Matagorda County emissions 

do not contribute to ozone 

formation in HGB 

traffic and commuting, growth, 

meteorology, topography, and emissions 

do not contribute to HGB Ozone formation
Declining Emissions and Declining 

Growth Do Not 

Support Nonattainment 

• Matagorda County is a Micropolitan Statistical Area

• Emission Corrections (2008)

• Emission Reductions (2008 - 2010)

• Emission Corrections (Oil and Gas lb/BBL local data)

• VOC Emissions are not driving ozone formation in HGB

– TCEQ Apportionment Analysis

– Area Source VOC Reduction Analysis for Counties Outside of

HGB

• Wind trajectory does not override declining emissions,

declining growth and additional technical data
Matagorda County is in a 

Micropolitan Statistical Area

• CAA only designates Metropolitan Statistical Areas or

CMSA for use with Serious, Severe or Extreme

nonattainment areas.

• Matagorda does not have sufficient “social or economic

ties" to be included in the 10 county Houston

Metropolitan Statistical Area ("Houston Metro").

• Instead, EPA uses the CSA, which only requires a

minimal 15% employment interchange with another

county. 

• This use of CSA is particularly arbitrary when the actual

CSA basis, VMT and population, for Matagorda County,

has declined from 2008 - 2010.
Emission Corrections (2008)

• Nonroad NOx

– 7,007 tpy in TSD

– (2,928) tpy (TCEQ January 11, 2012 Letter to EPA, p. 2)

– 4,079 Revised total NOx

• Nonroad VOC

– 3,153 tpy in TSD

– (664) tpy (TCEQ 1/12/12 EI Discrepancy Table)

– 2,489 Revised Nonroad VOC

• Oil and Gas VOC emissions

– 14,662 tpy VOC in 2008 for oil and gas area sources

– Local VOC lb/BBL data should be used (next slide)

• Pneumatic Controllers

– VOC Reductions associated with Hood and Wise Counties

– Suspect same should be attributed to Matagorda County
Emission Corrections 

Oil and Gas Condensate Tank 

Emissions

Source VOC 

Lbs/BBL

Basis of Estimate 2008 TPY 

VOCs

2010 TPY 

VOCs

Current TCEQ/TERC 

Report

33.3 

lbs/BBL

Statewide default 

emission factor 

from TCEQ study

13,302.03 7,570

Local 

Option

1

TCEQ/TERC –

weighted average 

for production 

rates (See Table 

3-3)

16.75 

lbs/BBL

TCEQ statewide 

factor weighted 

for production 

(BBL/day) at well

6,716 3,808 

Local 

Option

2

TCEQ/TERC –

modified for MClike wells (psig 

less than 50) (See 

Table 3-3 and 3-1)

6.972 

lbs/BBL

TCEQ statewide 

factor modified 

for discharge 

pressure

2,796 1,585

Local

Option 

3

Matagorda 

County

2.5 lbs/BBL MC Condensate 

sample taken 

from separator 

before discharge 

to tank 

1,002 568
Oil and Gas Analysis 

by PSI, lb/BBL and County

0

20

40

60

80

100

120

140

160

180

200

TERC

(Denton

Only)

TERC (All

Sites)

TERC

(Without

Denton)

Matagorda

County

(MC)

specific

PSI Avg lb/BBL Avg

*

#

* Avg. PSI based upon 

preliminary estimates 

from operators of 35% of 

2008 condensate BBL 

produced in MC.

# Based upon site 

specific sampling and 

modeling of one of the 

largest 2010 condensate 

producing leases in MC. Texas Environmental Research Consortium (TERC) Report on VOC 

Emissions from Olil and Condensate Strorage Tanks found at 

http://files.harc.edu/Projects/AirQuality/Projects/H051C/H051CFinalRep

ort.pdf
Oil and Gas Analysis 

by PSI, lb/BBL and County

TERC

(Denton Only)

TERC 

(All Sites)

TERC 

(Without Denton)

Matagorda County 

Specific

PSI Avg 200 119.1 45.7 45.4 *

VOC lb/BBL Avg 56.58 33.3 12.11 2.5 #

* Avg. PSI based upon preliminary estimates from operators of 35% 2008 

condensate BBL produced in Matagorda County.

