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07/01/13

 EMISSIONS INVENTORY AND REASONABLE FURTHER PROGRESS PLAN FOR 

THE HOUSTON-GALVESTON-BRAZORIA OZONE NONATTAINMENT AREA 

1997 EIGHT-HOUR SIP REVISION

This document provides a technical review of two revisions to the Houston-GalvestonBrazoria (HGB) State Implementation Plan (SIP) that address emissions inventory and “severe” 

area reasonable further progress (RFP) requirements for the 1997 8-hour ozone national ambient 

air quality standard. The first was adopted on March 10, 2010 and submitted to EPA by the 

Texas Commission on Environmental Quality (TCEQ) on April 1, 2010. The second was 

adopted on April 23, 2013, and submitted on May 6, 2013. Both SIP revisions also establish

motor vehicle emissions budgets (MVEBs) for each milestone year. This TSD will focus on the 

emissions inventory and RFP requirements as they relate to the attainment plan for the 1997 8-

hour ozone standard, as well as the Vehicle Miles Traveled (VMT) offset demonstration.

A. General Requirements

Section 182 of the Clean Air Act (CAA) and the Environmental Protection Agency’s (EPA’s) 

1997 8-hour ozone regulations (40 CFR 51.910) require each moderate and above 8-hour ozone 

nonattainment area to submit an emissions inventory and RFP SIP revision that describes how 

the area will achieve actual emissions reductions of volatile organic compounds (VOC) and 

nitrogen oxides (NOx) from a baseline emissions inventory. An emissions inventory is an 

estimation of actual emissions of air pollutants in an area. The emissions inventory for an ozone 

nonattainment area contains VOC and NOx emissions, which are precursors to ozone formation. 

In this case, a “baseline” emissions inventory is required for the year 2002.

Phase 1 of the 8-hour ozone implementation rule, published on April 30, 2004 (69 FR 23951), 

set out criteria for classifying nonattainment areas under the 1997 8-hour ozone standard. The 

Phase 1 rule also addressed revocation of the 1-hour NAAQS; how anti-backsliding principles 

will ensure continued progress toward attainment of the 8-hour ozone NAAQS; attainment dates; 

and the timing of emissions reductions needed for attainment. On November 29, 2005, EPA 

published the Phase 2 final rule for implementation of the 8-hour standard. The Phase 2 rule 

addressed the RFP control and planning obligations as they apply to areas designated 

nonattainment for the 1997 8-hour ozone NAAQS (70 FR 71612). The Phase 2 final rule was 

revised on June 8, 2007 (72 FR 31727). Among other things, the Phase 1 and 2 rules outline the 

SIP requirements and deadlines for various requirements in areas designated as moderate 

nonattainment and above. The rules set a due date of June 15, 2007 for the required base year

emissions inventory, RFP plan, modeling and attainment demonstration, MVEB, and

contingency measures (40 CFR 51.908(a), (c)).

Section 182(b)(l) of the CAA and EPA’s 1997 8-hour ozone implementation rule (40

CFR 51.910) require each 8-hour ozone nonattainment area designated moderate and above to

submit for review and approval into its SIP an emissions inventory and RFP plan that describes

how the area will achieve actual emissions reductions of VOC and NOx from a baseline
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emissions inventory. For a moderate 8-hour ozone nonattainment area with an attainment date

more than 5 years after designation, a 15 percent RFP reduction in ozone precursor emissions is

required within 6 years (2002-2008). For a moderate area with an approved 15 percent rate-of 

progress (ROP) plan under the 1-hour standard, states can use reductions from VOC or NOx or a

combination of either. For a moderate area without an approved ROP plan, a 15% reduction in 

VOC is required. The reductions may come from anywhere within the 8-hour nonattainment

area. Table 1 outlines these requirements.

Table 1. RFP Requirements for Moderate 8-Hour Ozone Nonattainment Areas with 

Attainment Dates More than 5 Years after Designation

Area Requirement 40 CFR Reference

With approved 15%

VOC ROP plan

15% VOC and/or NOx reductions

(2002 —2008)

51.910(a)(1)(iii)(B)(2) &

51.910(b)(2)(b)(ii)

Without approved15% VOC 

ROP plan

15% VOC reductions (2002 -2008) 

The reductions may come from

anywhere within the 8-hour

nonattainment area.

51.910(a)(l)(iii)(B)(1)

For an area classified as severe, which the Houston-Galveston-Brazoria (HGB) area is, additional 

reductions must be achieved according to the following schedule:

• 9% from 2009 through 2011; 

• 9% from 2012 through 2014; 

• 9% from 2015 through 2017; and

• 3% in 2018 (the attainment year).

This is 3% per year for each time period. 

In addition, RFP plans must include contingency measures, which are additional controls that 

would be implemented if the area fails to make reasonable further progress (See CAA section

172(c)(9)). Implementation of these measures would provide additional emissions reductions of 

up to three percent of the adjusted base year inventory (or a lesser percentage that will make up 

the identified shortfall). For more information on contingency measures, please see the April 16, 

1992 General Preamble (57 FR 13498, 13510) and the November 29, 2005 Phase 2 8-hour ozone 

standard implementation rule (70 FR 71612, 71650). RFP plans must also include MVEBs, 

which are the allowable on-road mobile emissions an area can produce and continue to 

demonstrate RFP. EPA’s regulations concerning MVEBs may be found at 40 CFR Part 93.

B. HGB Background

In 1997, EPA revised the health-based NAAQS for ozone, setting it at 0.08 parts per

million (ppm) averaged over an 8-hour time frame. EPA set the 8-hour ozone standard based on

scientific evidence demonstrating that ozone causes adverse health effects at lower ozone

concentrations and over longer periods of time, than was understood when the pre-existing

1-hour ozone standard was set. EPA determined that the 8-hour standard would be more

protective of human health, especially children and adults who are active outdoors, and

individuals with a pre-existing respiratory disease, such as asthma.
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On April 30, 2004 (69 FR 23951), EPA finalized its attainment/nonattainment

designations for areas across the country with respect to the 8-hour ozone standard. These

actions became effective on June 15, 2004. Among those nonattainment areas was the HoustonGalveston-Brazoria (HGB) moderate nonattainment area (NAA). This NAA includes the 

counties of Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and 

Waller. These counties were also classified as a severe nonattainment area under the 1-hour 

ozone standard (November 6, 1991, 56 FR 56694). EPA approved a 15% VOC Rate of Progress 

plan under the 1-hour standard on May 22, 1997 (62 FR 27964). Pursuant to Phase 1 of the 8-

hour ozone implementation rule, an area is classified under Subpart 2 of the CAA based on its 8-

hour design value if that area had a 1-hour design value at or above 0.121 ppm (the lowest 1-

hour design value in Table 1 of Subpart 2). Based on this criterion, the HGB NAA was classified 

under Subpart 2 as a moderate nonattainment area for the 1997 8-hour ozone standard.

Table 2 identifies the 1-hour ozone standard emissions inventory and rate of progress (ROP) 

SIPs approved by EPA for the HGB area. ROP refers to reasonable further progress for the 1-

hour ozone standard.

