governments to adopt energy efficiency 

programs; 

• provides additional incentives for electric utilities to expand energy conservation and 

efficiency programs; 

• includes municipal-owned utilities and cooperatives in efficiency programs; 

• increases incentives and provides consumer education to improve efficiency programs; 

and 

• supports other programs such as revision of building codes and research into alternative 

technology and renewable energies. 

Emissions reductions as a result of the above programs were not explicitly included in the 

photochemical modeling because local efficiency efforts may not result in local emissions 

reductions or may be offset by increased demand in electricity. The complex nature of the 

electrical grid also makes accurately quantifying emission reductions from EE/RE projects 

difficult. At any given time, it is impossible to determine exactly where on the electrical grid 

electricity comes from for any certain electrical user. The electricity for a user could be from a 

power plant in west Texas, a nearby attainment county or from within the nonattainment area. If 

electrical demand is reduced in the HGB area due to these kinds of measures, then emission 

reductions from power generation facilities may occur in any number of locations around the 

state. 

5.4.3.5 Clean Air Interstate Rule (CAIR)

The EPA projects that CAIR regional controls will improve air quality in the HGB area, as well 

as most of Texas, according to EPA’s Texas CAIR Web page, http://www.epa.gov/cair/tx.html. 

Under CAIR, 28 eastern states (plus the District of Columbia) are required to comply with a cap 

on sulfur dioxide (SO2) and NOX for EGU emissions. The definition of an EGU for the CAIR 

program is approximately the same definition as that for an FCAA Title IV Acid Rain unit (i.e., 

larger than 25 megawatt (MW) and more than one-third of its generation going to the public grid 

for sale). CAIR is a cap and trade program, with each of the CAIR-applicable states given a 

calculated NOX budget and a calculated SO2 budget by the EPA. The EPA modeled all of these 

states in order to test the effectiveness of controls. A result of EPA’s CAIR modeling was that 

Texas “significantly contributed” to the nonattainment of the particulate matter of 2.5 microns 

and less (PM2.5) standard of two counties in Illinois, therefore, Texas was included in CAIR for 

the transport of PM2.5. Texas is not covered under the CAIR program for 1997 eight-hour ozone 

standard contribution. 

CAIR is implemented in two phases: for NOX, Phase I covers the years 2009 through 2014 and 

Phase II is for the years 2015 and later; for SO2, Phase I covers the years 2010 through 2014 and 

Phase II is for the years 2015 and later. The Phase I NOX budget calculated and assigned to Texas 

was 181,014 tons per year, and the Phase II NOX budget was 150,845. Because 2018 is the HGB 

ozone attainment year, this SIP revision incorporates CAIR Phase II (post 2014 step-down of 

CAIR) which provides for a Texas state-wide NOX budget of 150,845 tons per year, or 413.3 tons 

per day. 

See Appendix B: Emissions Modeling for the HGB Attainment Demonstration SIP, Section 

2.3.1.2.1 for the procedural details that the TCEQ used to simulate CAIR Phase II in Texas and 

the regional states. 

On July 11, 2008, the United States Court of Appeals District of Columbia Circuit (Court) (No. 

05-1244) vacated CAIR and the CAIR Federal Implementation Plan (FIP). On December 23, 

2008, the Court issued a revised opinion to remand, without vacating, CAIR to the EPA. 

Therefore, CAIR will remain in effect while the EPA analyzes data and conducts rulemaking to 
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modify the program to comply with the Court’s July 2008 opinion. The Court declined to impose 

a schedule by which the EPA must complete the rulemaking, but reminded the EPA that the 

Court does “. . . not intend to grant an indefinite stay of the effectiveness of this Court’s 

decision.” For more information on the ruling, see EPA’s CAIR Web page, 

http://www.epa.gov/cair/, or the TCEQ CAIR/CAMR Web page, 

http://www.tceq.state.tx.us/implementation/air/sip/caircamr.html. 

Any future EPA revision to the CAIR program to comply with the court’s ruling may result in 

additional reductions. 

5.4.3.6 Texas Emission Reduction Plan (TERP)

The TERP program was created in 2001 by the 77th Texas Legislature to provide grants to offset 

the incremental costs associated with reducing NOX emissions from high-emitting internal 

combustion engines. To date the TERP program has funded over $700 million in grants for 

projects in Texas ozone nonattainment and near-nonattainment areas. Over $300 million of that 

amount has been awarded to projects in the HGB area since 2001, which will help reduce more 

than 66,000 tons of NOX emissions. Of that $300 million, $5 million was awarded to the H-GAC 

through a third-party grant to administer additional grants in the HGB area. 

Additional funds are expected to be awarded to the HGB area in subsequent grant application 

periods that will result in further NOX reductions. HB 1796, 81st Texas Legislature, 2009, 

extended the TERP program beyond its current 2013 date to 2019, which will result in continued 

reductions in the significant emissions source categories of on-road and non-road engines. 

5.4.3.7 Low Income Vehicle Repair Assistance, Retrofit, and Accelerated Vehicle Retirement 

Program (LIRAP)

SB 12, 80th Texas Legislature, 2007, enhanced LIRAP to expand participation by increasing the 

income eligibility to 300 percent of the federal poverty rate and increasing the amount of 

assistance toward the replacement of a retired vehicle. The program, known as AirCheckTexas 

Drive a Clean Machine (DACM), provides $3,500 for hybrids of the current or previous model 

year; $3,000 for cars of the current or three model years; and, $3,000 for trucks of the current or 

previous two model years. The retired vehicle must be 10 years or older or have failed an 

emissions test. In the HGB area, DACM is available to vehicle owners in five counties: 

Brazoria, Fort Bend, Galveston, Harris, and Montgomery. Between December 2007 and May 31, 

2009, LIRAP/DACM has retired and replaced 9,330 vehicles at a cost of $28,370,520. An 

additional 3,949 vehicles have had emissions-related repairs at a cost of $2,136,602. The total 

repair and retirement/replacement funding for the HGB area since December 2007 is 

$30,507,122. 

5.4.3.8 Clean School Bus Program

HB 3469, 79th Texas Legislature, 2005, established the Clean School Bus Program. The new 

program is codified in THSC, Chapter 390 and implemented through 30 TAC §§ 114.640 – 

114.648. 

The program is based on the EPA guidance documents, Improving Air Quality with Economic 

Incentive Programs (EPA-452/R-01-001) and Diesel Retrofits: Quantifying and Using Their 

Benefits in SIPs and Conformity (EPA-420-B-06-005). Under the economic incentive program 

guidance, the TCEQ is using the financial mechanism option, which is described as subsidies 

targeted at promoting pollution-reducing activities or products. 

The Clean School Bus Program was established to provide monetary incentives for school 

districts in the state for reducing emissions of diesel exhaust in school buses. Eligible 

technologies include those approved by the EPA, certified by the California Air Resources Board, 

or those that the executive director finds will bring about significant emissions reductions. Some 
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of the technologies eligible for funding under the program reduce NOX emissions. However, the 

technologies mainly reduce particulate matter and reduce only negligible amounts of NOX. The 

80th Texas Legislature, 2007, provided funding for the Clean School Bus Program. 

As of May 2009, the TCEQ Clean School Bus grant program has allocated $13.8 million in grants 

for nearly 5,000 school buses in Texas. In addition, through Supplemental Environmental 

Projects (SEPs), the TCEQ has also allocated over $3.5 million to third-party SEP receivers for 

the same kind of school bus retrofits. 

5.4.3.9 81st Texas Legislature, 2009

HB 432 requires state agencies that purchase passenger vehicles or other ground transportation 

vehicles for general use to ensure that not less than 25 percent of new vehicles purchased during a 

biennium meet or exceed EPA’s Tier II, Bin 3 emission standards. This bill also limits the 

purchase of state agency passenger vehicles or other ground transportation vehicles purchased for 

general use to only those vehicles that use compressed natural gas, liquefied natural gas, liquefied 

petroleum gas, methanol or methanol/gasoline blends of 85 percent or greater, ethanol or 

ethanol/gasoline blends of 85 percent or greater, biodiesel or biodiesel/diesel blends of 20 percent 

or greater, or electricity, including electricity to power a plug-in hybrid motor vehicle. 

HB 1796 establishes a New Technology Implementation Grants (NTIG) program for facilities 

and stationary sources under TERP, requires the current New Technology Research and 

Development under TERP to be administered by the TCEQ, and extends the TERP to August 31, 

2019. See Section 5.4.3.6, Texas Emission Reduction Plan (TERP), for additional information. 

SB 1759 establishes a Texas Clean Fleet Program to be administered by the TCEQ, funding it 

with 5 percent of the 87.5 percent of the Emission Reduction Incentives Grant within TERP. The 

Texas Clean Fleet Program will provide grants to encourage large fleets to replace dieselpowered fleet vehicles with hybrid vehicles or alternative fuel-powered vehicles. 

5.4.3.10 American Waterways Operators Tank Barge Emissions Best Management Practices

Using infrared gas imaging technology in field studies conducted in the summer of 2005, the 

TCEQ detected inadvertent VOC emissions from tank barges operating in the HGB area. The 

Louisiana Department of Environmental Quality (LDEQ) also detected inadvertent emissions 

from tank barges in similar field studies conducted in the same time period. In response to these 

field studies, the American Waterways Operators (AWO) voluntarily developed industry Best 

Management Practices (BMP) to reduce VOC emissions from tank barges. The BMP includes 

procedures to reduce VOC emissions from equipment and operations on tank barges. The 

recommendations are a combination of inspection, corrective action, preventative maintenance, 

operational, procedural, and training practices. 

The BMP was reviewed by the Chemical Transportation Advisory Committee (CTAC), United 

States Coast Guard, LDEQ, and TCEQ. The BMP was distributed to AWO members in 2006 for 

implementation on a voluntary basis. In 2009, AWO reconvened the Tank Barge Emissions 

Working Group to review the BMP and make further improvements to the document. The 

improved BMP will be sent to CTAC, the Coast Guard, LDEQ, and TCEQ for review once it has 

been finalized by industry. While the BMP is a voluntary measure and does not impose an 

enforceable commitment on AWO members, the implementation of the BMP, where applicable, 

may contribute to reducing inadvertent VOC emissions from barges during dock operations and 

during transit, which will help improve the air quality in the HGB area. A copy of the 2006 BMP 

document is provided in Appendix J: Recommendations for Best Management Practices to 

Control and Reduce Inadvertent Cargo Vapor Emissions in the Tank Barge Community. 
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5.4.3.11 Local Initiative Projects

SB 12, 80th Texas Legislature, 2007, allowed the use of unexpended LIRAP funds to be used for 

Local Initiative Projects. These projects provide funding to LIRAP-participating counties for 

implementation of air quality improvement strategies through local projects and initiatives. Local 

Initiative Projects may include: 

• expand and enhance the repair and replacement program; 

• develop and implement programs to remotely determine vehicle emissions and notify the 

vehicle’s operator; 

• develop and implement projects for coordinating with local law enforcement officials to 

reduce the use of counterfeit state inspection stickers; 

• develop and implement programs to enhance transportation system improvements; or 

• develop and implement new air control strategies designed to assist local areas in complying 

with state and federal air quality rules and regulations. 

5.4.3.12 Other Local Programs

The Houston-Galveston Area Council submitted the following programs, which were not 

committed to as Transportation Control Measures or Voluntary Mobile Emission Reduction 

Program measures, but may be implemented locally in the HGB area. For a detailed analysis of 

these programs, see Appendix F: Evaluation of Mobile Source Control Strategies for the 

Houston-Galveston-Brazoria State Implementation Plan (prepared by ENVIRON for the 

Houston-Galveston Area Council). 

Scrappage and Buy-Back Plan 

This measure would build on the existing LIRAP, implemented as part of the AirCheckTexas 

Vehicle Emissions Testing program, by increasing the number of on-road light-duty gasoline 

vehicles scrapped. The plan would also make separate funds available to help with the purchase 

of new on-road heavy-duty diesel vehicles (HDDV) to replace old, highly polluting vehicles. 

Pay-As-You-Drive Insurance 

Pay-As-You-Drive Vehicle Insurance, also called Distance-Based Vehicle Insurance and 

Mileage-Based Insurance, is a program that allows a vehicle’s insurance premiums to be based 

directly on how many miles the vehicle is driven during the policy term. Currently, vehicle 

insurance is structured where high-mileage drivers are, in essence, subsidized by low-mileage 

drivers since all drivers are charged the same premiums after accounting for driving history 

related to collisions and traffic violations. 

Limitations on Idling of Heavy-Duty Vehicles; Creation of Regional Government Idling 

Restrictions 

Idling of vehicles is inherently an inefficient operation that can produce unwanted air pollutants. 

Idling also occurs during normal driving and other operations such as when the engine powers 

necessary accessories, known as power take-off, including man-lifts or concrete tumblers. It is 

not possible to eliminate all idling, but idle reduction programs are typically low in cost and may 

result in a net savings to the owner/operator of the vehicle while also reducing air emissions. 

Encourage/Mandate Livable Centers

The EPA developed the Smart Growth Implementation Assistance (SGIA) program in response to 

communities' requests for help achieving their development goals. Through this program, the 

EPA provides technical assistance from private-sector experts to help communities find the best 

tools and resources for planning growth in ways that sustain environmental and economic 

progress and create a high quality of life. The Gulf Coast Institute, Main Street Coalition, and 

Texas A&M partnered to apply for and received an SGIA grant in 2006. While the City of 

Houston is not participating in the SGIA program at this time, the area has expressed interest in 

evaluating the potential effects of these measures on travel activity and emissions. 
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Enhanced Enforcement of Smoking Vehicles

This measure would encourage local law enforcement officers to enforce existing smoking 

vehicle laws and enable the emissions inspection status of smoking vehicles to be checked. 

Owners of smoking vehicles displaying a valid inspection sticker would be fined. Smoking 

vehicles not having a valid inspection sticker would be impounded if the sticker were found to be 

fraudulent. 

Limitation on Idling of Heavy-Duty Construction Equipment 

Idling is an inefficient use of equipment in general and generates unnecessary emissions. Idling 

however cannot be avoided in all cases, such as during normal work, when work is performed 

intermittently, and when the time to restart the engine would be considered a significant delay. 

This measure would seek to limit excessive idling when equipment is not required immediately. 

Suggested periods for limiting idling could be as little as 15 minutes maximum. Many on-road 

trucks have factory-installed engine shutdown systems that automatically shut down the engine 

after a set period, or devices could be added to existing equipment. To implement this measure, 

engine shutdown systems could be employed with idle timers set to a period that would not cause 

typical operational problems. Operator training could provide significant idle reduction perhaps 

beyond engine shutdown systems. 

5.5 CONCLUSIONS 

The TCEQ has employed several sophisticated technical tools to evaluate the past and present 

causes and effects of high ozone in the HGB area in an effort to predict the area’s future air 

quality. Photochemical grid modeling has been performed and its performance has been 

rigorously evaluated. Historical trends in ozone and ozone precursor concentrations and their 

causes have been investigated exhaustively. The following conclusions can be reached from 

these evaluations. 

First, the photochemical grid modeling performs relatively well. Problems observed with the 

modeling are those that are known to exist in all photochemical modeling exercises. In spite of 

the known shortcomings, the model can be used carefully to predict ozone concentrations. The 

photochemical grid modeling predicts that the control strategy package chosen by the TCEQ can 

lower the ozone design values in the HGB area down to a value very near the 0.08 ppm eighthour ozone standard. The dynamic model evaluations show that the model response to emission 

decreases is less than the response observed in the atmosphere, suggesting that the proposed 

emission controls are more likely to yield attainment of the eight-hour 0.08 ppm ozone standard 

than the absolute modeled design values indicate. 

Second, the ozone trend analyses show that ozone has decreased significantly since the late 

1990s. Meteorological variations alone cannot explain the significant downward trend. 

Decreases in background ozone cannot explain the downward trend either. Significant decreases 

in ozone precursors, however, coincide with the decreases in ozone, indicating that the ozone 

decreases observed in the HGB area are due to local emission controls. 

Third, many additional air quality improvement measures are being adopted in the HGB area that 

cannot be included in the photochemical modeling analysis because they cannot be accurately 

quantified. These additional measures can provide additional assurance that the HGB area is on 

the path toward attainment. 

Based upon the photochemical grid modeling results and these corroborative analyses, the weight 

of evidence indicates that the HGB area will attain the 1997 eight-hour ozone standard by June 

15, 2019. 
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satellite observed clouds, J. Geophys. Res., 112, D10302, doi:10.1029/2006JD007422. 

Robinson, R., T. Gardiner, and B. Lipscombe, 2008. Measurements of VOC emissions from 

petrochemical industry sites in the Houston area using Differential Absorption Lidar (DIAL) 

during summer 2007, Draft. Submitted to Russell Nettles, TCEQ, by Rod Robinson, Tom 

Gardiner, and Bob Lipscombe of the National Physical Laboratory, Teddington, Middlesex UK 

TW11 0LW, February 8, 86 pp. 

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petrochemical industrial emissions of reactive alkenes and NOX on tropospheric ozone formation 

in Houston, Texas. J. of Geophysical Research, 108:4249, doi:10.1029/2002JD003070. 

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over the Eastern United States. J. Appl. Meteor. Climatol., 46:1009–1019. 

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Unpublished analysis for TCEQ, February. 

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Byun, and D. Lee, 2009. Modeling the impact of ClNO 2 on ozone formation in the Houston 

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6-1 

CHAPTER 6: ONGOING AND FUTURE INITIATIVES

6.1 INTRODUCTION 

The Texas Commission on Environmental Quality (TCEQ) is committed to improving the air 

quality in the Houston-Galveston-Brazoria (HGB) area and continues to work toward identifying 

and reducing ozone precursors. Texas is investing resources into technological research and 

development for advancing pollution control technology, improving the science for ozone 

modeling and analysis, and refining quantification of volatile organic compound (VOC) 

emissions. Refining quantification of VOC emissions benefits SIP planning by improving 

understanding of ozone formation. Additionally, the TCEQ is working with the United States 

Environmental Protection Agency (EPA), local area leaders, and the scientific community to 

identify new measures for reducing ozone precursors. This chapter describes ongoing technical 

work that will be beneficial to improving air quality in Texas and the HGB area. 

6.2 ONGOING WORK 

6.2.1 Flare Task Force 

In November 2008, the TCEQ formed an agency-wide task force to comprehensively evaluate all 

aspects of flares in Texas. The Flare Task Force is evaluating how flares factor into air quality 

challenges with an emphasis on air toxics and ozone. Some of the specific issues under 

evaluation include: different factors affecting flare performance, such as waste gas flow rates, 

turndown ratio, and waste gas to steam assist ratios; the adequacy of existing monitoring 

requirements for flares; and alternatives to flaring routine emissions. A stakeholder group 

associated with the Flare Task Force has been formed to solicit comment on these issues related 

to flares. A report for executive management is planned that will include options, considerations, 

and recommendations for improving our understanding and regulation of flares with the goal of 

improving air quality. Additional information about the Flare Task Force is available at the 

stakeholder Web site: 

http://www.tceq.state.tx.us/implementation/air/rules/flare_stakeholder.html. 

6.2.2 Technologies for Detecting VOC 

6.2.2.1 Optical Gas Imaging Technology

Optical gas imaging technology offers a unique technological advancement in pollution detection 

capability and has proved to be highly effective in the detection of VOC emissions. An optical 

gas imaging system is a useful tool that assists the agency in actions such as facility 

investigations, reconnaissance investigations, mobile monitoring, and special projects. This 

technology is also useful in identifying sources of VOC emissions that are underestimated, 

underreported, unreported, or previously unregulated. The system also has the potential to 

advance leak detection and repair (LDAR) work practices and enable monitoring of components 

that are difficult to monitor with traditional LDAR methods. However, the commission has 

technical and enforcement concerns associated with the potential regulatory implementation of 

this technology. A standardized method or performance specification is necessary to ensure 

consistent and reliable application of optical gas imaging instrumentation. Methods and 

specifications are also necessary to set minimum standards of performance to evaluate different 

potential technologies. 

The TCEQ uses the optical gas imaging technology as a screening tool in the following areas: 

offsite surveillance to identify potential sources of contaminants in response to ambient or other 

monitoring results; identification of sites, or areas with a specific site, where a focused 

investigation may be conducted; identification of potential source control strategies or to assist in 

an assessment of existing strategies; and identification of sources for emissions inventory issues. 

6.2.2.2 Open Path Sensing Technology

Open path sensing technology allows specific pollutants to be monitored over a given distance 

(10 meters up to several kilometers) and generally provides very rapid measurements. Some of 

these techniques, such as solar occulation flux (SOF), differential absorption lidar (DIAL), and 
6-2 

imaging differential optical absorption spectroscopy (I-DOAS) provide specific capabilities that 

include the ability to monitor air pollutants not only at ground level but also along a given path 

length in the sky, which allows measurements of specific elevated sources such as flares, vents, 

and storage tanks. This information coupled with meteorological measurements and modeling 

tools are capable, in some cases, of providing emission estimates not otherwise available. These 

data can be helpful in evaluating actual emissions from specific sources. These measurement 

techniques also have limitations or challenges that include the following. 

• They are non-separatory techniques, i.e., do not physically isolate the chemical or 

chemicals of interest from other constituents, and as such are more prone to interference. 

• They normally measure a path length average concentration or number of molecules and 

as such do not provide a specific concentration at any given point and can thus be 

difficult to compare with standards or guideline concentrations. 

• They are difficult to assess from a data quality standpoint because they are an open path 

technology and thus have limitations for enforcement or compliance-related purposes. 

• They are complex instrumentation with limited commercial availability that requires a 

highly experienced operator and data analyst to obtain quality data. In some cases, such 

as SOF and DIAL, there may be only a few operational instruments and qualified 

personnel in the world, which limits the ability of Texas to either acquire and operate the 

instrumentation or contract operation on anything but a sporadic basis. 

6.2.2.3 DIAL Remote Sensing Technology

The TCEQ continued to advance the science of determining emissions from industrial sources by 

performing a five-week emissions monitoring study in the Texas City area during the summer of 

2007. For the first time, a regulatory agency in the United States used a mobile DIAL remote 

sensing technology to measure emissions from industrial sources. The study, funded by the EPA 

and the TCEQ, focused on gathering data from industrial sources that are difficult to measure 

using conventional sampling techniques. The resulting scientific data and future studies will help 

guide future research efforts and may result in additional control measures, refined emissions 

models for common sources, and improved emissions inventories. 

The TCEQ contracted with the National Physical Laboratory (NPL), based in the United 

Kingdom, to perform DIAL measurements on industrial emissions sources located in a refinery 

and a storage terminal near Houston during 2007. 

Measurements focused on those industrial sources that are difficult to measure using conventional 

sampling techniques. Specifically, the study involved: 

• identifying potentially under-reported industrial emissions sources; 

• conducting remote sensing measurements of these sources; 

• collecting process and operational data from these sources; and 

• comparing emissions determined using conventional EPA-approved determination methods 

to the remote sensing measurements. 

The NPL submitted a draft report in February 2008, which is expected to be finalized in fall 2009. 

An independent third party is currently comparing remote sensing measurements to 

conventionally determined emissions. Although these results are still being analyzed, preliminary 

total VOC measurements indicate that flare emissions may be underreported when emissions are 

determined using conventional material balance calculation methods. Additionally, preliminary 

results as well as other research indicate flare destruction and removal efficiency (DRE) may be 

reduced during certain operating conditions, such as combusting small volumes of waste gas and 

during flare air- or steam-assist operations. 

These preliminary results indicate the need to conduct a study that determines the relationship 

between flare design, operation, and DRE. 
6-3 

6.2.2.4 Helicopter-Mounted DIAL Imaging System

The TCEQ completed field work in June 2009 to demonstrate the capabilities of a helicoptermounted DIAL. The study’s major focus will be using the DIAL to locate sources of benzene 

emissions from industrial facilities in the Houston Ship Channel area. The DIAL system used 

was developed to detect methane leaks during flyovers of gas pipelines. The system uses the 

infrared absorption of methane to detect leaks. The system has been used extensively and 

successfully to find pipeline leaks in concentrations as low as 1.7 parts per million (ppm) of 

methane. Instrument sensitivity has been shown in the laboratory to be approximately 100 ppm 

for benzene. However, with tuning and adjustments during flight measurements, the benzene 

sensitivity could be as low as 10 ppm. While the primary purpose of this project will be to 

determine the capabilities of a helicopter-mounted DIAL, results from this project could also be 

used to determine potentially unreported or underreported sources of benzene. Successful 

location of benzene sources in the surveyed areas may show the potential benefit of a full-scale 

survey of the entire Houston Ship Channel as well as other industrial areas. A final report is due 

to the agency by August 2009 and the agency final evaluation of the technology should be 

completed by the fall of 2009. 

6.2.2.5 Flare Study

The purpose of the flare study is to measure flare emissions and collect required process and 

operational data in a controlled laboratory environment to determine the relationship between 

flare design, operation, and DRE. Direct measurement techniques of flare emissions, 

conceptually similar to those employed by the EPA flare studies in the 1980s, as well as remote 

sensing measurement techniques will be employed in the laboratory environment. Analysis of 

collected process and operational data will allow comparisons between traditional flare material 

balance emissions determinations, process stream measurements, and the emissions rates and 

concentrations measured by the direct and remote sensing technologies. 

The TCEQ anticipates that the results of the laboratory tests will be broadly applicable, since 

these measurements will be conducted under controlled conditions. The TCEQ also anticipates 

that the tests will provide insight to operational conditions that may impact flare VOC DRE and 

flare combustion efficiency, such as assist rates or waste gas volumetric flow rates. 

The primary study objectives include: 

• assessing the potential impact of waste stream flow rate turndown on flare DRE and 

combustion efficiency; 

• assessing the potential impact of steam/air assist on flare DRE and combustion efficiency 

at various operating conditions, including low flow rate conditions; 

• assessing whether flares operating over the range of requirements stated in 40 Code of 

Federal Regulations § 60.18 achieve the assumed hydrocarbon DRE of 98 percent at 

varying flow-rate turndown and assist ratios as well as variable waste stream heat 

content; and 

• identifying and quantifying the hydrocarbon species in flare plumes currently visualized 

with passive infrared cameras. 

Field tests should be conducted during the November 2009 to March 2010 time frame, depending 

on approval of the final test plan and the availability of a test facility. A final report is expected 

during the summer of 2010. 

6.2.2.6 Study of Houston Atmospheric Radical Precursors (SHARP) 

An extensive field study of ozone precursors and formation was conducted in the HGB area in 

April, May, and June 2009 using cutting-edge measurement technology. Approximately $2 

million of air quality research funds for this project were provided by the state legislature. The 

goal of the SHARP study is to investigate the: 
6-4 

• contribution of direct emissions of formaldehyde and nitrous acid from flares, stacks, and 

other point and mobile sources; 

• importance of secondary formation of formaldehyde from the ozonolysis of olefins; 

• identification of formation pathways of nitrous acid; 

• ambient levels of nitryl chloride and potential impact as a ozone precursor; and 

• spring and early summer ozone formation mechanisms in the HGB area. 

The data from this study will be analyzed in 2009 and 2010 and used to better understand HGB 

area emissions and chemistry, enhance model inputs and mechanisms, and aid in the evaluation of 

control strategy development. 

6.3 FUTURE INITIATIVES 

6.3.1 Mid-Course Review (MCR) 

The commission is soliciting comments on whether it is appropriate to perform a 1997 eight-hour 

ozone standard MCR analysis for the HGB area, and, if so, what elements should be contained in 

the analysis. The commission is also seeking input on the appropriate date to submit the MCR.

6.3.2 2008 Ozone National Ambient Air Quality Standard (NAAQS) 

On March 12, 2008, the EPA strengthened its NAAQS for ground-level ozone from 0.08 parts per 

million (ppm) to 0.075 ppm. Governor Rick Perry submitted the state's 

recommendation regarding boundaries and designations under the federal 2008 eight-hour ozone 

standard to the EPA on March 10, 2009. The HGB area (Brazoria, Chambers, Fort Bend, 

Galveston, Harris, Liberty, Montgomery, and Waller Counties) was included in the governor’s 

recommended nonattainment areas. Continued efforts to reduce ozone precursors will be 

necessary to address this new ozone standard. 
EXHIBIT 5
Evaluation of Implementation Experiences with 

Innovative Air Permits

Results of the U.S. EPA Flexible Permit Implementation Review

SUMMARY REPORT

Report prepared by:

EPA Office of Air Quality Planning and Standards (OAQPS)

EPA Office of Policy, Economics and Innovation (OPEI)

In consultation with:

EPA Office of Enforcement and Compliance Assurance (OECA)

EPA Office of General Counsel (OGC)

EPA Office of Policy Analysis and Review (OPAR)

With support from:

Ross & Associates Environmental Consulting, Ltd.

(Under contract to Industrial Economics, Inc.)

