i.tì., r.,r:'r,

Katlrleen Hartnett \Nhite, Clta innatt

Larr-y R. Soivard, Commissirtner

Glenn Shankle, Executiue Direclor

Tpxas CorørurrssroN oN ENVIRoNMENTAL QUALITy ?.

Protecting Texas bg Reducittg and Preuenting Pollution'

Docket Nos. 2006-1874-SIP, 2006-17 96-R[IL,r2006-1804-RUL r

June 13,2007

Richard E- Greene, Regional Adnrinistrator

U.S. Environmental Protection Agency - Region 6

1445 Ross Avenue

Dallas. Texas 7 5202-2733

3

Dear Mayor Greene: f

On May 23,2007, the Texas Commission on Environmental Quality (Commission) adopted revisions tõne

Implementation Plan (SlP) for the Houston-Galveston-Brazoriã lHGe) eiglrt-hour ozone nonattainlnenl al'ea.

These revisions include three components- The first component is a revision to the SIP for the HGB eight-hour ozone

nonattainment a¡ea that includes additional Voluntary Mobile Emission Reduction Program (VMEP) commitments. In

addition, the Commission adopted amendments to S 114.6 and $ 114.319 in 30 Tex. Admin. Code Chapter I14, Control of

Ai¡ Pollution frorn Motor Vehicles. These rules amend the definition of diesel fuel to include marine distillate fuels,

requiring thern to be compliant with low emission diesel (LED) standards i¡ the HGB nonattainment area, and amend the

compliance schedule for the infoduction of LED-compliant marine diesel fuels into the HGB area counties.

Lurtty, rhe commission adopred new $ 1l5.ll0 and amendmenrs ro s$ 115.1l2 - ll5.l17, I l5.l19, 115.541 - 1i5.547, andl

115.549 of 30 Tex- Admin. Code Chapter ll'5, Conh'ol of Ai¡Pollution from Volatile Organic Compounds. Specifically, I

the new section and amendúrents reduce emissions of volatile organic conipounds (VOC) û'om VOC storage and degassing I

operations by estabiishing lrore stringent controls for fittings on floating loof storage vessels, establishing control I

requiretnents or operational lirnitations on landing floating roofs, establislring control requirenrents for flash elnissions fi-om I

crude oil and condensate storage tanks, and establishing nore stringent control requirentents for degassing and cleaning ofJ

storage, transpoll, and marine vessels.

Enclosed are tlrese proposed revisions to the SIP, a cornplete record ofthe public hearings. the accompanying orders, and a

public lrearing certification. I look forward to your expeditious approval of these SIP rei,isiots.

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Enclosures 

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cc: The Honorable Rick Perr1,. Govenlor of Texas

Mr. Zal< CovaL- Offìce of Budget, Planning arrd Policy, Offìce of the Covenlor

Mr. Glen¡ Shankle, Executive Dù-ector. Texas Con'lllission on Envir-onrnenta) Quaìit1,

Sincerely,

P.(_).p-oi.':-3()87 6 A_ustirr. Te,.l¿rs 7åì7ìl-3û87 + 5l!,,!,?9-itl(tfl € ilrr.cr.na', ¿rcici.rr,s:: i¡'.r.r,rt.ictr¡.sLate.t:,..us
Texas Commission on Environmental Quality 

Public Hearings 

January 29 and 31, and February 1,6, and 8,2007 

Concerning Revisions to 30 TAC Chapter 11 5 

Control of Air Pollution from Volatile Organic Compounds 

Control of VOC Emissions from Storage 8, Degassing 

Operations in HGB for the Eight-Hour Ozone Standard 

Rule Project No. 2006-038-1 15-EN 
The Texas Commission on Environmental Quality (commission) held public hearings in Houston on 

January 29, 2007; Dallas on January 31, 2007; Arlington and Midlothian on February 1, 2007; 

Longview on February 6, 2007; and Austin on February 8, 2007, to receive testimony regarding 

revisions to 30 TAC Chapter 1 14, Control of Air Pollution from Motor Vehicles; Chapter 1 15, Control 

of Air Pollution from Volatile Organic Compounds; Chapter 117, Control of Air Pollution from 

Nitrogen Compounds; and corresponding revisions to the state implementation plan. 

The comment period closed on February 12, 2007. All testimony and comments have been 

reviewed and seriously considered. This hearing record contains a complete record of the public 

hearings and is divided into the followirrg four sections: 

o Public Notification and Proposal 

o Written and Oral Testimony 

0 Evaluation of Testimony 

o Staff Recommendations/Order 

Additional copies of this hearing record are maintained in the TCEQ central office at 12100 Park 35 

Circle, Austin, Texas 78753. For further information, please contact Teresa Hurley at (51 2) 239- 

531 6. 
EVALUATION OF 

TESTIMONY 
Texas Commission on Environmental Quality 1NTEROFFlCE MEMORANDUM 

To: Commissioners Date: May 4, 2007 

Thru: LaDonna Castafiuela, Chief Clerk 

I Glenn Shankle, Executive Director 

From: David C. Schanbacher, P. E., Chief Engineer 

b Docket No.: 2006- 1804-RUL 

Subject: Commission Approval for Rulemaking Adoption 

Chapter 115, Control of Air Pollution from Volatile Organic Compounds 

Control of VOC Emissions from Storage and Degassing Operations in HGB for the 

Eight-Hour Ozone Standard 

Rule Project No. 2006-038-1 15-EN 

Reasons for the rule package: 

The Environmental Protection Agency (EPA) designated the eightcounty Houston-GalvestonBrazoria (HGB) metropolitan area as a "moderate" ozone nonattainment area under the eight-hour 

ozone standard. The Federal Clean Air Act (FCAA), 42 United States Code (USC), 57410, 

requires states to submit to EPA by June 15, 2007, state implementation plan (SIP) revisions that 

contain enforceable measures to achieve the National Ambient Air Quality Standard (NAAQS). 