Table 2. HGB 1-hour Ozone Standard Emissions Inventory and Rate of Progress SIPs 

Approved by EPA

SIP Federal Register

Emissions Inventory 2/14/2005, 70 FR 7407 

15% VOC ROP Plan 11/14/2001, 66 FR 57195

Post 1996 ROP Plan 2/14/2005, 70 FR 7407

On May 23, 2007 the Texas Commission on Environmental Quality (TCEQ) adopted as a SIP 

revision the RFP plan for the HGB 8-hour ozone nonattainment area. The RFP plan was 

submitted to EPA on May 30, 2007. The plan documents required reductions in NOx emissions,

and includes a 2002 baseline emissions inventory and a MVEB for 2008. EPA approved this 

RFP Plan, Motor Vehicle Emissions Budgets, and Revised 2002 Base Year Emissions Inventory 

on April 22, 2009 (74 FR 18298).

On June 15, 2007, EPA received a request from Texas Governor Rick Perry seeking voluntary 

reclassification of the HGB area. The Governor requested that EPA reclassify the HGB area 

from a moderate nonattainment area to a severe nonattainment area under the 1997 8-hour ozone 

standard. Reclassification of the area to severe required Texas to develop and submit a revised 

RFP SIP. The EPA reclassified the eight-county HGB area from a moderate to a severe 

nonattainment area for the 1997 eight-hour ozone National Ambient Air Quality Standard 

(NAAQS) effective on October 31, 2008. (73 FR 56983). 

Required severe area RFP reductions are an average of 3 percent per year of VOC and/or NOx 

for: (1) the 6-year period following the baseline emissions inventory year (2002) and (2) all 
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remaining 3-year periods after the first 6-year period out to the area's attainment date (40 CFR 

51.910(a)(1)(B)). A severe area RFP plan was due to EPA by April 15, 2010. This RFP SIP 

revision was submitted to EPA on April 1, 2010.

Less than one month before (March 2, 2010) Texas submitted the April 1, 2010 submittal, EPA 

released a new mobile source emissions estimate model that better reflects real-world emissions 

from on-road vehicles. This model replaced the MOBILE 6.2 model that was used to create the 

April 2010 motor vehicle emission budgets (MVEBs) that are the basis for the RFP 

demonstration submitted in April 2010. Because states must begin demonstrating transportation 

conformity using MOVES by March 2, 2013, Texas updated its MVEBs using MOVES2010a in 

preparation for the 2013 transportation conformity requirement. Because this update involves a 

SIP revision, the state also has updated and replaced portions of the 2010 RFP demonstration to 

correspond to the new MVEBs based on the MOVES 2010a model. This revision was submitted 

on May 6, 2013.

C. EPA Review and Analysis

EPA reviewed the Texas submittal for consistency with the requirements of EPA 

regulations. The following is a summary of the analysis based on the information provided by 

Texas.

1. Base Year Emissions Inventory

An emissions inventory is a comprehensive, accurate, and current inventory of actual emissions 

from all sources. The Base Year Inventory is the starting point for calculating the reductions 

necessary to meet the requirements of the CAA. The emissions inventory is required by section 

172(c)(3) of the CAA. For ozone nonattainment areas, the emissions inventory needs to contain 

VOC and NOx emissions because these pollutants are precursors of ozone. EPA recommended 

2002 as the base year emissions inventory, and it is therefore the starting point for calculating 

RFP. On May 13, 2005, Texas submitted the 2002 base year inventory to EPA as part of a SIP 

revision for the HGB 8-hour ozone non-attainment area. It was approved by EPA on April 22, 

2009 (74 FR 18298).

The inventory includes all area, point, non-road mobile, and on-road mobile source emissions in 

the HGB ozone nonattainment area. The inventory also includes a description of the methods 

used to estimate emissions:

Point Source Emissions: Industrial sources are required to submit emissions data to TCEQ 

annually. TCEQ stores the data in the STARS database. Inventory data for 2002 was obtained 

from STARS in 2006, and point source emissions were calculated using TCEQ and EPA 

guidance documents. A more detailed description of point source emissions estimation can be 

found in chapter 2 and Appendix 2 of the state submittal. 

Area Source Emissions: TCEQ developed the area source emission inventory in 2003. Since 

then, TCEQ updated the inventory by using improved methods and improved emission factors to 
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estimate emissions from several area source categories, such as industrial and residential fuel 

usage, gasoline stations, oil and gas production, and industrial coatings. Texas has performed 

studies and conducted surveys in order to obtain more accurate data and revise the inventory 

accordingly. These studies are described in chapter 2, section 2.3 of the submittal. We have 

reviewed these approaches and have determined that they follow EPA guidance

On-road Emissions: TCEQ updated the on-road mobile emissions in the May 6, 2013 submittal

using the new MOVES2010a model. MOVES2010a is an emission factor model predicting 

gram per mile emissions of hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), 

carbon dioxide (CO2), particulate matter (PM), and toxics from cars, trucks, and motorcycles 

under various conditions. EPA reviewed the on road emission estimates approach and 

methodology and determined that they follow EPA guidance. A detailed description of on road 

emission estimates is found in chapter 7 of the TCEQ May 6, 2013 submittal.

Non-road Emissions Inventory: TCEQ updated the HGB non-road emissions by using data 

obtained from studies and surveys of industrial and construction equipment. The EDMS aircraft 

model was used to produce aircraft emission data, and locomotive emissions were updated using 

survey results of engine activities. Using this area-specific information and the latest version of 

the NONROAD model has resulted in a substantial improvement in the inventory over estimates 

based on EPA’s default values. We find the approach and methodology used by TCEQ follows 

EPA guidance. A full description of the approach is detailed in section 2.4 of the state’s 

submittal.

In the 2010 RFP SIP submittal, Texas updated the 2002 emissions inventory for point, 

area, on-road mobile and non-road mobile sources. In the 2013 SIP revision Texas further 

updated the on-road mobile source inventory using the EPA’s Motor Vehicle Emission Simulator 

(MOVES2010a) on-road emissions calculation model in lieu of the older EPA MOBILE6 model. 

Table 3 compares the previously approved base year emissions inventory with the updated base 

year inventory adopted by Texas in 2013.

Table 3: Revisions to the 2002 RFP Base Year Emissions Inventory (tons/day) 

Source Type NOx VOC

Old New Old New

Point 339.48 339.29 297.12 316.62

Area 40.15 89.11 219.51 407.61

On-road Mobile 283.20 371.89 114.30 124.47

Non-road Mobile 167.74 156.98 112.37 84.32

830.57 957.27 743.30 933.02
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Total

We find we can approve the updated 2002 base year emissions inventory.

2. Adjusted Base Year Inventory, Required Reductions and 2018 Target Level 

Emissions

The process for determining the emissions baseline from which the RFP reductions are 

calculated is described in section 182(b)(l) of the CAA and 40 CFR 51.910. This baseline value 

has been determined to be the 2002 adjusted base year inventory. Sections 182(b)(1)(B) and (D) 

require the exclusion from the base year inventory of emissions benefits resulting from the 

Federal Motor Vehicle Control Program (FMVCP) regulations promulgated by January 1, 1990 

and the Reid Vapor Pressure (RVP) regulations promulgated June 11, 1990 (55 FR 23666). The 

FMVCP and RVP emissions reductions are determined by the state using the new EPA on-road 

mobile source emissions modeling software MOVES2010a. The FMVCP and RVP emission 

reductions are then removed from the base year inventory by the state, resulting in an adjusted 

base year inventory. The emission reductions needed to satisfy the RFP requirement are then 

calculated from the adjusted base year inventory. These reductions are then subtracted from the 

adjusted base year inventory to establish the emissions target for the RFP milestone year (2018).