U.S. EPA Contract # 68-D9-9018

and

Midwest Research Institute
Table of Contents

Executive Summary ............................................................. 3

Background ............................................................. 3

What Is Flexible Air Permitting? .............................................. 3

Flexible Permit Implementation Review Findings ................................... 4

I. Introduction ................................................................. 8

A. Project Scope and Purpose ............................................... 8

B. Structure of this Report .................................................. 9

C. Review Approach and Process ............................................ 9

C.1 Flexible Permit Review Framework .................................. 9

C.2 EPA Review Team ............................................. 10

C.3 Permit Review Process .......................................... 10

C.4 Flexible Permit Selection .......................................... 11

D. What Are Flexible Permit Provisions? ...................................... 11

D.1 Description of Advance Approved Changes ........................... 11

D.2 Plant-wide Emissions Limits ....................................... 12

D.3 Replicable Testing Procedures ..................................... 12

D.4 Applicable Requirement Streamlining ................................ 12

D.5 Pollution Prevention Provisions ..................................... 13

E. Pilot Permit and Source Characteristics ...................................... 13

3M Company - St. Paul, Minnesota ..................................... 13

DaimlerChrysler Corporation - Newark, Delaware .......................... 13

Imation Corporation - Weatherford, Oklahoma ............................. 13

Intel Corporation - Aloha, Oregon ...................................... 14

Lasco Bathware - Yelm, Washington .................................... 14

Saturn Corporation - Spring Hill, Tennessee ............................... 14

II. Findings .................................................................. 15

Finding 1: The flexible permits contain adequate measures to assure compliance with all

applicable requirements. ............................................. 15

Finding 2: The flexible permits were considered to be enforceable by permitting authorities and

EPA. ........................................................... 18

Finding 3: The flexible permits facilitated and encouraged emissions reductions and pollution

prevention. ....................................................... 19

Finding 4: Companies with the flexible permits believe that air permitting is on their critical

response path. .................................................... 23

Finding 5: Companies with the flexible permits utilized their flexibility provisions. ........... 27

Finding 6: The flexible permits enhanced information sharing between the companies and

permitting authorities. ............................................... 30

Finding 7: The flexible permits generally provided to the public equivalent or greater information

than conventional permits.. ........................................... 34

Finding 8: The flexible permits produced or are anticipated to produce net financial benefits to

companies and permitting authorities. .................................... 37

Finding 9: Permitting authorities are generally supportive of flexible permits as an option. .... 42

Finding 10: Permitting authorities indicated that flexible permit provisions should be matched with

a company’s need for flexibility and technical capacity to implement effectively its

flexible permit requirements. .......................................... 44
III. Tables ................................................................... 46
4

Executive Summary

Background

In recent years, the U.S. Environmental Protection Agency (EPA) and some State and local permitting

authorities recognized a change in the manufacturing landscape. This change arose in today’s increasingly

competitive global markets, requiring companies to respond rapidly to market signals and demand, while

delivering products faster, at lower cost, and of equal or better quality than their competitors. As their market

response and product development time frames shrank, companies in several industries perceived the potential

administrative “friction” – costs, time, delay, uncertainty, and risk – resulting from operating under

conventional air permitting approaches to increase. This raised an important question: how to provide these

U.S. companies with the “flexibility” to compete effectively in global markets without decreasing

environmental protection? At the same time, the EPA and others sought ways to align the regulatory

framework to encourage emissions reduction and pollution prevention.

To address these challenges, the EPA and several State and local permitting authorities worked with selected

companies over the past few years in the context of individual permit pilots to develop innovative approaches

to air permitting. The EPA and the States launched these efforts to increase sources’ operational flexibility

while ensuring environmental protection and facilitating pollution prevention. Permitting authorities involved

in these pilot initiatives designed permits within the existing regulatory framework to address all applicable

air requirements. As interest in innovative approaches to air permitting increased, the EPA evaluated the

implementation experience with “flexible” permitting techniques developed under pilot permitting efforts, such

as the EPA’s Pollution Prevention in Permitting Program (P4) and various State innovation initiatives. The

EPA believes that careful evaluation of the implementation experience with such flexible permits can improve

the effectiveness and efficiency of future efforts and help to inform evolving air policymaking activities in

these areas. The EPA launched the Flexible Permit Implementation Review to meet these objectives.

What Is Flexible Air Permitting?

The term “flexible permit” is used in this report to describe air permits with conditions designed to reduce the

administrative “friction” – costs, time, delay, uncertainty, and risk – experienced by sources and permitting

authorities when implementing a permit or making certain changes under the permit. This is typically

accomplished by allowing a source to make certain types of changes (e.g., modifications to a source’s method

of operation, equipment, raw materials, emission factors, or monitoring parameters) without requiring

additional case-by-case permitting, provided the source meets certain criteria outlined in its operating or

construction permit. Such criteria might include the maintenance of plant-wide emissions levels below

enforceable caps. Over the past decade, the EPA and State and local permitting authorities have also piloted

specific permitting techniques and tools to accomplish advance-approval for certain types of changes that

might take place over the course of a permit term. While chosen solutions will depend on individual state

permitting rules and requirements, such techniques typically include descriptions of advance-approved

changes or categories of changes in the permit, procedures for testing pollution control device performance

and updating emission factors or parameter values without requiring the permit to be amended or re-opened,

elimination of redundant requirements by applying the most stringent applicable requirement, and provisions

to explicitly encourage pollution prevention.
5

Flexible Permit Implementation Review Findings

The EPA launched the Flexible Permit Implementation Reviews to examine the implementation experience

with innovative air permitting techniques. Under this initiative, the EPA assembled a Review Team,

representing multiple EPA offices supplemented by contractor support, to conduct in-depth reviews of six pilot

permits with innovative flexibility provisions and sufficient operating history. These pilot permits were

developed for the following companies: 3M, DaimlerChrysler, Imation, Intel, Lasco Bathware, and Saturn.

The reviews included detailed analyses of source and permitting authority experiences developing and

implementing flexible air permits, based on review of information in the public record, discussions with source

and permitting authority personnel, site visits to the source and permitting authorities, and verification of

recordkeeping and emissions calculation requirements.

The EPA’s review and analyses support the following findings for the six flexible permits covered in this

review.

Finding 1: The flexible permits contain adequate measures to assure compliance with all applicable

requirements.

Permitting authorities and the EPA found that the flexible permits contained monitoring, recordkeeping, and

reporting mechanisms sufficient to assure that identified regulatory requirements are met and that appropriate

measures are in place. The EPA Review Team did find, however, that certain topics related to renewal of

flexible permits warrant further discussion and clarification. These topics include determining acceptable

approaches for adjusting plant-wide emissions caps at permit renewal, and determining acceptable approaches

to transition back to conventional permitting approaches if flexible permits are allowed to expire.

Finding 2: The flexible permits were considered to be enforceable by permitting authorities and

EPA.

A key objective was to verify that the flexible permit provisions are enforceable by permitting authorities and

the EPA. The six permitting authorities involved in the pilots all reported the ability to detect non-compliance

with flexible permit conditions and to enforce the permit requirements, and expressed certainty that permit

requirements could be enforced, had the need arisen. For all permits, the EPA was able to replicate the

emissions calculations for selected time periods to demonstrate compliance. Permitting authorities reported

that conducting inspections of sources with flexible permits is comparable to conducting inspections of sources

with conventional permits.

Finding 3: The flexible permits facilitated and encouraged emissions reductions and pollution

prevention.

The flexible permits contain mechanisms designed to facilitate and encourage emissions reductions and

pollution prevention (P2). Five of the sources with flexible permits lowered actual plant-wide emissions during

their permit terms, and the sixth source lowered its emissions per unit of production during the permit term.

For example, using pollution prevention (P2), Intel lowered actual emissions of volatile organic compounds

(VOCs) from 190 tons/year to 56 tons/year while increasing production. After a substantial voluntary

reduction of VOC emissions from 10,000 tons/year, 3M further lowered its actual VOC emissions from 4,300

tons/year to below 1,000 tons/year. This reduction resulted primarily from increased pollution control device

performance, greater use of voluntary controls, P2, and reduced production. DaimlerChrysler lowered its
6

actual VOC emissions from 1,400 tons/year to less than 800 tons/year, primarily through P2 associated with

vehicle coatings and plant solvent usage.

The plant-wide emissions caps focused organizational attention on reducing plant-wide emissions. In many

cases, the advance approved change provisions reduced the administrative “friction” associated with P2

changes, making such changes more attractive for sources to undertake. The flexible permits increased

internal awareness and focus on pollution prevention at the sources through explicit P2 program, reporting,

and/or performance requirements.

Finding 4: Companies with the flexible permits believe that air permitting is on their critical

response path.

Each of the sources with flexible permits reported that conventional permitting approaches can constrain their

ability to compete effectively. The combination of increasingly globalized competition and a shift to new

modes of production substantially increased the pressure to operate highly flexible, nimble, and responsive

research, development, and production operations. For example, competitive pressures and computer design

advances in the automotive sector have compressed the new vehicle development process from five years

to less than 18 months, requiring increasingly flexible production systems and time sensitive equipment

changes. For products in the semiconductor and specialty tape industries, competitive pressures frequently

cause certain products to become obsolete within six to nine months, as customers’ specifications change and

technology evolves. Advance production concepts, such as lean manufacturing, designed to help firms

compete effectively, require rapid, and often iterative, operational and equipment changes for continuous

improvement of resource productivity, operational efficiency, and product quality. For these reasons,

companies report that conventional case-by-case permitting actions can be problematic due to the potential

delay and uncertainty of final permit actions. Companies with flexible permits identified similar needs at other

facilities and are interested in pursuing flexible permits for those facilities.

Finding 5: Companies with the flexible permits utilized their flexibility provisions.

Flexibility provision utilization during the permit terms exhibited rates and types of changes consistent with the

needs expressed by the companies during permit development. The actual number of changes made using

advance approval and other flexibility provisions varied by source, with Intel implementing the most changes

(e.g., approximately 150 to 200 equipment and operational changes per year). Other companies implemented

fewer changes (e.g., more in the range of 20 or fewer changes per year), but emphasized that the relative

value of making certain critical changes can be more important than the number of changes made. Some

companies did not utilize all of the flexible permit provisions, but generally anticipated using the flexibility

provisions in the future. The flexible permits accommodated a substantial number of advance approved

changes while providing sufficient clarity in describing the advance approved changes to ensure

enforceability. Additionally, flexible permits facilitated an increase in the rate and a shift in the type of

changes made, when compared to what might have occurred under a conventional permit.

Finding 6: The flexible permits enhanced information sharing between the companies and

permitting authorities.

The flexible permits enhanced the permitting authorities’ overall understanding of company activities and

emissions as compared to conventional permitting approaches. The flexible permit development process

provided the permitting authorities with a clearer understanding of the maximum emissions levels anticipated

during the permit terms. During permit development, companies provided more information regarding the type

of changes anticipated during the permit term. This provided a more comprehensive, up-front picture of
7

anticipated operational activities and associated environmental performance than a conventional permitting

process.

During permit implementation, information about a company’s specific changes under the advance approval

provisions was generally comparable to information provided under a conventional permitting process. The

flexible permits also required information about total source emissions and pollution prevention that is not

typically required under conventional permitting.

Finding 7: The flexible permits generally provided to the public equivalent or greater information

than conventional permits.

The flexible permits shifted the timing, type, and format of information made available to the public about

emissions performance, operational and equipment changes, and P2 activities. The specific format, timing,

and availability of certain types of information required by the flexible permits varied, particularly for advance

approved changes. In all cases, the flexible permits provided more information up-front about operational

changes (or categories of changes) that the sources anticipated making during the permit terms. This

provided the public with an opportunity to understand and comment on the companies’ anticipated changes.

During permit implementation, four of the flexible permits provided equivalent or greater information for

specific changes made under the advance approval provisions, although in a different format and timing than

typically available under conventional permitting. In two cases, the pilot permits resulted in less information

about certain changes implemented under the advance approval provisions. In the areas of total plant-wide

emissions information and/or P2 information, all of the pilot permits increased the availability of information

to the public for the companies’ emissions and activities. For all six permits, the permitting authorities

indicated that, on balance, the flexible permits improved the availability of information to the public, ensuring

the flow of significant and meaningful information regarding the current status and future direction of

operations and emissions.

Finding 8: The flexible permits produced or are anticipated to produce net financial benefits to

companies and permitting authorities.

Companies and permitting authorities reported that the flexible permits resulted in net financial benefits or are

anticipated to do so in the future. Companies and permitting authorities indicated that initial permit

development costs exceeded those required to develop conventional permits because of the innovative nature

of the permits and additional resources associated with developing site-specific flexible permit provisions.

In each case, however, companies and permitting authorities reported that the flexibility provisions decreased,

or are expected to decrease, the administrative costs of operating under the permit to more than offset the

initially higher permit development costs. Companies reported that the potential opportunity costs of project

delays from air permitting can be high, ranging as high as several million dollars in just a few days. In so far

as flexible permits can minimize project delays, the economic benefits to companies can be correspondingly

large. Permitting authorities typically reported that the additional permit development costs for flexible permits

were offset by resource savings within the first three years of permit implementation.

Finding 9: Permitting authorities are generally supportive of flexible permits as an option.

The six permitting authorities involved in the flexible permits indicated that they are pleased with the

environmental and administrative benefits of the permits. They believe flexible permitting techniques are

useful tools to address some sources’ operational flexibility needs, to foster environmental improvements

through emissions reductions, and to reduce required permitting resources and backlogs for permitting. This

increased permit efficiency allows the public agencies to focus resources on higher environmental
8

management priorities. Permitting authorities expressed interest in renewing the flexible permits and

expanding the use of flexible permits within their jurisdictions and believed that finalization of EPA policy

and/or guidance for flexible permits should increase national interest and efficiency in expanding their use.

Additionally, permitting authorities stated that various forms of EPA outreach, training, and assistance would

be useful to assist permitting authorities to develop effective flexible permits.

Finding 10: Permitting authorities indicated that flexible permit provisions should be matched with

a company’s need for flexibility and technical capacity to implement effectively its flexible permit

requirements.

Permitting authorities believe that flexible permits meet applicable requirements and are fully enforceable.

However, such permits may not be appropriate for all sources. Permitting authorities believe that two critical

factors should be considered when determining the appropriateness of flexible permitting for a particular

company. First, the company should be able to demonstrate that it has a sufficient need for the flexibility to

justify the additional up-front permitting authority time and resources required to develop flexible permit

provisions for the company. Second, the company should exhibit the technical capacity to operate effectively

under a flexible permit. Factors such as a source’s compliance history, commitment to pollution prevention,

and ability to track and manage operational changes and emissions should be considered by permitting

authorities when determining the appropriateness of a flexible permit for a company.
1

The term “flexible permits” has been primarily used to describe permits with conditions that enable

permitted sources to make certain changes (e.g., modifications to operations, equipment, raw material, emission

factors, monitoring parameters) without requiring further case-by-case review and approval or permit modifications

from the permitting authority. The term also encompasses those approved permit conditions which are sufficient to

enable a more expedited permit revision process, but not to accomplish a full advance-approval. This report and its

appendices use the terms “flexible permits,” “flexible permit conditions,” and “flexibility provisions” to denote

permits and permit conditions that include such provisions related to advance approval. See Section D for a

discussion of flexibility provisions examined by the EPA’s Flexible Permit Implementation Review.

9

I. Introduction

A. Project Scope and Purpose

Over the last several years, the U.S. Environmental Protection Agency (EPA) and several State and local

permitting authorities worked with several companies to develop innovative approaches to air permitting. The

EPA and States launched these pilots to increase operational flexibility while ensuring environmental

protection. Permit developers sought to encourage and facilitate emissions reductions and pollution prevention

with the flexible permits. The permits were also designed to reduce the administrative “friction” – costs, time,

delay, uncertainty and risk – associated with making certain types of operational and equipment changes.

Additionally, permitting authorities desired to reduce the resources needed for case-by-case applicability

determinations and for the approval process of subject minor and major New Source Review (NSR) permit

applications and other permitting amendments. Permitting authorities designed these “flexible permits” within

the existing regulatory framework (i.e., approaches were not precluded under any relevant Federal or State

regulation) to address all applicable air requirements.1

As interest in flexible air permitting increased, the EPA saw the need to evaluate the implementation

experience with flexible permits developed under pilot efforts such as EPA’s Pollution Prevention in

Permitting Program (P4) and State innovation activities. Particular interest has focused on flexible permitting

techniques such as plant-wide emissions limits (e.g., plant-wide applicability limits, or PALs; potential-to-emit

caps).

In response to this need, the EPA launched the Flexible Permit Implementation Review to conduct in-depth

reviews of six flexible permits developed since 1993. The EPA’s Office of Air Quality Planning and

Standards (OAQPS) initiated this effort, in partnership with EPA’s Office of Policy, Economics, and

Innovation (OPEI). The EPA Office of Policy Analysis and Review (OPAR), the Office of General Counsel

(OGC), and the Office of Enforcement and Compliance Assurance (OECA) provided support for this effort.

The purpose of the Flexible Permit Implementation Review is to help the EPA:

• Determine whether the flexible permits work as envisioned, providing the desired operational

performance improvements and environmental protection.

• Obtain more detailed and better organized information regarding these efforts.

• Improve communication of the details and results of these efforts.

• Understand how such flexible permitting approaches might be improved.

• Assess the level of environmental benefit achieved under flexible permits.

• Learn how similar flexible permit development processes can be streamlined in the future.

• Provide input, as appropriate, into the final development of corresponding EPA policy.
10

B. Structure of this Report

This report presents the EPA’s findings from the Flexible Permit Implementation Review. The Executive

Summary briefly addresses the review’s purpose, scope, approach, and findings. The Introduction includes

a more detailed account of the project purpose and scope (Section A), the structure of this report (Section

B), and the review approach and process (Section C). Section D introduces the primary types of flexibility

provisions that are included in the six flexible permits reviewed in this evaluation. Section E summarizes the

flexibility provisions contained in the six flexible permits, and briefly discusses the sources’ operations,

emissions, emissions sources, and emissions control equipment. The Findings Section presents the EPA’s ten

major findings from this flexible permit evaluation. Each finding is explored in detail, drawing on examples

from the six Permit Review Reports.

C. Review Approach and Process

The EPA’s Flexible Permit Implementation Review involved detailed analysis of company and permitting

authority experiences implementing six flexible air permits. To structure the six permit reviews, OAQPS

developed a “Flexible Permit Review Framework” that includes specific evaluation questions grouped into

eight areas of inquiry. The Flexible Permit Review Framework was developed by OAQPS in consultation

with other EPA offices, including OPAR, OECA, OGC, and OPEI.

C.1 Flexible Permit Review Framework

The areas of inquiry in the Flexible Permit Review Framework are listed below. Each of the six Permit

Review Reports accompanying this report are structured based on this review framework, and they include

the specific questions and areas of inquiry that were addressed by the reviews.

• Background: This section examines background information on the permitting authority’s structure,

capacities, and processes; the pilot source’s operations and characteristics; and the company’s need

for flexibility.

• Flexible Permit Design Features: This section examines the specific flexibility provisions

contained in the permit and the terms which assure compliance with them, including monitoring,

recordkeeping, and reporting requirements.

• Public Participation and Public Perception: This section assesses the public’s participation in the

development of the flexible permit through examination of the public involvement process and the

record of public comments. It examines the flows of information during development and

implementation of the pilot permit, and compares these to what might have been experienced under

conventional permitting.

• Implementation of Flexible Permit Provisions: This section examines when and how flexible

permit provisions were actually utilized by the source during permit implementation. It explores how

the flexible permit implementation might compare to the experience under a conventional permit.

This section also assesses the quality and quantity of information generated under the flexible permit

and discusses any problems that were encountered.
11

• Design Adequacy of the Flexible Provisions: This section assesses whether the flexible permit

design features, such as advance-approved change provisions, were adequate to assure compliance

with all applicable requirements.

• Practical Enforceability of the Flexibility Provisions: This section assesses the ability of the

source and permitting authority to determine compliance with the permit conditions and applicable

requirements. It also examines the ease of inspection associated with the flexible permit.

• Permit Costs, Environmental Benefits, and Value Added: This section assesses the relative

costs and benefits of the flexible permit to the source and permitting authority, as compared to a

conventional permit. In particular, this section examines whether the permit actually provided desired

flexibility to the source as well as equivalent or better environmental protection.

• Other Issues: This section addresses ways in which flexible permits can be improved and how the

EPA can support such improvements in the future.

C.2 EPA Review Team

The EPA assembled a core Permit Review Team consisting of representatives from various EPA offices,

including OAQPS, OPEI, and OECA. Ross & Associates Environmental Consulting, Ltd., under subcontract

to the EPA through Industrial Economics, Inc., provided overall team coordination services and compiled

review results. In addition, representatives from Midwest Research Institute, under contract to the EPA,

participated in the reviews to support the EPA’s evaluation of the emissions monitoring, recordkeeping, and

reporting requirements and practices. At least six representatives from this group participated in each of the

six individual permit reviews and associated site visits. In some cases, the EPA Review Team was

supplemented by representatives from the EPA Regional Office in which the pilot permit was developed.

C.3 Permit Review Process

The Flexible Permit Review Framework was completed for each of the six flexible permits. This was

accomplished through extensive off-site research, on-site visits to the source and the permitting authority, and

a review process for finalizing responses to the Flexible Permit Review Framework. Prior to each site visit,

preliminary responses to many of the review questions were drafted by the EPA and its contractors based

on information collected through pre-site visit conference calls with each company and permitting authority.

Background research also included review of the flexible permits and other publicly available records,

including permit applications, public comments received during permit review or implementation, inspection

reports, monitoring data summaries, compliance certifications, notices, and other records.

The on-site reviews consisted of visits to the source and the permitting authority. The EPA Review Team’s

one to one-and-a-half day visits were designed to collect and verify evidence and data to complete the

Flexible Permit Implementation Review Reports. The EPA on-site reviews were not conducted as

compliance audits of the sources. Rather, they assessed the company and permitting authority’s experience

with developing and implementing the flexible permits, so as to help improve similar permits in the future. The

site visits included discussions with company and permitting authority personnel and a walk-through of the

plant, as well as a detailed examination of on-site records, including monitoring data. Representatives from

the permitting authority participated in the source site visits and discussions. The plant site visits were

typically followed by a half-day visit of the EPA Review Team to the permitting authority offices to discuss

specific aspects of the review framework relevant to the permitting authority. Company personnel did not

participate in meetings and discussions at the permitting authorities.
12

Following each site visit, extensive steps were taken to ensure the accuracy of information catalogued in the

Flexible Permit Review Frameworks. EPA contractors prepared initial drafts of the Permit Review Reports.

EPA contractors conducted follow-up discussions, as necessary, with the sources and the permitting

authorities to complete these draft Permit Review Reports. The EPA Review Team provided preliminary

review and comment on the draft Permit Review Reports. The revised Permit Review Reports were then

forwarded to the relevant company and permitting authority contacts for review and comment. Companies

and permitting authorities were asked to verify the accuracy and completeness of the responses contained

in the Permit Review Reports. Based on these comments, the EPA contractors worked with OAQPS and

OPEI staff to finalize the six Permit Review Reports. This Summary Report was prepared by OAQPS and

OPEI, with support from contractors, and was reviewed and commented on by other members of the EPA

Review Team.

C.4 Flexible Permit Selection

EPA selected six pilot permits for review based on the following criteria.

• Extent of permit implementation and/or duration since permit issuance.

• Likelihood of source and permitting authority voluntary participation in the review.

• Number and type of flexibility provisions in permit.

• Unique features of flexible permit.

• Diversity of emissions and applicable requirements.

• Number of inspections completed.

• Relevance of permit to inform ongoing EPA efforts to develop policy.

Table 1.1 lists the six flexible permits selected for inclusion in the Flexible Permit Implementation Review (see

end of report).

D. What Are Flexible Permit Provisions?

The term “flexible permit” is frequently used to describe pilot permits with conditions that reduce the

administrative “friction” – costs, time, delay, uncertainty, and risk – experienced by companies and permitting

authorities when making certain changes under the permit. Such changes could include modifications to a

source’s method of operation, equipment, raw materials, emission factors, or monitoring parameters. The six

flexible permits examined in this review contain flexibility provisions which advance approve such changes

or categories of changes. While flexible permit solutions will depend on individual state permitting rules and

requirements, a variety of flexible permit provisions have been developed by the EPA and State and local

permitting authorities to accomplish advance approval for a category of changes. Several types of flexible

permit provisions utilized in permits reviewed in this report are summarized below.

D.1 Description of Advance-Approved Changes

The six flexible permits include descriptions that enable the advance-approval of specific changes and/or

categories of changes. Advance approved change descriptions typically allow companies to make a fairly

broad spectrum of modifications, eliminating the need for additional case-by-case review and approval by the

permitting authority at the time the plant makes the change. Changes that trigger new applicable requirements

(i.e., requirements unaddressed by the advance approval provisions) or require modifications to monitoring,

recordkeeping, and reporting requirements are not advance approved. To implement advance approved

changes, sources must maintain plant-wide emissions below applicable limits. In addition, they typically must

submit notice to the permitting authority and maintain on-site logs providing documentation of the changes
2

This assumes the sources is in an attainment area. SERs also differ depending on the pollutant in

question.

13

implemented under the advance approval provisions (e.g., the addition of a new emissions unit).

Some of the flexible permits contain provisions that only partially advance approve particular types of changes,

providing a streamlined review and approval process. Permitting authorities believe this to be useful as an

interim approach for certain types of changes and review requirements. For example, a flexible permit might

advance approve a set of changes to which a source must apply best available control technology (BACT).

The permit, however, could preserve the conventional process for public comment on the company’s proposed

BACT approach, as well as the permitting authority’s opportunity to reject or comment on the proposed

BACT approach at the time of the change.

D.2 Plant-wide Emissions Limits

All six flexible permits contain one or more plant-wide caps on emissions of Volatile Organic Compounds

(VOC) and/or criteria air pollutants. These emissions caps typically included annual/12-month rolling limits

(e.g., tons/year) and short-term limits (e.g., pounds/hour) that cover emissions from all emissions sources at

a plant, including any that may be “grandfathered” under the Clean Air Act.

Emissions caps can function in different ways. First, caps can serve as a basis for ensuring new applicable

requirements are not triggered. In other words, caps can be set in such a way that (as long as there is no

violation of the limit) new applicable requirements will not be triggered. Potential-to-emit (PTE) caps typically

establish “synthetic” minor source status for applicability purposes under one or more regulations by setting

a limit on plant-wide emissions below the emissions threshold that would trigger major source status. In

addition, for major sources, Plant-wide Applicability Limit (PAL) baselines are typically set at an average of

the actual plant emissions for the previous two years (or another more representative period) plus 39

tons/year, an increment just under the Significant Emissions Rate (SER) for VOC emissions of 40 tons/year

that would trigger major New Source Review.2 In another variation, Oregon rules establish an annual and

short-term Plant-Site Emissions Limit (PSEL) for sources in the State, based on each source’s actual

emissions in 1978, that is contained in the State Implementation Plan (SIP). The PSEL also functions to

define the aggregate emissions level below which major NSR would not apply to changes made at the site.

Short-term emissions caps, where required, also act to assure that the advance approved changes in

combination with existing emissions do not adversely impact the National Ambient Air Quality Standards

(NAAQS) (in attainment areas). Finally, emissions caps serve to bound the magnitude of advance approved

changes so as to define them in a reasonably anticipated alternative operating scenario for title V permitting

purposes. Often, when more than one cap was involved, these caps can be streamlined into one plant-wide

emissions limit (i.e., combined into the most stringent form) so as to serve multiple functions at the same time.

D.3 Replicable Testing Procedures

Several of the flexible permits contain replicable testing procedures that enable sources to update the

monitored parameter levels of concern (e.g., pollution control device efficiencies, emission factors), based

on approved testing results, without requiring a permit modification. Permit provisions describe the replicable

procedure to be used when testing and updating parameters, and the actual parameter values are documented

in required correspondence between the permitting authority and company, which are maintained at the

source and in the permitting authority’s files along with the permit.

D.4 Applicable Requirement Streamlining

Pursuant to EPA guidance presented in White Paper Number Two, several of the flexible permits streamlined
14

applicable requirements to reduce permit complexity. In these instances, overlapping and redundant

requirements were subsumed under the most stringent requirement(s). This technique was particularly

effective when it was used as part of a “clean building” approach. A “clean building” is a separate structure

or collection point within a plant site containing emissions units that are (or will be in the case of new units)

routed to one or more dedicated, state-of-the-art air pollution control devices. To advance approve

modifications or new unit additions in a “clean building” with respect to all technology-based requirements,

the control device must assure compliance for all the advance approved changes (as well as for all unchanged

existing operations in the same building) with the most stringent requirement that could apply to any of the

activities being advance approved to occur within the “clean building.”

D.5 Pollution Prevention Provisions

Several of the flexible permits contained explicit pollution prevention (P2) conditions designed to focus greater

plant attention on P2 and to take full advantage of the P2 that often takes place when flexible permit

provisions are established. These conditions ranged from P2 program development and reporting

requirements to enforceable P2 performance targets.

E. Pilot Permit and Source Characteristics

While the flexible permits contain provisions to accomplish advance approval that are generally similar, each

permit has a unique combination of conditions that are tailored to the company’s flexibility needs, operations,

and State-specific requirements. This section introduces the six flexible permits evaluated by the EPA’s

Flexible Permit Implementation Review. Table 1.2 highlights the key flexibility provisions in each permit (see

end of report). The company operations, emissions sources, and emissions control equipment are summarized

below. Detailed descriptions of source characteristics, flexible permit provisions, monitoring requirements,

and other background information are available in the six Permit Review Reports.

3M Company - St. Paul, Minnesota

3M’s St. Paul tape plant manufactures more than 550 specialty tape products, including automotive and

medical tapes, graphics tape, offset printing tape, and foam and double-sided tapes. To produce tape

products, adhesives are mixed at the plant and then applied to a tape backing, or “web”, on one of 18 coaters.

The coated web is fed through ovens to volatilize excess solvent from the adhesives, and is then wound into

rolls and cut for packaging and shipment. VOC emissions result from volatilized solvents coming off the

adhesive mixing areas and evaporation ovens and are controlled through a highly efficient regenerative

thermal oxidizer (RTO). The flexible permit, issued in 1993, was needed to provide for an extensive program

of renovations to maintain the long-term viability of this plant in 3M’s network of plants.

DaimlerChrysler Corporation - Newark, Delaware

DaimlerChrysler’s Newark Assembly Plant (NAP) began producing the Dodge Durango, a sports utility

vehicle, in 1997. While vehicle production levels tend to be cyclical due to model changeovers and economic

demand cycles, vehicle production in July 2001 was about 600 vehicles per day (200,000 vehicles/year). The

NAP’s initial flexible permit, issued in 1995, enabled the source to retool for Durango production and to

construct a new vehicle coatings building adjacent to the assembly buildings. Most VOC emissions result

from the various steps in the vehicle coating process (e.g., electro-coat dip tanks, paint booths, curing ovens),

and are controlled through pollution prevention (P2) efforts and, to a lesser extent, by a regenerative thermal

oxidizer. The NAP emits criteria pollutants (PM10, SO2, NOx, and CO) from operation of the thermal
15

oxidizer, five boilers, paint curing ovens, and other combustion sources.