The rulemaking is part of the state's efforts to reach attainment with the eight-hour standard. The 

rule would require owners or operators of VOC storage tanks, transport vessels, and marine 

vessels located in the HGB eight-hour ozone nonattainrnent area to better control their storage and 

degassing operations, thereby reducing VOC emissions. The revised requirements have been 

developed to reduce VOC emissions that have previously been unreported or under-reported in 

emissions inventories. 

. Under what authority are we adopting these changes? The rule changes are adopted under 

Texas Water Code (TWC), 55.102, concerning General Powers, 55.103, concerning Rules, and 

55.105, concerning General Policy, that authorize the commission to adopt rules necessary to carry 

out its powers and duties under the TWC; and under Texas Health and Safety Code (THSC), 

5382.017, concerning Rules, that authorizes the commission to adopt rules consistent with the 

policy and purposes of the Texas Clean Air Act. The amended rules are also adopted under 

THSC, 5382.002, concerning Policy and Purpose, that establishes the commission's purpose to 

safeguard the state air resources, consistent with the protection of public health, general welfare, 

and physical property; 5382.011, concerning General Powers and Duties, that authorizes the 

commission to control the quality of the state's air; 5382.012, concerning State Air Control Plan, 

that authorizes the commission to prepare and develop a general, comprehensive plan for the 

control of the state's air; 5382.016, concerning Monitoring Requirements; Examination of 

Records, that authorizes the commission to prescribe requirements for owners or operators of 

sources to make and maintain records of emissions measurements; and 5382.021, concerning 
Commissioners 

Page 2 

May 4, 2007 

Re: Docket No. 2006- 1804-RUL 

Sampling Methods and Procedures, that authorizes the commission to prescribe the sampling 

methods and procedures to determine compliance with its rules. 

a Is this rulemaking required by federal rule or state statute? Which ones? Yes. The FCAA, 

42 USC, $7410, requires states to submit SIP revisions that contain enforceable measures to 

achieve the NAAQS. 

Are there any legal deadlines by which these rules must be adopted or effective? Yes. The 

commission is required to submit a SIP revision by June 15, 2007. Controls must be in place by 

the beginning of the ozone season prior to the attainment date. For the HGB area, that is January 

1, 2009. 

• What issue(s) or problem(s) are we trying to solve? The proposed rulemaking would reduce 

VOC emissions from storage tanks and from degassing of storage tanks, transport vessels, and 

marine vessels in the HGB area in order to advance the attainment of the eight-hour ozone 

standard. 

Why is it important that we do this rule package? The FCAA requires states to submit SIP 

revisions containing enforceable measures to attain the NAAQS. Additional VOC emission 

reductions will help the HGB area attain the eight-hour ozone NAAQS and benefit the public by 

improving the air quality. This rulemaking would reduce VOC emissions that have previously 

been unreported or under-reported in the emissions inventories. 

Other important background or historical information. When TCEQ and its research partners 

began TexAQS I1 in May 2005, one of the study's goals was to identify VOC emission sources 

that have been historically unreported or under-reported in the EI and could potentially be 

contributing to the discrepancy between measured and reported emissions. TexAQS I1 remote 

sensing VOC project results indicate that certain types of storage tank emissions, including 

degassing, flash, and landing loss emissions, generally have been unreported or under-reported in 

the TCEQ EI. Recent data analysis, a landing loss emissions survey, and other TCEQ studies 

indicate that these unreported emissions could total several thousand tons per year; unreported or 

under-reported landing loss emissions alone in the HGB area totaled approximately 7,250 tons in 

2003. The proposed rulemaking would reduce emissions from these sources as well as other 

sources of potentially unreported tank emissions, such as slotted guidepoles and other tank fittings. 

Scope of the rulemaking: 

The proposed rulemaking subjects owners or operators of VOC storage tanks, transport vessels, and 

marine vessels located in the HGB eight-hour ozone nonattainment area to revised control, monitoring, 

testing, recordkeeping, and reporting requirements. Compliance would be required by January 1, 2009, 

unless compliance would require the emptying and degassing of the storage tank. In that case, compliance 

would be required the next time the tank is emptied and degassed but no later than January 1, 2017. 

(Tanks are generally taken out of service at least once every ten years.) 

Changes required by federal rule: 
Commissioners 

Page 3 

May 4, 2007 

Re: Docket No. 2006- 1804-RUL 

The FCAA requires states to submit SIP revisions containing enforceable measures to attain the 

NAAQS. The rulemaking would help reduce VOC emissions as a part of the strategy for the area 

to attain the eight-hour ozone standard. 

. Changes required by state statute: None. 

Staff recommendations that are not expressly required by federal rule or state statute: 

Require more stringent controls for tank fittings on floating roof tanks, such as slotted 

guidepoles and other openings in internal and external floating roofs. 

Limit the circumstances under which tank landings are allowed to times when the landing 

is necessary in order to carry out inspections or maintenance or to support a change in 

service to a liquid that is incompatible with the previously stored liquid. Convenience 

landings would not be allowed unless vapors are routed to a control device during the 

landing, are authorized under an emission limit or cap in a permit issued under 30 TAC 

Chapter 116, or fall within a 25 tpy exemption level. 

Require the control of VOC flash emissions from crude oil and condensate storage tanks at 

upstream oil and gas exploration and production sites and midstream pipeline breakout 

stations with uncontrolled flash emissions greater than 25 tons per year. Provide options 

for estimating the uncontrolled flash emissions. 

Require the control of VOC emissions from the degassing of storage tanks with a nominal 

capacity of 250,000 gallons or more, or with a nominal capacity of 75,000 gallons or more 

storing liquids with a true vapor pressure greater than 2.6 psia. 

Require degassing vapors from storage vessels, transport vessels, and marine vessels in the 

HGB area to be vented to a control device until the VOC concentration of the vapors is 

reduced to less than 34,000 parts per million by volume as methane. 