For severe areas like the HGB NAA, the CAA specifies a 15 percent reduction in ozone 

precursor emissions over an initial 6-year period, plus 9% for each milestone year, and 3% for 

each year past the milestone year. In the Phase 2 Implementation Rule (70 FR 71612), EPA 

interpreted this requirement for areas that were also designated nonattainment and classified as 

moderate or higher for the 1-hour ozone standard. In the Phase 2 Rule, EPA provided that an 

area classified as moderate or higher that has the same boundaries as an area, or is entirely 

composed of several areas or portions of areas, for which EPA fully approved a 15 percent plan 

for the 1-hour NAAQS, is considered to have met the requirements of section 182(b)(1) of the 

CAA for the 8-hour NAAQS. In this situation, a severe nonattainment area is subject to RFP 

under section 172(c)(2) of the CAA and shall submit, no later than 3 years after designation for 

the 8-hour NAAQS, a SIP revision that meets the requirements of 40 CFR 51.910(b)(2). The 

RFP SIP revision must provide for a 15 percent emission reduction (either NOx and/or VOC) 

accounting for any growth that occurs during the 6-year period following the baseline emissions 

inventory year, that is, 2002-2008, plus 3% per year as described above out to the attainment 

year.

The HGB ozone nonattainment area under the 1997 8-hour ozone standard has the same 

boundary as the HGB NAA under the prior 1-hour ozone standard. Under the 1-hour ozone 

standard, the HGB nonattainment area was classified as severe. EPA fully approved Texas’s 

15% plan for the HGB 1-hour severe ozone NAA (66 FR 57105) on November 14, 2001. The 

Post 1996 ROP Plan was approved by EPA on 2/14/2005 (70 FR 7407). Therefore, according to 

the Phase 2 Rule, the RFP plan for the HGB 8-hour ozone NAA may use either NOx or VOC 

emissions reductions (or both) to achieve the required 15 percent emission reduction.
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According to section 182(b)(1)(D) of the CAA, emission reductions that resulted from the 

FMVCP and RVP rules promulgated prior to 1990 are not creditable for achieving RFP emission 

reductions. Therefore, the 2002 base year inventory must be adjusted by subtracting the VOC 

and NOx emission reductions that are expected to occur between 2002 and the future milestone 

years due to the FMVCP and RVP rules. The adjustments are calculated in the following 

manner:

A) Estimate the actual anthropogenic base year inventory for both VOC and NOx in 2002 

with all 2002 control programs in place. 

B) Using the same highway vehicle activity inputs used to calculate the actual 2002 

inventory, run the appropriate motor vehicle emissions model for 2002 and for 2008 with all 

post-1990 CAA measures turned off. Any other local inputs for vehicle inspection and 

maintenance (I/M) programs should be set according to the program that was required to be in 

place in 1990. Fuel RVP should be set at 9.0 or 7.8 depending on the RVP required in the local 

area as a result of fuel RVP regulations promulgated in June 1990.

C) Calculate the difference between 2002 and 2008 VOC emissions factors calculated in 

Step B and multiply by 2002 VMT. The result is the VOC emissions reductions that will 

occur between 2002 and 2008 without the benefits of any post-1990 CAA measures. 

These are the non-creditable VOC reductions that occur over this period. Calculate the 

difference between 2002 and 2008 NOx emissions factors calculated in Step B and 

multiply by 2002 VMT. This result is the NOx emissions reductions that will occur 

between 2002 and 2008 without the benefits of any post-1990 CAA measures. These are 

the non-creditable NOx reductions that occur over this period.

D) Subtract the non-creditable VOC reductions calculated in Step C from the actual

anthropogenic 2002 VOC inventory estimated in Step A. Subtract the non-creditable 

NOx reductions calculated in Step C from the actual anthropogenic 2002 NOx inventory 

estimated in Step A. These adjusted VOC and NOx inventories are the basis for 

calculating the target level of emissions in 2008.

E) The target level of VOC and NOx emissions in 2008 needed to meet the 2008 ROP

requirement is any combination of VOC and NOx reductions from the adjusted 

inventories calculated in Step D that total 18 percent. For example, the target level of 

VOC emissions in 2008 could be a 10 percent reduction from the adjusted.

Texas set forth its updated calculations for the adjusted base year inventory and 2018 RFP target

levels in Chapter 7, section 7.2.5.3, of the 2013 submittal, Updated 2002 Adjusted Base Year 

Inventories for the Base and Milestone Years. The following demonstrates the steps A-E listed 

above for the HGB NAA.
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A) The HGB NAA 2002 anthropogenic base year inventories for VOC and NOx are found in 

Table 2-13 through Table 2-16 in Chapter 2.7 of the 2010 RFP Plan and Table 7-3 of the 

2013 RFP update. Biogenic emissions are not included in the inventories used to 

demonstrate RFP. The updated 2002 base year emissions are summarized in Table 4 

below. 

Table 4. RFP 2002 Base Year Emissions Inventory Summary

RFP 2002 Baseline Emissions Inventory Summary

Source 

Type

NOx VOC NOx VOC

Uncontrolled Controlled

Point 339.29 316.62 339.29 316,62

Area 89.11 407.61 89.11 407.61

Onroad 

Mobile

552.30 205.76 371.89 124.47

Nonroad 

Mobile

166.98 100.15 156.98 84.32

Total 1147.68 1030.14 957.27 933.02

B & C) Texas calculated the non-creditable emission reductions between 2002 and 2008

by modeling its 2002 and 2018 motor vehicle emissions with all post-1990 CAA measures

“switched off’, and calculating the difference. See summary Tables 7-4 and 7-5 of the 2013 RFP 

update plan. The non-creditable reductions are calculated in Table 5, below.

Table 5. Houston-Galveston-Brazoria NAA Non-Creditable Emission Reductions from 2002-

2008 (Ozone Season tpd)

Source Category VOC NOx

(i) 2002 On-Road (Adjusted) 205.76 552.30

(ii) 2008 On-Road (Adjusted) 205.89 578.29

Non-creditable Reductions 

(i)-(ii)

- 0.13 - 25.99

D & E) Texas’s calculation of its portion of the HGB NAA 2002 VOC and NOx inventories 

adjusted relative to 2008 and VOC and NOx target levels for 2008 are found in Table 7-17 of the 

2013 RFP update plan, and are summarized in Table 6, below.
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Table 6. HGB NAA 2008 RFP Target Level Calculations with NOx Substitution (Ozone Season 

tpd)

Description Formula NOx VOC

A 2002 Rate-Of Progress Base Year 

Inventory

957.27 933.02

B FMVCP/RVP Reductions Between 2002 

And 2008

-25.99 -.013

C 2002 Adjusted Base Year Inventory 

Relative To 2008

A- B 983.26 933.15

D RFP Ratio 17% 1%

E Emissions Reductions Required Between 

2002 & 2008

C * D 167.15 9.33

F Target Level for 2008 C-E 816.10 923.82

We agree with the adjusted base year inventory set forth in the submittal.