Imation Corporation - Weatherford, Oklahoma

Imation’s Weatherford plant consists of two separate buildings. The North Building houses Printing and

Publishing Division operations and manufactures products for the graphics arts and printing industries. Digital

and conventional proofing systems are produced by coating thin films with colored, solvent-borne solids. The

South Building contains Data Storage Division operations and produces data storage products such as

computer diskettes. VOC emissions result from the solvent-borne coatings as they are mixed, applied to the

film, and heated in curing ovens. Production areas are maintained with negative pressure and VOC emissions

from the coaters and ovens are routed to voluntarily installed pollution control devices, including a regenerative

thermal oxidizer, a catalytic oxidizer, and a carbon absorber. The pollution control equipment, two on-site

boilers, and other miscellaneous combustion sources emit criteria pollutants. The design of the permit was

critically needed for Imation to test new raw materials and processes in a timely manner.

Intel Corporation - Aloha, Oregon

Intel’s Aloha, Oregon semiconductor fabrication plant produces semiconductor chips for use in computers

and other electronic devices. An iterative sequence of steps, including application of photoresist, UV light

exposure, developing, etching, rinsing with deionized water, doping, and rinsing with acid and solvent is

employed to transform silicon wafers into semiconductors. Plant air emissions consist of VOCs and organic

and inorganic hazardous air pollutants (HAPs) from production processes and cleaning activities, as well as

criteria pollutants from on-site boilers. The flexible permit was designed to rely primarily on a campaign of

P2 to advance approve a myriad of small equipment changes and process modifications.

Lasco Bathware - Yelm, Washington

Lasco’s Yelm source produces fiberglass reinforced plastic (FRP) bathtubs, shower stalls, and whirlpools.

The source operates a gelcoat line and an acrylic line. Coats of plastic and fiber-reinforced resins are

sprayed in successive layers into molds (gelcoat line) or on preformed acrylic plastic sheets (acrylic line).

Styrene emissions result from the spray booth operations. Lasco, through P2, limited its emissions per unit

of production so as to allow greater overall production under its emissions cap. During the flexible permit

term, Lasco also installed a regenerative thermal oxidizer to control these VOC emissions from various steps

in the gelcoat line.

Saturn Corporation - Spring Hill, Tennessee

Saturn operates an integrated automotive production plant that produces a range of Saturn-brand vehicles.

Production, which peaked in 1996 at 314,035 vehicles, has declined in recent years due to weakness in the

subcompact car market segment. The flexible PSD permit, issued in June 2000, has enabled Saturn to retool

to produce a new, fuel-efficient sport utility vehicle, the Saturn VUETM. VOC emissions result from the

vehicle paint lines and the lost-foam aluminum foundry operations. VOC emissions are controlled by eleven

recuperative thermal oxidizers, two regenerative thermal oxidizers, and a hybrid carbon adsorption/thermal

oxidation system. Criteria pollutants arise from operation of the pollution control equipment, ovens, boilers,

and other miscellaneous natural gas combustion sources. The Saturn PAL PSD permit is a hybrid permit

consisting of a PSD permit for a major expansion with permitted emissions based on projected future actual

emissions in combination with a PSD permit for existing emissions units with allowable emissions based on

current actual emissions at the existing emissions units.
16

II. Findings

Drawing on information collected through the Flexible Permit Implementation Review, the EPA identified the

following findings. Where appropriate, specific examples are drawn from the six individual permit

implementation experiences. Readers should refer to the six Permit Review Reports for the full details of

the individual permit reviews.

Finding 1: The flexible permits contain adequate measures to assure

compliance with all applicable requirements.

Evaluation of the design adequacy of the flexible permits requires consideration of the objectives of the permit

developers. Permitting authorities generally had two primary objectives in mind. The first was to ensure that

all applicable air requirements were met. This design objective meant that the flexible permits were

developed to function within the current regulatory framework without new rulemakings. The permit design

teams believed that it was imperative to address all substantive requirements (e.g., technology, emissions

performance, or work practice requirements) and procedural requirements (e.g., public notification, review,

and comment processes; and reporting and information availability requirements). If any applicable

requirement were omitted, this could necessitate obtaining construction approval and/or revising the operating

permit solely to address the missing applicable requirement. This would erode most, if not all, of the potential

benefits from advance approval of the other applicable requirements. The design challenge was to do so

through techniques and altered administrative practices that would improve company and permitting authority

operational performance and promote P2. The second design objective focused on improving the

performance, or outcomes, achieved under the permit when compared with performance that would likely

be experienced under a conventional permit. Specific aspects of this performance improvement goal are

addressed later in this report.

All of the permitting authorities stated that the flexible permits were fully supported by current Federal and

State rules. They believed that no rulemaking was required to support any of the flexible permitting efforts.

While many of the flexibility techniques are not explicitly described or addressed in existing rules, the

permitting authorities determined that current rules accommodated the flexible permits, since no existing

regulation expressly precluded them and because the approaches did not bypass established substantive and

procedural regulatory requirements.

In several cases, rule interpretations were important to enable certain flexibility provisions.

• Oregon DEQ and OAPCA representatives both reported that their ability to interpret “emissions unit”

as an entire production line or building, as opposed to a specific piece of equipment or process step,

was instrumental to enabling the advance approval provisions.

• DNREC determined that it had the ability to allow advance approvals in a manner consistent with

construction time limit requirements.

The EPA found no evidence indicating that any air-related requirements applicable to the sources and their

advance approved changes were missed during permit development. The EPA also found that the flexible

permits adequately identified all requirements applicable to the advance approved changes.
17

The flexible permits contained adequate monitoring, recordkeeping, and reporting mechanisms to

ensure that regulatory requirements are met and that appropriate measures are in place.

Permitting authorities and the EPA found that the flexible permits included monitoring, recordkeeping, and

reporting (MRR) approaches that are appropriate given source operations. They also found that MRR

approaches used in the flexible permits are sufficient to determine ongoing compliance with the permit

conditions and applicable requirements. Table 2.1 summarizes the MRR requirements contained in the

flexible permits (see end of report). Please refer to the Permit Review Reports for a more detailed discussion

on the design adequacy of MRR approaches used in the six flexible permits. In several cases, the permitting

authorities required enhanced MRR requirements to ensure that plant demonstration of compliance with

established emissions caps was performed on a more frequent basis. These measures were partly designed

to enable sources and permitting authorities to quickly identify problems or trends that could result in potential

emissions cap exceedances, reducing the risk and potential severity of permit violations.

• 3M’s St. Paul tape plant was required to calculate daily and rolling annual emissions totals within 41

hours of the end of each day, comparing these totals with the established VOC emissions caps.

• DaimlerChrysler was required to submit monthly reports to DNREC documenting plant-wide VOC

and NOx emissions in tons per year for the previous 12 months, as well as plant-wide daily emissions

totals for the month.

In all cases, plant-wide emissions totals and calculations that demonstrated the companies’ compliance with

applicable emissions caps were required to be maintained on-site and were available to agency inspectors

upon request. The EPA did, however, identify areas in which several of the flexible permits could be

improved to ensure that specific monitoring techniques are consistent with current EPA guidance. The EPA

did not find that any of these areas for improvement affected the companies’ abilities to monitor actual

emissions, or to ensure compliance with the emissions caps or advance approved change provisions.

However, the EPA Review Team recommends that these improvements be considered in subsequent

versions of the permits. Several of these recommendations are summarized below.

• Although the monitoring requirements for the VOC scrubber for Intel’s Fab 4 at the Aloha plant used

an appropriate methodology (i.e., operating parameter monitoring), the elements of the monitoring

approach, were they relevant to the companies’ ability to assure compliance, could be improved by

including an operation and maintenance requirement that relates water flow rate with the flow

corresponding to the optimum VOC removal efficiency, as verified through source testing.

• The EPA found that Saturn is conducting appropriate monitoring for the emissions caps, and has

submitted a complete monitoring protocol to TDEC, in accordance with permit condition C.2. The

EPA recommends the addition of several specific monitoring procedures and performance indicator

ranges in the final Title V permit. These recommended measures are associated with monitoring of

the carbon bed adsorber control equipment.

• For the Imation permit, the EPA found that continuous measurement of the air flow rate from coaters

12W and 15W and going to the catalytic oxidizer is appropriate parametric monitoring for monitoring

capture efficiency. However, the permit did not identify any indicator range for this parameter (i.e.,

an operating range outside of which a deviation would require corrective action and reporting was

not identified). Current monitoring guidance would recommend establishing such an indicator range.

The periodic monitoring of capture efficiency and control device performance using inlet and outlet

THC measurements was identified as an appropriate technique.
18
3At the time of the EPA site visit in June 2001, the 3M St. Paul Tape Plant was operating under its State air

operating permit, although the advance-approval conditions in the permit expired in March 1998. The plant has

submitted its Title V permit application and is awaiting its draft Title V permit.

19

Implementation of flexible permit monitoring, recordkeeping, and reporting provisions was consistent

with that envisioned and intended during permit design.

Permitting authorities reported that the sources’ implementation of monitoring, recordkeeping, and reporting

(MRR) requirements was consistent with that intended during permit development. They also found that the

scope, timing, and availability of MRR information was sufficient for the permitting authorities to monitor

companies’ compliance with permit conditions and applicable requirements. In two cases, adjustments were

made to clarify or alter MRR requirements during permit implementation.

• During a 1995 inspection, MPCA identified potential deficiencies in the recordkeeping approach for

temperature monitoring of the thermal oxidizer emissions control device at 3M’s St. Paul Tape Plant.

3M was able to demonstrate that no violations of the control device temperature level or the VOC

emissions cap had occurred. 3M and MPCA clarified and agreed on an acceptable approach for

recording future control device temperature readings.

• In 1996, MPCA eliminated the requirement for a ten-day advance written notice from 3M of changes

implemented under permit condition 2.3.4. MPCA reported that the agency believed that the postcommencement notice for changes (submitted within two weeks of an actual change) was sufficient

to provide the agency and the public with a documented record of advance approved changes

actually made at the source.

Certain topics related to the renewal of flexible permits warrant further thinking to clarify acceptable

approaches.

While the flexible permits operated well during the initial permit terms, companies and permitting authorities

identified two areas that could benefit from further thinking and clarification. The first involves clarifying

acceptable approaches for updating PALs at permit renewal. Companies and permitting authorities indicated

that revising PAL levels based on the average of actual emissions for the prior two years (or some similar

approach) can create disincentives for emissions reductions and P2 if the correction is too extreme. At the

same time, permitting authorities and companies acknowledged that some approach for revising PAL levels

at permit renewal is important to address new considerations that may have arisen, such as new applicable

requirements or changes in local air quality or attainment status.

The second area involves the clarification of acceptable approaches to transition back to conventional

permitting approaches if flexible permits are allowed to expire and the company or permitting authority does

not wish to renew the flexibility provisions. For example, in the case of the 3M St. Paul Tape Plant flexible

permit, the advance approved change provisions expired at the end of the permit term, while the plant-wide

VOC emissions cap has remained in place.3 This has raised questions regarding what level of changes (if

any) would be allowed before New Source Review (NSR) would be triggered.
4

The number of inspections conducted of sources with flexible permits by the time of the EPA’s review

varied primarily based on the length of time the source had been operating under the flexible permit. Permitting

authorities typically reported that they conduct annual inspections of the sources, although in some cases (e.g.,

MPCA’s inspection of 3M’s St. Paul Tape Plant) the frequency of inspections was reduced as permitting authorities

focused on higher priority activities (e.g., issuance of Title V permits).

20

Finding 2: The flexible permits were considered to be enforceable by permitting

authorities and EPA.

A key objective of the EPA’s Flexible Permit Implementation Review was to verify that company compliance

with the flexible permits is enforceable in a practical manner by permitting authorities and the EPA.

Permitting authorities expressed their belief that the flexible permit provisions are practicably enforceable,

and the EPA agrees with these permitting authority assertions based on the findings from the reviews of the

six flexible permits.

The flexible permits contain sufficient monitoring, recordkeeping, and reporting requirements to

enable permitting authorities and the EPA to assure compliance.

Permitting authorities believe that the flexible permits are enforceable in a practical manner. They believe

that they have the ability to detect source compliance with the flexibility provisions, as well as all applicable

requirements, based on the monitoring, recordkeeping, and reporting requirements established in the permits.

Permitting authorities further reported that their experiences during implementation of the permits confirmed

that the flexible permits are enforceable in practice. See Finding 1 above for additional discussion of the

adequacy of permit design related to monitoring, recordkeeping, and reporting requirements.

The EPA agrees with the permitting authorities’ statements regarding the ability to determine company

compliance with permit conditions and applicable requirements based on the findings from this review. The

EPA found the monitoring, recordkeeping, and reporting information implemented by the companies for

calculating emissions and determining control equipment parameter values to be sufficient to determine

compliance. The EPA Review Team was able to reproduce the exact compliance values for each flexible

permit using actual emissions and monitoring data (e.g., material usage data, VOC content data, control device

parameter data) and established emissions calculations procedures. The EPA found that all data necessary

to perform compliance verification calculations was available and well-organized at the sources.

Permitting authorities reported that conducting inspections of sources with flexible permits is

comparable to conducting inspections of sources with conventional permits.

While the number of inspections conducted by permitting authorities varied, permitting authorities generally

indicated that inspecting sources with flexible permits was straightforward and comparable to conducting

inspections for sources with conventional permits.4 A few permitting authorities stated that some up-front

education was required of permitting authority inspectors to ensure their familiarity with the flexibility

provisions in the permits. They indicated such orientation was necessary since the flexible permits contained

some requirements not typically required in conventional permits, such as on-site logs of alternate operating

scenarios and changes implemented under the advance approval provisions, as well as plant-wide emissions

calculations.
21

In some cases, permitting authorities indicated that the flexible permits resulted in less difficult or timeconsuming inspections. This was primarily attributed to the reduced need to verify compliance with numerous

requirements for specific equipment or activities that are commonly included in conventional permits (e.g.,

limitations on production rates for process lines, equipment, or process level emissions). Instead, inspectors

were able to direct attention to ensuring compliance with the plant-wide emissions limits.

Finding 3: The flexible permits facilitated and encouraged emissions reductions

and pollution prevention.

The flexible permits were designed to bring sharper attention to the current level of actual plant-wide

emissions and emissions per unit of production. While the permits generally did not require actual emissions

reductions during the permit term, they contained provisions to facilitate and encourage emissions reductions

and P2. The permit implementation experience, supported by statements from the sources and permitting

authorities, indicates that the permits were effective in facilitating emissions reductions and P2. Of the five

sources which had been operating under their flexible permits for three or more years, all five accomplished

a significant lowering of actual plant-wide emissions and/or emissions per unit of production. Achieving such

environmental benefits was attributed by the companies to several factors, as discussed below.

Companies accomplished a significant lowering of actual plant-wide emissions and/or emissions per

unit of production during their flexible permit terms.

• 3M lowered its actual VOC emissions from 4,300 tons/year to 700 tons/year due to increased

pollution control device capture of VOCs, greater use of voluntary controls, P2, and reduced

production.

• DaimlerChrysler lowered its actual VOC emissions from 1,165 tons/year to 776 tons/year, primarily

through P2 associated with vehicle coatings and plant solvent usage.

• Lasco tested its emission factor as part of developing its flexible permit, leading to a voluntary

reduction in emissions of approximately 100 tons/year prior to obtaining the flexible permit. During

the permit term, Lasco implemented P2 measures and installed a thermal oxidizer to increase

production while remaining under the emissions cap. These efforts resulted in per unit emissions

reductions of approximately 32 percent.

• Using P2 projects, Intel lowered its actual VOC emissions over three-fold, from 190 tons/year to 56

tons/year, to become a synthetic minor source while simultaneously increasing production.

• As Saturn had only operated under the flexible permit for 13 months (at the time EPA’s review was

conducted), it is difficult to determine trends in VOC emissions per unit of production. VOC

emissions for the first year of the flexible permit implementation were about 580 tons/year, compared

with 798 tons/year in the year prior to the issuance of the flexible permit (1999).

• Imation reported that it has achieved about an 11 percent reduction in the pounds of VOC emissions

generated per unit of production in 2000 when compared with 1997 baseline levels.

Companies reported that the plant-wide emissions caps focused organizational attention on reducing

plant-wide emissions.

Several of the flexible permits shifted the allowable level of plant-wide emissions downward.
22

• The flexible permit for 3M’s St. Paul Tape Plant enforceably limited VOC emissions to less than half

those previously emitted by this source. With respect to actual emissions, MPCA indicated that the

State of Minnesota does not have a technology requirement (such as one for best available state-ofthe-art technology) as part of their State minor New Source Review program. As a result, air

pollution sources are in a position to maintain their historical emissions and to increase their emissions

in 39-ton increments through minor changes on an ongoing basis. Under the flexible permit in 1993,

3M became subject to an annual VOC emissions cap of 4,283 tons. Prior to the flexible permit, 3M

was “grandfathered” to emit up to 65,000 tons annually. In 1988, 3M had 10,600 tons of actual VOC

emissions and then voluntarily installed controls, bringing emissions down to 4,300 tons/year in 1991.

• The establishment of VOC PALs for the Saturn plant was part of a PSD permit revision process to

allow approximately a doubling of production capacity. Even with a substantial increase in production

capacity, the new PSD permit (including incorporation of VOC PALs) sets maximum VOC

emissions at a level of about 50 percent of the allowable VOC emissions under the original,

superceded PSD permit for the plant.

• Imation’s flexible Title V permit extended emissions limits to the 12W coating line that was previously

“grandfathered” under the Clean Air Act. Without the voluntary emissions controls that Imation

installed (prior to the flexible permit), the coating line had a potential to emit (PTE) of approximately

4,000 tons/year of VOC. The permit enforceably limited VOC emissions to one site-wide cap of 249

tons/year, creating “synthetic minor” status for purposes of PSD applicability. Imation could have

requested two such caps since its operations at Weatherford involved two separate sources [i.e,

different operations with different Standard Industrial Classification (SIC) codes].

While limits on allowable emissions do not necessarily affect actual emissions, several of the companies

reported that the emissions caps had a “focusing effect,” drawing company personnel’s attention to managing

activities so as to minimize plant-wide emissions. They added that conventional air permits typically contain

a more diffuse set of emissions limitations on specific equipment or production lines that lack this focusing

effect. With company attention focused on managing plant-wide emissions levels in relation to an emissions

cap, several companies reported that this created structural incentives for the companies to pursue emissions

reduction opportunities that increase the margin of compliance - the difference between the emissions cap

and actual emissions. First, companies indicated that emissions reductions result in larger compliance margins

that typically reduce the risk of non-compliance associated with emissions cap exceedances. Second, per unit

emissions reductions can create room under the cap to accommodate future production increases.

• Lasco representatives indicated that the 249 tons/year PTE cap on VOC emissions created a strong

P2 and emissions reduction incentive, particularly since the source’s margin of compliance was not

large (e.g., actual emissions were 244.5 in 1998) and since the cap created a real production

constraint.

• DaimlerChrysler representatives reported that the flexible permit conditions are easier to

communicate to operations personnel since the focus on a plant-wide emissions cap and P2 is more

intuitive and provides more “clarity of focus” than specific equipment or production line requirements.

As a result, it has been easier to engage operations personnel in exploring and implementing P2

projects under the flexible permit. By eliminating numerous requirements on individual emissions

sources at the plant, the flexible permit has also complemented DaimlerChrysler’s lean manufacturing

initiatives designed to reduce complexity throughout the plant.

While emissions caps, in general, can encourage emissions reductions, certain permit designs can also create

disincentives for reducing emissions. As mentioned above, several companies voiced a major concern that
23

their over-control and/or use of P2 to create emissions “head room” under an emissions cap could be lost due

to five year contemporaneous “ratcheting.” A significant compliance margin between actual emissions and

applicable emissions caps is desired by sources to buffer against risk of emissions cap exceedances and to

accommodate production fluctuations linked to changing market demand for plant products. Companies

indicated that a counter-productive “ratcheting” situation can arise if a PAL is totally adjusted downward at

permit renewal to reflect recent actual emissions levels (e.g., average of prior two years actual annual

emissions).

Advance approved change provisions reduced the administrative “friction” associated with P2

changes, making such changes more attractive for companies to undertake.

Advance approval provisions for selected operational, equipment, and raw material changes can significantly

reduce the administrative “friction” of making changes, including delay and costs for undertaking

modifications that have P2 benefits. Companies indicated that under conventional permits, administrative

friction often arises from two activities. First, desired changes are typically evaluated by company

environmental personnel to determine whether any regulatory requirements apply to or are triggered by the

desired modification. Several companies reported that such applicability determinations are often not

straightforward, and that they frequently require careful interpretation and necessitate seeking guidance or

clarifications from the permitting authority. Second, changes triggering minor NSR are typically subjected

to a notice of construction permitting process to seek approval from the permitting authority in advance of

initiating the modification. Staff time needed to conduct applicability determinations and individual permit

applications increases transaction costs for each modification. Additionally, the time frame between when

the desired change is first identified and when it is reviewed and permitted can extend beyond the company’s

desired implementation time frame, resulting in a disincentive to change.

Companies reported that modifications designed to improve resource productivity, process efficiency, or

reduce pollution are often implemented in an iterative manner, as source personnel initiate a modification,

observe and measure results, and then make further refinements to optimize system performance. This could

involve trying multiple raw materials to find one with optimal product quality and emissions performance

characteristics. Several companies indicated that under such iterative change processes, increased

transaction costs and time delays - or even perceived uncertainty about such costs and delays - can produce

significant “barriers to entry,” causing the plant to forego modifications with positive environmental outcomes

that lack significant strategic, operational, or competitiveness advantages. 

• For example, Intel representatives indicated that operations personnel are less willing to engage with

environmental staff in exploring potential P2 opportunities if they perceive that there is a significant

potential for delay or time intensive regulatory evaluations and communications. Due to the iterative

nature of many P2 projects, operations personnel typically need to conduct a series of experiments

on a manufacturing process to see if the changes produce the desired results. Intel indicated that

many of these individual changes could be subject to individual construction permitting actions thus

imposing a very jagged, stop-and-go aspect to the experimentation process. Intel indicated that, under

such conditions, operations personnel might well view experimentation for purposes of pollution

prevention as being too disruptive of the manufacturing process to proceed.

Even when emissions-reducing projects “pay” (e.g., exhibit a positive return on investment), increased

transaction costs, time delays, and uncertainty can reduce the projects’ ability to compete effectively for

internal resources and organizational attention. The net result can be environmental benefits left on the table.
24

Companies reported that advance approval provisions can significantly improve the attractiveness of making

modifications that result in reduced emissions by reducing their transaction costs and the potential for time

delays. The examples below illustrate ways in which utilization of advance approved change provisions

facilitated P2 activities at several of the sources with flexible permits.

• Between 1994 and 1998, Intel’s Aloha plant made at least 18 P2-related equipment and material

changes, utilizing the permit’s advance approval provisions, that resulted in VOC emissions reductions

of over 100 tons/year.

• DaimlerChrysler’s NAP has undertaken numerous P2 activities utilizing the advance-approved

change provisions in their flexible permit, including steps to reduce VOC and HAP emissions from

vehicle coating processes. DaimlerChrysler representatives reported that, in the absence of a flexible

permit, the source might have still pursued some of these P2 initiatives, but that they may well have

been delayed to coincide with permit renewal time frames due to the cost and staff resources

required to secure case-by-case permit approvals. They emphasized that the flexible permits

significantly reduce the regulatory friction associated with making P2 changes, increasing incentives

for P2.

• Lasco representatives stated that the flexibility provisions allowed the Yelm plant to test and

undertake changes that reduced styrene emissions without having to wait for conventional case-bycase permit approval. The advance approved change provisions substantially increased the likelihood

that Lasco would actually research and implement such changes, due to Lasco’s corporate

reluctance to undertake changes that would trigger NSR permitting actions. Lasco has implemented

several changes utilizing the advance approval provisions that have reduced emissions, including

installation of a new putty station and expansion of emissions control capacity.

Several flexible permits increased company awareness and focus on pollution prevention through

explicit P2 program, reporting, and performance requirements.

Four of the flexible permits contained explicit conditions requiring the companies to implement formal P2

programs, report on P2 performance, and/or meet certain P2 performance targets. While these companies

had histories of P2 accomplishment prior to issuance of the flexible permits, the companies generally reported

that the explicit P2 permit conditions served to increase the visibility of P2 among plant personnel. When

combined with the new focus on managing plant-wide emissions against a cap and the relative administrative

ease for accomplishing such changes under the advance approval provisions, the P2 commitments and

programs have empowered some company environmental personnel to expand P2 activities.

• Intel found that the flexible permit provided clear incentives to favor P2 over new emissions control

technology for meeting the required source-specific, performance-based VOC Reasonably Available

Control Technology (RACT) determination (permit condition 14). The explicit focus on P2 in the

permit increased environmental personnel’s leverage in their efforts to engage operations personnel

in exploring and implementing P2 efforts.

• The P2 performance requirement included in the DaimlerChrysler NAP’s flexible permit has

prompted a clear organizational focus on reducing VOC emissions associated with vehicle coating

operations. DaimlerChrysler is to begin utilizing a powder clearcoat by September 2003 if it is

commercially available; if not, the company is to employ P2 measures that will reduce topcoat VOC

emissions to below seven pounds of VOCs per gallon of applied coating solids on a daily weighted

basis until a powder clearcoat option is commercially available.

• Even though a Washington State P2 expert familiar with the RFP industry identified Lasco as a “first
25

in class” pollution preventer, Lasco found that the flexible permit encouraged and facilitated company

efforts to pursue additional P2 opportunities. To fulfill the flexible permit’s P2 program requirement

(which is linked to Lasco’s BACT determination for advance approved changes), Lasco instituted

a “P2 Task Force” at the Yelm plant. The task force is charged with identifying P2 opportunities and

coordinating P2 activities throughout the plant. Lasco representatives stated that its employees are

now more cognizant of how source emissions affect the community and of the importance of P2 as

a result of the flexible permit development process and the increased organizational focus on P2.

• As part of its required P2 program, Imation conducted routine P2 meetings with a cross-functional

team of plant managers and personnel at the Weatherford plant. P2 training for plant employees and

research and development staff further heightened organizational focus on identifying P2

opportunities. Imation representatives also reported that the formal tracking of progress towards the

plant’s ten percent emissions reduction goal (i.e., based on emissions per unit of production) has

increased plant personnel’s awareness of and attentiveness to P2.

Finding 4: Companies with the flexible permits believe that air permitting is on

their critical response path.

Companies participating in the review reported that conventional permits can constrain their ability to compete

effectively. Though the factors differ somewhat for each source, the companies indicated that the

combination of increasingly globalized competition and a shift to new modes of production substantially

increased the pressure to operate highly flexible, nimble, and responsive research, development, and

production operations. In this context, conventional, case-by-case air permitting, which the companies state

can cause delay and uncertainty, can act as a mission-critical bottleneck to their operations.

Global competition across multiple industry sectors has shortened product life-cycles and increased

the importance of moving new products quickly from development to market.

Companies report that global competition, which intensified during the 1990s through the integration of

financial markets, reductions in trade barriers (e.g., NAFTA), increased industrial development in Asia and

other regions, and substantially shortened product development time frames, has exposed U.S.-based

operations to more and often lower cost producers. Examples of specific company competitiveness needs

include the following.

• Intel reported that it operates in a highly competitive market and needs to meet aggressive product

development schedules. Intel currently introduces a new generation of semiconductor chips every

12 to 24 months, with each new product cycle supported by a major “fab revamp.” These

operational changes are very time sensitive, to meet product release schedules from computer and

electronics manufacturers, and involve highly interdependent and sequenced steps.

• 3M management indicated that the reduction in trade barriers associated with NAFTA and other

international trade agreements, combined with the overall globalization of competition and the ability

of potential competitors to purchase and install rapidly "off-the-shelf" production equipment, enables

other companies to reach rapidly into 3M's market share with low cost product. In this context, 3M

reports that "first to market" (where a week delay can be very significant) has become a critical

business success factor, particularly in specialty product markets, such as the automotive and medical

sectors. 3M reported that many specialty tape products become obsolete, and are replaced by newer
26

products, within six to nine months of initial production.

• DaimlerChrysler indicated that its vehicle development process, in part due to advances in

computer-assisted design, has decreased from five years to about 18 months, substantially reducing

its ability to accommodate conventional permitting time frames while meeting product development

schedules.

• Saturn indicated that the automotive market has shifted significantly in recent years, necessitating

more rapid responsiveness to market demands. In this context, Saturn has recently expanded its

available product line and expects further changes in the near future, each of which requires

significant production line retooling and process adjustments. Saturn also indicated that the vehicle

development process has significantly shortened from five years to about 18 months. Previous lead

times allowed ample time, in most cases, to secure needed permits while remaining on product

development and release schedules. Under the new time frames, air permitting is now on its critical

path.

Advance production concepts, designed to help firms compete effectively, encourage rapid, and

sometimes iterative operational and equipment changes to continuously improve resource productivity,

operational efficiency, and product quality.

Production theory and techniques have undergone substantial revision with emphasis placed on continuous

resource productivity improvements. This emphasis - as reflected in such advanced production concepts as

Lean Manufacturing and Six Sigma - substantially influences the day-to-day operating environments at many

companies. These systems are characterized by a major drive to increase the velocity of production

processes (reduce the time required to transform raw materials into product), increase asset utilization and

cash flow, substantially shorten research and development time frames, continually improve process yields,

and respond to heightened customer expectations for quality, product features, and delivery responsiveness.

Specific examples from the permit reviews include the following.

• Intel reported a need to make rapid (and sometimes iterative) process and equipment adjustments in

production processes to improve yield, lower costs, reduce chemical usage, and otherwise improve

operations. Many of these changes involve switching chemicals used in tools and process chemical

formulations, adjusting gas flow rates, and moving or adding tools (e.g., photo lithography equipment,

plasma etchers, liquid acid baths).