Require the VOC concentration of the vapors to be monitored periodically during the 

degassing process using an appropriate monitoring device. 

. Require additional recordkeeping and reporting requirements to validate compliance with 

the proposed regulations. 

Impact on the regulated community: 

. Who will be affected? The adopted rule changes would affect owners and operators of storage 

tanks, transport vessels, and marine vessels located in the HGB nonattainment area only. The 

proposed new storage tank requirements will affect owners or operators storing volatile organic 

liquids in tanks located at petroleum refineries, chemical plants, gasoline storage terminals, bulk 

terminals, pipeline breakout stations, and oil and natural gas production sites. The limitations on 

landing floating roofs would have the largest impact on for-hire bulk storage terminals. The 

proposed changes to the degassing rules would affect owners or operators of storage 'arks, 

transport vessels, and marine vessels and owners or operators of facilities that clean transport and 
Commissioners 

Page 4 

May 4, 2007 

Re: Docket No. 2006- 1804-RUL 

marine vessels. Owners and operators of tanks with capacities between 75,000 and one million 

gallons would be most impacted since these tanks would no longer be exempt from the degassing 

control requirements. Tanks with capacities between 75,000 and 250,000 gallons would only be 

subject to the degassing rules if the materials stored have a true vapor pressure greater than 2.6 

psia. 

Does it create a group of affected persons who were not affected previously? How? Yes. 

Owners or operators of tanks with capacities between 40,000 and 210,000 gallons storing crude oil 

and condensate at oil and natural gas production sites would lose their exemption from control 

requirements. Tanks storing crude oil and condensate at oil and natural gas production sites and at 

pipeline breakout stations would also be affected by the control requirement for flash emissions. 

The change in criteria for determining when the tank or vessel can be vented to atmosphere would 

not require the use of degassing control where it was not required previously, but would result in 

the control equipment being used for a longer time period and thus increasing operating costs. The 

rule change would also add a requirement for measuring the VOC concentration of the vented 

gases and for keeping records of the measurements. Owners or operators of tanks with capacities 

of 75,000 - 250,000 gallons storing materials with true vapor pressure greater than 2.6 psia and 

tanks with capacities of 250,000 - 1,000,000 gallons would no longer be exempt from the 

degassing control requirements. 

Will there be a fiscal impact? If so, estimate. Yes. Costs for controlling tank fittings are 

estimated at $900 per tank for an existing tank. Estimated costs for equipping slotted guidepoles 

with controls are $10,000 per tank. Costs for limiting tank landings will depend on whether the 

site chooses to revise operating practices to limit landings, to employ add-on control devices to 

control emissions from tank landings, or operate under a permitted emission limit or cap that 

includes landing losses. Vapor recovery equipment for flash emissions could be installed on crude 

oil or condensate storage tanks at a capital cost of $60,000 - $95,000. Operating costs would be 

more than offset by the value of the recovered gases. Costs associated with vessel degassing vary 

greatly, with the maximum cost associated with large stationary storage tanks or barges estimated 

at $25,000 per day and a minimum cost estimated at $5,000. Any costs continuing beyond 2009 

would be operating, maintenance, and recordkeeping requirements. There will be no increase in 

fees directly resulting from this rule. 

Impact on the public: 

Who will be affected? The general public in the HGB and surrounding areas would benefit from 

improved air quality due to lower VOC and ozone levels. 

Does it create a group of affected persons who were not affected previously? No. How? 

Will there be a fiscal impact? If so, estimate. The rules are not anticipated to have fiscal 

implications for the general public. 

Impact on agency programs: 

There will be no new activities or responsibilities required by TCEQ as a result of this rulemaking. 

However, the increased regulation of crude oil and condensate storage at oil and gas production 
Commissioners 

Page 5 

May 4,2007 

Re: Docket No. 2006- 1804-RUL 

sites will result in additional accounts to be inspected by Field Operations Division (FOD) regional 

investigators to ensure compliance. Enforcement of these rules should not significantly increase 

the number of facilities inspected by state and local governments. The rules may increase the 

Office of Compliance and Enforcement's workload when inspecting affected facilities to ensure 

they meet the additional requirements. The rulemaking could also result in many entities 

recognizing the need to obtain or modify a new source review permit under Chapter 1 1 6 and a 

Title V operating permit under Chapter 122, thus increasing the work load for the Air Permits 

Division (APD). The increased number of Title V permits would also lead to an increased 

workload for the FOD to review compliance certifications. The rulemaking itself does not require 

permitting actions, but because many entities have not previously accounted for emissions 

addressed under this rulemaking, they may need to take some action such as obtaining additional 

authorization. The Industrial Emissions Assessment Section (IEAS) would review requests to use 

computer simulation programs to estimate flash emissions. The IEAS would already be reviewing 

emissions inventory submittals, which are required for sites with VOC emissions greater than 10 

tons per year (tpy), and would incorporate the additional tasks into the current reviews. 

Stakeholder meetings: 

The TCEQ participated in an H-GAC stakeholder meeting in March 2006 to discuss potential 

control strategies. The TCEQ also conducted an informational meeting October 5, 2006, to 

present the rule concepts and answer questions. 

Policy issues: 

What policy issues are affected? Elements of the tank landing policy being developed by the 

APD would be incorporated in the proposed rule. 

Are any policies'that are not currently based on rule being made into a rule? No. 

What are the consequences if this rulemaking is not approved to go forward? If this 

rulemaking is not approved, large recently-discovered sources of VOC emissions that have not 

been accurately accounted for in air quality modeling would continue unabated unless sources are 

required to limit their emissions by another mechanism. 

Are there alternatives? More stringent emission reduction requirements could be applied to NOx , 

sources or other VOC sources located within and surrounding the HGB nonattainrnent area. 