# Based upon site specific sampling and modeling of one of the largest 

2010 condensate producing leases in Matagorda County. 
Emission Reductions 

2008 - 2010

• NOx Reductions to 2010

– (180.86) tpy NOx emission reductions 2008 to 2010 from point sources

– VMT Reduction by 1%

• VOC Reductions to 2010

– TCEQ estimates 8,758 tpy VOCs from oil and gas operations

• (5,904) tpy VOC emission reductions from 2008 to 2010 from area sources

(TCEQ Emission Inventory)

– Local VOC lb/BBL data should be used (previous slides)

– VMT Reduction by 1%
VOC Emissions Do Not Drive 

Ozone Formation in HGB

EPA has approved the current SIP strategy based 

upon primarily on NOx reductions with targeted 

HRVOC controls:

These [Texas SIP] revisions result from more recent information on ozone

formation in the Houston/Galveston area indicating that a combination of

controls on oxides of Nitrogen (NOx) and highly reactive volatile organic

compounds (HRVOCs) should be more effective in reducing ozone than the

measures in the previously approved plan which relied almost exclusively on

control of NOx.

EPA's proposed approval of TCEQ's HRVOC SIP rule, 70 FedReg 58119

(October 5, 2005)
HGB Attainment Demonstration SIP Revision for 

the 1997 Eight-Hour Ozone Standard 

(Project No. 2009-017-SIP-NR)

Adoption Date: 03/10/2010
Reduction of 273 tpd VOCs (99,645 tpy VOCs) from 

several counties within 200 km of HGB, including 

Matagorda County, resulted in no change to the 

Wallisville Monitor 2018 future case.

HGB Attainment Demonstration SIP Revision for the 1997 Eight-Hour 

Ozone Standard (Project No. 2009-017-SIP-NR) Adoption Date:

03/10/2010
Eliminating All VOC and NOx Emissions 

From Matagorda County Will Not 

Meaningfully Contribute to Ozone 

Reduction

TCEQ Technical Analysis Support Documentation by the TCEQ 

Regarding U.S. EPA Responses to State and Tribal 2008 Ozone 

Designation Recommendations

All Matagorda County Emissions Contribute 

Less than 0.20 ppb in 2018 APCA Modeling
D.C. Circuit requires a "rational 

connection between the facts found and 

the choices made"

In the recent ATK designation decision out of the D.C. Circuit:

Growth was a factor: "A county with rapid population or VMT growth is generally an

integral part of an urban area and is likely to be contributing to fine particulate

concentrations in the area." EPA TSD for county designated nonattainment.

– The proposed counties at issue in ATK had double digit, higher than expected growth

in population and VMT. 

Topography and Meteorology: Without seasonal inversions, trapped by the mountains,

Salt Lake City would not be in violation of the air quality standards. ATK Launch

Systems Inc. v. EPA (February 24, 2012).

– EPA's RTC recognized that the closed air basin trapped the emissions for several

days regardless of the wind patterns tracked in the wind trajectories.

Emissions impact was exaggerated because trapped by mountains:

– One proposed county had the second highest PM2.5 carbon emissions in the

proposed area.
In case-by-case analysis, Matagorda County Wind 

Trajectory Data Does Not Outweigh Declining Growth, 

Declining Emissions and more Detailed Modeling Data

Declining emissions and population and VMT growth is well documented.

No meaningful contribution to HGB ozone levels.

• 2005 – 2010 data

– Wind data shows only 0.43% - 1.9%, at most, of the wind impacting an

elevated monitor potentially originated in Matagorda County. (TCEQ

January 11, 2012 Letter, p. 16.)

– Within this small percentage of time, the greatest impact expected from all

combined mobile, non-road, point and area sources Matagorda County

emissions, as modeled by TCEQ, is an average of .18 and a max of 1.54

ppb for 2005 and 2006. (TCEQ January 11, 2012 Letter as corrected in

discussions between EPA and TCEQ.)

No meaningful contribution potential to Ozone formation or reduction

– 2018 TCEQ sensitivity analysis demonstrated that 273 tpd had no ozone

reduction impact on the Wallisville monitor. 

– 2018 TCEQ APCA results for all MC emissions indicates, that if all combined

mobile, non-road, point and area sources were eliminated, the greatest

reduction impact would be 0.20 ppb at the Wallisville monitor.