• 3M indicated that, in response to competitive pressures, it is involved in a major corporate-wide drive

to reduce cycle times and improve asset utilization and cash flow. These initiatives require for their

success an in-plant culture of continual improvement and substantial flexibility for production

operations.

• Lasco indicated that the key focus in the bathtub industry is making minor product modifications on

an ongoing basis (rather than launching major new products like in the semiconductor industry). In

this context, Lasco's competitive strategy focuses on continually increasing material yields, which

requires seeking ways to utilize less and/or increase the capture of its input materials on a per unit

basis. Lasco also needed flexibility to change production lines rapidly to accommodate different

product types as short-term demand fluctuated among them.

• Saturn identified factory “agility” as a key to its ability to compete within the General Motors network

of plants for new product lines, citing its flexible permit (and the factory responsiveness it provided)

as a critical factor in its selection to produce the L850 “world engine.”

• Imation representatives indicated that the company desired to use the Weatherford plant to

experiment with and pilot new coating technologies and product recipes to respond quickly to changes
27

in customer demand, as well as new production innovation opportunities. These changes involve

short-term experimental use of manufacturing equipment, at times requiring changes to equipment

configurations and the emissions profiles of the equipment. Imation further indicated that market

demands frequently require rapid process changes, including substituting or introducing new raw

material, relocating, modifying or adding new equipment, and/or interchanging pollution control

devices.

Companies indicated that responding effectively to increasingly industry competitiveness requires operating

environments capable of responding rapidly to changing market circumstances (e.g., develop and introduce

new products rapidly and adjust production to address customer requests), moving production rapidly among

facilities to achieve optimal asset utilization, and generally engendering a culture of continual operational

improvement. The companies indicated that this results in an operating environment where changes to

equipment, operating parameters, equipment configurations, and locations are more common and are often

subject to tight deadlines.

Companies report that conventional permitting can be problematic due to the potential delay and

uncertainty associated with such actions.

Although some variability exists, Federal and State and local air permitting rules generally prohibit an air

pollution source from constructing, modifying, reconstructing, or operating an emissions unit, stationary source,

or control device without explicit approval (typically in the form of an air permit or permit modification

undertaken on a case-by-case basis at the time a source desires a change). The typical process for obtaining

any needed New Source Review (NSR) approval involves the following:

• Communicating the nature of prospective changes to the permitting authority and discussions to

determine if NSR would apply.

• Determining all the applicable regulatory requirements that the desired change would “trigger.”

• Preparing and submitting any necessary permit application providing the details of the desired change.

In many cases, permitting authorities may request additional information before a source’s permit

application is considered to be complete.

• Reviewing the application at the permitting authority and framing a draft permit (to ensure all

applicable requirements are met, air quality protection is maintained, and needed technology

requirements are imposed).

• Seeking and addressing public comments on the draft permit or permit modification, if required by

Federal, State, or local rules governing the applicable requirements. In some cases, this step may

involve public hearings.

• Issuance of the permit or revision required to undertake the change.

Permitting authorities reported that this process can take as little as 30 days (for a minor change that does

not require public comment), but can extend to six or more months depending on the type of change,

environmental impacts, applicable requirements, and public concerns. A typical time frame (required or

strongly suggested by agency rules) for most minor source construction permit actions is 90 to 180 days,

although certain permitting authorities indicated that past or current permit back logs inhibit their ability to

respond within these time frames. Some states such as Oregon have provisions that allow "minor" operational

changes (as defined by their specific rules) to proceed in parallel with the permitting process. Companies

indicated that they utilize this option with some hesitancy since the outcome of the review is uncertain and

the consequences of failing to obtain the permit (or be subject to an unexpected requirement) can be
28

substantial.

Companies indicated that this case-by-case permit process can introduce significant delay and uncertainty

into their operational decision-making and research, development, and production activities. Although

case-by-case permitting actions can impose administrative costs from applicability determinations and permit

application development, companies’ concerns focused on the potential opportunity costs and competitiveness

costs associated with delay and uncertainty in the permit process.

Companies reported that operational change delay results from the need to obtain a permit prior to

“constructing” each planned operational change (or aggregated group of changes). In the new competitive

environment described by the companies, they often do not have substantial advance notice of the specific

operational changes needed to address customer demands or market opportunities. As a result, the need to

delay implementation of the change to meet conventional permitting requirements can lead to lost market

opportunity. Companies further indicated that many of the continual resource productivity improvements they

desire to undertake require experimentation and highly iterative process changes. In this context, the need

to obtain a permit before each iterative step turns continual improvement into an uncertain process that

operations managers are disinclined to undertake.

• Intel identified 150 to 200 changes per year that they believe would have triggered minor NSR

permitting. This number of changes, combined with the Oregon DEQ approval time frame of up to

60 days per change, suggest that there would likely have been significant delay under a conventional

permit. Even if few delays would have resulted in production downtime or missed market

opportunities, the costs would likely have been significant under a conventional permitting scenario,

as many of the changes improved the cost-competitiveness of Intel’s products through resource

productivity improvements. Industry estimates of the opportunity costs of production downtime and

time delays run as high as several million dollars in just a few days, due to lost sales to computer

makers and other factors. Intel representatives indicated that the impact of continued time delays

would likely be to redirect Intel’s production investment and operating facilities to locations where

changes could be accommodated within existing environmental regulations (e.g., other U.S. States

or to other countries where Intel operates, such as Ireland or Israel) as they had done prior to

receiving their flexible permit.

• DaimlerChrysler and General Motors (Saturn’s parent company) reported that they have experienced

PSD review processes lasting more than 2 years.

Several of the companies indicated that uncertainty in the permitting process creates "friction" for the

operational change process because it increases risk. Companies indicated that uncertainty emerges from

a number of aspects of the permitting process. First, companies reported that they are at times unsure about

the applicability of permitting requirements to maintenance, repair, and replacement activities. Second, future

permit requirements can be unpredictable due to the discretion inherent in setting emissions limits, making

technology determinations, and establishing monitoring, recordkeeping, and reporting requirements. Third, the

length of the permit review and approval process can be unpredictable, due to such factors as permitting

authority backlogs and the degree of public interest. According to the companies, these factors combine to

make it difficult for a company to accurately estimate the time frame and cost of a permitting action and,

therefore, how the need to permit will affect the financial attractiveness and overall viability of an operational

change.

Companies with flexible permits stated that they have similar needs at other facilities and are
29

interested in pursuing flexible permits for those facilities.

The six companies reported that they have identified similar flexibility needs at other facilities, and they

expressed interest in pursuing flexible permits for those facilities. For example:

• Imation’s Camarillo, California source has been issued a flexible permit through the EPA’s Project

XL initiative, modeled in several respects on the Weatherford permit. Imation representatives stated

that they believe the flexibility techniques used in the Weatherford permit would be beneficial to other

Imation facilities as well.

• DaimlerChrysler pointed to a plant in the Midwest as a primary example of the company’s need to

expand the use of flexible permitting approaches to other facilities. The plant’s eight existing permits

have multiple, unit-specific technology limits, emissions limits for different time periods, and a variety

of operating conditions specific to each emissions unit, for a total of 128 specific permit conditions

(as compared to only 16 for the Newark Assembly Plant’s permit). Since the late 1980s, the source

has been addressing permit modifications and other concerns on a continuous basis. More

specifically, since 1992 the plant obtained 12 permits or permit revisions, with two involving Federal

NSR. Three recent amendments took, on average, over a year to complete. DaimlerChrysler

believes that had the plant been operating under a flexible permit, this number of permit transactions

could have been reduced to only two, saving time and money as well as facilitating timely completion

of P2 activities. DaimlerChrysler representatives indicated that the company has set a goal of having

flexible permits for all DaimlerChrysler facilities in the U.S. within two years. However,

DaimlerChrysler reported that permitting authorities in several other States are opting to hold off on

negotiating such permits until EPA guidance and/or rulemaking are complete.

Finding 5: Companies with the flexible permits utilized their flexibility

provisions.

Flexibility provision utilization during the permit terms exhibited rates and types of changes consistent

with the needs expressed by the companies during permit development.

All of the companies have utilized advance approval provisions contained in their flexible permits.

• As mentioned, Intel reported that the Aloha plant made an average of approximately 150 to 200

operational and equipment modifications per year during the Title V permit term that would likely

have been subject to Oregon’s case-by-case Notice of Construction approval process under a

conventional permit. These changes, primarily associated with “fab revamps” to scale-up production

of new semiconductors and iterative changes to optimize existing production processes (including P2-

driven changes), were implemented using the advance approval provisions in the Title V permit.

• 3M made 34 equipment and operational changes that utilized the advance approval conditions. 3M

estimated that 15 to 20 of the changes would likely have required some form of permitting action

under Minnesota’s conventional permitting process, with two of these changes likely having triggered

at least case-by-case PSD permitting analyses. 3M indicated that the advance approval provisions

accommodated all of the source’s change needs (i.e., no additional construction permitting actions

were necessary), enabling the company to upgrade aging equipment and improve the yield and per

unit emissions performance associated with coating lines.
30

• DaimlerChrysler’s NAP made over 90 operational and equipment changes utilizing the permits’

advance approval provisions between 1995 and 2000. Advance approved modifications were made

to coating system components, coatings, cleaning activities, fuel-fired sources, source locations,

ventilation systems, and emissions control systems.

• Lasco made five changes during the Title V permit term (as of July 2001) that utilized the advance

approval provisions. The advance approvals enabled Lasco to add two new emissions units, increase

its stack height to remedy odor concerns, modify its emission factor to account for improved

emissions performance, and modify its control technology without requiring case-by-case permitting

actions.

• Despite only having about one year of implementation experience under its flexible permit, Saturn has

made several of the changes outlined in its PSD permit application, including construction of the L850

engine line and the second assembly line in General Assembly. Saturn reported that it is likely that

changes to existing emissions units have been made during the first year of the permit term (i.e., June

2000 to August 2001) that utilize the advance approval provision in permit condition B.10.1. Saturn

is not required to maintain records of these changes, provided the changes meet established criteria

in the permit and plant-wide emissions remain below established caps.

• Imation and Oklahoma DEQ reported that the Weatherford plant has made frequent use of the

flexibility provisions that advance-approve the use of alternative raw materials. In at least four cases,

this included a streamlined toxics evaluation by the State, allowing the source to rapidly implement

raw material changes at the source. Imation also utilized the advance approved alternative operating

scenarios for control devices and methods on three occasions.

In addition, some companies stated that the number of changes made is not the only indicator or importance

to them. Equally important to them is the ability to make certain critical changes when other business factors

dictate.

Companies reported that the advanced approval provisions in the flexible permits fully addressed their

operational change needs. With the exception of Lasco, the companies did not need to undertake any nonadvance approved construction permitting actions (e.g., minor NSR and major NSR) during their flexible

permit terms (i.e., typically a 5 year period). Also, the permitting authorities indicated that the sources did not

make any changes under the advance approval provisions that were not authorized under the advance

approval provisions.

• Lasco was required to submit a Notice of Construction permit application and seek a Title V permit

amendment to install a regenerative thermal oxidizer during the flexible permit term. This was

necessary since this change was not advance approved in the permit, and since the change required

new MRR requirements.

Some companies did not utilize all of the flexibility provisions in their permits, but they anticipated

using these flexibility provisions in the future.

While all six companies utilized at least some of the flexibility provisions in their permits, not all flexibility

provisions had been used at the time of this review (with the exception of Intel). Several sources indicated

that, while they can reasonably anticipate desired operational and equipment changes (or types of changes)

well in advance, the exact timing of change implementation is often influenced by multiple factors, such as

changing organizational investment priorities and resources and fluctuations in customer demand. Companies

typically reported that they anticipate using their unused flexibility provisions later in their permit terms or
31

following permit renewal. For example:

• During the first 14 months under the flexible permit, Saturn did not implement the advance approval

provisions which allow construction of new emissions sources (i.e., permit condition B.10.2). Saturn

and TDEC anticipate that this provision will be useful in the future to accommodate changes

associated with vehicle model year changeovers.

• As of December 2001, the Weatherford site had not implemented two changes that were specifically

described in the advance approved minor NSR change provisions (i.e., permit condition Section H,

Subsection 2, Requirement 1b and 1c). Imation indicated that the source may undertake these

changes in the future.

The flexible permits appear to accommodate a substantial number of advance approved changes while

providing sufficient clarity to support practical enforceability.

The permitting authorities indicated that the actual changes made under the flexible permits were fully

consistent with those envisioned during permit design and that the changes were made in a manner consistent

with the constraints imposed by the permits. The flexible permits vary in the degree of specificity with which

advance approved modifications are described in the permits. Each of the permits, however, imposes clear

boundaries for determining which changes would not be covered under the advance approval conditions.

Changes triggering new applicable requirements, including new or modified MRR requirements, that were

not already addressed in the permit, are subject to conventional permitting and approval procedures.

• Changes advance approved in Intel’s Title V permit were clearly defined categorically and by

conditions documented in the permit. For example, advance approved changes could only be made

at the stationary sources comprising Emissions Unit 1 (EU1); construction of entirely new stationary

sources are not covered; changes to a pollution control device are not covered; and no new applicable

requirement can be triggered by an advance approved change. In addition, advance approved

changes must not result in source non-compliance with the VOC RACT requirement and the source

PSELs.

• 3M’s flexible permit contained specific categories of changes advance approved by the permit, such

as updating drive mechanisms and electrical components on coating equipment and replacing or

upgrading coater ovens, provided that 3M satisfied specific requirements described in the permit (e.g.,

remain below emissions caps and meet applicable New Source Performance Standards). If 3M

desired to make a change not specifically covered by the listed advance approved categories of

changes, they would be required to proceed with a conventional permitting process for the

modification, unless MPCA agreed that the change was “consistent with” the changes advance

approved by the permit.

• For DaimlerChrysler, some changes made under the flexible permit were not fully advance approved,

but were eligible to go through an expedited review process if all applicable requirements were met

and if no public hearing was requested during the public notice period.

Several companies reported that they did feel a need to contact their permitting authority during the permit

term to discuss or clarify whether a particular modification would be allowed under the advance approval

provisions in their pilot permit.

• 3M indicated that on two or three occasions, they contacted MPCA to discuss planned changes that

were not explicitly addressed by the permit but appeared to be covered by the “consistent with”
32

phrasing included in the permit. In each of these instances, MPCA indicated that the planned change

would not require a permitting action.

• On one occasion, Lasco filed a Notice of Construction permit application to change the venting of

the regenerative thermal oxidizer (RTO). After the application was submitted, OAPCA informed

Lasco that the proposed change was covered by the advance approval provisions and the application

was unnecessary.

Some companies indicated the flexible permits have facilitated an increase in the rate and a shift in

the type of changes made, when compared to a conventional permitting approach.

Some of the companies indicated that they would not have made certain changes, had such changes not been

advance approved in their flexible permit. They typically stated that the time frames associated with

conventional minor NSR and other types of air permitting, as well as uncertainty regarding the applicability

of certain regulatory requirements, often creates sufficient “friction” (e.g., cost, delay, and risk) to make a

proposed change unattractive. The EPA found evidence that proposed P2 changes are particularly vulnerable

to being shelved under a conventional permitting approach, since they often involve iterative experimentation

that could heighten regulatory transaction costs. In addition, P2 modifications often receive lower

organizational investment priority unless they simultaneously address an important operational need. Advance

approval provisions facilitated research and development into alternative processes. When research

uncovered a promising process technique, the company could implement the change without waiting for caseby-case approval and permitting.

• Intel reported that successful pollution prevention initiatives directed at ongoing processes can be

iterative in nature. The company typically conducts a series of experiments on its manufacturing

process to see if the changes produce the desired results. Many of these individual changes could

be subject to construction permitting actions, thus imposing a stop-and-go aspect to the experimental

process. Intel indicated that, under such conditions, operations personnel might well view

experimentation for purposes of pollution prevention as being very disruptive of the manufacturing

process and therefore recommend that it not proceed.

• Lasco reported that the company is inclined not to make changes that have potential to trigger

additional air permitting requirements, attributing this reluctance to potential costs, delay, and

uncertainty associated with permitting actions. For example, Lasco installed more complex putty

systems for attaching boards to the inside of bath units at other Lasco facilities to prevent the systems

from triggering air permitting requirements. The advance approval provisions enabled Lasco to

incorporate a new putty station design into the product production line at the Yelm site in a

streamlined manner, resulting in material savings and VOC emissions reductions.

Finding 6: The flexible permits enhanced information sharing between the

companies and permitting authorities.

All six permitting authorities stated that the flexible permits enhanced their overall understanding of company

activities and emissions as compared to conventional permitting approaches. The flexible permits did,

however, alter the timing and format of certain types of information, such as information regarding changes

implemented under advance approval provisions, when compared with information available under

conventional permits. In several areas, such as plant-wide emissions performance and P2 performance, the
33

flexible permits typically required information that is not required by conventional permits.

The flexible permit development process provided permitting authorities with a clearer understanding

of the maximum plant-wide emissions levels anticipated during the permit terms.

The flexible permits provided clear information regarding the maximum level of emissions that would be

allowed during the permit term, in the form of established emissions caps. If a source desired to exceed its

emissions cap, it would thereafter be required to undergo a major NSR permitting process that would require

public comment. For example, in accepting the PTE cap of 249 tons/year of VOC emissions, Lasco had to

reduce its actual emissions, providing assurances to local residents that plant-wide emissions would thereafter

be held relatively steady, despite company plans to increase production during the permit term.

During permit development, companies were required to share more information regarding the type

of changes anticipated during the permit term, providing a more comprehensive, up-front picture of

anticipated operational activities and associated environmental performance than a conventional

permitting process.

The permitting authorities believe that the flexible permit development process, through the discussions of

advance approved changes, provided them with a clear advance understanding of the types of modifications

that the companies anticipated during the permit term. Under a conventional permitting approach, change

information would typically only be available in a more fragmented, incremental manner, as companies

pursued approval to make changes on a case-by-case basis. Under the flexible approach, applicable

requirements associated with each advance approved change are identified up-front in the permit, affording

a long-term view of potential applicable requirements, resulting emissions control requirements, and

environmental outcomes. This enabled the permitting authority to have a more comprehensive picture of

changes, and associated environmental performance outcomes, that would likely occur over the permit term

(e.g., 5 years).

During permit implementation, information regarding changes made by the companies using the

advance approval provisions varied among the flexible permits but was generally comparable to or

greater than that produced under a conventional permitting process; the flexible permits did alter the

timing and format of change information, as compared to conventional permitting approaches.

Variability is evident across the six flexible permits with respect to how advance approved changes were

required to be documented and reported. Most of the flexible permits required some form of notices and/or

summary lists of advance approved changes made to be submitted to the permitting authority, in addition to

maintenance of an on-site log of advance approved changes. At one end of the range, 3M was required to

submit advance notices and post-construction notices to MPCA for each change implemented using the

advance approval provisions (note: during the permit term, MPCA eliminated the advance notice requirement,

streamlining relevant information into the post-construction notices). 3M was also required to submit annual

summaries of advance approved changes made during the year. At the other end of the range, Intel’s permit

did not require the company to report information on specific changes implemented using the advance

approval provisions for a given six-month period if the maximum capacity to emit for the source declined

through P2 or other means during this period, when compared to the previous six-month period. Saturn’s

permit requires the source to register new advance approved emissions sources with TDEC, although

reporting on specific advance approved changes to existing emissions sources listed in the permit is not
34

required. Under the Intel and Saturn pilot permits, it is likely that less information on certain specific advance

approved changes was available to the permitting authorities, when compared with a conventional permitting

approach, in cases where such changes would have triggered the need for a NSR permit application. This

assessment assumes that these advance approved changes would have been undertaken by the companies

under a conventional permitting approach. The permitting authorities indicated that the information available

under the flexible permits was, at a minimum, sufficient to verify compliance with all applicable requirements

and to keep them appropriately informed of source activities.

Permitting authorities generally indicated that some form of recordkeeping and reporting regarding source

implementation of advance approved changes is important. Inspectors with DNREC and OAPCA reported

that it is helpful to have information on changes made using advance approval provisions during their

inspections, whether this information was reported in advance or maintained in logs at the source.

Under a conventional permitting approach, a company typically submits a notice of construction or other such

permit application to the permitting authority for approval prior to implementing a change that triggers NSR.

These applications typically include specific information on proposed modifications. In addition, companies

are generally required to submit a notice of completion to the permitting authority once the company has

finished “construction” of the change. While the same type of change information is typically made available

under a flexible permit, the timing and format of the information differs from that required under a

conventional approach. First, the advance approval provisions in flexible permits provide some information

at the beginning of the permit term regarding specific changes or categories of changes that are anticipated

during the permit term. No such advance information is required under conventional permitting approaches.

Second, under flexible permits, companies generally do not submit permit applications for individual changes,

unless the changes are only partially advance approved. Instead, information on actual changes made that

fit the advance approval descriptions is typically provided to the permitting authority soon after the change

is implemented, typically in the form of a post-construction notice. In addition, most pilot sources operating

under flexible permits are required to record information on changes made using the advance approval

provisions in an on-site log that is available to agency inspectors. Third, the flexible permits frequently require

some form of aggregated summary reporting on changes made using the advance approval provisions. The

companies are typically required to list all advance approved changes made during a particular reporting

period, such as the past month, quarter, or year. Permitting authorities indicated that the summary reporting

further helps to create an aggregated picture of changes made at the source, when compared with a series

of case-by-case permit applications in the agency file.

The section below discusses more detail regarding the timing, type, format, and accessibility of change

information available under the flexible permits.

• 3M’s permit required the company to provide written notice to MPCA for each change implemented

by the plant that utilized the advance approval provisions in the permit. A written notice was due to

MPCA ten days prior to beginning actual construction and a subsequent notice was required to

MPCA two weeks after commencing operation. In May 1996, MPCA representatives reported that

the agency believed that the post-commencement notice for changes was sufficient to provide the

agency and the public with a documented record of advance approved changes actually made at the

source. 3M was also required to submit an annual summary report of advance approved changes

implemented during the past year.

• Imation is required to submit a notice of completion 30 days after the completion of construction of

advance approved changes.
35

• Lasco’s flexible permit required the company to submit notices of construction completion to

OAPCA for each advance approved change undertaken. Lasco is also required to maintain an onsite log of changes implemented under the advance approval provisions. The permit also requires

Lasco to submit a semi-annual summary of advance approved changes undertaken.

• DaimlerChrysler is required to submit monthly reports listing changes made using the advance

approval provisions during the prior month. The NAP is also required to maintain an on-site log of

changes made under these provisions and to submit an annual summary list of advance approved

changes implemented.

• Saturn is required to register with TDEC new emissions sources constructed under the advance

approval provisions of the permit. This registration includes the submission of a completed application

form, a brief process description, documentation of BACT or minor source BACT (for sources below

established emissions threshold levels) for the new source, and periodic monitoring parameters for

any control equipment. The permit also requires Saturn to submit a plan to assess the emissions of

toxic, volatile pollutants from the source within two years of permit issuance.

• Intel’s permit required the company to submit a list of advance approved changes made during each

six-month period, if there was a net increase in the maximum capacity to emit at the source for that

period, when compared with the maximum capacity to emit for the previous six-month period. This

occurred once during the five-year permit term.

Several permitting authorities reported that they received more change information from companies operating

under the flexible permits than would have been available under a conventional permitting approach. These

permitting authorities reported that the flexible permits encouraged sources to report on operational and

equipment changes, even if these changes would not have triggered minor NSR applicability under a

conventional approach. Since the advance approval provisions removed the need to make case-by-case

determinations of NSR applicability for individual changes implemented during the permit term (companies

only needed to determine whether the changes satisfied the advance approval criteria specified in the permit)

companies tended to report more changes. For example, 3M indicated that the company viewed the permit

as a valuable asset, and they indicated that they desired to protect this asset by ensuring a high level of

communication with MPCA. Some permitting authorities indicated that the conventional NSR program may

sometimes create disincentives for companies to report changes for which the applicability of NSR is

uncertain, since such discussions with the permitting authority to determine applicability could prove time

intensive and lengthy. Permitting authorities indicated that the flexible permits remove any incentive for

companies to “push the interpretation” of applicability determinations in a direction that would result in less

change reporting.

• MPCA representatives reported that 3M reported information on changes that would not have

triggered minor NSR applicability under a conventional permitting approach, providing MPCA

inspectors and the public with more information on changes implemented at the source.

• DNREC inspectors indicated that DaimlerChrysler reported information on changes beyond those

that would have been required under a conventional permitting approach. The inspectors indicated

that this enhanced their understanding of company activities.

During permit implementation, the flexible permits required the provision of more comprehensive and

useful information on plant-wide emissions performance to permitting authorities.

Permitting authorities reported that the plant-wide emissions reporting required under the flexible permits

provides more comprehensive and easy-to-understand information on actual environmental performance
36

during the permit term. In some cases, such as for the DaimlerChrysler and 3M permits, the frequency of

emissions reporting information was also greater than that typically required under a conventional permit.

Even when more frequent emissions reporting was not required, however, the companies were required to

maintain current emissions calculations on-site to demonstrate compliance with the established plant-wide

emissions caps. The flexible permits all require companies to make these emissions calculations available to

permitting authority inspectors and personnel upon request. Conventional permitting approaches typically

require preparation of an emissions inventory by the source on an annual basis.

• DaimlerChrysler is required to submit monthly emissions reports to DNREC that include

comprehensive, plant-wide information on VOC and NOx emissions. The monthly frequency of these

reports is greater than what would typically be available under conventional permits. 

• The 3M flexible permit required the St. Paul Tape Plant to submit quarterly reports to MPCA on the

source’s plant-wide emissions. The permit required 3M to report on all plant emissions units,

including those that had been "grandfathered" by the Clean Air Act. These previously

“grandfathered” emissions units were also required to be included in the plant’s emissions monitoring

activities and enforceable compliance limits. MPCA indicated that daily and annual rolling totals of

VOC emissions provided near "real time" information on actual plant-wide emissions.

• The Intel Title V permit retained Intel’s original PSELs, pollutant-specific, plant-wide short-term and

annual caps on actual emissions. Intel submitted semi-annual monitoring reports to Oregon DEQ

containing semi-annual compliance certification, emissions statements, and excess emissions upset

log. Since Oregon regulation required PSEL, Oregon DEQ stated that their emissions reporting was

very similar to that required by other Title V facilities in the State.

• Oklahoma DEQ indicated that Imation’s flexible permit requires annual emissions reporting, similar

to that required under a conventional Title V permit, including annual compliance certification and an

annual emissions inventory. Oklahoma DEQ indicated that the flexible permit incorporates a

previously “grandfathered” source that would not have been included in compliance reporting under

a conventional permit.

• Under its flexible PSD permit, Saturn is required to monitor and log monthly plant-wide emissions

data which are maintained on-site and available for TDEC inspection. Saturn and TDEC indicated

that plant-wide emissions reporting will be required in the forthcoming Title V permit for the source.

During permit implementation, four of the six flexible permits required companies to share information

regarding P2 activities and performance with the permitting authorities. Conventional permits do not

typically require companies to share P2 information with the permitting authority or public. 

The flexible permits developed for Intel, Imation, and Lasco under EPA’s P4 program each require the

companies to implement P2 programs. The companies were required to report information on their P2

programs to the permitting authority, in addition to periodic reports on P2 activities, accomplishments, and

performance. DaimlerChrysler is also required to submit routine reports documenting P2 activities.

• Imation’s implementation of a P2 program is voluntary, but there is an explicit link in the permit

between adoption of an approved pollution prevention program and the BACT determination for

advance approved changes. Therefore, to access advance approvals that require BACT, Imation

must have an approved P2 program in place, which Imation did implement during the permit term.

The Lasco permit contained a similar connection between BACT and a P2 program. The flexible

permit requires Imation to submit an annual P2 executive summary describing the pollution prevention

activities and programs adopted on site, as well as progress against a P2 target of 10 percent per unit
37

emissions reduction during the permit term.

• Intel was required to submit an annual P2 progress report to Oregon DEQ, and a final report at the

end of the permit term.

• DaimlerChrysler is required to report annually on their P2 activities as part of the annual compliance

certification.

• Lasco is required to submit an annual P2 progress report, which documents P2 techniques, goals and

accomplishments. Additionally, prior to the end of the third and fifth year of the permit term, Lasco

is to submit a report demonstrating compliance with the P2 Program.

Finding 7: The flexible permits generally provided to the public equivalent or

greater information than conventional permits.

The EPA’s examination of the public record and the availability of information to the public during the

development and implementation of the flexible permits indicates that the permits shifted the timing, type, and

format of information to the public on emissions performance, operational and equipment changes, and P2

activities. As discussed in Finding 6 above, the six permits vary in the specific format, timing, and availability

of certain types of information required, particularly related to certain specific advance approved changes

implemented under the permits. In areas such as plant-wide emissions performance and P2 information, most

of the flexible permits clearly increased the availability of information to the public. In all six cases, the

permitting authorities indicated that, on balance, the flexible permits improved the availability of information

to the public.

During permit development, the flexible permitting efforts followed or exceeded the permitting

authorities’ conventional communications and public involvement procedures.

Permitting authorities indicated that the availability and flow of information to the pubic during the

development of the flexible permits satisfied or exceeded all requirements associated with the agency's

standard operating procedures for permit development. This procedure typically includes making the draft

permit available to the public at the permitting authority offices and at a local public library, publishing notice

of the draft permit and public comment opportunities in one or more newspapers, holding a public comment

period (e.g., typically 30 days), and conducting a public hearing if requested by the public. Some permitting

authorities also publicize draft permits on their website or through other communication mechanisms.

In four of the flexible permit development efforts, including the three permits developed under the EPA’s P4

program, the permitting authorities and companies voluntarily conducted one or more public meetings (i.e.,

in addition to any opportunity to hold a public hearing as part of the formal review process). While these

meetings were not requested by the public, the permitting authorities and companies believed that the

innovative nature of the permits increased the importance of taking active steps to inform local communities

about the efforts. In addition, several of the permits experienced local media coverage about the innovative

nature of the permits.