Potentially controversial matters: 

Legislative interest may be high as this SIP revision will coincide with the 80th Legislature. There 

has been ongoing legislative interest in the agency's efforts to address eight-hour ozone issues. 

Key points in adoption rulemaking schedule: 

Texas Register proposal publication date: December 29, 2006 

. Anticipated effective date: Juile 14, 2007 

rn Six-month Texas Register filing deadline: June 29, 2007 
Commissioners 

Page 6 

May 4, 2007 

Re: Docket No. 2006- 1804-RUL 

Public comment: 

The commission received comments on the rule package from 13 industry representatives, three 

environmental groups, the EPA, Harris County Public Health and Environmental Services, and 

one individual. The environmental groups and the individual requested that the rules be made 

more stringent. EPA expressed general support for the rules and requested certain clarifications. 

Industry representatives requested more flexibility for controls on tank fittings and slotted 

guidepoles and consistency with EPA rules in 40 CFR Part 63, Subpart WW, more flexibility in 

allowing landings of floating roofs, limitations on the applicability of flash emission controls to oil 

and gas exploration and production sites, a higher tank size applicability threshold for storage tank 

degassing requirements, and more flexibility for measuring VOC concentrations during degassing. 

No changes were made in response to requests that the rules be made more stringent, because the 

requests were mostly beyond the scope of the current rulemaking. Minor clarifications were made 

in response to the EPA comments. Several changes were made in response to the industry 

comments, as discussed below. 

Significant changes from proposal: 

In response to comments, revisions were made to $1 15.112(d)(2) to allow additional 

flexibility for slotted guidepole controls and to provide consistency with 40 CFR Part 63, 

Subpart WW. 

In response to comments, revisions were made to 5 115.1 12(d)(2)(H) to allow additional 

flexibility for landing floating roofs. 

In response to comments, requirements for control of flash emissions in $115.112(d)(4) 

and (5) have been limited to storage of crude oil and condensate at upstream oil and gas 

exploration and production sites and midstream pipeline breakout stations. Control of 

flash emissions at refineries is not being pursued at this time. 

In response to comments, the requirement to control emissions from tank degassing from 

tanks as small as 40,000 gallons has been changed. The degassing control requirements 

would apply to tanks with nominal capacity of 250,000 gallons or greater and to tanks with 

nominal capacity of 75,000 to 250,000 gallons storing materials with true vapor pressure 

greater than 2.6 psia. 

In response to comments, more options have been specified in §115.545(11) for 

measurement of VOC concentration. 

Agency contacts: 

Teresa Hurley, P.E., Rule Project Manager, 239-5316, Air Quality Division 

Brad Patterson, Staff Attorney, 239-1201, Environmental Law Division 

Patricia Durbn, Texas Register Coordi~tor, 239-6087, General Law Division 

Attachments 

cc: Chief Clerk, 5 copies 

Executive Director's Office 

Jason Skaggs 

Ashley K. Wadick 
EVALUATION OF TESTIMONY 

The Texas Commission on Environmental Quality (TCEQ or commission) adopts new 

8115.110 and amendments to 8§115.112 - 115.117, 115.119, 115.541 - 115.547, and 115.549. 

New 5115.1 10 and amendments to 88115.112, 115.115 - 115.117, 115.119, and 115.541 - 

115.547 are adopted with changes to the proposed text as published in the December 29, 2006, 

issue of the Texas Register (3 1 TexReg 10525). Amendments to 881 15.1 13, 115.114, and 

115.549 are adopted without changes and will not be republished. 

The amendments will be submitted to the United States Environmental Protection Agency 

(EPA) as a revision to the state implementation plan (SIP). 

BACKGROUND AND SUMMARY OF THE FACTUAL BASIS FOR THE ADOPTED 

RULES 

On June 15, 2004, the Houston-Galveston-Brazoria (HGB) ozone nonattainment area was 

classified as a moderate nonattainment area under the eight-hour national ambient air quality 

standard (NAAQS) under the Federal Clean Air Act (FCAA) Amendments of 1990 (42 United 

States Code (USC), 887401 et seq.). For the HGB area, defined by Brazoria, Chambers, Fort 

Bend, Galveston, Harris, Liberty, Montgomery, and Waller Counties, the TCEQ has developed 

this eight-hour ozone SIP revision in accordance with 42 USC, 87410. Hence, this rulemaking 

and HGB SIP revision is part of the first step in addressing the eight-hour ozone standard for 

the area. 

The one-hour ozone NAAQS, which preceded the eight-hour ozone standard, was revoked June 

15, 2005 (69 FR 23951). However, the one-hour ozone control strategies in the HGB area will 
remain in place. This set of strategies will continue to reduce the amount of ozone precursors 

and ozone in the HGB airshed. On September 6, 2006 (71 FR 52656), EPA published approval 

of the HGB nonattainment area's one-hour ozone attainment demonstration and associated 

rules. The approval was published in six parts, covering the rules for the control of highlyreactive volatile organic compounds (HRVOC), the HRVOC emission cap and trade (HECT) 

program, the mass emission cap and trade (MECT) program for nitrogen oxides (NOx), the 

one-hour ozone attainment plan, the emissions credit banking and trading program, and the 

discrete emission credit banking and trading program. For a more complete background on the 

one-hour ozone SIP revisions please refer to Chapter 1 of the eight-hour SIP revision that has 

been submitted for adoption concurrent with this rule package (Project Number 2006-027-SIPNR) . 

The rulemaking subjects owners or operators of volatile organic compound (VOC) storage 

tanks, transport vessels, and marine vessels located in the HGB eight-hour ozone nonattainment 

area to more stringent control, monitoring, testing, recordkeeping, and reporting requirements. 

The revised requirements have been developed to reduce VOC emissions that have previously 

been underreported in emissions inventories (EI). 