3. Control Measures

The control measures that achieved the necessary emission reductions to meet the RFP 

requirements are discussed in chapter 4 of the March 10, 2010 submittal and again in Chapter 7 

of the 2013 submittal at 7.4 Control Measures to Achieve Target Levels. The mass emissions 

cap and trade program (MECT) at such sources as utility boilers, turbines, duct burners, heaters 

and furnaces, IC engines, and industrial burners provides large reductions in the 2002-2008 time 

period. After that the Federal Motor Vehicle Control Program (FMVCP) continues to provide 

the most emission reductions through the 2018 attainment year. Non-road emission reductions 

are from Federal controls on non-road engines. The mobile non-road emission reductions were 

estimated using the NONROAD 2005 model, with customized data files to reflect emissions 

generated by non-road mobile equipment in Texas. Emissions from locomotives, aircraft and 

support equipment, and commercial marine vessels were calculated outside of the NONROAD 5 

model using EPA approved methodologies. EPA agrees with Texas’ projected emissions and 

emission reductions for these three non-road mobile sources. Reductions in on-road mobile 

source emissions come from the inspection and maintenance (I/M) program, summer

reformulated gasoline, the Federal Motor Vehicle Control Program (FMVCP), and the Texas low 

emission diesel program. A description of the control measures and a summary of the emission 

reductions are listed in table 4. EPA agrees with the emission reduction projected from these 

rules. The state rules relied on in this plan were previously approved at various times and listed 

in Table 7. Other than the Tank Landing Loss Rule, the other three rules have been revised and 

approved as revised by EPA since the initial approval. 

Table 7. EPA Approved State Rules for RFP

State Rule EPA Approval

Mass Emissions Cap and Trade 66 FR 57252, November 14, 2001

Tank Landing Loss Rule 75 FR 15348, March 29, 2010

Vehicle Inspection and Maintenance 66 FR 57261, November 14, 2001
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Texas Low Emission Diesel (On- and non-road) 66 FR 57196, November 14, 2001

In the section discussing Control Measures, the on-road mobile source controls were 

updated from the 2010 RFP submittal to reflect the new mobile model MOVES2010aIn the final 

submittal, the state provided the cumulative emission reductions by year and by pollutant, in 

easily understood tables.

In addition, in the final submittal, the state consolidated some of the measures into 

broader categories than were presented in the 2010 submittal. These were the FMVCP category 

and the I/M control strategy category. The broader categories were then footnoted to define what 

individual measures were in them. This is an acceptable approach that makes reviewing the 

submittals easier. Tables 8 and 9 contain a list of the control measures and the emission 

reductions achieved by milestone year and pollutant.

Table 8. Summary of HGB RFP NOX Emission Reductions (Tons/Day)

Control Strategy Description 2008 2011 2014 2017 2018

Mass Emissions Cap and Trade Program 

(MECT) 

219.83 227.65 243.87 263.23 269.94

Tank Landing Loss Rule 0.00 0.00 0.00 0.00 0.00

Federal Portable Fuel Container (PFC) Rule 0.00 0.00 0.00 0.00 0.00

Federal Motor Vehicle Control Program

(FMVCP)

150.64 319.72 409.05 486.84 510.15

Federal Reformulated Gasoline (RFG) 150.64 189.54 213.44 235.00 241.29

Inspection and Maintenance (I/M) 17.35 16.62 11.80 8.03 7.10

On-road Texas Low Emission Diesel (TxLED) 6.03 5.08 3.52 2.55 2.36

Tier I and II Locomotive NOX standards 11.74 12.75 14.09 15.24 16.04

Small Non-Road Spark Ignition (SI) Phase I -0.301 -0.391 -0.471 -0.561 -0.581

Heavy-Duty Non- Road Engines 5.76 7.91 9.64 12.02 12.56

Tier 2 and 3 Non-Road Diesel Engines 8.13 14.01 18.76 23.25 24.29

Federal Standards for New Small Non-Road

Spark Ignition (SI) Engines (Phase II) 

1.25 1.65 1.85 1.99 2.04

Federal Standards for New Large Non-Road SI

and Recreational Marine

12.27 20.30 27.01 31.10 32.13

Non-road TxLED 2.87 2.59 2.14 1.73 1.59

Non-road RFG 0.00 0.00 0.00 0.00 0.00

Tier 4 Federal Standards for Diesel Engines 0.00 0.52 4.67 10.96 12.82

Federal Marine Diesel Tier 2 1.96 3.23 4.72 6.20 6.90

Sum of Control Reductions 678.70 821.18 964.09 1097.58 1138.63

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The negative NOx emissions reductions number from Small Non-Road SI Phase I engines is 

attributed to fleet growth in light of more stringent standards.

Table 9. Summary of HGB RFP VOC Emission Reductions in tons per day

Control Strategy Description 2008 2011 2014 2017 2018

Mass Emissions Cap and Trade Program 0.00 0.00 0.00 0.00 0.00
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(MECT)

Tank Landing Loss Rule 0.00 11.50 11.50 11.50 11.50

Federal Portable Fuel Container (PFC) Rule 0.00 3.68 9.65 10.10 10.25

Federal Motor Vehicle Control Program

(FMVCP) 109.17 148.83 188.98 222.89 232.44

Reformulated Gasoline (RFG) 22.03 22.79 17.27 14.12 13.48

Inspection and Maintenance (I/M) 9.56 9.77 7.99 6.86 6.51

On-road Texas Low Emission Diesel (TxLED) 0.00 0.00 0.00 0.00 0.00

Tier I and II Locomotive NOX standards 0.27 0.34 0.43 0.53 0.59

Small Non-Road Spark Ignition (SI) Phase I 1.77 2.50 3.23 3.95 4.19

Heavy-Duty Non- Road Engines 4.73 6.82 8.54 10.17 10.58

Tier 2 and 3 Non-Road Diesel Engines 0.95 1.68 2.32 2.95 3.10

Small Non-Road Spark Ignition (SI) Engines (Phase II) 16.70 20.81 22.72 24.13 24.57

Large Non-Road SI and Recreational Marine 4.14 7.96 11.37 14.03 14.76

Non-road TxLED 0.00 0.00 0.00 0.00 0.00

Non-road RFG 0.04 0.13 0.22 0.30 0.33

Tier 4 Diesel Engines 0.00 0.03 0.26 0.52 0.59

Federal Marine Diesel Tier 2 0.08 0.12 0.18 0.24 0.26

Sum of Control Reductions 169.44 236.96 284.66 322.29 333.15

 

4. RFP Demonstration

Chapter 3 of the March 10, 2010 submittal discusses in detail the approach and 

methodology used to calculate both the target emission levels and RFP demonstration. EPA 

reviewed the approach and methods Texas used to calculate the rate of progress emission 

reductions and target levels and found them to be performed in accordance with EPA guidelines. 

The 2013 submittal provides a revised summary of the RFP demonstration that includes the new 

on-road modeling conducted with MOVES2010a. Texas documented the correct amount for the 

total expected reductions in the nonattainment area by showing each step, discussing any 

assumptions made, and stating the origins of the numbers used in the calculations. The EPA 

guidelines are found in Appendix A of the Phase 2 8-hour ozone implementation rule (November 

29, 2005 Federal Register, 70 FR 71642).

To show that the reductions associated with these control measures are adequate to meet 

the reduction requirement, the 2002 base year emissions are projected to 2018. The total amount 

of NOx emissions in the 2018 projection inventory must be equal to or less than the 2018 target 

inventories (shown in Line 1 of Table 10 below). Texas developed the 2008 projection inventory 

through a two-step process. First, Texas applied a model that incorporated a number of 

economic, industrial, and population growth factors (the EGAS model). Next, Texas applied the 

control measures described above. As illustrated in Table 10, for both pollutants the projected 

2018 inventory is less than the target level of emissions. Therefore, the control measures 
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included in the 2008 projection inventory are adequate to meet the 15% RFP requirement plus 

3% contingency requirement, the 9% requirement for 2009-2011, the 9% requirement for 2012-

2014, the 9% requirement for 2015-2017, the 3% requirement for 2018, and 3% for contingency 

measures.