• At the beginning of the flexible permit development effort in 1996, citizens of Yelm, Washington did

not view Lasco as a “good cooperate neighbor” due to past odor issues. The subsequent level of

information flow to the public surrounding the Lasco permit development consisted of several

meetings, many public notices, and extensive communication between Lasco and OAPCA. At the
38

end of the permit development process, the Sierra Club submitted a letter supporting Lasco's flexible

permit and thanking EPA Region 10, OAPCA, and Lasco for their proactive efforts to involve the

community in the permit development process.

• Companies and permitting authorities involved in the development of the Imation, 3M, and Intel

flexible permits each deemed an up-front public meeting in conjunction with the public comment

period to be helpful in communicating to the public about the flexible permits, due to their innovative

nature. In addition, the companies and permitting authorities were interested to understand early on

any potential public questions or concerns about the permits. No adverse comments were

subsequently received from the public for any of these permits.

The flexible permit development process increases the availability of information to the interested

public regarding anticipated changes and emissions levels, as compared to a conventional permit

development process.

As discussed in Finding 6 above, the flexible permit development processes provided clear information to the

public regarding the maximum level of source emissions that would be allowed over the permit term, in the

form of established emissions caps. Permitting authorities indicated that the emissions cap requirements in

the draft permits and communicated during public meetings (when held) provide useful information to

interested members of the public. If a source desires to exceed its emissions cap, it would thereafter be

required to undergo a major NSR permitting process that would require public comment. The Lasco example

demonstrates how such up-front information on total allowable plant-wide emissions can increase public

understanding of the permit and anticipated environmental performance. In accepting the PTE cap of 249

tons/year of VOC emissions, Lasco had to reduce its actual emissions, providing assurances to local residents

that emissions would thereafter be held relatively steady, despite company plans to increase production during

the permit term. This awareness allayed one of the key concerns voiced by members of the Yelm

community.

During development of the flexible permits, more information was available to interested members of the

public regarding the type of changes the sources anticipated making during the permit term, when compared

to a conventional permit development process. As discussed in Finding 6, the permitting authorities believed

that the flexible permit development process, through the discussions of advance approved changes, provided

them and interested members of the public with a clear advance understanding of the types of modifications

that the sources planned to make during the permit term. Under a conventional permitting approach, change

information would typically only be available in a more fragmented, incremental manner, as companies

pursued approval to make changes on a case-by-case basis. Under the flexible approach, applicable

requirements associated with each advance approved change are identified up-front in the permit, affording

a long-term view of potential applicable requirements, resulting emissions control requirements, and

environmental outcomes. This enabled the permitting authority and interested members of the public to have

a more comprehensive picture of changes, and associated environmental performance outcomes, that would

likely occur over the permit term.

During permit implementation, the flexible permits varied in the availability of information to the

public about plant-wide emissions, operational and equipment changes, and pollution prevention

activities; all permitting authorities indicated that, on balance, the flexible permits enhanced the

availability of information to the public as compared to information typically available under

conventional permitting approaches.
39

During permit implementation, the flexible permits required the provision of more comprehensive and, from

several of the permitting authorities’ perspectives, more useful information on plant-wide emissions

performance to permitting authorities. As discussed in Finding 6, permitting authorities reported that the plantwide emissions reporting required under the flexible permits provides more comprehensive and easy-tounderstand information on actual environmental performance during the permit term. In some cases, such

as for the DaimlerChrysler and 3M permits, the frequency of emissions reporting information was also greater

than that typically required under a conventional permit. In other cases, such as for Imation and 3M, the

flexible permits required the companies to report emissions from previously “grandfathered” emissions

sources in their plant-wide emissions reporting. For all the flexible permits, the reports containing information

on plant-wide emissions were available to the public in the permitting authorities’ files.

The EPA found that there are a variety of techniques for making information available to the public regarding

changes made using the advance approval provisions. These techniques include advance notices, postconstruction notices, change registration, and periodic summaries of changes made (e.g., monthly, quarterly,

or annual). For changes that do not meet the advance approval provisions, or that would cause a company

to increase its emissions caps, the company would be required to undergo a conventional permitting process

that would include submission of required application materials and completion of required public notice and

comment procedures. When combined with the information on anticipated changes identified during the

permit development process, as well as information on plant-wide emissions and P2 activities, the permitting

authorities believe that flexible permits ensure the flow of sufficient information to enable the permitting

authorities to effectively enforce for all applicable requirements, to ensure that air quality is protected in

accordance with their SIPs, and to ensure consistency with the Clean Air Act’s intent to provide for effective

opportunities for public input into air permitting decisions.

As discussed in Finding 6, there was variability in the reporting requirements for changes implemented using

the advance approval provisions. For four of the flexible permits, including those for 3M, DaimlerChrysler,

Imation, and Lasco, the EPA found that approximately equivalent information on advance approved changes

made was available to the public under the flexible permits, as compared to what permitting authorities

indicated would have been available under conventional permitting approaches. In these cases, the timing

and format of the advance approved change information was shifted when compared to conventional

permitting approaches. In general, more general information on advance approved changes was available

up-front during permit development, and more detailed information on specific changes made was available

in the form of notices and lists of changes made, as opposed to minor NSR construction permitting

applications. In addition, MPCA and DNREC found that the companies reported changes in addition to those

that would likely have triggered minor NSR permit applications under a conventional permitting approach.

For the Intel and Saturn flexible permits, as discussed in Finding 6, more general information on anticipated

changes was available up-front during permit development, but less information on individual changes

implemented using the advance approval provisions was available during permit implementation when

compared to a conventional permitting approach, assuming that these changes would have been made under

a conventional permitting approach.

During permit implementation, four of the flexible permits required companies to report information regarding

P2 activities and performance to the permitting authorities. This information is available to interested

members of the public through the permitting authority files for these sources. P2 information would not

typically be available to the public under a conventional permitting approach.

• The Imation pilot permit required the company to submit annual P2 reports to Oklahoma DEQ

describing the P2 activities and programs adopted at the site, as well as progress against an
40

established P2 target. This information is available to the public in the permitting authority’s files.

• Intel was required to submit an annual P2 progress report to Oregon DEQ, and a final report at the

end of the permit term. This information is available to the public in the permitting authority’s files.

• DaimlerChrysler is required to report annually on their P2 activities. This information is available to

the public in the permitting authority’s files.

• Lasco is to submit an annual P2 progress report, which documents P2 techniques, goals, and

accomplishments. Additionally, prior to the end of the third and fifth year of the permit term, Lasco

is to submit a report demonstrating compliance with the P2 Program. This information is available

to the public in the permitting authority’s files.

Finding 8: The flexible permits produced or are likely to produce net financial

benefits to companies and permitting authorities.

Companies and permitting authorities reported that the flexible permits have resulted in net financial benefits,

or that they anticipate that this will be the case. Companies and permitting authorities indicated that initial

permit development costs exceeded those required to develop conventional permits, due to factors related to

the pilot nature of the permits, as well as to factors inherent to developing flexible permitting techniques. In

each case, however, companies and permitting authorities reported that the flexibility provisions have

decreased, or are expected to decrease, the administrative costs of operating under the permit sufficiently

to more than offset the higher initial permit development costs.

Permit development costs for the flexible permits were significant, but these higher costs were largely

attributed to the pilot nature of the permits.

Companies and permitting authorities involved in the flexible permitting efforts reported that the costs,

primarily resulting from staff time devoted to development of the flexibility provisions, were greater than those

typically experienced in the development of conventional permits. 

• MPCA representatives estimated that about 1000 hours of MPCA staff time were devoted to

development of the permit. MPCA representatives noted that a primary factor contributing to the

length of the permit development was that this was the first flexible permit developed in Minnesota,

as well as one of the first developed and issued in the U.S.

• The development of Lasco’s flexible Title V permit spanned approximately 16 months, from initiation

of discussions (e.g., P4 group discussions) until the permit was issued. However, in addition to this

being a team-oriented “demonstration” project necessitating additional review and public participation

(see below), this was OAPCA’s first Title V permit. OAPCA representatives reported that these

factors contributed to the overall length of the permit development process. In the future, OAPCA

indicated that flexible Title V permits will likely take only slightly more time to develop and issue than

conventional Title V permits (e.g., approximately 180 hours versus 160 hours).

Permitting authorities indicated that a substantial amount of the higher permitting costs were attributable to

the pilot nature of the permits. These pilot costs stemmed partly from the need for frequent conference calls

or meetings between the permitting authorities, the EPA Regional Offices, and the EPA headquarters to

ensure the flexible permitting techniques would be approved by the EPA in the absence of guidance on

flexible permitting. Additional costs also resulted from the fact that each of the six flexible permits were the

first developed under these permitting authorities’ jurisdictions, and there was limited national experience with
41

specific flexibility provisions from which to draw upon. Permitting authorities indicated that the pilot-related

transaction costs would likely be reduced significantly or eliminated if the EPA were to issue guidance and/or

rulemaking that clarified the flexible permitting approaches and techniques that are acceptable to the EPA.

Some portion of the higher permit development costs, however, were associated with tailoring of flexible

permitting techniques to address the specific applicable requirements, needs, and circumstances of the

sources. Permitting authorities and companies indicated that these costs would be incurred in the

development of any new permit containing flexibility provisions, even if the use of flexible permitting

techniques becomes routine and is supported by EPA guidance or rulemaking. For example, communications

between the companies and permitting authorities regarding the changes that companies’ anticipate making

during the permit term are typically necessary to develop advance approval provisions. Other flexible

permitting techniques, such as the development of replicable operating and testing procedures and streamlining

of applicable requirements, also entail more significant interactions between a company and permitting

authority during permit development.

• 3M and MPCA reported that additional time was required during permit development to develop the

advance approval descriptions. This involved discussions to identify the specific changes and

categories of changes that 3M anticipated making during the permit term.

Companies and permitting authorities that have renewed their flexibility provisions in subsequent permits

indicated that the renewal costs have been minimal, as compared to costs required under a conventional

permit renewal process. While some advance approval provisions may need to be updated at permit renewal,

to accommodate new change needs anticipated by the company over the subsequent permit term, this process

generally requires significantly less company and permitting authority resources than were required for the

initial development of flexibility provisions for the source. This means that potential financial benefits for

companies and permitting authorities can be extended to subsequent permit terms.

• Oregon DEQ incorporated many of Intel’s flexibility provisions into the company’s subsequent

synthetic minor air permit without requiring additional permitting authority resources.

• DNREC reported that it was able to incorporate the flexibility provisions in DaimlerChrysler’s original

pilot flexible permit into the company’s Title V air operating permit without requiring resources

beyond those necessary to issue a conventional Title V permit.

Companies and permitting authorities reported that they experienced financial benefits from

implementation of the flexible permits that more than offset the higher up-front permit development

costs.

Companies and permitting authorities reported that financial benefits arose during permit implementation from

the reduced administrative costs associated with company operational and equipment changes made under

the advance approval provisions. Companies indicated that the advance approval provisions reduced the staff

time and resources necessary to implement changes covered by these provisions. Company personnel found

that they did not need to perform detailed applicability determinations for individual changes, provided that the

changes satisfied the advance approval conditions listed in the permit. Such applicability determinations for

advance approved changes were performed during permit development and clarified in the permit.

Companies indicated that this streamlined applicability determination process and the improved certainty

related to how changes would be addressed under the permit reduced the companies’ staff time needed to

process changes. Further savings resulted from the companies’ reduced need to prepare applications for
42

construction permits and/or permit modifications for individual changes, due to the advance approval

provisions. Companies indicated that the time necessary to complete permitting authority notifications of

advance approved changes and/or to record such changes in on-site logs was significantly less than the staff

time necessary to prepare permit applications under a conventional permitting approach.

• DaimlerChrysler representatives estimated that the flexible permits save the company significant staff

time that would have been associated with applicability determinations and permit actions for changes

made using the advance approval provisions. They estimated that approximately 505 hours of staff

time were saved under the initial flexible permit. These savings are projected to increase in the

future as the company makes more changes utilizing the advance approval provisions in the permit.

• Under a conventional permit, Intel would have needed to prepare approximately 150 to 200 notice

of construction applications per year (that were not required under the flexible permit). Intel

estimated that each application would have required an average of approximately 8 hours, resulting

in 1,200 to 1,600 hours of staff time per year.

• Lasco estimated that to execute a construction permit requires approximately 50 staff hours.

Additionally, to process a permit modification, Lasco would need to submit a pubic notice (with an

estimated cost of $350) and to hold a public hearing (with an estimated cost of $400). For all five

changes made using the advance approval provisions, Lasco estimated a cost savings of more than

$20,000.

Permitting authorities also reported that they have experienced, or anticipate experiencing, administrative cost

savings during permit implementation.

• MPCA representatives indicated that they view flexible permits as saving agency resources by

reducing the number of case-by-case change reviews and permitting actions. MPCA estimated that

each of their minor NSR permit actions (if straightforward) require an average level of effort

equivalent to approximately $1,000, and 3M estimated that approximately 15 to 20 of the 34 changes

undertaken likely would have required a minor permitting action. From MPCA’s standpoint then, the

flexible permit provided an administrative savings benefit of between $15,000 and $20,000. Further,

3M indicated at least two of their changes may have been major permit actions requiring

approximately 100 hours of processing by MPCA. At $125 per hour, this would represent an

additional savings to MPCA of $25,000.

• Oklahoma DEQ representatives stated that the Imation permit has saved time for DEQ personnel,

enabling them to “operate more effectively” with their limited staff. They indicated that most of the

time savings result from the reduced need for administrative processing of case-by-case construction

permitting actions and air toxics approvals. DEQ representatives stated that they have identified at

least five changes made under the advance approval provisions that would have required a permitting

action under a conventional permitting approach, but that only required written notices under the

flexible Title V permit. They indicated that, minus the flexibility provisions, each of these permitting

actions would have required a 45-day review and approval process that could have extended well

beyond that in some cases. They further indicated that this resource savings enables DEQ to focus

scarce resources on inspections and other environmental and permitting priorities.

• The Intel permit saved Oregon DEQ significant staff time associated with processing notice of

construction applications from Intel. Intel estimated that in the absence of the flexible permit, Oregon

DEQ would have needed to process approximately 150 to 200 additional notice of construction

applications per year. Even at a very low estimate of two staff hours per application, the staff time

implications are significant (e.g., 300 to 400 hours).
43

• During the flexible permit term, Lasco made five advance approved changes that would have

otherwise triggered case-by-case minor NSR permit actions. OAPCA estimated that Lasco’s

flexible permit saved them approximately 20 to 40 staff hours per advance approved change. The

time savings includes time spent drafting a permit to construct, ensuring NAAQS compliance,

modifying the Title V permit, and conducting the change-specific public review process. At $75/hour,

the estimated administrative costs saved by the flexible permit for all five advance approved

conditions ranges from $7,500 to $15,000.

• TDEC reported that the Saturn flexible permit has reduced agency paperwork associated with

processing individual construction permit applications and permit modifications, allowing agency staff

to focus on higher environmental priorities. They further indicated that the permit saved TDEC

significant staff time associated with processing notice of construction applications from Saturn. The

permit eliminates the need for full minor NSR permitting. Traditionally, permitting for minor NSR

takes approximately 24 to 40 staff hours, plus issuance of a public notice and a town meeting or

public hearing. This process has been streamlined to a State control technology review for new unit

additions not subject to major BACT. TDEC representatives believe that during the life of the permit,

TDEC will need to invest less hours of staff time to address the future air permitting needs associated

with the Saturn plant, due to the anticipated future use of the advance approval provisions. 

It should be noted that companies and permitting authorities cautioned that it is difficult to precisely estimate

cost savings and financial benefits associated with flexible permit implementation, since it involves comparison

with hypothetical experience under a conventional permitting approach. Companies and permitting authorities

noted that the flexible permit provisions sufficiently altered the applicability determination for individual

changes so as to make it difficult to retrospectively determine the precise level of effort and timing that would

have been necessary to accommodate the changes under a conventional permitting approach. That said,

companies and permitting authorities indicated that the estimated financial benefits identified in this report

provide a reasonable approximation of the financial benefits that resulted from implementation of the flexible

permits, compared to those costs that would likely have been expected had the companies been operating

under conventional permits.

In additional to administrative cost savings, several companies identified financial benefits stemming from the

ability to implement advance approved changes without the potential delay associated with conventional

permitting time frames. Several companies indicated that this streamlined ability to implement advance

approved changes improved the predictability of change implementation time frames for project planning and

avoided what can be substantial opportunity costs. They further reported that this predictability and

elimination of potential delay from air permitting provided important competitive advantages that enabled them

to compete more effectively.

• From 3M’s perspective, the flexible permit allowed the company to proceed as needed with

operational change. This was critical from two perspectives: it allowed the plant to avoid acting as

a bottleneck along the critical path of any particular product line that would be moving among 3M

plants; and it allowed the plant to remain highly responsive to its marketplace and avoid either lost

sales and/or permanent loss of market share. 3M did indicate that the changes made that potentially

involved PSD permitting likely would not have been undertaken if handled on a conventional basis.

• DaimlerChrysler representatives indicated that the permit has increased the company’s ability to

respond to short-term changes in market demand, as well as to accommodate the tight project time

lines associated with periodic model changeovers. DNREC and DaimlerChrysler representatives

reported that under a conventional permitting approach, some of these changes would likely have

triggered case-by-case applicability determinations and potential permitting actions that could have
5

Estimates from Intel of the number of changes made per year under the flexible permit that would have

triggered the need for notice of construction approval under a conventional permit.

6Under Oregon rules, ODEQ has up to 60 days to process notice of construction approval applications. 

Twenty-one days was selected as a reasonable estimate of the average actual time associated with receiving notice

of construction approval from ODEQ.

44

extended to 6 to 9 months each.

• The advance approved changes in Intel’s flexible permit likely saved the Intel Aloha plant hundreds

of business days associated with making operational and process changes to ramp up production for

new products, respond to market demands, and optimize production processes. Industry estimates

of the opportunity costs of production downtime and time delays run as high as several million dollars

in just a few days due to lost sales to computer makers and other factors. The estimated 150 to 200

changes per year5, combined with the Oregon DEQ approval time frame of up to 60 days per

change6, indicate that there would likely have been significant delay under a conventional permitting

approach. Even if few delays would have resulted in production downtime or missed market

opportunities, the costs would likely have been significant, as many of the changes improved the costcompetitiveness of Intel’s products. Intel representatives indicated that it is likely that the impact of

continued time delays would be to redirect Intel’s production investment and operating facilities to

locations more conducive to change.

• Imation representatives reported that the flexibility provisions in the Title V permit enabled the

company to experiment with new materials and to introduce the production of new products at the

Weatherford plant with minimal delay associated with air permitting and material toxicity

assessments. Under the flexibility provisions, Imation is authorized to use alternative raw materials

without receiving case-by-case approval or permit modifications that typically can take two to three

months, provided that they follow established procedures and ensure emissions remain below

specified limits. Even for materials for which Oklahoma had not previously reviewed, DEQ agreed

to complete toxicity evaluations and establish MAAC limits within 72 hours of receiving a request

from Imation. Imation representatives stated that these streamlined administrative procedures for

addressing Oklahoma’s air toxics requirements have eliminated air permitting delay associated with

raw material changes. Among other product transitions, the flexibility provisions in the Title V permit

have facilitated Imation’s development of digital proofing films for graphic design applications. In

addition to various product quality benefits, digital proofing films also require fewer coating layers

during manufacturing than conventional proofing films. This results in fewer VOC emissions from

solvents per unit. While customer demand for digital proofing materials is increasing, it is likely to

take several years before digital proofing technology is in widespread use, due to the cost of

converting to digital proofing hardware.

• Lasco engaged in a series of advance approved changes, updated its emission factor, and voluntarily

installed an RTO. These actions combined to create “head room” under Lasco’s cap, which Lasco

then used to increase production. Lasco indicated that typically (and as reflected by the Yelm plant’s

lack of operational change prior to the flexible permit and experience at other Lasco facilities) the

company is very averse to making changes that trigger permitting actions. At most, they wait to

undertake such changes at the time of permit renewal. Contrary to its typical corporate behavior,

Lasco Yelm engaged in a series of modifications that created the opportunity to increase production

from 126,045 units/year (in 1997) to 132,548 units/year (in 2000) generating a significant annual

increase in profit. In 2001, after the RTO was installed, Lasco decreased emissions per unit further

to 3.13 lbs./unit, allowing production to increase to 147,429 units and reducing costs associated with
45

styrene loss.

• Saturn indicated that the flexible permit was a principle factor in General Motors’ selection of the

source to manufacture the L850 engine, leading to the creation of 700 jobs. Saturn was awarded the

contract primarily because it could implement the necessary changes within 24 months and

accommodate future changes with minimal delay. The flexible PSD permit is enabling Saturn to add

and modify coating, assembly and machining lines in a timely manner, while ensuring that best

available pollution control technologies are installed and that air emissions remain under approved

limits. Using a combination of the PAL emissions caps and advanced approvals, the flexible permit

will allow Saturn to upgrade the plant over the next few years, with minimal delays, to produce

several new vehicles, including Saturn’s new fuel-efficient sport utility vehicle, the Saturn VUETM.

Saturn representatives stated that the flexible permit avoids a potential NSR backlog associated with

the conventional permitting process, thereby providing a competitive advantage to Saturn.

Finding 9: Permitting authorities are generally supportive of flexible permits

as an option.

The permitting authorities reported that they are pleased with the benefits from the flexible permits.

Additionally, they believe flexible permitting techniques are useful tools to address some companies’

operational flexibility needs, to foster environmental improvements through emissions reductions, and to lessen

permitting authority resource needs and backlogs associated with construction permitting, so that these public

agencies can focus resources on higher environmental management priorities. Finding 10 discusses permitting

authority perspectives on matching flexibility provisions with appropriate source candidates. 

Permitting authorities are supportive of flexible permits, and they expressed their interest to renew the

pilot flexible permits and to expand the use of flexible permits in their jurisdictions.

Permitting authorities demonstrated their support of flexible permits by retaining the flexibility provisions in

the subsequent permit for the source, or by indicating their interest to do so.

• Oregon DEQ retained the advance approval provisions in Intel’s synthetic minor air operating permit

that replaced the Aloha plant’s Title V permit in 1999.

• MPCA indicated that the agency is supportive of renewing 3M’s flexibility provisions in the

forthcoming Title V permit. In discussing options for the plant’s Title V permitting application (under

consideration by MPCA at the time of the EPA review), however, 3M management decided not to

pursue such provisions due to uncertainty surrounding how the next VOC emissions limit would be

defined. 3M voiced concerns that significantly lowered emissions caps could constrain the plant’s

ability to accommodate increased product demand or transfers of product lines from other 3M

facilities.

• DNREC supported the renewal of all flexibility provisions from DaimlerChrysler’s initial flexible

construction and air operating permit into the plant’s Title V permit, issued in October 1999.

Two permitting authorities further demonstrated their support of flexibility provisions by incorporating

flexibility techniques into permits for other sources within their jurisdiction.

• MPCA reported that the agency has issued “dozens” of minor source and synthetic minor source
46

permits that include flexibility provisions (e.g., plant-wide emissions caps and advance approval

provisions) since the issuance of the 3M St. Paul Tape Plant pilot permit in 1993. MPCA also issued

a permit to 3M’s Maplewood, Minnesota research and development plant that included an advance

approved BACT determination.

• DNREC has issued a Title V permit for DuPont’s Edge Moor, Delaware plant that includes PALs

and advance approval provisions, as well as several permits containing alternate operating scenarios.

Permitting authorities indicated that finalization of EPA policy and/or guidance on flexible permitting

would increase their interest and efficiency in expanding the use of flexible permits.

Permitting authorities indicated that finalization of rulemaking and/or guidance related to flexible permitting

is desired to provide greater clarity and certainty around the EPA’s expectations. Most permitting authorities

stated that, while they are supportive of flexible permitting approaches, they are somewhat hesitant to invest

resources of any significant amount into new flexible permits in the absence of increased clarity regarding

approaches that are acceptable to the EPA. Permitting authorities generally did not want to find themselves

in a position where they have developed numerous flexible permits based on an approach or regulatory

interpretation that does not correlate with the EPA’s approved flexible permitting rules and/or guidance

developed at some point in the future.

Several permitting authorities also noted the high transaction costs associated with developing “pilot” permits

as an additional deterrent to expanding the use of flexibility techniques without EPA policy or guidance. Pilot

initiatives typically demand a high level of interaction between the permitting authority, EPA Regional Offices,

and various offices within the EPA headquarters to verify that the pilot approaches are acceptable.

Permitting authorities indicated that EPA policy and/or guidance could reduce the amount of time spent in

conference calls and meetings, and in the development of flexible permit language that does not meet the

EPA’s expectations, while also reducing the overall time frame for developing a flexible permit. One

permitting authority believed that additional guidance was not needed for it to act but agreed with the other

permitting authorities that EPA rules and/or guidance on flexible permitting might serve to improve the

consistency of regulatory interpretations, expectations, and comments communicated by various EPA offices

and regions.

While permitting authorities supported promulgation of EPA policy and/or guidance on flexible permitting, they

hoped that any such policy would be accommodative of the approaches employed in the pilot flexible permits.

In addition, DNREC representatives urged the EPA to not be overly prescriptive in any policy or guidance

and to allow permitting authorities reasonable discretion in the implementation of approved flexibility

techniques.

Permitting authorities stated that various forms of EPA outreach, training, and assistance would be

useful to assist permitting authorities to develop effective flexible permits.

Permitting authorities and companies emphasized that the EPA could take several steps, in addition to

promulgation of flexible permitting policy and/or guidance, to support the implementation of effective flexible

permits. Suggestions included:

• Make documentation available regarding flexible permitting techniques. Materials should include

examples of flexible permits, fact sheets on various flexible permitting approaches and tools, draft

permit language related to various flexibility approaches, training materials, and other resources.

• Formalize a network of EPA flexible permitting experts who would be available to support permitting

authorities interested to develop permits containing flexibility provisions.
47

• Conduct workshops and training sessions for EPA and permitting authority personnel who are

interested to learn about flexible permitting techniques. Similar workshops or training sessions could

be designed for sources to help them determine whether or not they may be appropriate candidates

for flexible permitting techniques.

• Develop a tool to assist sources and permitting authorities to determine the appropriateness of flexible

permitting techniques to potential source candidates.

• Develop an EPA website clearinghouse for information on flexible permitting techniques.

Finding 10: Permitting authorities indicated that flexible permit provisions

should be matched with a company’s need for flexibility and technical capacity

to implement effectively its flexible permit requirements.

Permitting authorities indicated that while they believe flexible permitting techniques to be appropriate and

beneficial for use with some companies, they may not be appropriate for all companies. They indicated that

there are two critical factors that should be considered when determining the appropriateness of flexible

permitting for candidate sources. First, the company should be able to demonstrate that it has a need for the

flexibility. Second, the permitting authority should be confident that the source has sufficient capacity to

operate effectively under a flexible permit, which typically includes additional monitoring, recordkeeping, and

reporting requirements.

Permitting authorities believe that a candidate company should be able to demonstrate sufficient need

for flexibility to justify the additional up-front staff time and resources needed for the permitting

authority to tailor flexible permitting techniques to the source.

Permitting authorities indicated that they want to have some assurance that any additional up-front investment

will result in benefits for the company, permitting authority, and/or environment before investing in the

development of a flexible permit. Such need could be demonstrated by a company’s ability to clearly

articulate its operational change needs. Permitting authorities indicated that some companies seldom

implement changes that trigger air permitting requirements, making them less appropriate candidates for

flexible permits.

Permitting authorities indicated that a candidate company should exhibit the technical capacity to

operate effectively under a flexible permit, as indicated by factors such as the source’s compliance

history, attentiveness to pollution prevention, and ability to track and manage operational changes and

emissions.

Permitting authorities indicated that while they believe company compliance with flexible permits to be fully

verifiable and enforceable, they believe that companies lacking sufficient capacity to operate effectively under

a flexible permit could be at an increased risk of non-compliance. Additional monitoring, reporting, and

recordkeeping conditions, such as the calculation of plant-wide emissions and maintenance of logs

documenting operational changes and alternate operating scenarios, are typically required to assure

compliance with flexible permit provisions. Permitting authorities indicated that some companies may not

have sufficient capacity and capabilities to effectively meet such permit requirements on a sustained basis.

Permitting authorities stated that they view a company’s past compliance history as the primary indicator of

the company’s capacity to operate under a flexible permit. Past patterns of compliance violations often signal

that a company is not sufficiently able to handle additional monitoring, recordkeeping, and reporting
48

requirements necessary under a flexible permit. Permitting authorities pointed to several other indicators of

a company’s capacity to operate effectively and in compliance under a flexible permit. These include:

• A company’s capacity to track and manage operational and equipment changes.

• A company’s ability to accurately monitor plant-wide emissions.

• A company’s track record of communication and openness with the permitting authority.

• The presence of trained personnel at the source who understand air requirements.

• The presence of a P2 program and/or a track record of P2 accomplishment.

Permitting authorities indicated, however, that rigid criteria for determining the appropriateness of flexible

permitting techniques for a company candidate, such as the complete absence of historic compliance

violations, should not be established. They indicated that permitting authority personnel are accustomed to

matching appropriate permitting techniques and requirements to address individual sources’ applicable

requirements and circumstances.
7

The permit expires on December 31, 2005, but the plant-wide applicability limits (PALs) extend to July 2010. 

49

Table 1.1 Pilot Flexible Permits Evaluated in the EPA Flexible Permit Implementation Review 

Source Permitting Authority Permit Type & Permit # Permit Issuance Permit Expiration

3M Company - 

St. Paul, Minnesota Tape Plant

Minnesota Pollution Control

Agency (MPCA)

State Air Operating Permit (not a Title V

permit); ( Permit No. 23GS-93-OT-1)

March 4, 1993 March 4, 1998

DaimlerChrysler - 

Newark, Delaware Automobile

Assembly Plant

Delaware Department of

Natural Resources and

Environmental Control

(DNREC)

Construction/Operation Permit; (APC95/0569-Construction/Operation)September 1995 October 1999

Title V Air Operating Permit; (AQM003/00128)October 1999 October 2004

Imation Corporation - 

Weatherford, Oklahoma Plant

Oklahoma Department of

Environmental Quality

(Oklahoma DEQ)

Title V Air Quality Permit; (Permit No.