The fvst Texas Air Quality Study (TexAQS 2000) measured ambient VOC concentrations in 

the Houston Ship Channel to be in greater proportions to NOx emissions than what would be 

expected based on the reported point source emissions inventories. Therefore, when TCEQ and 

its research partners began TexAQS I1 in May 2005, one of the study's primary goals was to 

identify VOC emission sources that have been historically unreported or underreported in the 

EI and could potentially be contributing to the discrepancy between measured ambient 

concentrations and reported point source emissions. 
TexAQS 11 remote sensing VOC project results indicate that certain types of storage tank 

emissions, including degassing, flash, and floating roof landing loss emissions, generally have 

been unreported in the EI. Recent data analysis, a floating roof landing loss emissions survey, 

and other TCEQ studies indicate that these unreported emissions could total several thousand 

tons per year (tpy); unreported or underreported floating roof landing loss emissions alone in 

the HGB area totaled approximately 7,250 tons in 2003. The rulemaking will help reduce 

emissions from these sources as well as other sources of potentially unreported tank emissions, 

such as slotted guidepoles and other tank fittings. 

SECTION BY SECTION DISCUSSION 

Grammatical, style, and other non-substantive corrections are made throughout the rulemaking 

to be consistent with Texas Register requirements, to improve readability, and to conform to the 

drafting standards in the Texas Legislative Drafring Manual, August 2006. Such changes 

include appropriate and consistent use of acronyms, section references, and certain terminology 

such as "that" and "which" and "shall" and "must." These changes are not discussed further. 

Subchapter B, General Volatile Organic Compound Sources 

Division 1, Storage of Volatile Organic Compounds 

Adopted $1 15.1 10 adds ten definitions used in regulatory text. Adopted $ 115.1 lO(3) defines 

Incompatible liquid as the term is used in $115.112(d)(2)(H)(ii). The definition is intended to 

allow tank landings when necessary for change of service to a material that would be 

contaminated by the previously stored material. For example, a change in service to gasoline 

with a lower Reid vapor pressure (RVP) that must be performed to comply with applicable fuel 

requirements is considered an incompatible liquid. The definition has been revised in response 

to comments to specify that different chemical mixtures and different grades of liquid material 
would also be considered incompatible liquids if the liquid being introduced into the tank would 

be made unusable for its intended purpose due to contamination from the previously stored 

liquid. Adopted $1 15.1 10(10) defines Tank battery as the term is used in $1 15.112(d)(4) and 

(d)(5). In response to comments, the definition has been modified to clarify that a collection of 

tanks at a pipeline breakout station, petroleum refinery, or petrochemical plant is not considered 

to be a tank battery. In response to comments, definitions have been added for the terms deck 

cover, pole float, pole sleeve, pole wiper, slotted guidepole, internal sleeve emission control 

system, and flexible enclosure system. These definitions have been added to clarify additional 

options for controlling emissions from slotted guidepoles that have been incorporated into 

$ 1 15.1 12(d)(2)(G). The commission has also added a definition for pipeline breakout station 

because the term is used in clarifying the applicability of requirements for control of flash 

emissions in $1 15.112(d)(4) and (5). 

Adopted changes to $ 115.1 12 amend $ 1 15.112(a) to specify that the existing requirements 

apply to the HGB area until January 1, 2009. Adopted changes also add subsection (d) to 

specify additional requirements for storage vessels in the HGB area that will take effect on 

January 1, 2009. In response to comment, the phrase "beginning January 1, 2009," has been 

added to clarify when the new requirements take effect. Adopted $1 15.1 12(d)(l) specifies the 

tank size and vapor pressure criteria that determine control requirements for tanks. These are 

the same criteria and control requirements that are now effective in the HGB area. These 

requirements are being moved to subsection (d) to be at the same location as new provisions 

that will apply to tanks in the HGB area. 

Adopted $ 1 15.1 12(d)(2) changes the control requirements for tank fittings. In response to 

comments, rule language has been changed to be more consistent with language in the EPA 
regulations in 40 CFR Part 63, Subpart WW, National Emission Standards for Storage Vessels 

(Tanks) Control Level 2. 

The proposed requirement in $1 15.112(d)(2)(A) that all openings in an internal or external 

floating roof except for automatic bleeder vents, rim space vents, and roof drains must provide 

a projection below the liquid surface and be equipped with a cover, seal, or lid has been 

modified. The requirements for all openings except automatic bleeder vents (vacuum breaker 

vents) and rim space vents to provide a projection below the liquid surface is separate from the 

requirement for all openings except automatic bleeder vents (vacuum breaker vents), rim space 

vents, leg sleeves, and roof drains to be equipped with a cover. The proposed wording would 

have incorrectly required the use of covers on fixed roof support columns. The proposed 

wording that the cover, seal, or lid must be equipped with a working gasket and kept in a 

closed position (with no visible gaps) at all times except when the opening is in actual use has 

been revised in response to comments to specify that required deck covers must be closed (with 

no gap of more than 118 inch) at all time, except when they must be opened for access. 

Adopted $1 15.112(d)(2)(B) specifies that automatic bleeder vents (also known as vacuum 

breaker vents) and rim space vents must be equipped with a gasketed lid, pallet, flapper, or 

other closure device and must be closed at all times except when required to be open to relieve 

excess pressure or vacuum, in accordance with the manufacturer's design. The current rule 

requires only that the automatic bleeder vents and rim space vents be closed. In response to 

comments, the language has been changed to allow use of a gasketed lid, pallet, flapper, or 

other closure device instead of a working gasket. Also in response to comments, language 

allowing automatic bleeder vents to open in accordance with the manufacturer's design has been 

added. For convenience, the requirements for automatic bleeder vents and rim space vents have 
been combined in 8 115.1 12(d)(2)(B). 

Section 115.112(d)(2)(C) has been revised in response to comments to allow openings for fixed 

roof support columns to be equipped with flexible fabric sleeve seals instead of deck covers. 