Table 10 is a summary of the RFP demonstration for the HGB RFP SIP and shows that 

the severe area RFP requirements are met for the HGB area. Chapter 7 of the 2013 SIP describes 

the RFP demonstration. The measures in table 4-1 and table 4-2 of the SIP are included in the 

RFP demonstration and captured in table 10 below.

Table 10. Summary of RFP Demonstration for HGB (Tons/Day)

Inventory NOx VOC

1 2018 Target 555.22 907.50

2 2018 Uncontrolled Emissions 1636.21 1210.28

3 2008-2017 RFP Emission Reductions 1097.60 302.46

4 2017-2018 RFP Emission Reductions 41.03 10.86

5 Controlled RFP Emissions Forecast (Line 2 

minus Line 3 minus Line 4)

497.59 896.95

6 Amount of Creditable Reductions Reserved 

for 2009-2018 Contingency 

24.58 4.67

7 2018 Projected Emissions after RFP 

Reductions (Add Lines 5 and 6)

522.17 901.62

8 Excess(+)/Shortfall(-) (Line1 minus Line 7) +33.04 +5.88

9 RFP Met? (Line 7 < Line 1) Yes Yes

It is worth noting here that in our review, we discovered a discrepancy in the calculation 

of VOC emission reductions that does not influence the final outcome of the RFP demonstration. 

In examining the values for the creditable RFP reductions for each milestone year starting in 

2008, we found that the values listed in Tables 7-29 through 7-31 of the submittal did not match 

with the values for the cumulative emission reductions for VOCs shown in Tables 7-33 through 

7-36 of the submittal. The values in Tables 7-29 through 7-33 did, however, match with the 

corresponding values shown in Appendix C, starting with Sheet 5. We consulted with TCEQ 

about this discrepancy. TCEQ discovered an error in their spreadsheet calculations that lowered 

the VOC values in Tables 7-29 through 7-31 by 19.82 tons/day of VOC. This error resulted in a 

conservative projection of VOC emission reductions taking place by that amount. The resulting 

surplus of VOCs could have been greater by 19.82 tons/day. TCEQ does not intend to submit a 

correction to this RFP demonstration, but will address the error in their next applicable SIP 

submittal.

We agree that the demonstration for RFP is met even with the discrepency.

5. Contingency Measures

For ozone nonattainment areas classified as moderate or above, states must include in 

their submittal contingency measures to be implemented if the area fails to make reasonable 
13

further progress (CAA sections172(c)(9) and 182(c)(9)). Contingency measures are additional 

controls to be implemented in the event the area fails to meet a RFP milestone. They are 

intended to achieve reductions over and beyond those relied on in the RFP demonstrations. This 

could include federal measures and local measures already scheduled for implementation. The 

CAA does not preclude a state from implementing such measures before they are triggered. EPA 

interprets the CAA to require sufficient contingency measures in the RFP submittal, so that upon 

implementation of such measures, additional emissions reductions of up to three percent of the 

adjusted base year inventory (or a lesser percentage that will make up the identified shortfall) 

would be achieved in the year after the failure has been identified. For more information on 

contingency measures please see the April 16, 1992 General Preamble (57 FR 13512) and the 

November 29, 2005 Phase 2 8-hour ozone standard implementation rule (70 FR 71612).

Texas used emission reductions in excess of those needed for RFP as the contingency 

measures for the HGB RFP SIP (see Tables 7-47 and 7-48 in the state’s submittal). Tables 11

and 12 below demonstrate that the requirement for contingency measures is met for the 

milestone years and the 2018 attainment year in the HGB RFP SIP.

Table 11. Contingency Measure Demonstration for the 2018 Attainment Year (Tons/Day)

Description NOx VOC

2018 Adjusted Base Year emissions 

inventory

1003.92 935.59

Percent for contingency calculation (total 

of 3%)

2.50 0.50

3% needed for contingency 25.10 4.68

Total contingency reductions 55.04 11.53

Contingency excess (+) or shortfall (-) +29.95 +6.85

Contingency met? Yes Yes

Table 12. Contingency Measure Demonstration for Milestone Years 2008-2017 (Tons/Day)

Description NOx VOC

2008 Adjusted Base Year Inventory 983.26 933.15

Percent for milestone year 2011 

contingency calculation (total of 3%)

2.50 0.50

2008 to 2009 required contingency 

reductions (ABY emissions inventory x 

contingency percent)

24.58 4.67

Reserved surplus reduction from 2008 

RFP demonstration

24.58 4.67

Contingency excess (+) or shortfall (-) 0 0
14

Contingency met? Yes Yes

We agree with the contingency measure demonstration for the RFP SIP.

6. VMT, On-Road Emissions, and Transportation Control Measures

The Texas RFP SIP contains a serious area element under this heading. The April 1, 

2010, SIP at 4.6 states, “Transportation control measures (TCM) are required to offset growth in 

vehicle miles traveled (VMT) that results in an increase in vehicle emissions for nonattainment 

areas classified as serious [emphasis added] under the National Ambient Air Quality Standards 

(NAAQS).” In the CAA this serious area element is found in 182(c)(5), Transportation Control. 

This element may have been confused in the 2010 submittal with the severe area Vehicle Miles 

Traveled requirement in 182(d)(1), often referred to as the VMT offset demonstration. EPA 

commented on this and the State revised the VMT offset portion of the SIP in the May 6, 2013 

submittal.

The serious area Transportation Control requirement has the state develop a 

transportation control program demonstration based on section 108(f) “that will reduce emissions 

to levels that are consistent with emission levels project in such [attainment] demonstration.” 

CAA section 182(c)(5). This includes considering “current aggregate vehicle mileage, aggregate 

vehicle emissions, congestion levels, and other relevant parameters...consistent with those used 

for the area’s demonstration of attainment.” Id.

The severe area Vehicle Miles Traveled requirement calls for “specific enforceable 

transportation control strategies and transportation control measures to offset any growth in 

emissions from growth in vehicle miles traveled or number of vehicle trips in such area and to 

attain reduction of motor vehicle emissions as necessary...to comply with the requirement of 

subsection (b)(2)(B) and (c)(2)(B) (pertaining to periodic emissions reduction requirements).” 

This requirement also advises states to “consider measures specified in section 108(f)...” Id.

The serious area Transportation Control requirement is a more general demonstration that 

shows how the TCMs adopted by the state will help show achievement of attainment in the 

attainment demonstration. The VMT Offset requirement must also include/consider 

transportation control strategies and demonstrate how any TCMs (“as necessary”) are used to 

reduce emissions enough to offset the emissions resulting from an increase in emissions from an 

increase in VMT. This is a more rigorous demonstration than the Transportation Control 

requirement.

As stated above, the RFP SIP contains a demonstration that satisfies the serious area 

Transportation Control measure. The state shows how VMT grows from 2002 (128.1 million 

miles per day) steadily to 2018 (184.0 million miles per day). The RFP controlled emissions for 

NOx and VOC (which do not include TCMs) are shown to decrease steadily from 2002 through 

2018. See Table 7-43 of the 2013 submittal. Although the TCMs are not needed to meet the 
15

RFP requirements, they are included as part of the control strategy for the attainment 

demonstration. 

EPA has determined that such a demonstration, while required in the CAA, does not have 

to be submitted as part of a SIP. We find that what was submitted is approvable as it

demonstrates how the emissions from on-road vehicles steadily declines to at least 2030 while, at 

the same time, the VMT continues to increase. See section 7.4.6.1 of the 2013 submittal.