97-380-TV)

June 9, 1998 June 9, 2003

Intel Corporation - 

Aloha, Oregon Semiconductor

Fabrication Plant

Oregon Department of

Environmental Quality

(Oregon DEQ)

Title V Permit; (Oregon Permit No. 34-

2681)

October 1995 October 1999

Lasco Bathware Corporation - 

Yelm, Washington Plant

Olympic Air Pollution

Control Authority (OAPCA)

Title V Air Operating Permit; (Permit No.

01-97)

June 7, 1997 July 7, 2001

Saturn Corporation - 

Spring Hill, Tennessee Automobile

Manufacturing & Assembly Plant

Tennessee Department of

Environment and

Conservation (TDEC)

Permit to Construct or Modify an Air

Contaminant Source; (Permit No. 952233)

June 6, 2000 December 31, 20057
50

Table 1.2 Flexibility Provisions in Pilot Permits Reviewed by the EPA

Source Key Flexibility Provisions

3M

St. Paul, Minnesota

• Plant-wide emissions limits for VOC (4,596 tons/year; 30,600 lbs./day).

• Advance-approvals for specified categories of renovations and other changes deemed to be “consistent with” the specified change categories.

• Replicable testing procedure enabling updates to capture and destruction efficiency parameters for pollution control devices without requiring permit

modifications.

DaimlerChrysler

Newark, Delaware 

• Plant-wide applicability limits (PALs) for NOx

 (150.71 tons/year; 4.86 tons/day) and VOC (1,112.8 tons/year; 5.3 tons/day).

• Advance-approvals for specified projects and categories of changes.

• Case by case technology determination for significant new units.

• Enforceable P2 performance requirement for topcoat emissions and P2 reporting requirements. 

• Replicable testing procedure for updating pollution control device parameters.

• Permit conditions streamlining.

Imation

Weatherford, Oklahoma

• Plant-wide PTE limit for VOC emissions (249 tons/year).

• Advance-approvals for specified changes and classes of changes.

• Advance-approvals for raw material changes, including streamlined determinations under State Air Toxics Program.

• Alternative control device operating scenarios that provide flexibility in controlling or otherwise reducing VOC emissions.

• Permit conditions streamlining, including streamlining of applicable MACT standards.

• P2 Program and reporting requirements.

Intel

Aloha, Oregon 

• Plant Site Emissions Limits (PSELs) for VOC (190 tons/year; 8 tons/week) and CO (32 tons/year).

• Potential-to-emit (PTE) limits on organic and inorganic hazardous air pollutants (HAPs).

• Advance-approvals for a broad class of changes, provided no new applicable requirements and MRR requirements not covered in the permit.

• Source-specific RACT limit based on units of production, designed to encourage P2.

• Pollution Prevention (P2) Program and reporting requirements.

Lasco Bathware

Yelm, Washington

• Plant-wide PTE limits for VOC emissions (249 tons/year; 1.71 tons/day).

• Advance-approvals for categories of changes, including BACT and P2 requirements to address minor NSR requirements.

• Replicable testing procedures for updating emission factors without requiring permit modifications.

• P2 Program with goals and reporting requirements. 

Saturn

Spring Hill, Tennessee 

• Variable PALs for VOC based on production (1,563 tons/year at 500,000+ vehicles per year; 198.5 tons/month).

• PALs for NOx, PM, SO, and CO (PALs are hybrids based on actual and allowable source emissions).

• Advanced approvals for changes to existing emissions sources and construction of new emissions sources (with conditions).

• BACT for all existing emissions units.

• Case by case BACT determination for all new units.

• Permit conditions streamlining.
51

Table 2.1 Key Emissions MRR Requirements in Pilot Permits Reviewed by the EPA

Source Key Emissions Monitoring, Recordkeeping, and Reporting Requirements

3M

St. Paul, Minnesota

• Mass balance approach to VOC emissions measurement; applies an overall control efficiency (capture and destruction) to the VOC input (derived from

material usage tracking system); parametric monitoring is conducted of selected control system operating parameters (e.g., combustion temperature,

exhaust gas flow).

• Control device performance testing is required every two years for both capture efficiency and destruction efficiency.

• Uncontrolled fugitive emissions from churn and mogul rooms measured by CEMS.

• Daily calculation of VOC emissions from all emissions units (required within 41 hours) are maintained on-site.

• Quarterly reporting to MPCA of daily plant-wide VOC emissions and 365-day rolling totals.

DaimlerChrysler

Newark, Delaware

• Mass balance approach to VOC emissions measurement, based on EPA’s “Protocol for Determining the Daily Volatile Organic Compound Emission Rate

of Automobile and Light-Duty Truck Topcoat Operations” (EPA-450/3-88-018, December 1988); parametric monitoring is conducted of selected control

system (RTO) operating parameters (e.g., combustion temperature, inlet pressure); booth/oven splits, transfer efficiency, and incinerator efficiencies use

in calculations are based on the most recent tests completed using the protocol.

• Compliance with EDP primecoat operations is demonstrated pursuant to procedures in New Source Performance Standards (40 CFR 60.393 (c)(2))

through the use of capture and control. VOC RACT standards apply to the miscellaneous metal parts coating and final repair operations and dictate the

compliance method. Compliance with these limits is demonstrated through the use of complying coatings or daily weighted averages.

• Oven burners and miscellaneous NOx

 sources use AP-42 emission factors in conjunction with monitored parameters to calculate emissions; source-speci

emission factors were developed for the antichip, topcoat and EDP primecoat incinerators and the boilers.

• Monthly reporting to DNREC of plant-wide VOC and NOx

 emissions (daily, monthly, and 12-month rolling totals).

Imation

Weatherford, Oklahoma

• Mass balance approach to VOC emissions measurement; parametric monitoring is conducted for all capture and control devices (RTO, catalytic oxidizer,

and carbon adsorber).

• Criteria air pollutant emissions are determined using fuel type, monthly fuel usage to the boilers and oxidizers, and appropriate AP-42 emission factors.

• Daily and monthly calculation of VOC emissions (prorated hourly, daily, and 12-month rolling totals) are maintained on-site.

Intel

Aloha, Oregon

• Mass balance approach to VOC emissions measurement; bi-monthly VOC emissions based on actual solvent monitoring; bimonthly emissions data with

production activity data (i.e., total surface area of wafers processed, square centimeters[cm2]) provides the information necessary to calculate an overall

emission factor (EF) for the fab. Using the recent bimonthly EF with weekly production data provides total weekly VOC emissions (tons/wk).

• Criteria air pollutant emissions are determined using fuel type, monthly fuel usage to the boilers and oxidizers, and appropriate AP-42 emission factors,

except for Emission Unit 3 boiler’s NOx and CO emission factors which are based on manufacturer’s data and verified by source test.

Lasco Bathware

Yelm, Washington

• VOC emissions calculations based on raw material usage, VOC (styrene) content of the raw materials, and site-specific emission factors (pounds [lbs.] of

emissions per lb. of styrene); site-specific emissions factors are based on source testing; material usage is calculated on a daily basis.

• Monthly plant-wide VOC emissions are calculated each month, along with 12-month rolling totals.
Source Key Emissions Monitoring, Recordkeeping, and Reporting Requirements

52

Saturn

Spring Hill, Tennessee

• Mass balance approach to VOC emissions measurement, based on EPA’s “Protocol for Determining the Dai

Emission Rate of Automobile and Light-Duty Truck Topcoat Operations” (EPA-450/3-88-018, December 19

conducted of selected control system operating parameters (e.g., combustion temperature, exhaust gas flow 

transfer efficiency, and incinerator efficiencies used in calculations are based on the most recent tests com

• Criteria air pollutant emissions are determined using monthly natural gas usage data and appropriate AP-42 

• Monthly calculation of monthly and 12-month rolling plant-wide VOC emissions totals.
EXHIBIT 6 

 Attached are TIP’s comments on related EPA dockets for two, related Texas SIP 

submittals. TIP submits these comments as a supplement to the comments on the abovenumbered docket.
HOU2:1184196.7 1

November 23, 2009

TIP COMMENTS ON EPA PROPOSED DISAPPROVAL OF TCEQ

QUALIFIED FACILITY PROGRAM RULES AND GENERAL DEFINITIONS

Docket ID No. EPA–R06–OAR–2005-TX-0025

74 Fed. Reg. 48,450 (Sept. 23, 2009)

The Texas Industry Project (“TIP”) submits the following comments in response 

to the proposed disapproval of Texas's state implementation plan (“SIP”) revisions relating to 

Qualified Facilities and general definitions by the U.S. Environmental Protection Agency 

(“EPA”), published in the Federal Register on September 23, 2009. TIP is comprised of 62 

companies in the chemical, refining, oil and gas, electronics, forest products, terminal, electric 

utility, and transportation industries with operations in Texas.1 

I. Introduction

TIP strongly supports full approval of the Qualified Facility provisions and 

definitions. The Texas air quality permitting program, including the Qualified Facility 

provisions, is stringent, comprehensive and protective of both the environment and public health. 

Under Texas’s integrated air permitting regime, air quality in the state is

demonstrating strong, sustained improvement. Between 1999 and 2005, NOX emissions in the 

Houston-Galveston area decreased from almost 1,200 tons per day, to under 600 tons per day.

2

 

Ozone as measured under the one-hour standard in the Houston-Galveston area has declined 

from 220 parts per billion (“ppb”) in 1991 to 127 ppb in 2009.3 Under the eight-hour standard, 

ozone in the Houston-Galveston area has declined from 119 ppb in 1991, to 84 ppb in 2009.4 .

5

 

 

1

 TIP members participating in these comments are: Albemarle Corporation, Arkema Inc., Ascend Performance 

Materials LLC, BASF Corporation, BP, Celanese Chemicals, Ltd., CenterPoint Energy Houston Electric, LLC, 

Chevron Corporation, Chevron Phillips Chemical Company LP, CITGO Petroleum Corporation, ConocoPhillips, 

DCP Midstream, LLC, Degussa Engineered Carbons, LP, Delek Refining Ltd., Dixie Chemical Company, Inc., Dow 

Chemical Company, The Dynegy Inc., Eagle Rock Energy, Eastman Chemical Company, E. I. Du Pont de Nemours 

& Company, Entergy Texas, Enterprise Products Operating LLC, Exelon Power Texas, ExxonMobil Chemical 

Company, Firestone Polymers, LLC, GB Biosciences Corporation, Halliburton Company, Huntsman Corporation, 

INEOS NOVA LLC, Intercontinental Terminals Company, International Paper Company, International Power, 

Kinder Morgan Liquids Terminals, LLC, LANXESS Corporation, LBC Houston, LP, Lyondell Chemical Company, 

Marathon Petroleum Company LLC, MeadWestvaco Corporation, Merisol USA, L.L.C., NRG Texas Power LLC, 

Occidental Chemical Corporation, Odfjell Terminals (Houston) LP, Oiltanking Holding USA, Inc., Pasadena 

Refining System, Inc., PL Propylene, Praxair, Inc., Rohm and Haas Texas, Incorporated, Shell Oil Company, 

Shintech, Inc., Sterling Chemicals, Inc., Stolthaven Houston Inc., Suez Energy North America, TARGA, TempleInland Inc., Texas Instruments Incorporated, Texas Petrochemicals LP, Total Petrochemicals USA, Inc., Union 

Pacific Railroad Company, Valero Energy Corporation, Vopak Logistics North America, Inc., Western Refining 

Co., L.P.

2

 Susana M. Hildebrand, TCEQ Chief Engineer, Update of Air Quality in Texas (presented at Oct. 29, 2009 

Commission Work Session, and available at TCEQ.com), 13 (attached as Exhibit 1).

3

Id. at 13.

4

Id.

5

Id.
HOU2:1184196.7 2

Moreover, between 1988 and 2008, there has been an 80% reduction in VOC compound 

indicators in the Houston area.6 There has been a similar improvement in toxic air emissions. 

Between 2003 and 2008, there has been a 50% decrease in highly reactive volatile organic 

compounds (“HRVOCs”) in the Houston area.7 Similarly, in the Dallas-Fort Worth area, ozone 

as measured under the one-hour standard declined from 140 ppb in 1991 to 115 ppb in 2009.8 

Ozone for the Dallas-Fort Worth area under the eight-hour standard has declined from 105 ppb 

in 1991 to 86 ppb in 2009 Notably, according to recent TCEQ review, all areas of Texas are in 

attainment for nitrogen dioxide, sulfur dioxide, and carbon monoxide.9

Further, the data show that stationary sources have contributed more substantial 

emissions reductions than any other category during the period of most dramatic air quality

improvements. In the Houston-Galveston area between 1993 and 2008, NOX emissions from 

stationary sources declined from 695 tons per day (“tpd”), to 156 tpd, a decrease of 539 tpd.10 

During that same period, emissions from on-road source declined from 416 tpd to 175 tpd, a 

decrease of 241 tpd.11 Similarly, stationary sources made significant decreases for VOC. 

Between 1993 and 2009 in the Houston-Galveston area, VOC emissions from stationary sources 

decreased from 411 tpd, to 170 tpd, a decrease of 241 tpd.12 On-road sources from that same 

period decreased from 199 tpd, to 86 tpd, a decrease of 113 tpd.13 As the figures indicate, 

stationary sources in Texas have made the most significant strides in reducing emissions.

The submitted revisions strengthen a previously SIP-approved Texas program. 

Under the federal Clean Air Act (“CAA” or “Act”), SIP revisions are approved when those

revisions do not interfere with the attainment of the National Ambient Air Quality Standards 

(“NAAQS”). States have the primary responsibility for developing plans for the attainment and 

maintenance of the NAAQS. In fact, as the Fifth Circuit recently explained:

Although EPA is required to approve SIPs that provide for the timely 

attainment and subsequent maintenance of primary and secondary ambient 

air standards as well as satisfy other CAA general requirements, see 42 

U.S.C. § 7410(a)(3), the EPA has no authority to question the wisdom of a 

 

6

 Houston Regional Monitoring, Annual Average Trends for VOC Indicator Compounds for HRM Network from 

1988 through 2008 (attached as Exhibit 2).

7

 Houston Regional Monitoring, Total HRVOC Network Average Concentrations: Houston Ship Channel PAMSGC Monitoring Sites (attached as Exhibit 2).

8

Id. at 16.

9

 Susana M. Hildebrand, TCEQ Chief Engineer, Update of Air Quality in Texas (Oct. 29, 2009), 10.

10 Compare TEXAS NAT’L RES. CONSERVATION COMM’N, Revision to the State Implementation Plan (SIP) for the 

Control of Ozone Air Pollution: Post-1999 Rate-of-Progress and Attainment Demonstration SIP for the 

Houston/Galveston Ozone Nonattainment Area, (Dec. 2000), at 2-5 (attached as Exhibit 3); with TEXAS COMM’N ON 

ENVIRONMENTAL QUALITY, Revision to the State Implementation Plan for the Control of Ozone Air Pollution:

Houston-Galveston-Brazoria 1997 Eight-Hour Ozone Standard Nonattainment Area (Sept. 23, 2009), at 2.3-2.5 

(attached as Exhibit 4).

11 Id.

12 Id.

13 Id.
HOU2:1184196.7 3

State’s choices of emission limitations if they are part of a SIP that 

otherwise satisfies the standards set forth in 42 U.S.C. §7410(a)(2).14

Rather, the proper test for determining whether a SIP revision can be approved is whether the 

revision interferes with attainment of the NAAQS (i.e. that the plan does not make air quality

worse).15 The last ten years have seen an unprecedented improvement in Texas air quality. The 

submitted revisions have been fully integrated components of the Texas air quality permitting 

program for all that time. Because the current SIP submittals function to strengthen the existing 

SIP, such submittal does not raise interference concerns, and should be fully approved.

II. Background on the Qualified Facilities Program

A. Overview

The Texas Qualified Facility program is a minor New Source Review (“minor 

NSR”) applicability trigger. Under the program, existing emissions units (defined in the Texas 

rules as “existing facilities”) that employ up-to-date best available control technology (“BACT”) 

may make physical and operational changes without a minor NSR review, so long as the changes 

do not result in net emissions increases above their current, protective limits.16 

The Qualified Facilities program is statutory. All of its key provisions are laid out 

in the Texas Clean Air Act.17

The program applies to “existing facilities.” A “facility” is defined as “[a] 

discrete or identifiable structure, device, item, equipment, or enclosure that constitutes or 

contains a stationary source, including appurtenances other than emission control equipment.”18 

Notably, the definition of “facility” here is similar to the federal definition of “emissions unit,” 

used in Texas’s Title V program.19 

Qualified facilities may make physical or operational changes so long as the 

change does not result in a net increase in allowable emission of any air contaminant or the 

emission of any new air contaminant. Changes that meet this criterion are not considered 

“modifications” subject to minor NSR review by TCEQ.20 

The program only reaches changes to an existing facility.

21 Thus, the program 

does not authorize the construction of new facilities.

 

14 Clean Coalition v. TXU Power, 536 F.3d 469, 472 (5th Cir. 2008).

15 Galveston-Houston Assoc. for Smog Prevention v. EPA, 289 Fed. Appx. 745, 754 (5th Cir. 2008).

16 TEXAS NAT’L RES. CONSERVATION COMM’N, Modification of Existing Facilities under Senate Bill 1126: 

Guidance for Air Quality (April, 1996), 1 (Attached as Exhibit 5).

17 TEX. HEALTH & SAFETY CODE § 382.003(9); § 382.0512 (2009).

18 30 TAC § 116.10(6).

19 30 TAC § 122.10(8) “Emission unit--A discrete or identifiable structure, device, item, equipment, or enclosure 

that constitutes or contains a point of origin of air pollutants, including appurtenances.”

20 30 TAC § 116.10(11)(E).

21 30 TAC § 116.10(11); §116.116(e)(5)(A).
HOU2:1184196.7 4

The Texas Legislature established the Qualified Facility program in order to 

provide additional incentives for sites to employ up-to-date (i.e., no more than 10-year-old) 

BACT. Accordingly, a facility may remain a Qualified Facility only so long as it (1) was issued 

a permit or permit amendment or was exempted from pre-construction permit requirements no 

earlier than 120 months before the change will occur, or (2) uses air pollution control methods 

that are at least as effective as the BACT that was required or would have been required for the 

same class or type of facility by a permit issued 120 months before the change will occur.22 

Status as a qualified facility is not perpetual. A facility may lose its status as a 

qualified facility if its permit, exemption or control method falls outside the 10-year window. 

“For example, if a facility obtained a permit on January 15, 1991, it would be a qualified facility 

on the basis of the permit until January 14, 2001, and would be eligible to have changes made 

under the qualified facility flexibility. After that date, the facility is no longer eligible to have 

changes made under the qualified facility flexibility unless the status as a qualified facility is 

continued or regained by a subsequent permit action or appropriate control methods.”23 

B. The Qualified Facility Program Safeguards Major NSR

TCEQ rules ensure that the Qualified Facility flexibility is not to be used to 

circumvent federal NSR. Section 116.117(a)(4) requires that an owner or operator wishing to 

use the program must document: 

[S]ufficient information as necessary to show that the project will comply with 

§116.150 and §116.151 of this title (relating to Nonattainment Review) and §§ 

116.160-116.163 of this title (relating to Prevention of Significant Deterioration 

Review) . . . .24

Additionally, §116.117(d) states that “[n]othing in this section shall limit the applicability of any 

federal requirements.”25 To ensure that the regulated community understands the federal NSR 

safeguards, the associated TCEQ guidance document states:

SB 1126 only revised the Texas “minor new source review” program to allow 

some changes to be made without a requirement to obtain a permit or other 

“approval” from the [TCEQ]. SB 1126 does not supersede federal requirements 

such as Nonattainment (NA) review and Prevention of Significant Deterioration 

(PSD) review of new major sources and major modifications to existing sources, 

which are incorporated into Chapter 116. . . . In making changes under SB 1126, 

owners and operators must consider the potential for these other federal and sate 

requirements to limit their ability to make a desired change. The owner/operator 

 

22 30 TAC § 116.116(e).

23 TEXAS NAT’L RES. CONSERVATION COMM’N, Modification of Existing Facilities under Senate Bill 1126: 

Guidance for Air Quality, (April, 1996) 5.

24 30 TAC § 116.117(a)(4).

25 30 TAC § 116.117(d).
HOU2:1184196.7 5

is responsible for ensuring that any change to a facility complies with all 

applicable regulations.26

TCEQ guidance also specifically states that the program does not supersede other state 

regulations on emissions or TCEQ’s powers and duties to take action to control air pollution.

TCEQ guidance also addresses the interplay of changes under the Qualified 

Facility program and special conditions in the permits a facility holds. “If a change made under 

the qualified facility flexibility would result in the violation of a permit special condition, the 

permit holder must revise the permit special conditions to stay in compliance with the permit,”27

through either the permit alteration process of 30 TAC §116.116(c) or the notification process of 

30 TAC § 116.117(d). As explained above, 30 TAC § 116.117(d) states that “[n]othing in this 

section shall limit the applicability of any federal requirements.” Thus, any changes to a facility

must comply with federal NSR and PSD rules.

C. The Qualified Facility Program Exceeds Federal Benchmarks for 

Allowables-Based Minor NSR Triggers

As outlined above, the Qualified Facility program is a minor NSR applicability 

trigger. As such, the program is one of the flexibility mechanisms encouraged by EPA in its 

2009 Flexible Air Permitting Rule.28 In reflecting on its decade-long flexible permit pilot 

program, EPA observed:

Upon examining the provisions of their minor NSR programs, most of the 

States in which pilot permits were conducted . . . found that they could 

issue advance approvals under existing minor NSR authority for a wide 

spectrum of changes, provided that certain boundary conditions were 

established in the minor NSR permit.29

The Texas Qualified Facility program functions in a similar manner. However, by requiring upto-date BACT as a requirement to use the flexibility, the Texas program is more stringent than 

the federal model. 

Similarly, the Qualified Facility program is comparable to the proposed 

allowables-based minor NSR trigger in EPA’s 2006 proposed Indian Country Rule. EPA 

proposed the Indian Country rule based on a composite of state minor NSR programs, in order to 

create a level playing field with the states. “[W]e seek to establish a flexible preconstruction 

permitting program for minor stationary sources in Indian [C]ountry that is comparable to that 

which applies outside of Indian [C]ountry . . . .”30 As such, the rule represents a clear indication 

of the scope of statutory flexibility in crafting minor NSR tools. “[T]his proposal . . . represents 

 

26 TEXAS NAT’L RES. CONSERVATION COMM’N, Modification of Existing Facilities under Senate Bill 1126: 

Guidance for Air Quality (April, 1996), 2.

27 Id. at 9.

28 74 Fed. Reg. 51,418 (Oct. 6, 2009) at 51,423.

29 Id.

30 71 Fed. Reg. 48,696, 48,700 (Aug. 21, 2006).
HOU2:1184196.7 6

how we would implement the program in Indian [C]ountry in the absence of an EPA-approved 

implementation plan. However, if a tribe is developing its own program, this can serve as one 

example of a program that meets the objectives and requirements of the Act.”31

EPA set an allowables trigger for minor NSR in its Indian Country rule. Under 

EPA’s rule, “a modification is defined . . . as any physical or operational change at a stationary 

source that would cause an increase in the allowable emissions of the affected emissions unit.”32 

In justifying the allowables-based minor NSR trigger in this rule, EPA distinguished the 

definition of “modification” under minor NSR from that used for major NSR: 

In a recent decision, the D.C. Circuit Court of Appeals, ruled that, based 

on the wording of the definition of “modification” in section 111(a)(4) of

the Act, the applicability of major NSR to modifications must be based on 

changes in actual emissions (State of New York, et., v. U.S. EPA, June 24, 

2005). However, because the statutory basis for the minor NSR program 

is section 110(a)(2)(C) of the Act, which does not define or refer to a 

definition of “modification,” we believe that we have discretion in 

defining the term as we think best for the minor NSR program in Indian 

Country . . . .

33

 

In the same fashion, Texas’s Qualified Facility program uses allowables as its minor NSR 

“modification” trigger. Again, however, the Texas program is more stringent, as it only extends 

the flexibility to well-controlled facilities. 

III. TIP Comments on EPA’s Specific Asserted Deficiencies for the Qualified Facility 

Program

EPA’s concerns on specific aspects of the Texas Qualified Facilities program and 

air permitting definitions are reproduced and addressed below. Headings are for convenience 

only—all comments are intended to address all aspects of EPA’s proposal.

A. The Definition of Facility

EPA Comment:

 “It is our understanding of State law, that a ‘facility’ can be an 

“emissions unit,” i.e., any part of a stationary source that emits or 

may have the potential to emit any air contaminant. A ‘facility’ 

also can be a piece of equipment, which is smaller than an 

‘emissions unit.’ A ‘facility’ can be a ‘major stationary source’ as 

defined by Federal law. A ‘facility’ under State law can be more 

than one ‘major stationary source.’”

 

31 Id. at 48,700-701.

32 Id. at 48,701.

33 Id.
HOU2:1184196.7 7

TIP Response:

For purposes of the Qualified Facility program, TCEQ regulations make clear that 

“facility” is comparable to the federal definition of an “emissions unit.” Section 116.10(6) 

defines a facility as: 

A discrete or identifiable structure, device, item, equipment, or enclosure 

that constitutes or contains a stationary source, including appurtenances 

other than emission control equipment. A mine, quarry, well test, or road 

is not a facility.

34

Section 116.10 clearly states that the definitions contained in the section apply to all provisions 

contained in the Chapter.35 Thus, the facility definition of §116.10(10)(6) expressly applies to

Qualified Facility rules contained in Chapter 116. 

This definition is similar to the definition of “emission unit” in Texas’s Title V 

rules. There, “emissions unit” is defined as:

A discrete or identifiable structure, device, item, equipment, or enclosure 

that constitutes or contains a stationary source, including appurtenances 

other than emission control equipment.36

Under the express terms of § 116.10, the definition of “facility” is clear, and 

applies directly to the Qualified Facility rules.

B. Major NSR Safeguards

1. The program is not clearly limited to Minor NSR, thereby 

allowing new major stationary sources to construct without a 

Major NSR permit.

EPA Comments:

 “Both the SIP-codified Chapter 106, Subchapter A for Permits by 

Rule and the SIP-codified Chapter 116, Subchapter F for Standard 

Permits, contain clear regulatory applicability requirements 

limiting their use to Minor NSR, clear regulatory requirements 

prohibiting their use for any project that constitutes a major 

modification subject to Major NSR, and clear regulatory 

provisions prohibiting the use of these Minor NSR permits from 

circumventing Major NSR. There are no similar regulatory 

applicability requirements, regulatory provisions prohibiting the 

use for Major NSR, and no regulatory provisions prohibiting 

 

34 30 TAC § 116.10(6).

35 30 TAC §116.10 (“[T]he following words and terms , when used in this chapter, shall have the following 

meanings, unless the context clearly indicates otherwise.”)

36 30 TAC § 122.10(8).
HOU2:1184196.7 8

circumvention of Major NSR, in the submitted Qualified Facilities 

State Program’s rules and definitions.”

TIP Response:

As outlined above, the Qualified Facility program establishes an allowables-based 

trigger for minor NSR. The Qualified Facility program has no effect on a permit holder’s 

compliance obligations under the federal PSD or NNSR programs. 

The CAA does not mandate a methodology for determining minor NSR 

applicability.

 Federal regulations that govern minor NSR programs at 40 CFR §§ 51.160-.164 

do not mandate a methodology for determining minor NSR applicability.

 In 2000, the U.S. EPA’s Environmental Appeals Board (EAB) confirmed that 

there is no “legally prescribed methodology” for the emissions test used for minor 

NSR applicability determinations, and rejected the argument made by EPA 

enforcement personnel that, in the absence of an explicit minor NSR methodology 

in State rules, the minor NSR applicability test must be consistent with that used 

for federal PSD purposes.37 

 EPA’s own August 2006 proposal for minor NSR programs in Indian Country 

employs an “allowable-to-allowable” test to determine if a modification subject to 

minor NSR requirements has occurred.38

States have great flexibility under the CAA in determining the applicability of

minor NSR requirements, and that flexibility includes the authority to use allowable emission 

rates in establishing whether minor NSR is triggered. 

TCEQ rules articulate an overriding obligation to comply with federal NSR 

requirements. Section 116.117(a)(4) requires that an owner or operator wishing to use the 

Qualified Facility program to make a change must document 

[S]ufficient information as necessary to show that the project will comply 

with §116.150 and §116.151 of this title (relating to Nonattainment 

Review) and §§ 116.160-116.163 of this title (relating to Prevention of

Significant Deterioration Review) . . .39

 

37 In re Tennessee Valley Authority, 9 EAD 357, 461 (EAB Sept. 15, 2000). 

38 See 71 Fed. Reg. 48,695, 48,701 (Aug. 21, 2006) (“For the purposes of this rule, a modification is defined at 

proposed 40 CFR 49.152(d) as any physical or operational change at a stationary source that would cause an 

increase in the allowable emissions of the affected emissions units for any regulated NSR pollutant or that would 

cause the emission of any regulated NSR pollutant not previously emitted.”).

39 30 TAC §116.117(a)(4).
HOU2:1184196.7 9

Additionally, §116.117(d) states that “[n]othing in this section shall limit the applicability of any 

federal requirements.”40 The current Qualified Facility rules, therefore, constrain the regulated 

community from making major changes without complying with major NSR requirements. 

2. The program does not require that first an applicability 

determination be made whether the construction or 

modification is subject to Major NSR.

EPA Comment:

 “We do not find any provisions in the submitted Program that 

require a Major NSR applicability determination for changes. The 

submitted Program’s rules and definitions are not clear on their 

face that first one must determine the threshold question of 

whether the change is a major stationary source or a major 

modification subject to Major NSR.”