Adopted 8 115.112(d)(2)(D) requires that any roof drain that empties into the stored liquid must 

be equipped with a slotted membrane fabric cover or equivalent control. The current rule 

specifies the use of the slotted membrane fabric cover; the adopted rule allows the use of other 

controls. EPA regulations allow controls other than slotted membrane fabric covers. Other 

controls can provide equivalent or superior emission reduction performance. Examples include 

weighted ball or ball in cage type controls. The adopted rule also specifies that the requirement 

does not apply to stub drains on internal floating roof tanks. Stub drains are found on internal 

floating roof tanks that have bolted decks. Their purpose is to allow stored liquid @at collects 

on the roof to drain back into the tank. Covers or other controls on these stub drains would 

provide minimal, if any, reduction in VOC emissions. In response to comments, the phrase "no 

visible gap" has been changed to "no gap of more than 118 inch." 

Adopted 8115.1 12(d)(2)(E) states that there must be no visible holes, tears, or other openings in 

any seal or seal fabric. Adopted $1 15.1 12(d)(2)(F) states that secondary seals on external 

floating roof tanks must be rim-mounted and specifies a maximum allowable area of gaps 

between the secondary seal and the tank wall. In response to comments, the phrase 'with the 

exception of gaps that do not exceed the following specification" has been added to clarify that 

a limited gap area is allowed. 

Adopted $1 15.112(d)(2)(G) requires each slotted guidepole well to be controlled. The quantities 

of emissions reduced would depend on various factors including the tank size and materid 

stored. As an example, a 100-foot diameter external floating roof tank with 4,000,000-gallon 
capacity that stores gasoline with an RVP of 9 pounds per square inch absolute (psia) and has 

25 turnovers per year with an uncontrolled slotted guidepole would emit 11.85 tpy VOC from 

the guidepole alone and 14 tpy total VOC from the tank. The same tank with a controlled 

slotted guidepole would have 4.5 tpy VOC from the guidepole alone and 6.6 tons tpy total VOC 

emissions. For this case, controlling the slotted guidepole would result in a 62% decrease in 

annual VOC emissions from the guidepole and a 53% decrease in total annual tank VOC 

emissions. In response to comments, the wording has been changed to allow additional control 

options for slotted guidepoles consistent with the EPA regulations for tanks in 40 CFR Part 63, 

Subpart WW, and the Storage Tank Emissions Reduction Partnership Program (STERPP). 

These additional controls include a pole wiper and a pole float, a pole wiper and a pole sleeve, 

an internal sleeve emission control system, retrofit to a solid guidepole system, a flexible 

enclosure system, and a cover over the external floating roof. Emission calculations using the 

EPA TANKS program indicate that emissions from a slotted guidepole in a tank storing 

gasoline with an RVP of 10 psia could be reduced from 13.5 tpy down to 0.2 tpy by installing a 

cover over the roof. The language in $1 15.1 12(d)(2)(G) has also been revised to qualify that the 

controls for slotted guidepoles are only required for external floating roof tanks. Based on the 

emission calculations, emissions from slotted guidepoles in internal floating roof tanks or 

domed external floating roof tanks would be equivalent to emissions expected by installing 

slotted guidepole controls on external floating roof tanks. 

Adopted $1 15.112(d)(2)(H) specifies that a floating roof must be kept floating on the liquid 

surface at all times except when it must be supported by leg supports during initial fill and other 

limited circumstances. Instances when the roof is supported by its legs are referred to as 

"landings." Adopted $1 15.112(d)(2)(H) limits the circumstances under which tank landings are 

allowed to times when the landing is necessary either to carry out inspections or maintenance, 
or to support a change in service to a liquid that is incompatible with the previously stored 

liquid. Change in service to gasoline with a lower RVP that must be performed to comply with 

applicable fuel requirements is considered a change to a liquid that is incompatible with the 

previously stored liquid and would be allowed. Different chemical mixtures and different 

grades of liquid material would also be considered incompatible liquids if the liquid being 

introduced into the tank would be made unusable for its intended purpose due to contamination 

from the previously stored liquid. Tank landings for the purposes of inventory control (also 

known as convenience landings) would not be allowed unless vapors are routed to a control 

device during the time that the roof is landed, or landing emissions are within an emissions 

limit or cap established under a 30 TAC Chapter 116 permit. Convenience landings would also 

be allowed if sitewide landing emissions are less than 25 tpy. Emissions from tank landings are 

higher than those that would occur while the roof is floating and have generally not been 

included in EI. A recent survey by the Air Quality Division's Industrial Emissions Assessment 

Section indicates that an additionaI 7,250 tons from tank landings should have been reported in 

2003. The adopted rule helps to reduce these previously unreported emissions. Storage tanks 

with a capacity less than 25,000 gallons and those storing material with a vapor pressure less 

than 1.5 psia are not subject to the control requirements because such tanks are not required to 

be equipped with floating roofs. As an alternative to the adopted requirements of 

5 115.112(d)(2)(H)(i) - (iv), 5 1 15.1 12(d)(2)(H)(v) provides a compliance option where a 

floating roof storage tank emissions limit or cap could be established in pennits issued under 30 