The 2010 submittal attempted to use the above demonstration to meet the VMT offset 

requirement in 182(d)(1). We commented during comment period as follows: 

In section 7.4.6 of the 2012 proposal, the U.S. Ninth Circuit Court of Appeals Decision is 

mistakenly discussed in relation to a serious area requirement, Transportation Control, 

section 182(c)(5). This is a once every three year exercise to demonstrate that the increase 

in VMT does not result in parameters or emission levels that exceed those projected for 

purposes of the attainment demonstration. The court’s decision was directed at the severe 

area requirement, 182(d)(1), Vehicle Miles Traveled, a one-time demonstration also 

referred to as the VMT Offset demonstration because it’s purpose is to offset any growth in 

emissions with the use of transportation control measures and/or transportation control 

strategies, that may result from growth in VMT. The VMT offset demonstration should be 

presented in the context of 182(d)(1). In the final adoption and submittal to EPA, please 

separate the discussions and demonstrations on these two similar-sounding topics and 

clearly distinguish between them.

The state complied with the comment and provided an analysis using the guidance 

provided by EPA after the state SIP was adopted. Our analysis of the VMT Offset 

demonstration follows.

1. What Is a VMT Offset Analysis?

 Section 182(d)(1)(A) of the Act directs states containing ozone nonattainment areas classified 

as severe, pursuant to section 181(a) of the Act, to adopt specific enforceable transportation 

control strategies (TCSs) and transportation control measures (TCMs) to offset increases in 

emissions resulting from growth in vehicle miles traveled (VMT) or numbers of vehicle trips and 

to obtain reductions in motor vehicle emissions as necessary (in combination with other emission 

reduction requirements) to comply with the Act's Reasonable Further Progress milestones 

(section 182(b)(1) and (c)(2)(B)) and attainment demonstration requirements (section 

182(c)(2)(A)). Section 182(d)(1)(A) of the Act directs states to submit the VMT Offset SIP by 

November 15, 1992, for any severe and above ozone nonattainment area. Texas has one severe

1997 8-hour ozone nonattainment area, the HGB area, with an attainment deadline of 2018.

The EPA originally interpreted section 182(d)(1)(A) in the April 16, 1992, General 

Preamble to Title I of the Act (57 FR 13498, 13521–13523, the General Preamble). In that 

interpretation, EPA allowed areas to meet the requirement by using the aggregate motor vehicle 

emissions from a prior year as the appropriate baseline against which to measure the change in 

emissions to determine whether VMT offsets are required. In other words, a plan was approvable 
16

if it showed decreases in aggregate year-over-year motor vehicle emissions from a base year 

through the applicable attainment year. EPA applied this interpretation in approving numerous 

states’ VMT offset demonstrations, including our 2001 approval of the HGB area’s first VMT 

offset demonstration. Although a commenter objected to this interpretation in our 2001 

approval, it did not challenge it in court. However, EPA’s historical interpretation of section 

182(d)(1)(A), as applied to California’s 2003 South Coast 1-Hour Ozone SIP, was finally 

challenged in the U.S. Court of Appeals for the 9th Circuit. In 2011, that court rejected EPA’s 

interpretation, stating that section 182(d)(1)(A) requires VMT offsets if there is “any increase in 

the level of emissions solely from VMTs (italics added).” 1

 The court explained that EPA 

incorrectly interpreted the phrase “growth in emissions” as meaning a growth in “aggregate 

motor vehicle emissions” versus a growth solely from VMT. As a result, the court held that EPA 

should have required the State to implement TCMs to offset growth in emissions from growth in 

VMT. However, the Court acknowledged that “clean car technology” advances could result in 

there being no increase in emissions even in the face of VMT growth, which would then allow 

VMT to increase without triggering the requirement to adopt offsetting TCMs. In response to the 

court’s decision, EPA provided new guidance for states with severe or above areas. The 

guidance, Implementing Clean Air Act Section 182(d)(1)(A): Transportation Control Measures 

and Transportation Control Strategies to Offset Growth in Emissions Due to Growth in Vehicle 

Miles Travelled, 2 recommends that both TCSs and TCMs should be included in calculations for 

the purpose of determining the degree to which any hypothetical growth in emissions due to 

growth in VMT should be offset.

On May 6, 2013, the State submitted an analysis based on the new guidance, which

demonstrates how the HGB area meets the VMT Offset requirement of CAA 182(d)(1)(A). This 

was done in concert with the revised emission inventory, the RFP, and the MVEBs for 2018.

2. How Is the VMT Offset Requirement Satisfied?

 The August 2012 guidance cited above explains how States may demonstrate that the VMT 

requirement is satisfied. States are recommended to estimate emissions for two different years: 

the nonattainment area’s base year and three different scenarios for the attainment year. One 

emission inventory is developed for the base year and three different inventory scenarios are 

developed for the attainment year. For the attainment year the state would present three 

emissions estimates, two of which would represent hypothetical emissions scenarios that would 

provide the basis to identify the “growth in emissions” due to growth in VMT, and one that 

would represent projected actual motor vehicle emissions after fully accounting for projected 

VMT growth and emissions reductions obtained by all creditable TCMs and TCSs. See the 

guidance for specific details on how states might conduct the calculations. To properly construct 

these inventories, a special version of MOVES2010 was provided to the State, 

MOVES2010bROP, which was designed by EPA to be used exclusively for VMT Offset 

 1 Association of Irritated Residents v. EPA, 632 F.3d 584, at 596-597 (9th Cir. 2011), reprinted as amended on 

January 27, 2012.

2 Office of Transportation and Air Quality, EPA-420-B-12-053, August 2012. This guidance is available at

http://www.epa.gov/otaq/stateresources/policy/general/420b12053.pdf.
17

demonstrations. MOVES2010bROP is identical to the original April 2012 release of 

MOVES2010b except that it allows users to set a base year other than 1990 for the purposes of 

the VMT offset calculation. 

 

The base year (2002) VOC on-road emissions should be based on VMT in that year and it 

should reflect all enforceable TCSs and TCMs in place in the base year. This would include the 

vehicle emissions standards, state and local control programs such as inspection and maintenance 

programs or fuel rules, and any implemented TCMs that were already required by or credited in 

the SIP as of that base year. 

The first of the attainment year emissions calculations for the attainment year (2018) 

would be based on the projected VMT for that year, and assume that no new TCSs or TCMs 

have been put in place since the base year. This calculation demonstrates how emissions would 

hypothetically change if no new TCSs or TCMs were implemented, and VMT was allowed to 

grow at the projected rate from the base year. This estimate would show the potential for an 

increase in emissions due solely to growth in VMT. This represents a no–action-taken scenario.

Emissions in the attainment year may be lower than those in the base year due to the fleet that 

was on the road in the base year gradually being replaced through fleet turnover, but they would 

still be higher than they would have been assuming VMT had held constant.