TIP Response:

TIP reiterates its comments from Section III.B.1 above. The overriding obligation 

to comply with federal NSR requirements is made explicit in TCEQ’s rules. The current

regulations constrain the regulated community from making major changes without complying 

with major NSR requirements. The clear provisions in the Texas rules safeguarding federal NSR 

are supported by well-developed TCEQ guidance.41 Neither EPA’s Indian Country rule, nor any 

of several recently SIP-approved state minor NSR rules, contain explicit language calling for a 

major NSR applicability determination before use of the minor NSR tools.42 Accordingly, there 

are no federal requirements, nor any federally-approved analogues, for the provisions that EPA is 

now suggesting should exist. To the contrary, EPA’s own Indian Country preamble, quoted 

above, notes the absence of such benchmarks. Requiring additional language in Texas would be 

arbitrary, and would contravene the principle articulated by the Fifth Circuit that, 

Although EPA is required to approve SIPs that provide for the timely 

attainment and subsequent maintenance of primary and secondary ambient 

air standards as well as satisfy other CAA general requirements, see 42 

U.S.C. § 7410(a)(3), the EPA has no authority to question the wisdom of a 

State’s choices of emission limitations if they are part of a SIP that 

otherwise satisfies the standards set forth in 42 U.S.C. §7410(a)(2).43

 

40 30 TAC § 116.117(d).

41 TEXAS NAT’L RES. CONSERVATION COMM’N, Modification of Existing Facilities under Senate Bill 1126: 

Guidance for Air Quality (April, 1996).

42 ALASKA ADMIN. CODE tit. 18, §50.502, approved 72 Fed. Reg. 45,378 (Aug. 14, 2007); 7 DEL. CODE REGS. § 

1102. Granted limited approval based on EPA’s concerns about public participation provisions. 65 Fed. Reg. 2,048 

(Jan. 13, 2000).

43 Clean Coalition v. TXU Power, 536 F.3d 469, 472 (5th Cir. 2008).
HOU2:1184196.7 10

3. The program does not include the requirement to make Major 

NSR applicability determinations based on actual emissions 

and on emissions increases and decreases (netting) that occur 

within a major stationary source.

EPA Comment:

 “[T]his submitted Program allows an evaluation using allowable, 

not actual emissions as the baseline to calculate the project’s 

proposed emission increase and for many of the netting emission 

reduction, thereby in many case possibly circumventing the major 

modification applicably requirements under the Major NSR rules, 

rules that are based upon using actual emissions to calculate 

baseline emissions.”

TIP Response:

TIP reiterates its comments from Section III.B.1 above. The overriding obligation 

to comply with federal NSR requirements is made explicit in TCEQ’s rules. Moreover, states 

have great flexibility under the CAA in determining the applicability of minor NSR 

requirements, and that flexibility includes the authority to use allowable emission rates in 

establishing whether minor NSR is triggered. 

C. Minor NSR Approval Issues

1. The program is not clearly limited to Minor NSR thereby 

allowing major modification to occur without a Major NSR 

permit.

EPA Comment:

 “There are no statutory and/or regulatory provisions that clearly 

prohibit the use of the Program for major modifications. Nor are 

there any statutory and/or regulatory provisions clearly limiting 

the use of the Program to minor modifications.”

TIP Response:

TIP reiterates its comments from Section III.B.1 above. The overriding obligation 

to comply with federal NSR requirements is made explicit in the statute, TCEQ’s rules, and 

guidance on the program. The current regulations and guidance, therefore, constrain the 

regulated community from making major changes without complying with major NSR 

requirements.

2. The program in not an enforceable Minor NSR Permitting 

program.
HOU2:1184196.7 11

EPA Comments:

 “The Program is not clear that each Qualified Facility involved in 

the netting transaction must submit a permit application and 

obtain a permit revision reflecting all of the changes made to 

reduce emissions (relied upon in the netting analysis) as well as 

reflecting the change itself that increased emissions.” 

 “At a minimum, the State must revise its rules to make it clear that 

a permit application must be submitted by each participating 

Qualified Facility and the changes made by the participating 

Qualified Facilities are reflected in revised permits issued by the 

TCEQ.”

TIP Response:

As explained above, the Qualified Facility program is a minor NSR triggering 

provision. Instead of a permit review, a facility must give TCEQ notification of any changes 

made using the program rules and must document the changes and retain that documentation at 

the plant site.

TCEQ guidance makes clear that the facilities involved in a change must be 

qualified facilities at the time the change is to occur. Any facility that is not a qualified facility at 

the time of the change cannot be involved in the netting analyses.44

In two situations, a facility must qualify with TCEQ prior to making a change, but 

this is not a permitting procedure. Rather a facility must be qualified by TCEQ when:

(1) The facility is qualified on the basis of BACT, but the specific control method 

has not yet been approved by TCEQ as qualifying BACT, or 

(2) The facility does not have established allowable emissions for an air 

contaminant relevant to the change in a MAERT or Form PI-E document.45

In these two scenarios, an owner or operator must submit a Form PI-E to TCEQ justifying the 

BACT or the determination of allowable emissions for the air contaminants relevant to the 

change. TCEQ then has 45 days to review the request and either accept it or object.

Additionally, an owner or operator making a change under the program must 

notify TCEQ, either prior to or after the change. Post change notification must come either 30 

days after the change, or in an annual report. Pre-change notification is required when, in order 

to achieve a result of no net increase in allowable emissions, the owner or operator makes an 

intra-plant trade above set limits, depending on the location of the facility from the plant’s 

 

44 TEXAS NAT’L RES. CONSERVATION COMM’N, Modification of Existing Facilities under Senate Bill 1126: 

Guidance for Air Quality, (April, 1996), 6.

45 30 TAC § 116.118.
HOU2:1184196.7 12

boundaries. An intra-plant trade is when an emission reductions is made at another qualified 

facility at the plant and is traded to the facility where the change is being made.46 

Two important aspects of the program are implicit in the pre-change notification 

requirement. First, the rule only contemplates intra-plant trading. Trading among different 

plants held by a common owner is not authorized under the program. Second, TCEQ must be 

notified of intra-plant trading when the amounts traded are above a set limit. 

If a change implicates a permit special condition, the permit holder must revise its 

permit special condition using the procedures specified in Chapter 116, New Source Review.47 

3. The program lacks safeguards to ensure that the changes will 

not violate a Texas control strategy and would not interfere 

with attainment and maintenance of NAAQs.

EPA Comments:

 “The submitted Program’s netting is not based upon all 

contemporaneous increases at the same major stationary 

source and not all decreases at the same major stationary 

source. We propose, however, to find that such an approach 

satisfies the minimum requirements for an approvable Minor 

NSR netting program as long as the ambient air is protected in 

the trading.”

 “The reductions in the Program’s netting are based upon the 

most stringent of the permitted emissions rate (which includes 

the highest achievable actual emission rate) or any applicable 

state or federal rule. Therefore, this Program’s netting is not 

based totally on changes in actual emissions. We are proposing 

to find that this still is acceptable as a Minor NSR netting 

program as long as the ambient air is protected in the 

trading.”

TIP Response:

Qualified Facility flexibility is only available where the change will not result in a 

net increase above existing BACT-reviewed levels at well controlled facilities. The program 

contemplates changes under existing limits that were set to protect the NAAQS and other air 

quality standards.

The existing Qualified Facility rules contain adequate safeguards that ensure that 

air quality, including NAAQS, are protected when changes are made under the program. 

 

46 Id.

47 30 TAC § 116.116 (b)(3).
HOU2:1184196.7 13

Additionally, under the existing rules, changes are sufficiently documented and quantified so that 

a decrease at a facility will only be used in one netting analysis.

Section 116.117 governs the documentation and notification of changes made to 

qualified facility. That provision specifies that a facility making a change under the program 

must document the change. This documentation must include:

(1) [Q]uantification of all emissions increases and decreases associated 

with the physical or operation change;

(2) [A] description of the physical or operation change;

(3) [A] description of any equipment being installed;

(4) [S]ufficient information as necessary to show that the project will 

comply with § 116.150 of this title (relating to Nonattainment Review) 

and §§ 116.160-116.163 of this title (relating to Prevention of Significant 

Deterioration Review) and with Subchapter C of this chapter (relating to 

Hazardous Air Pollutants: Regulations Governing Constructed Major 

Sources (FCAA, § 112(g), 40 CFR Part 63)).48

Section 116.117 goes on to require that a facility notify TCEQ of the changes made under the 

program.49 

The intersection of the requirements to document and to report the change to 

TCEQ means that a change may only be used in one netting analysis. Additionally, the 

requirement that a source document compliance with NNSR and PSD review safeguards 

NAAQS.

4. The program fails to demonstrate that, if viewed as an 

exception to the Texas Minor NSR permitting rules, it will not 

interfere with any applicable requirement of the Act.

EPA Comment:

 “The submitted Program could be considered an exemption 

from Minor NSR. To be approvable as an exemption from the 

Texas Minor NSR SIP, the State must demonstrate that this 

exemption will not permit changes that will violate the Texas 

control strategies or interfere with NAAQS attainment.”

TIP Response:

 

48 30 TAC § 116.117(a).

49 30 TAC § 116.117(b).
HOU2:1184196.7 14

The Qualified Facility program is correctly analyzed as a minor NSR applicability

trigger. As such, it could be viewed as an exemption to the Texas Minor NSR permitting review 

requirements. The existing rules, however, sufficiently prevent changes that will violate the 

Texas control strategies or interfere with NAAQS attainment.

Qualified Facility flexibility is only available where the change will not result in a 

net increase above existing BACT-reviewed levels at well controlled facilities. The program 

contemplates changes under existing limits that were set to protect the NAAQS and other air 

quality standards.

Further, as explained in Section III.B.3 above, § 116.117 requires that a 

modification under the program must be documented and an owner or operator specifically must 

show compliance with NNSR and PSD requirements.50 The state NNSR and PSD rules exist to 

promote NAAQS attainment. The Qualified Facility provisions, therefore, incorporate Texas’s 

control strategies, thus safeguarding the NAAQS.

IV. Substance of Asserted Deficiencies for Definitions

A. The removal of the incorporation by reference of the federal PSD definition 

of BACT.

EPA Comments:

 “The 2006 submittal also removed from the State rules, the 

PSD SIP requirement at 40 CFR 52.21(r)(4). . . [This revision 

provides that] if a project becomes a major stationary source 

or major modification solely because of a relaxation of an 

enforceable limitation on the source or modification’s capacity 

to emit a pollutant, then the source or modification is subject to 

PSD applies as if construction had not yet commenced.”

 “As the mechanism in Texas for ensuring that permits contain 

such a requirement, the State PSD SIP must both require 

BACT and apply the federal definition of BACT (or one that is 

more stringent) to be approved pursuant to part C and Section 

110(l) of the Act.”

TIP Response:

Texas submitted a revision to 30 TAC 116.160(a) and a new section 116.160(c)(1) 

and (2) on February 1, 2006, as a SIP revision to the Texas PSD SIP. This SIP revision 

reorganized the earlier SIP-approved rules.

 

50 30 TAC §116.117(a).
HOU2:1184196.7 15

Prior to the currently-reviewed revisions, Texas had incorporated by reference 

certain provisions of 40 CFR 52.21. The current SIP-approved rule was adopted by the State on 

October 10, 2001, and EPA approved this recodified SIP rule citation on July 22, 2004.51 

Since 1972, Texas has correctly imposed a control technology review on 

applications for an air quality permit.52 Section 382.0518(b)(1) of the Texas Clean Air Act 

(“TCAA”) requires that “the proposed facility for which a permit, permit amendment, or a 

special permit is sought will use at least the best available control technology, considering the 

technical practicability and economic reasonableness of reducing or eliminating the emissions 

from the facility.”

53 This requirement is echoed in Section 116.111(a)(2)(C) of TCEQ’s rules, 

which requires that “the proposed facility utilize BACT, with consideration given to the technical 

practicability and economic reasonableness of reducing or eliminating the emissions from the 

facility.” 54

The term BACT has been defined by TCEQ in strict accordance with the statutory 

BACT requirement in the TCAA. Specifically, 30 TAC § 116.10(3) defines BACT as “BACT 

with consideration given to the technical practicability and the economic reasonableness of

reducing or eliminating emissions from the facility.” The TCEQ has stated that this definition 

shall apply to all use of the term “BACT” in Chapter 116 of its rules, unless the context clearly 

indicates otherwise.55 

The Texas regulations have continuously carved out 40 CFR 52.21(j), concerning 

control technology review, which is the federal BACT requirement, from the Texas PSD 

regulations. This is true from 1992 when EPA first granted authority to Texas to administer PSD 

permitting. As part of the 1992 approval, EPA explained why the federal control technology

review requirement of Section 52.21(j) could be properly excluded by Texas under the federal 

Clean Air Act. EPA explained:

This provision of the Federal PSD regulations has been excluded 

from the TACB Regulation VI because the TACB claims that the 

Texas Clean Air Act and the existing State regulations have 

provisions for application of BACT as stringent as the Federal 

requirements in reviewing the permit applications. The EPA 

review of the Texas Clean Air Act and Regulation VI (Sections 

116.3(a)(3) through 116.3(a)(5)) have indeed revealed that existing 

TACB permit requirements meet the provisions of the Federal PSD 

regulations . . . .

56

 

51 69 Fed. Reg. 43,752 (July 22, 2004).

52 See TACB, Regulation VI § I(B)(2) (July 5, 1972). 

53 TEX. HEALTH & SAFETY CODE § 382.0518(b)(1).

54 30 TAC § 116.111(a)(2)(C).

55 30 TAC § 116.10.

56 54 Fed. Reg. 52,824-25 (Dec. 22, 1989) (emphasis added).
HOU2:1184196.7 16

EPA then stated in the final rule approving the Texas PSD program that the federal control 

technology review requirement, which requires BACT for PSD applications, was “not necessary 

for approval of the Texas Program.”57

The preamble to the 2006 revisions to §116.160 in which the incorporations by 

reference of 40 CFR 52.21 were changed, demonstrate a consistency with the approach taken by 

the State in the preceding years. The preamble explains the incorporation by reference of certain 

sections of 40 CFR 52.21 and further states, “[o]ther definitions used for the PSD program or 

visibility in Class I areas program are currently in [TCEQ’s] rules.”58 

The appropriate BACT definition exists in Texas’s rules, as demonstrated by 

EPA’s past approval of those rules. All permits Texas has issued under the existing permitting 

program reflect the current TCEQ SIP-approved approach to BACT, and are valid and 

enforceable.

B. The definition of “insignificant increases” as not requiring a permit does not 

meet EPA’s NSR SIP requirements.

EPA Comments:

 “The TCAA seems to be clear that a Permit by Rule, Standard 

Permit, or an Exemption by Rule cannot be used for a major 

source or major modification. EPA is aware that in the past 

the State has reasonably interpreted an applied the SIP term 

‘insignificant’ for allowing only minor modifications and 

minor sources. There is information; however, e.g., the State’s 

adoption of a Permit by Rule for Startup, Shutdown, and 

Maintenance Emissions that belies the EPA being able to rely 

upon such a submittal of the relevant statutory provisions. This 

type of Permit by Rule cannot be construed to apply only to 

minor modifications and construction of minor sources. A 

submittal by the State of the applicable statutory sections for 

EPA to approve as part of the Texas SIP no longer seems 

sufficient in view of the issuance of this particular Permit by 

Rule.”

 “With the State’s issuance of the Startup, Shutdown, and 

Maintenance Permit by Rule that is not clearly limited to minor 

modifications and the continued expressions by the public, 

regulated entities, and government entities on the lack of

clarity in the submittals’ language of (A) and (B), EPA is 

proposing to disapprove the submittals for 30 TAC 

116.10(11)(A) and (B) because they are vague and 

unenforceable.”

 

57 57 Fed. Reg. 28,093-94 (June 24, 1992).

58 31 Tex. Reg. 519 (Jan. 27, 2006).
HOU2:1184196.7 17

TIP Response:

EPA’s concerns that Texas’s adoption of a Permit by Rule (“PBR”) for 

Maintenance Start-up and Shutdown (“MSS”) prevents it from approving the definition of

modification of an existing facility as excluding “insignificant increase” are unfounded. TCEQ 

proposed that rule in December of 2005.59 TCEQ, however, never actually adopted the rule. 

Consequently, it was withdrawn in July of 2006.60 EPA’s ability to rely on the state submittal of

the applicable statutory sections, therefore, should not be undermined by a rule that was never 

adopted.

Additionally, the definition specifying that a modification of an existing facility 

does not include (1) an insignificant increase of an air contaminant that is authorized by one or 

more commission exemptions, or (2) an insignificant increase at a permitted facility

61 is not 

vague. As EPA recognizes, the Texas Clean Air Act clearly prevents an exemption from being 

used for a major source or major modification.62 Consequently, the definition is limited to minor 

modifications.

V. Conclusion

TIP strongly supports full approval of existing Texas Qualified Facility provisions 

and the existing definitions. The Texas permitting program, including the definitions and 

Qualified Facility program provisions, is stringent, comprehensive and protective of both the 

environment and public health. The Texas SIP revisions, including Qualified Facility provisions 

and defined terms, further the attainment of NAAQS, and so should be fully approved.

 

59 30 Tex. Reg. 8,802 (Dec. 30, 2005).

60 31 Tex. Reg. 5,797 (July 21, 2006).

61 30 TAC §116.10(11).

62 74 Fed. Reg. at 48,465.
HOU02:1183339.12 1

November 23, 2009

TIP COMMENTS ON EPA PROPOSED DISAPPROVAL OF TCEQ

FLEXIBLE PERMIT PROGRAM RULES

Docket ID No. EPA-R06-OAR-2005-TX-0032

74 Fed. Reg. 48,480 (Sept. 23, 2009)

The Texas Industry Project (“TIP”) submits the following comments in response

to the proposed disapproval of Texas's state implementation plan (“SIP”) submittals relating to 

flexible permits for air quality permitting issued by the U.S. Environmental Protection Agency 

(“EPA”) and published in the Federal Register on September 23, 2009. TIP is comprised of 62 

companies in the chemical, refining, oil and gas, electronics, forest products, terminal, electric 

utility, and transportation industries with operations in Texas.1 

I. Introduction

TIP strongly supports full approval of the flexible permit provisions. The Texas 

air quality permitting program, including the flexible permit provisions, is stringent, 

comprehensive and protective of both the environment and public health. 

Under Texas’s integrated air permitting regime, air quality in the state is

demonstrating strong, sustained improvement. Between 1999 and 2005, NOX emissions in the 

Houston-Galveston area decreased from almost 1,200 tons per day, to under 600 tons per day.

2

 

Ozone as measured under the one-hour standard in the Houston-Galveston area has declined 

from 220 parts per billion (“ppb”) in 1991 to 127 ppb in 2009.3 Under the eight-hour standard, 

ozone in the Houston-Galveston area has declined from 119 ppb in 1991, to 84 ppb in 2009.4 

 

1

 TIP members participating in these comments are: Albemarle Corporation, Arkema Inc., Ascend Performance 

Materials LLC, BASF Corporation, BP, Celanese Chemicals, Ltd., CenterPoint Energy Houston Electric, LLC, 

Chevron Corporation, Chevron Phillips Chemical Company LP, CITGO Petroleum Corporation, ConocoPhillips, 

DCP Midstream, LLC, Degussa Engineered Carbons, LP, Delek Refining Ltd., Dixie Chemical Company, Inc., Dow 

Chemical Company, The Dynegy Inc., Eagle Rock Energy, Eastman Chemical Company, E. I. Du Pont de Nemours 

& Company, Entergy Texas, Enterprise Products Operating LLC, Exelon Power Texas, ExxonMobil Chemical 

Company, Firestone Polymers, LLC, GB Biosciences Corporation, Halliburton Company, Huntsman Corporation, 

INEOS NOVA LLC, Intercontinental Terminals Company, International Paper Company, International Power, 

Kinder Morgan Liquids Terminals, LLC, LANXESS Corporation, LBC Houston, LP, Lyondell Chemical Company, 

Marathon Petroleum Company LLC, MeadWestvaco Corporation, Merisol USA, L.L.C., NRG Texas Power LLC, 

Occidental Chemical Corporation, Odfjell Terminals (Houston) LP, Oiltanking Holding USA, Inc., Pasadena 

Refining System, Inc., PL Propylene, Praxair, Inc., Rohm and Haas Texas, Incorporated, Shell Oil Company, 

Shintech, Inc., Sterling Chemicals, Inc., Stolthaven Houston Inc., Suez Energy North America, TARGA, TempleInland Inc., Texas Instruments Incorporated, Texas Petrochemicals LP, Total Petrochemicals USA, Inc., Union 

Pacific Railroad Company, Valero Energy Corporation, Vopak Logistics North America, Inc., Western Refining 

Co., L.P.

2

Susana M. Hildebrand, TCEQ Chief Engineer, Update of Air Quality in Texas (presented at Oct. 29, 2009 

Commission Work Session, and available at TCEQ.com), 13. (Attached as Exhibit 1)

3

Id. at 13.

4

Id.
HOU02:1183339.12 2

There has been a similar improvement in toxic air emissions. Between 2003 and 2008, there has 

been a 50% decrease in highly reactive volatile organic compounds (“HRVOCs”) in the Houston 

area.5 Similarly, in the Dallas-Fort Worth area, ozone as measured under the one-hour standard 

declined from 140 ppb in 1991 to 115 ppb in 2009.6 Ozone for the Dallas-Fort Worth area under 

the eight-hour standard has declined from 105 ppb in 1991 to 86 ppb in 2009.7 Moreover, 

between 1988 and 2008, there has been an 80% reduction in VOC compound indicators in the 

Houston area.8 Notably, according to recent TCEQ review, all areas of Texas are in attainment 

for nitrogen dioxide, sulfur dioxide, and carbon monoxide.9

Further, the data show that stationary sources have contributed more substantial 

emissions reductions than any other category during the period of most dramatic air quality

improvements. In the Houston-Galveston area between 1993 and 2008, NOX emissions from 

stationary sources declined from 695 tons per day (“tpd”), to 156 tpd, a decrease of 539 tpd.10 

During that same period, emissions from on-road source declined from 416 tpd to 175 tpd, a 

decrease of 241 tpd.11 Similarly, stationary sources made significant decreases for VOC. 

Between 1993 and 2009 in the Houston-Galveston area, VOC emissions from stationary sources 

decreased from 411 tpd, to 170 tpd, a decrease of 241 tpd.12 On-road sources from that same 

period decreased from 199 tpd, to 86 tpd, a decrease of 113 tpd.13 As the figures indicate, 

stationary sources in Texas have made the most significant strides in reducing emissions.

The submitted revisions strengthen a previously SIP-approved Texas program. 

Under the federal Clean Air Act (“CAA” or “Act”), SIP revisions are approved when those 

revisions do not interfere with the attainment of the National Ambient Air Quality Standards 

(“NAAQS”). States have the primary responsibility for developing plans for the attainment and 

maintenance of the NAAQS. In fact, as the Fifth Circuit recently explained:

Although EPA is required to approve SIPs that provide for the timely 

attainment and subsequent maintenance of primary and secondary ambient 

air standards as well as satisfy other CAA general requirements, see 42 

U.S.C. § 7410(a)(3), the EPA has no authority to question the wisdom of a 

 

5

 Houston Regional Monitoring, Total HRVOC Network Average Concentrations: Houston Ship Channel PAMSGC Monitoring Sites. (Attached as Exhibit 2)

6

Id. at 16.

7

Id.

8

 Houston Regional Monitoring, Annual Average Trends for VOC Indicator Compounds for HRM Network from 

1988 through 2008. (Attached as Exhibit 2)

9.

 Susana M. Hildebrand, TCEQ Chief Engineer, Update of Air Quality in Texas (Oct. 29, 2009), 10.

10 Compare TEXAS NAT’L RES. CONSERVATION COMM’N, Revision to the State Implementation Plan (SIP) for the 

Control of Ozone Air Pollution: Post-1999 Rate-of-Progress and Attainment Demonstration SIP for the 

Houston/Galveston Ozone Nonattainment Area, (Dec. 2000), at 2-5 (Attached as Exhibit 3); with TEXAS COMM’N ON

ENVIRONMENTAL QUALITY, Revision to the State Implementation Plan for the Control of Ozone Air Pollution:

Houston-Galveston-Brazoria 1997 Eight-Hour Ozone Standard Nonattainment Area (Sept. 23, 2009), at 2.3-2.5 

(Attached as Exhibit 4).

11 Id.

12 Id.

13 Id.
HOU02:1183339.12 3

State’s choices of emission limitations if they are part of a SIP that 

otherwise satisfies the standards set forth in 42 U.S.C. §7410(a)(2).14

Rather, the proper test for determining whether a SIP revision can be approved is whether the 

revision interferes with attainment of the NAAQS (i.e. that the plan does not make air quality

worse).15 Far from “worse” air quality, the last ten years have seen an unprecedented 

improvement in Texas air quality. The submitted revisions have been fully integrated 

components of the Texas air quality permitting program for all that time. Because the current 

SIP submittals function to strengthen the existing SIP, such submittal does not raise interference 

concerns, and should be fully approved.

II. Flexibility in Federal Permitting Rules

A. Title V Operating Permits

For twenty years, federal air permitting regulations have consistently recognized 

the importance of providing operational flexibility to the regulated community. In 1990, 

Congress added Title V to the Clean Air Act (“CAA” or “the Act”). The Act specifies what 

EPA must require of states’ federal operating permit programs. Specifically, state Title V 

programs must contain: 

Provisions to allow changes within a permitted facility . . . without 

requiring a permit revision, if the changes are not modifications under any 

provision of title I and the changes do not exceed the emissions allowable 

under the permit (whether expressed therein as a rate of emissions or in 

terms of total emissions).16

Thus, Congress specifically envisioned emission cap permits in structuring the Title V program.

Two years later, in 1992, EPA promulgated its rules for Title V permit programs 

in 40 C.F.R. Part 70. In order to provide operational flexibility, EPA promulgated section 

70.4(b)(12), which requires that states put in place Title V programs that allow three specific 

avenues for operational flexibility, including permits that establish federally-enforceable 

emission caps in their Title V programs. Specifically:

The program shall require the permitting authority, if a permit applicant 

requests it, to issue permits that contain terms and conditions, . . . allowing 

for the trading of emissions increases and decreases in the permitted 

facility solely for the purpose of complying with a federally-enforceable 

emissions cap that is established in the permit independent of otherwise 

applicable requirements. 17

 

14 Clean Coalition v. TXU Power, 536 F.3d 469, 472 (5th Cir. 2008).

15 Galveston-Houston Assoc. for Smog Prevention v. EPA, 289 Fed. Appx. 745, 754 (5th Cir. 2008).

16 CAA § 502(b)(10) (emphasis added). 

17 40 CFR §70.4(b)(12) (iii) (emphasis added).
HOU02:1183339.12 4

EPA emphasized the importance of enabling plant sites to maintain operational 

flexibility in the preamble to Part 70. There, EPA stated:

[I]t is possible to use the combination of several provisions in these 

regulations to allow for operational flexibility around 

federally-enforceable emission limits or caps which are more strict than 

otherwise required by the Act's applicable requirements. A source may 

request that the permit provide for emissions trading under 

§ 70.4(b)(12)(iii), as discussed above. For example, a source could 

structure its permit so that the emissions caps at the permitted facility 

created a pool of unused emissions under the voluntary limit on the 

source's potential to emit. 18

At least 24 states and the District of Columbia have adopted the language of 

Section 70.4(b)(12) into their Title V permit programs.19 Several of these states embraced the 

concept of “federally enforceable emission caps” that authorize emissions, not only as a title V 

revision trigger, but also as an authorization tool under NSR.20 Thus, emission cap permits have 

deep roots outside Texas. 

B. Flexible Permit Pilot Study

EPA again focused on the importance of operational flexibility when it conducted 

its decade-long Flexible Permit pilot study. EPA reviewed flexible emission cap permits in six 

states, and found that flexible permits worked well and could be used to further both

environmental protection and administrative flexibility.

21 Behind the project was a recognition 

by both the states involved and EPA that “in today’s increasingly competitive global markets,” 

companies are required “to respond rapidly to market signals and demand, while delivering 

products faster, at lower cost, and of equal or better quality than their competitors.”22 EPA 

recognized that flexible permits could reduce the administrative “friction” of time, costs, delay,

uncertainty, and risk associated with certain types of operational changes.23

 

18 57 Fed. Reg. 32,250, (July 21, 1992) at 32,267.

19 Alabama, AL ADC 335-3-16-.05; Arkansas AR ADC 014 01 026; Washington, D.C., 20 DC ADC § 302; 

Delaware, DE ADC 7 1000 1130; Florida, 62 FL ADC 62-213.415; Georgia, GA ADC 391-3-1-.03; Illinois, 415 

ILCS 5/39.5.12; Iowa, IA ADC 567-22.108(455B); Louisiana, LA ADC. 33-507; Mississippi, MS ADC 08 034 006; 

Montana, MT ADC 17.8.1224; Nebraska, 129 NE ADC Ch. 8, § 019; New Hampshire, NH ADC ENV-A 612.02; 

New Jersey, NJ ADC 7:27.28B(f); New York, 6 NY ADC 201-6.5; North Dakota, N.D. ADC § 33-15-14-06; Ohio, 

Ohio ADC § 3745-77-07; Pennsylvania, 25 Pa. Code §127.448.; Rhode Island, RI ADC 12 031 029; South Carolina, 

SC ADC 61-62.70; South Dakota, SD ADC 74:36:05:30; Texas, 30 TAC §122.222(c); Utah, UT ADC R307-415; 

Washington, WA ADC 173-401-722; West Virginia, WV ADC § 45-30-5.

20 See, e.g., New Jersey’s Facility-Specific Emissions Averaging program; 7 N.J. ADMIN. CODE 27:-22.28B (2009); 

Oregon’s Plant Site Emissions Limit program, OR. ADMIN. R. 340-222-0010, et seq. (2008).