TAC Chapter 116 to control floating roof tank landing emissions along with standing and 

working loss emissions from the tank. The commission has recently established enforceable 

storage tank emission caps with several independent, for-hire petroleum and bulk liquid 

terminals in the HGB region and will allow operation under these caps to demonstrate 

compliance with the rules for reducing emissions from tank landings. The emission limits or 
caps enable these terminals to reduce landing emissions through a combination of measures, 

including operational roof landing restrictions where feasible, lowering of leg position to 

minimize vapor space, restricting landed tank refill rates, degassing with controls following 

landings, and new and emerging control techniques. In response to comments, the proposed 

restriction specifying the cap could not include any increase in emissions due to tank landings 

that would otherwise be prohibited under 6 115.112(d)(2)(H)(i) - (iv) has been deleted. Also in 

response to comments, 6 115.112(d)(2)(H)(vi) has been added to allow facilities with sitewide 

landing emissions less than 25 tpy to be exempt from the restrictions on tank landings. The 

meaning of 'initial fill" in 61 15.112(d)(2)(H) has been clarified in response to comments to 

indicate that refilling a tank that has been emptied, degassed, and cleaned according to the 

provisions of Chapter 115, Subchapter F, Division 3, is allowed. The word 'required" has 

been deleted from 61 15.112(d)(2)(H)(i) in response to comments to clarify that landings are 

allowed for maintenance performed according to company or site maintenance plans and not 

just in response to regulatory requirements. The wording in $1 15.112(d)(2)(H)(ii) has been 

revised in response to comments to use the term 'incompatible liquid" in 6115.110. Also in 

response to comments, $1 15.1 12(d)(2)(H)(iv) has been changed to require control of VOC 

emissions until the roof is within 10% by volume of being refloated, instead of until the roof is 

completely refloated. Commenters expressed concern that requiring control until the roof was 

completely refloated could result in liquids being drawn into the control device and causing 

damage. 

Adopted 5 115.112(d)(3) specifies that vapor recovery systems used as a control device must 

maintain a minimum control efficiency of 90%. This is the same requirement that currently 

applies. 
Adopted $ 1 15.1 12(d)(4) specifies that flash emissions from condensate storage tanks must be 

controlled if condensate throughput for an individual tank or the collection of tanks in a tank 

battery prior to custody transfer is greater than 1,500 barrels (63,000 gallons) per year, unless 

the owner or operator demonstrates that the emissions from the individual tank or the collection 

of tanks in the tank battery are less than 25 tpy. Adopted $1 15.1 12(d)(5) specifies that flash 

emissions from crud oil or condensate storage tanks must be controlled if uncontrolled VOC 

emissions from an individual tank at an upstream oil or gas production site or a midstream 

pipeline breakout station, or collectively from a tank battery at an upstream oil or gas 

production site, would be greater than 25 tpy. This limit was proposed as $1 15.1 12(d)(4). The 

throughput limit for condensate was added to the adopted rule as $1 15.112(d)(4) for ease of 

enforcement. Using default emission factors described later in this preamble, a throughput of 

1,500 barrels per year of condensate would be expected to have 25 tpy of VOC emissions. If an 

owner or operator can demonstrate that a condensate tank with throughput greater than 1,500 

barrels per year would have emissions less than 25 tpy, the tank would not be subject to the 

flash emission controls, as allowed under the new exemption in $1 15.117(a)(9). Crude oil and 

condensate typically contain dissolved gases that flash as the pressure on the liquid is reduced. 

For example, flashing occurs when the liquids are routed from a separator or other pressurized 

vessel to an atmospheric storage tank. The flashed gases may contain VOC in addition to 

methane and ethane, and may also entrain VOC from the stored liquid. In many cases, these 

gases can be economically routed to a vapor recovery device so that the energy content can be 

recovered for use at the production site or the gas can be compressed and routed to the sales 

line. If the volume of gas is sufficient, the capital cost for these vapor recovery devices can be 

repaid in a short time because of the high economic value of the recovered gas. The 25 tpy 

threshold for control was chosen because it defines the major source level for severe 

nonattainment areas. The HGB area was classified as severe under the one-hour ozone standard 
before the one-hour standard was replaced with the eight-hour standard. The adopted 25 tpy 

threshold also represents the maximum emission rate that a site would be authorized to operate 

under a pennit by rule (PBR). The 25 tpy threshold applies to an individual tank or to an 

aggregation of tanks in a tank battery at an oil and gas exploration and production site. Because 

flash emissions could occur from any of the connected tanks, the adopted rule requires that the 

total emissions from all connected tanks be considered in determining whether the 25 tpy 

threshold is met. In response to comments, the commission has specified that the requirements 

for controlling flash emissions apply only to tanks and tank batteries storing crude oil and 

condensate prior to custody transfer at. exploration and production sites and to individual tanks 

at midstream pipeline breakout stations. Crude oil and condensate stored at downstream sites 

such as pipeline terminals, refineries, or petrochemical plants may be a source of flash 

emissions, but in response to comments, the commission has decided not to subject these 

downstream sites to the new rule at this time because the test data and test methods in support 

of the rule were designed to be used at oil and gas production sites. The commission will 

continue to evaluate the extent of flash emissions at downstream sites and may regulate such 

emissions in the future. The adopted rule gives several options for estimating the uncontrolled 

flash emissions. The methods are based on estimating an emission factor in terms of pounds of 

VOC emitted per barrel (lblbbl) of crude oil or condensate produced. Railroad Commission 

regulations in 16 TAC $3.58(b) require producers to file a monthly report of the amount of oil, 

casing head gas, natural gas, and condensate produced during the month. Owners or operators 

can use these production records for the previous 12 months (rolling) along with the emission 

factor to estimate the total VOC emissions. The emission factor can be determined by direct 

measurement of the gas over a 24-hour period. Gas volume can be measured by manifolding all 

of the tanks together and using a device such as a mass flow meter or positive displacement 

meter. A saniple of the gas can be analyzed using Gas Processors Association Method 2286, 
Tentative Method of Extended Analysis for Natural Gas and Similar Mixtures by Temperature 

Programmed Gas Chromatography, or accepted EPA methods to measure the composition of 

the flashed vapors. These measurements can be used to calculate the pounds of VOC emitted 

over the 24-hour measurement period. The pounds of VOC can then be divided by the oil or 

condensate production rate in barrels to determine the emission rate in pounds of VOC per 

barrel. Instead of making direct measurements, the owner or operator can use default emission 

factors of 33.3 lblbbl of condensate or 1.6 lblbbl of crude. These factors were determined in a 

study titled VOC Emissionsfrom Oil and Condensate Storage Tanks. This study, conducted in 