The second of the attainment year’s emissions calculations for the attainment year would 

also assume that no new TCSs or TCMs beyond those already credited were added or 

implemented after the base year and would also assume that there was no growth in VMT 

between the base year and attainment year. This estimate would reflect the hypothetical 

emissions level that would have occurred had no further TCMs or TCSs been adopted or 

implemented and had VMT levels held constant. Like the first estimate, emissions in the 

attainment year may be lower than those in the base year due to the fleet that was on the road in 

the base year gradually being replaced through fleet turnover. This emissions estimate would 

reflect a ceiling on the emissions that should be allowed to occur under the statute as interpreted 

by the Court in the attainment year because it shows what would happen under a scenario in 

which no new TCSs or TCMs are put in place and VMT is “held constant” during the period 

from the area’s base year to its attainment year. This hypothetical status quo is a necessary step 

in identifying the target level of emissions from which states would determine whether further 

TCMs or TCSs would need to be adopted and implemented in order to offset “any increase in 

emissions due solely to VMT” as shown by the first calculation. The comparison of these first 

two calculations would thus identify whether there is a hypothetical growth in emissions from 

growth in VMT that would need to be offset. 

Finally, the state would present the emissions that are actually expected to occur in the 

area’s attainment year, giving credit to all enforceable post-baseline-year TCSs and TCMs that 

have actually been adopted. This estimate would be based on the VMT that is expected to occur 

in the attainment year (i.e., the VMT level from the first estimate) and all of the TCSs and TCMs 

that are in reality expected to be in place and for which the SIP will take credit in the area’s 

attainment year, including any TCMs and TCSs adopted and credited since the baseline year. If 
18

this emissions estimate is less than or equal to the emissions ceiling that was established in the 

second of the attainment year calculations, the credited TCSs or TCMs for the attainment year 

would be sufficient to offset the hypothetical growth in emissions represented by comparing the 

first two calculations. If, instead, the estimated attainment year emissions are greater than the 

ceiling which was established in the second of the emissions attainment year calculations, the 

state would need to implement additional TCSs or TCMs to further offset the growth in 

emissions and bring the actual emissions down to at least the “had VMT held constant” ceiling 

estimated in the second of the attainment year calculations. 

3. What Does Texas' Demonstration Show?

 The May 6, 2013, VMT analysis, found in section 7.4.6.3 of the submittal, provides a 2002 

base year inventory that includes all TCSs and TCMs in place in 2002. It also provides the 

suggested three attainment year inventories depicting the No-Action On-Road scenario, the VMT 

Offset Ceiling On-Road scenario, and the 2018 Attainment Year On-Road scenario prepared 

using MOVES2010bROP. In addition the 2002 and 2018 On-Road Mobile Control scenarios are 

provided along with a list of those control scenarios and the year those programs started. A 

summary of what Texas provided is illustrated in their Table 7-45, shown here.

Table 7-45: VMT Offset Inventory Scenarios and Results

VMT Offset

Scenario

Number

Description VMT Year Control Year

Fleet

Turnover

Year

VOC 

Emissions

Scenario 1 Base Year 2002 2002 2002 124.47

Scenario 2 No Action 2018 2002 2018 87.32

Scenario 3 VMT Offset

Ceiling

2002 2002 2018 58.15

Scenario 4 Attainment

Year

2018 2018 2018 51.84

The mobile control strategies shown in Table 7-46 of the May 6, 2013 submittal, shown below, 

shows which control strategies were used in making the calculations including vehicle inspection 

and maintenance, federal on-road and non-road emission control programs, and state and federal 

clean fuel programs.

Table 7-46: Summary 2002 and 2018 On-Road Mobile Control Scenarios

Control Program

Description

Year Control

Program Started Included in 2002 Control Scenario

Pre-1990 FMVCP1 Pre-1990 Pre-2003 Control

1992 Federal Controls 

on Gasoline Volatility1 1992

Pre-2003 Control. Maximum Reid 

Vapor Pressure of 7.8 pounds per 

square inch

Anti-Tampering

Program1 1986 Pre-2003 Control

I/M Program1 1997 Pre-2003 Control
19

Tier 1 FMVCP1 1994 Pre-2003 FMVCP

RFG1 1995 for Phase One,

2000 for Phase Two

Pre-2003 Control Strategy

NLEV Program1 2001 Pre-2003 FMVCP

Tier 2 FMVCP1 2004 Post-2002 FMVCP, Phase in 2004 to

2009

TxLED1 2006

Post 2002 Control Strategy: Low 

aromatic hydrocarbon and high cetane 

number to control NOX

Federal Low-Sulfur

Highway Diesel

1 2006 Post 2002 Control Strategy: 15 parts 

per million maximum sulfur content

2007 Heavy Duty

FMVCP1 2007 Post-2002 FMVCP, Phase in 2007 to2010

1 Information on the modeling of the control strategiesis documented in the Summary of Control Programs

Modeled section of Appendix E.

The TCMs relied on for this demonstration include those from the 2007 1997 8-hour 

ozone attainment demonstration which are described as various measures in the HGAC’s longrange transportation plan, and the 2010 1997 8-hour attainment demonstration SIP, Both are 

being acted on in a separate action on a similar timeline. The list of TCMs that will reduce NOX

emissions in the HGB area by .015 tons per day (tpd) are found in Appendix G of the attainment 

demonstration submitted May 6, 2013: Transportation Control Measures for the HGB 

Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard (prepared by 

ENVIRON for the H-GAC) in the 2010 HGB Attainment Demonstration. 

Appendix E of the May 6, 2013 submittal further demonstrates this in Appendix E, 

Table 2, shown here.

Table 2. HGB Emissions Inventories for the VMT Offset Demonstration (Tons/Day).

Inventory1 VMT Speed VOC NOx

2002 Base Year 128,145,285 36.40 124.47 371.89

2018 with Pre-2003 Controls 

with Growth 184,065,162 35.87 87.32 414.80

2018 with Pre-2003 Controls 

without Growth 128,145,285 36.40 58.15 282.75

2018 Attainment Year

Control Strategy 184,065,162 35.87 51.84 109.98

1 Emissions estimates are based on EPA’s MOVES2010bROP model (September 2012).

A comparison of the inventories in Table 2 shows that the estimated 2018 attainment year 

control strategy scenario emissions (last row in Table 2) are below the emissions “ceilings” 

estimated as the 2018 with pre-2003 controls and without growth scenario (third line in Table

2). According to the 2012 EPA guidance, this demonstrates that the increased emissions due to 

increased VMT are adequately offset.
20

The companion attainment demonstration, which is the subject of a separate 

rulemaking, also contains transportation control measures (TCMs) and voluntary mobile 

emission reduction measures (VMEP). The VMEP measures were not used in the calculations 

for the VMT offset analysis. The list of TCMs can be found in Appendix G: Transportation 

Control Measures for the HGB Attainment Demonstration SIP Revision for the 1997 Eight-Hour 

Ozone Standard (prepared by ENVIRON for the H-GAC) of the attainment demonstration. The 

TCMs focus on pedestrian, transit, and bikeway improvements that encourage alternate modes of 

transportation. For reference only, the VMEP is described in Appendix H: Voluntary Mobile 

Emission Reduction Programs for the HGB Attainment Demonstration SIP Revision for the 1997 

Eight-Hour Ozone Standard (prepared by ENVIRON for the H-GAC) of the attainment 

demonstration. The VMEP measures focus on alternative commuting options, regional traffic 

flow improvement, vehicle retrofit and replacement, and off-road measures.

In summary, the VMT is projected to increase without a corresponding increase in 

emissions. The state’s analysis can be found in the 2013 submittal at section 7.4.6.3. A 

comparison of the actual 2018 attainment year inventory (51.84 tpy of VOC) with the VMT 

Offset Ceiling On-road inventory (58.15 tpy of VOC) shows that the 2018 attainment inventory 

is less than the VMT Offset Ceiling On-road inventory. A graphic depiction of this data was also

provided in Figure 7-5: VMT Offset Demonstration, of the submittal. In this case, the VMT 

Offset requirement is met, and no additional TCSs or TCMs beyond those already identified are 

required.