21 EPA OFFICE OF AIR QUALITY PLANNING AND STANDARDS & EPA OFFICE OF POLICY, ECONOMICS AND 

INNOVATION, Evaluation of Implementation Experiences with Innovative Air Permits, 4 (Attached as Exhibit 5). 

22 Id.

23 Id. at 9.
HOU02:1183339.12 5

C. Plantwide Applicability Limits

EPA recognized the advantages of emissions cap permits in promulgating its NSR 

reform in 1996 and 2002. In introducing the plantwide applicability limit (“PAL”) concept in 

1996, EPA noted:

Rather than face complicated, piecemeal applicability decisions every 

time a change at a plant is contemplated, plant managers may prefer to 

work within an emissions cap or emissions budget, an annual emissions 

limit that allows managers to make almost any change anytime as long as 

the plant’s emissions do not exceed the cap.24

When promulgating its final NSR reform rule in 2002, EPA reiterated the benefits of emission 

caps, reflecting on its experience with the flexible permit pilot project. EPA stated:

Overall, we found that significant environmental benefits occurred for 

each of the permits reviewed. In particular, the six flexible permits 

established emissions cap-based frameworks that encouraged emissions 

reductions and pollution prevention, even though such environmental 

improvements were not an explicit requirement of the permits. We found 

that in a cap-based program, sources strive to create enough headroom for 

future expansions by voluntarily controlling emissions. For instance, one 

company lowered its actual VOC emissions over threefold in becoming a 

synthetic minor source (that is, 190 tpy to 56 tpy). Other companies 

lowered their actual VOC emissions by as much as 3600 tpy by increasing 

capture, by using voluntary pollution prevention and other voluntary 

emissions control measures, and by reducing production rates.25 

D. EPA’s Proposed Indian Country Rule

In 2006, EPA proposed an air permitting rule for Indian Country. In the preamble 

to that proposed rule, EPA once again expressed the importance of flexibility in air permitting 

programs. EPA intended the rule to be a representative template of state NSR programs that 

serve to provide operational flexibility while leveling the regulatory playing field:

[W]e seek to establish a flexible preconstruction permitting program for 

minor stationary sources in Indian country that is comparable to that 

which applies outside of Indian country, in order to create a more level 

regulatory playing field . . . . [T]his can serve as one example of a

program that meets the objectives and requirements of the Act.26

 

24 61 Fed. Reg. 38,250, at 38,251 (July 23, 1996).

25 67 Fed. Reg. 80,186, at 20, 207 (Dec. 31, 2002).

26 71 Fed. Reg. 48,696, at 48,700 (Aug. 21, 2006) (emphasis added).
HOU02:1183339.12 6

Moreover, the proposed rule for Indian Country contains a permit structure that embraces the 

emissions cap principle in the form of minor and major PALs. 27

E. EPA’s Flexible Air Permit Rule

Most recently, in October of 2009, EPA promulgated the federal Flexible Air 

Permitting (“FAP”) Rule. Through this rulemaking, EPA incorporated changes into Title V 

rules that were “intended to clarify and reaffirm opportunities for accessing operational 

flexibility under existing regulations.”28 

In the preamble to the rule, EPA supported flexibility in air permitting. “[W]e . . . 

intend to support states and sources who wish to explore the flexibilities available under the 

existing major NSR regulations.”29 Additionally, EPA recognized that state permitting 

authorities have discretion to preapprove minor NSR changes. “As a general matter, the 

permitting authorities have authority to decide, on a case-by-case basis, the merits of granting an 

advance approval of minor NSR to a particular requesting source.”30 The final rule does not call 

for state Title V or NSR program revisions, but reaffirms pre-existing authority for states to craft 

three forms of flexible air permits. “The purpose of this rulemaking is to clarify and reaffirm 

opportunities within the existing regulatory framework to encourage the wider use of the FAP 

approaches.”31

III. Overview of Texas Flexible Permit Program

The TCEQ's flexible permit regulations in 30 TAC Chapter 116, Subchapter G 

were promulgated in 1994 as a flexible mechanism to comply with State minor NSR permitting 

requirements. This program was established as a way to encourage facilities to install controls 

that would not otherwise be required in exchange for operational flexibility associated with 

emission caps. Under the flexible permit program, a permittee can seek pollutant-specific caps 

that cover certain facilities at the site. These caps are established based on the application of

BACT to all of the facilities contributing to the emissions cap.32 In exchange for this greater 

level of control, sites are provided with an alternative to individual facility emission limits (for 

the covered facilities) as long as the site complies with the emission limits set by the cap. 

The flexible permit also calls for the use of individual emission limitations in 

certain situations.33 Individual limits are used when it is necessary to control off-property

impacts, such as impacts from air toxics, or to meet the NAAQS. Specific emission limits that 

an individual facility cannot exceed may also be established to ensure that federal permitting 

requirements are not circumvented.34 

 

27 Id. at 48,727; 48,744.

28 74 Fed. Reg. 51,418 (Oct. 6, 2009).

29 Id. at 51,422.

30 Id. at 51,426.

31 Id. at 51,429.

32 30 TAC § 116.716(a). Note, however, that a site may have an implementation period to install the new control 

devices. Under this period, an initial cap will be higher than the final cap, which is based on BACT.

33 30 TAC § 116.715(b) and 116.716(b). 

34 30 TAC § 116.715(d).
HOU02:1183339.12 7

The flexible permit program has been quite successful in achieving emission

reductions. For example, flexible permitting has resulted in a reduction of more than 25,000 tons 

tpy of SO2 and more than 10,000 tpy of NOx at a coal and petroleum coke fired power plant and 

a reduction of more than 4,800 tpy of SO2 and CO from a petroleum refinery. 

Issuance of a flexible permit has no impact on the permit holder's obligation to 

comply with federal PSD or nonattainment NSR (“NNSR”) requirements. In fact, for projects 

that constitute major sources or modifications, TCEQ issues a major source permit (PSD or 

NNSR) in addition to the state flexible permit. 

IV. Substance of Asserted Deficiencies

EPA’s concerns on specific aspects of the Texas flexible permit program are 

reproduced and addressed below. Headings are for convenience only—all comments are 

intended to address all aspects of EPA’s proposal.

A. Major NSR Safeguards

1. The Texas definition of “modification” is not clearly at least as 

stringent as the definition of “modification” in EPA’s Major 

NSR SIP rules.

EPA Comment:

 “In evaluating Major NSR SIP revision submittals impacting 

‘‘major modifications,’’ that differ from EPA’s, our review is 

primarily guided by section 111(a)(4) of the Act that describes 

when a ‘‘source’’ is to be considered modified: ‘‘The term 

‘modification’ means any physical change in, or change in the 

method of operation of, a stationary source which increases the 

amount of any air pollutant emitted by such source or which 

results in the emission of any air pollutant not previously emitted.’’ 

Texas did not submit any demonstration showing how its use of the 

definition ‘‘modification’’ was at least as stringent as the 

definition of ‘‘modification’’ in EPA’s Major NSR SIP rules. In 

conducting our review, we particularly were mindful of the United 

States Court of Appeals for the District of Columbia Circuit 

regarding the scope and requirements of Section 111(a)(4) for 

determining whether a change is a ‘‘major modification.’’ See e.g., 

New York v. EPA, 413 F.3d 3 (D.C. Cir. 2005) (‘‘New York I’’) 

(evaluating EPA’s 2002 revised major NSR rules and interpreting 

Section 111(a)(4)).”
HOU02:1183339.12 8

TIP Response:

TCEQ rules provide two separate “modification” definitions. Briefly, a “major 

modification” is a project action that triggers federal NSR review (PSD or Nonattainment).35 In

contrast the TCEQ’s minor source program uses the definition of “modification of an existing 

facility” to determine if a proposed change triggers minor NSR review, and the scope of the 

change is not limited to pollutants that are federally regulated.36 TCEQ has explicitly stated that 

the flexible permit rules and the definition of “modification of an existing facility” do not act as

a shield for federal NSR permitting.37 

Moreover, EPA itself distinguished the definition of “modification” under minor 

NSR from that used for major NSR. In the preamble to its proposed Indian Country rules, EPA 

explained:

In a recent decision, the D.C. Circuit Court of Appeals, ruled that, based 

on the wording of the definition of “modification” in section 111(a)(4) of

the Act, the applicability of major NSR to modifications must be based on 

changes in actual emissions (State of New York, et., v. U.S. EPA, June 24, 

2005). However, because the statutory basis for the minor NSR program 

is section 110(a)(2)(C) of the Act, which does not define or refer to a 

definition of “modification,” we believe that we have discretion in 

defining the term as we think best for the minor NSR program in Indian 

Country . . . .

38

Similarly, Texas has discretion in defining the term for purposes of minor NSR.

Additionally, in 2000, the U.S. EPA’s Environmental Appeals Board (EAB) 

confirmed that there is no “legally prescribed methodology” for the emissions test used for minor 

NSR applicability determinations, and rejected the argument made by EPA enforcement 

personnel that, in the absence of an explicit minor NSR methodology in State rules, the minor 

NSR applicability test must be consistent with that used for federal PSD purposes.39 

2. The program is not clearly limited to Minor NSR, thereby 

allowing new major stationary sources to construct without a 

Major NSR permit.

 

35 30 TAC § 116.12(18) , defined as “a physical change or change in the method of operation of a major stationary 

source that causes a significant project emissions increase of a federally regulated new source review pollutant, and 

a significant net emissions increase of a federally regulated new source review pollutant which triggers federal 

review, such as PSD or nonattainment review.”

36 30 TAC § 116.10(11), defined as “a physical change or change in the method of operation of a facility which 

causes an increase in the amount of any air contaminant emitted by the facility into the atmosphere or results in an 

emission of any air contaminant not previously emitted.”

37 Letter from Richard Hyde, Director, TCEQ Air Permits Division, to Jeff Robinson, Chief, Air Permits Division, 

EPA Region 6, Aug. 30, 2007 (Attached as Exhibit 6).

38 71 Fed. Reg. 48,696, at 48,701 (Aug. 21, 2006).

39 In re Tennessee Valley Authority, 9 EAD 357, 461 (EAB Sept. 15, 2000). 
HOU02:1183339.12 9

EPA Comments:

 “[U]nlike the minor NSR SIP rules for Standard Permits in 30 

TAC 116.610(b) and Permits by Rule in 30 TAC 106.4(a)(3) 

and(4), the submitted rules do not require that construction of a 

major stationary source or a major modification, as defined in the 

Major NSR SIP regulations, must meet the Major NSR permitting 

requirements.”

 “If Texas truly intends for the submitted Flexible Permits State 

Program to apply only to minor NSR, at a minimum Texas must 

amend Subchapter G to include additional provisions that clearly 

limit its applicability to minor NSR as it did in the Texas minor 

NSR SIP at 30 TAC Chapter 106 for Permits by Rule and 30 TAC 

Chapter 116 Subchapter F for Standard Permits.”

TIP Response:

A flexible permit may be used for major and minor projects under the Texas rules. 

The rules make clear, however, that every project for which a flexible permit is issued must also 

comply with federal NSR requirements. As explained above, for projects that constitute major 

sources or modifications, TCEQ issues a major source permit (PSD or NNSR) in addition to the 

state flexible permit. 

The flexible permit rules distinguish between flexible permit and federal NSR 

requirements, and make explicit a flexible permit holder's obligation to comply with those 

federal NSR requirements:

● § 116.711(1) states that a flexible permit application must demonstrate that "[t]he 

emissions from the proposed facility, group of facilities, or account . . . will 

comply with all rules and regulations of the commission," which includes 

Division 5 (nonattainment NSR) and Division 6 (PSD) of Subchapter B.40

● § 116.711(8): "Nonattainment review. If the proposed facility, group of facilities, 

or account is located in a nonattainment area, each facility shall comply with all 

applicable requirements concerning nonattainment review of this chapter."41

● § 116.711(9): "Prevention of Significant Deterioration (PSD) Review. If the 

proposed facility, group of facilities, or account is located in an attainment area, 

each facility shall comply with all applicable requirements in this chapter 

concerning PSD review."42

 

40 30 TAC § 116.711(l).

41 Id. § 116.711(8).

42 Id. § 116.711(9).
HOU02:1183339.12 10

● § 116.718 states that the emissions increase at a facility covered by a flexible 

permit that does not exceed the emission cap is insignificant "for the purposes of 

state new source review under this subchapter." The flexibility provided flexible 

permit holders to make physical or operational changes under the cap is limited to 

minor NSR.43

● § 116.720: “Neither operational nor physical changes authorized under this 

subchapter may result in an increase in actual emissions at facilities not covered 

by the flexible permit unless those affected facilities are authorized pursuant to 

§116.110 of this title (relating to Applicability).” Section 116.110 requires an 

applicability review that can trigger nonattainment NSR or PSD review.

In light of these safeguards, the flexible permit rules constrain the regulated 

community from making major changes without complying with major NSR requirements. 

Regulated entities are subject to clear requirements for the applicability of PSD and NNSR. Any 

attempts by a permittee to circumvent the federal NSR rules is properly addressed through the 

enforcement process, not by mandating redundant rule language as an approval condition.

3. The program does not require that first an applicability 

determination be made whether the construction or 

modification is subject to Major NSR.

EPA Comment:

 “The submitted Program fails to require that the applicability 

of the Major NSR requirements be evaluated prior to 

considering whether the construction of a new source or 

making a change can be authorized under a Flexible Permit.”

TIP Response:

As outlined above, Texas regulations explicitly require permit holders to comply 

with federal NSR rules. Additionally, TCEQ rules such as § 116.150, governing New Major 

Source or Major Modification in Ozone Nonattainment Areas, § 116.151, governing New Major 

Source or Major Modification in Nonattainment Area Other than Ozone, and §§ 116.160-163 

governing the Prevention of Significant Deterioration Requirements, make clear that applicants 

for a flexible permit are subject to an applicability demonstration for both Nonattainment review 

and PSD review. In light of these regulations, the Texas structure contains adequate safeguards 

to ensure that flexible permit applications are subject to federal NSR analyses and comply with

federal NSR.

4. The Texas definition of “account” may result in an emission 

cap applying to multiple major stationary sources.

EPA Comments:

 

43 Id. § 116.718.
HOU02:1183339.12 11

 “Texas SIP defines an “account” to include an entire company 

site, which could include more than one plant and certainly more 

than one major stationary source. . . Accordingly, under a Flexible 

Permit, a single emissions limitation in the emission cap could 

apply to multiple major stationary sources.”

 “By allowing an emission cap to be established for an account, 

which can include multiple major stationary sources, the submitted 

SIP revisions may allow a major stationary source to net a 

significant emissions increase against a decrease occurring 

outside the major stationary source, from facilities on the 

account’s site that are covered under the Flexible Permit.”

TIP Response:

TCEQ rules provide that the definition of “Account” is tied to the definition of

“Site.” 30 TAC 101.1(1) defines “Account”: 

For those sources required to be permitted under Chapter 122 of this title 

(relating to Federal Operating Permits Program), all sources that are 

aggregated as a site. For all other sources, any combination of sources 

under common ownership or control and located on one or more 

contiguous properties, or properties contiguous except for intervening 

roads, railroads, rights-of-way, waterways, or similar divisions.44

Therefore, an account for any major stationary source is limited to a specific plant site. The Title 

V rules, specifically § 122.10(27), provide that a Site is defined as “[t]he total of all stationary 

sources located on one or more contiguous or adjacent properties, which are under common 

control of the same person . . . .” The flexible permit rules specify that only one flexible permit 

may be issued at an account site and a flexible permit may not cover sources at more than one 

account site.45 

Moreover, the regulations governing NNSR and PSD are clear that emissions 

increases are evaluated on a project level rather than increases across a site. For example, 

§116.150 states that the NNSR netting analysis is required unless “the proposed emissions 

increases associated with a project, without regard to decreases, is less than 5 tons per year of 

the individual nonattainment pollutant in areas classified . . . as Serious or Severe.”46 Similarly, 

§ 116.160 states that “netting is required for all modification to existing major sources of 

federally regulated new source review pollutants, unless the proposed emissions increases 

associated with a project, without regard to decreases, are less than major modification 

thresholds for the pollutant . . . .”47 

 

44 30 TAC § 101.1(1).

45 30 TAC § 116.710(a)(1) and (4).

46 30 TAC §116.150(c)(1).

47 30 TAC §116.160(b).
HOU02:1183339.12 12

Reading these rules together shows that they provide sufficient safeguards against

a major stationary source netting a significant emissions increase against a decrease occurring 

outside a site using a flexible permit.

5. Lack of a program requirement for "crosswalks" from prior 

Minor and Major NSR permit terms. 

EPA Comments:

 “The more intricate a plan, the greater the need for detailed 

requirements.”

 “[T]he lack of a program requirement for records with 

detailed crosswalks and of tracking and reporting 

requirements, one cannot determine which grandfathered units 

on a site are covered or not by a Flexible Permit, or which preexisting minor NSR permitted units are covered or not by a 

Flexible Permit, much less which permit terms, limits, and 

conditions are covered, are not covered, are retained, or not.”

TIP Response:

The flexible permit rules require special conditions and other necessary 

conditions, such as requirements for monitoring, testing, recordkeeping, and reporting.48 When a 

flexible permit incorporates facilities that were previously authorized under an existing PSD 

and/or nonattainment permit, TCEQ identifies the special conditions initially contained in those 

federal permits with the appropriate notation (PSD), (NA), or (PSD and NA) in the conditions.49 

The permit representations are also carried forward into the flexible permit.50

An owner or operator can request to change the conditions contained in every 

Texas permit if the circumstances warrant, the applicable requirements are met, and TCEQ 

approves the change.51 Consequently, the rules contemplate that a permittee may request a 

change in conditions from earlier-issued permits when applying for a flexible permit.52 If such 

changes to representations are proposed, those changes are reviewed, and monitoring and 

recordkeeping requirements, consistent with any proposed changes in representations, are then 

added to the special conditions of the permit.53 

For flexible permits that contain major sources authorized under existing PSD 

and/or nonattainment permits, the PSD and/or nonattainment permits are consolidated into the 

 

48 30 TAC § 116.715(c)(6) and (d).

49 Letter from Richard Hyde, Director, TCEQ Air Permits Division, to Jeff Robinson, Chief, Air Permits Division, 

EPA Region 6, Aug. 30, 2007.

50 Id.

51 See 30 TAC §§ 116.110(b); 116.116(a)-(c).

52 30 TAC § 116.721.

53 Id. § 116.715(c)(6).
HOU02:1183339.12 13

flexible permit for tracking purposes. There is no removal of control requirements, or reduction 

in the level of monitoring or testing.54

B. Minor NSR Approval Issues

1. The program is not clearly limited to Minor NSR, thereby 

allowing new major stationary sources to construct without a 

Major NSR permit.

EPA Comment:

 “There are no statutory and/or regulatory provisions that 

clearly prohibit the use of the Program for major stationary 

sources and major modifications. Nor are there any statutory 

and/or regulatory provisions clearly limiting the use of the 

Program to minor sources and/or minor modifications. There 

are no provisions that prohibit the use of the Program for 

construction of new major stationary sources and major 

modifications of existing major stationary sources and minor 

sources.”

TIP Response:

TIP reiterates the points made in Section IV.A.1 above. A flexible permit may be 

used for major and minor projects under the Texas rules. The rules make clear, however, that 

every project for which a flexible permit is issued must also comply with federal NSR 

requirements. As explained above, for projects that constitute major sources or modifications,

TCEQ issues a major source permit (PSD or NNSR) in addition to the state flexible permit. 

Texas’s flexible permit rules explicitly state that sources applying for flexible 

permits are subject to federal NSR. The rules constrain the regulated community from making 

major modifications without complying with federal NSR requirements. 

2. The program lacks replicable, specific, established 

implementation procedures for establishing the emission cap in 

a Minor NSR Flexible Permit.

EPA Comments:

 “There are not specific, established, replicable procedures 

providing available means to determine independently, and for 

different scenarios, how the State will calculate a Flexible 

Permit’s cap and/or individual emissions limitations for a 

company’s site, plants on the site, major stationary sources on 

 

54 Letter from Richard Hyde, Director, TCEQ Air Permits Division, to Jeff Robinson, Chief, Air Permits Division, 

EPA Region 6, Aug. 30, 2007.
HOU02:1183339.12 14

the site, a facility within a major stationary source on the site, 

facilities on the site, a group of units on the site, for one 

pollutant but not another, etc.”

 “Because applicants can choose to establish caps or individual 

emission limitations for just certain pollutants rather than for

all pollutants emitted from the source(s) included in the 

Flexible Permit, the submitted Program also must contain 

legally enforceable procedures for determining both the cap 

and individual emissions limitations for each relevant pollutant 

for each source and address how sources or pollutants not 

included in the Flexible Permit will be regulated.”

TIP Response:

Under the Texas rules, an emissions cap is calculated using the maximum 

expected activity or operating level of a facility and the current BACT applied to each facility. In 

other words, the emissions cap is the sum of the well-controlled emissions of each facility under 

the cap.55 Emission caps are generally calculated for each specific criteria pollutant and other 

pollutants as necessary or desired by the company obtaining the flexible permit. The permittee is 

required to meet BACT as applied to all facilities individually contributing to a particular 

emission cap.

The flexible permit also allows for the use of individual emission limitations.56 

Individual emission limits are used when it is necessary to ensure protection of off-property 

impacts, such as control of air toxics, or to meet the NAAQS. Specific emission limits that an 

individual facility can not exceed may also be established to ensure that federal permitting 

requirements are not circumvented.57

The rules do contain an established and replicable method for determining an 

emissions cap. Namely, the rules require that each flexible permit involve the summing of

BACT emission rates. While BACT determinations may vary between specific types of sources, 

the use of federal and state BACT guidance results in a replicable procedure for establishing 

caps.

Additionally, the rules require that an applicant indentify “each facility” to be 

included in the flexible permit and to identify “each contaminant for which an emission cap is 

desired.”58 

The flexible permits rules do not change the rule governing facilities and 

pollutants not addressed in a plant’s flexible permit. Facilities not incorporated into a plant’s 

flexible permit remain subject to their existing authorizations. This applies with equal force to 

 

55 30 TAC §116.716.

56 30 TAC §§ 116.715(b) and 116.716(b).

57 Id. § 116.715(c)(1) and (d).

58 Id. §116.713 (13).
HOU02:1183339.12 15

pollutants not covered by a flexible permit. If a pollutant is not addressed by a flexible permit, 

the emissions of that pollutant remain subject to existing permit limits.

3. Lack of a program requirement for "crosswalks" from prior 

Minor and Major NSR permit terms and other requirements 

of the Texas SIP. 

EPA Comment:

 “We also are proposing to disapprove the submitted Program 

because it would allow holders of a Flexible Permit to make de 

facto amendments of existing SIP permits including changes in 

the terms and conditions (such as throughput, fuel type, hours 

of operation) of minor and major NSR permits, without a 

preconstruction review by Texas.”

TIP Response:

TIP reiterates the points made in Section IV.A.4 above. 

4. The program lacks the necessary more specialized monitoring, 

recordkeeping, and reporting (MRR) requirements required 

for this type of Minor NSR program.

EPA Comment:

 “The submitted Program lacks provisions explicitly addressing 

the type of monitoring requirements that are necessary to 

ensure that all of the movement of emissions between the 

emission points, units, facilities, plants, etc., still meet the cap 

for the pollutant, still meet the individual emissions limitations, 

and still meet any other applicable state or federal 

requirement.”

TIP Response:

The Texas rules’ stringent provisions for monitoring, recordkeeping, and 

reporting require the regulated community to monitor and submit information sufficient to 

safeguard environmental quality.

As explained above, TCEQ issues flexible permits with conditions on 

recordkeeping, monitoring, and reporting. All flexible permits require recordkeeping that 

contains:

[D]ata sufficient to demonstrate continuous compliance with the emission 

caps and individual emission limitations contained in the flexible permit 
HOU02:1183339.12 16

shall be maintained in a file at the plant site and made available at the 

request of personnel from the commission or any air pollution control 

program having jurisdiction. . . . This information may include, but is not 

limited to, emission cap and individual emission limitation calculations 

based on a 12-month rolling basis and production records and operating 

hours. Additional recordkeeping requirements may be specified in special 

conditions attached to the flexible permit.59

The flexible permit rules contemplate that additional recordkeeping requirements may be tailored 

to the type of source covered by a flexible permit. In this way, the Texas recordkeeping 

requirements are as stringent, if not more stringent, than federal rules.

TIP believes that a comparison of Texas’s reporting requirements to the reporting 

requirements of the proposed Indian Country minor NSR rules highlight that the Texas 

requirements are as stringent, if not more stringent. That rule requires:

(i) Annual submittal of reports of monitoring required under paragraph 

(a)(3) of this section, including the type and frequency of monitoring, and 

a summary of results obtained by monitoring.

(ii) Prompt reporting of deviations from permit requirements, including 

those attributable to upset conditions as defined in the permit, the probable 

cause of such deviations, and any corrective actions or preventive 

measures taken. Within the permit, the reviewing authority must define 

‘‘prompt’’ in relation to the degree and type of deviation likely to occur 

and the applicable emission limitations.60

Further, with respect to emission events and MSS, Texas requirements go far

beyond federal benchmarks. The Texas flexible permit rules require that permit holders comply

with Sections 101.201 and 101.211, which govern reporting and recordkeeping of emissions 

events and maintenance, startup, and shutdown reporting.61 Section 101.201 requires that the 

owner or operator of a regulated entity experiencing an emissions event “shall create a final 

record of all reportable and non-reportable emissions events as soon as practicable, but no later 

than two weeks after the end of an emissions event.”62 This two-week period is even more 

stringent than the proposed Indian Country provision requiring “prompt” reporting of emissions 

events. 

Section 101.201 of the Texas rules also requires that permit holders retain records 

both for emissions events that are reportable and those that are not reportable. The provisions for 

non-reportable events contain requirements similar to the proposed Indian Country rule. Those 

records must be maintained on-site for a minimum of five years and be made readily available 

upon request to commission staff or personnel of any air pollution program with jurisdiction.63 

Additionally, records on non-reportable emissions events are required to include: 

 

59 Id. §116.715(c)(6) (emphasis added).

60 71 Fed. Reg. 48,696 at 48,738.

61 30 TAC § 116.715(c)(9).

62 Id. §101.201(b).

63 Id.
HOU02:1183339.12 17

(1) the physical location of the points at which emissions to the atmosphere 

occurred;

(2) the date and time of the discovery of the emissions event; 

(3) the estimated duration of the emissions; 

(4) the compound descriptive type of the individually listed compounds or 

mixtures of air contaminants, from all emission points involved in the emissions 

event, that are known through common process knowledge or past engineering 

analysis;

(5) the estimated total quantities and the authorized emissions limits for those 

specified compounds or mixtures;

(6) the preconstruction authorization number or rule citation of the standard 

permit, permit by rule, or rule, if any, governing the facilities involved in the 

emissions event; and the authorized emissions limits, if any, for the facilities 

involved in the emissions events;

(7) the basis used for determining the quantity of air contaminants emitted;

(8) the best known cause of the emissions event at the time of recording; 

(9) the actions taken, or being taken, to correct the emissions event and minimize 

the emissions; and 

(10) any additional information necessary to evaluate the emissions event.64

There is, in addition, a wide array of additional Texas rules specifying MRR 

requirements. A cross-section of these provisions are summarized below:

 § 101.10 requires permit holders to submit emissions inventories that detail “actual 

emissions of VOC, NOx, carbon monoxide (CO), sulfur dioxide (SO2), lead (Pb), 

particulate matter of less than 10 microns in diameter (PM10), any other contaminant 

subject to NAAQS, emissions of all HAPs identified in FCAA §112(b), or any other 

contaminant requested by the commission from individual emission units within an 

account.”65

 § 115.116 requires recordkeeping for specified storage tanks for VOCs. Permit

holders must inspect those tanks and record, among other things, a calculation of

emissions for all secondary seal gaps that exceed 1/8 inch (0.32 centimeter) where the 

accumulated area of such gaps is greater than 1.0 square inch per foot (21 square 

centimeters per meter) of tank diameter. These calculated emissions inventory 

reportable emissions must be reported in the annual emissions inventory submittal 

required by §101.10 of this title (relating to Emissions Inventory Requirements).66

 § 117.801 requires reporting on stack testing for NOX emissions. These reports 

include data summarizing emission rates found, reported in the units of the applicable 

emission limits and averaging periods, the maximum rated capacity, normal

maximum capacity, and actual operating level of the unit during the test (in million 

 

64 30 TAC §101.201(b)(2).

65 30 TAC § 101.10.

66 30 TAC §115.116.
HOU02:1183339.12 18

British thermal units, horsepower, or megawatts, as applicable), and description of the 

method used to determine such operating level; the operating parameters of any active 

nitrogen oxides (NOX ) control equipment during the test; and documentation that no 

changes to the unit have occurred since the compliance test was conducted that could 

result in a significant change in NOX emissions.67

 § 111.111 requires that flare logs be kept that detail when flares are observed 

including the time of day and whether or not the flare was smoking. “Flare operators 

shall record at least 98% of these required observations.”68

A review of all Texas MRR requirements shows that sources operating under 

flexible permits are subject to a thorough and rigorous MRR regime.

V. Conclusion

TIP strongly supports full approval of existing Texas flexible permit provisions. 

The Texas permitting program, including the flexible permit provisions, is stringent, 

comprehensive and protective of both the environment and public health. Consistent with the 

findings of EPA’s Flexible Permit Pilot Study,

69 flexible permits in Texas have contributed to the 

sustained improvement of air quality in Texas. The Texas SIP revisions, including flexible 

permits, further the attainment of NAAQS, and so should be fully approved.

 

67 30 TAC § 117.801.

68 30 TAC §111.111.

69 EPA OFFICE OF AIR QUALITY PLANNING AND STANDARDS & EPA OFFICE OF POLICY, ECONOMICS AND 

INNOVATION, Evaluation of Implementation Experiences with Innovative Air Permits, 21.