We agree with the state’s VMT Offset analysis. 

7. Motor Vehicle Emissions Budgets

Transportation conformity is required by CAA section 176(c)(2). The 1997 8-hour 

ozone RFP plan must include MVEBs for transportation conformity purposes. See 40 CFR 

section 93.109(c) through (g). Texas submitted its RFP MVEBs for VOCs and NOx. 

Conformity to a SIP means that transportation activities within the areas of concern will not 

produce new air quality violations, worsen existing violations, delay reaching reasonable further 

progress milestones, or delay timely attainment of the NAAQS. 

A MVEB is the maximum amount of emissions allowed in the SIP for on-road motor 

vehicles. The MVEB is the mechanism to determine if the future transportation plans conform to 

the SIP. The MVEB establishes an emissions ceiling for the regional transportation network. For 

the MVEBs to be approvable, 40 CFR 93.118(e)(4) requires that: (i) the SIP revision was

endorsed by the Governor and subject to a State public hearing; (ii) before the SIP is submitted 

to EPA, consultation among federal, State, and local agencies occurs; full implementation plan 

documentation is provided to EPA; and EPA's stated concerns, if any, are addressed; (iii) the 

MVEB must be clearly identified and precisely quantified; (iv) the MVEB, when considered 

together with all other emissions sources, must be consistent with applicable requirements for 

RFP, attainment, or maintenance (whichever is applicable); (v) the MVEB must be consistent 

with and clearly related to the emissions inventory and the control measures in the submitted SIP 
21

revision; and (vi) revisions to previously submitted SIPs must explain and document any changes 

to previously submitted budgets and control measures, impacts on point and area source 

emissions, any changes to established safety margins (see § 93.101 for definition), and reasons 

for the changes (including the basis for any changes related to emission factors or estimates of 

VMT).

 TCEQ worked with the Houston-Galveston Area Council to establish the budgets for 2008 and 

beyond. The HGB RFP SIP contains VOC and NOx MVEBs for the RFP milestone year 2008. 

The emissions budget for VOC is 102.50 tpd, and the NOx emissions budget is 261.95 tpd. Onroad emissions must be shown in future transportation plans to be less than the MVEB for 2008 

and subsequent years. The VOC and NOX RFP emissions budgets are acceptable because when 

added to the other components of the 2008 emissions inventory (including non-road, stationary 

source, and area source emissions) the total level of emissions is below the 2008 RFP emissions 

target level. 

We have found the RFP MVEBs (also termed transportation conformity budgets) 

submitted in May 6, 2013, adequate through EPA’s substantive criteria for determining 

“adequacy” of a MVEB found in 40 CFR 93.118(e)(4). On May 14, 2013, the availability of 

these budgets was posted on our website for the purpose of soliciting public comments. The 

comment period closed on June 13, 2013, and we received no comments. We published the 

Notice of Adequacy Determination for these RFP MVEBs on July xx, 2013 (78 FR xxxx). Once 

determined adequate, these RFP budgets must be used in future HGB transportation conformity 

determinations. The adequacy determination represents a preliminary finding by EPA of the 

acceptability of the MVEB. 

As of March 2, 2013, EPA required that the new MOVES mobile emission estimation 

model must be used to demonstrate transportation conformity. Consequently the previous 

MOBILE6.2 model-based MVEBs submitted in 2010 were not available to be used for the

purpose of 2013 RFP analysis. The state submitted new MVEBs in a SIP revision adopted April 

23, 2013 and submitted on May 6, 2013. Finding the budgets adequate before they are fully 

approved allows the budgets to be in-place, effective and useable more quickly than waiting for 

the approval process.

Development of the MVEBs is discussed in Chapter 5 of the April 1, 2010 submittal, 

Chapter 7 at 7.5 in the May 6, 2013 submittal, and in Appendix D of the 2013 submittal. The 

State took these budgets out for public hearing as part of the SIP process. They submitted the 

SIP under the authority of the Governor’s designee. EPA bases its conclusion on comparison of 

the NOx and VOC MVEBs with emissions allotted to on-road emission categories within each 

SIP, and determined that these emission levels are available within the context of on-road RFP 

and attainment emissions for the budget years demonstrated. Therefore the budgets satisfy the 

requirements of 40CFR 93.118(e)(4)(iv). The state conducted consultation among federal, State, 

and local agencies as required, and provided full implementation plan documentation to EPA. 

EPA stated no concerns with the process or the budgets for the state to address. Because this is a 

revision to a previously submitted SIP, the state explained and documented the changes to 

previously submitted budgets and control measures, and the changes to established safety 
22

margins. There were no changes to area, point source, and nonroad inventories. The revised 

budgets were provided solely because of the requirement to use the newest version of the 

MOVES model discussed elsewhere in this TSD.

We agree that the MVEBs are fully consistent with RFP, and the RFP plan is fully 

approvable, as it sets the allowable on-road mobile emissions the HGB area can produce and 

continue to demonstrate RFP.

Table 13 lists the MVEBs for HGB. Table 14 demonstrates that the MVEBs for NOx

and VOC are consistent with the RFP SIP.

Table 13. RFP Motor Vehicle Emissions Budgets for HGB

Year NOx (Tons/Day) VOC (Tons/Day)

2008 261.95 102.50

2011 234.92 93.56

2014 171.63 71.56

2017 130.00 59.76

2018 120.99 57.02

Table 14. Comparison of 2018 RFP Onroad NOx and VOC Emissions with 2018 MVEB 

(tons/day)

Inventory NOx 

(Tons/Day)

VOC 

(Tons/Day)

2018 Onroad Uncontrolled Emissions 870.89 304.27

2018 Onroad RFP Emission Reductions 760.90 252.43

2018 Emissions after RFP Controls 109.99 51.84

2018 Excess Emission Reductions for Safety Margin 11.00 5.18

2018 Emissions after RFP Controls with Safety Margin 120.99 57.02

Is MVEB acceptable? Yes Yes

We agree with the MVEBs submitted May 6, 2013.

E. Summary and Recommendations:

TCEQ used acceptable techniques and methodologies to develop the base year and 

milestone year inventories, the emission reductions for the milestone years, and the effects of 

non-creditable reductions and pre-1990 CAA rule corrections. Table 15 demonstrates that the 

RFP and contingency measure requirements are met in the HGB RFP SIP. NOx emissions for

the period between 2002 and 2018 were well below the target level for 2018 and emissions in 

2018 will be below the target needed for RFP and contingency measure requirements. Therefore 

we recommend approval of the Houston-Galveston-Brazoria RFP Plan. 

Table 15. Summary of RFP and Contingency Measures Reductions
23

Description NOx 

(Tons/Day)

a 2008 Target 670.11

b 3% Needed for Contingency (a x 0.03) 23.65

c Adjusted Target Emissions 646.46

d 2008 Uncontrolled Emissions 1026.63

e 2008 RFP Emission Reductions 472.67

f 2008 Projected Emissions after RFP

Reductions (d minus e)

553.96

Adjusted Target Met? (f < d) Yes

We also recommend the approval of the TCEQ adopted MVEBs which are based on the 

RFP Plan. We recommend approval of the revised emissions inventory that was used for the 

RFP and also for the 2010 attainment demonstration. And finally, we recommend approval of 

the VMT Offset analysis that shows no additional TCMs or TCSs are needed to demonstrate 

compliance with CAA 182(d)(1)(A).