2006, was sponsored by the TCEQ and the Houston Advanced Research Center (HARC) and is 

identified as project H51C. For crude oil, owners or operators can use a chart found as Exhibit 

2 of the EPA publication Lessons Leamedfrom Natural Gas STAR Partners: Installing Vapor 

Recovery Units on Crude Oil Storage Tanks, October 2003, to estimate the volume of flash gas 

per barrel of oil. The VOC mass emission rate can then be determined by assuming that the 

hydrocarbon vapors have a molecular weight of 34 pounds per pound mole and are 48% by 

weight VOC. These values came from the HARC H51C study. Finally, the owner or operator 

can use a computer simulation or other method approved by the executive director to estimate 

flash emissions. These options are specified to minimize the burden on owners and operators to 

make direct measurements or complex calculations. If the regulated entity chooses to make 

direct measurements and they yield emission rates that are higher than those determined by the 

default emission factors, EPA chart, or simulation, or if computer simulation yields results 

higher than the default emission factors or chart, the higher rates must be used. In response to 

comments, rule language has been added to 5 1 15.1 12(d)(5) to specify that the higher rates must 

be used. The proposed rule only noted this restriction in the preamble. The commission has 

deleted the proposed 5 115.112(d)(4)(E) and combined the option to use a computer simulation 

with the option to use another method approved by the executive director. This language was 
previously in $1 15.112(d)(4)(F). The accuracy of computer simulations is entirely dependent on 

the accuracy of the inputs and the use of appropriate model parameters. Regulated entities will 

still have the option to use a computer simulation to estimate flash emissions, but the use must 

be pre-approved by the executive director to ensure that the results are accurate. Staff of the 

Industrial Emissions Assessment Section who review such calculations for EI reporting will 

review the simulation use. 

Nothing in the adopted rule implies authorization of flash emissions. All emissions must be 

authorized according to a permit or other authorization under 30 TAC Chapters 106 or 116. 

The adopted rule regulates flash emissions from crude oil and condensate storage at oil or gas 

production sites and pipeline terminals. Flash emissions may also occur at storage terminals, 

refineries, and petrochemical plants, and crude oil and condensate are not the only sources of 

flash emissions. Processes in petroleum refineries and chemical plants can generate liquids 

containing dissolved gases that will flash when the liquid is routed from higher pressure 

equipment to an atmospheric storage tank. Although flash emissions from these other liquids 

are not regulated under the adopted rule, the commission is not implying that these emissions 

are authorized. Methods specified in the EPA Compilation of Air Pollutant Emission Factors 

(AP-42) to calculate emissions from storage tanks do not include emissions from flash. Unless 

these flash emissions have been separately estimated and included in best available control 

technology (BACT) and health effects reviews during permitting, the emissions are not 

authorized even if they are not expressly prohibited by regulation in Chapter 115. 

Adopted $ 115.1 15(c) specifies appropriate measuring instruments and test methods for 

determining flash emissions if the owner or operator chooses to demonstrate compliance with 

the 25 tpy limit by direct measurement. The use of a mass flow meter, positive displacement 
meter, or similar device must be used for determining flash gas flow rate. Conventional pitot 

tube or orifice plate techniques may not be appropriate for the relatively low flow rates from oil 

and condensate storage tanks. Flow measurements must be made over a 24-hour period 

representative of normal operation to make sure that the measurements capture emissions 

during a typical working cycle including pumping into and out of the tanks. The language in 

$1 15.1 15(c) has been changed to specify that at oil and gas production sites, flow 

measurements must be made while the producing wells are operational. The proposed rule 

listed this requirement, but the adopted language has been changed to clarify that it applies to 

measurements made at oil and gas production sites and not to measurements made at pipeline 

breakout stations that could be at some distance from the producing wells. Gas composition 

must be determined using Gas Processors Association Method 2286, Tentative Method of 

Extended Analysis for Natural Gas and Similar Mixtures by Temperature Programmed Gas 

Chromatography, or approved EPA test methods. The listed test methods have been changed 

since proposal to include standard EPA test methods for the determination of VOC composition 

in addition to the Gas Processors Association Method 2286. 

In response to comments, the term "reportable emissions" in $115.116(a) has been replaced 

with the term "emissions inventory reportable emissions" to avoid confusion with the use of the 

term "reportable emissions" as used in the general air quality rules in 30 TAC Chapter 101. 

Adopted $1 15.116(c)(l) specifies that owners or operators of storage tanks that are not required 

to be equipped with a floating roof or vapor recovery system because the vapor pressure of the 

stored material is less than 1.5 psia shall keep records of the material stored and the vapor 

pressure. These records are necessary to document that material stored in fmed roof tanks 

meets the criteria for exemption from control requirements. In response to comments, the 
wording "length of time material is stored" has been replaced with the more precise wording 

"starting and ending dates when the material is stored." Commenters had expressed confusion 

over the meaning of the phrase. 

Adopted 5 1 15.1 16(c)(2) specifies that owners or operators of crude oil or condensate storage 

tanks with flash emissions shall keep records to verify that emissions from these tanks are 

below the 25 tpy criteria for exemption from control requirements. Records must be sufficient 

to allow investigators to determine whether flash emissions have been calculated by an 

appropriate method. If a computer simulation is used, records of the input and output must be 

retained. In response to comments, the wording has been changed to clarify that the 

requirements apply only to tanks or tank batteries at exploration and production sites or to tanks 

at pipeline breakout stations. Also in response to comments, the requirement to project 

emissions for the next year upon request has been deleted. 

The adopted amendment to 5 1 15.117(a)(2) specifies that in the HGB area, the storage of crude 

oil and condensate prior to custody transfer in tanks with capacity less than 210,000 gallons will 

no longer be exempt from the control requirements of Subchapter B, Division 1 after January 1, 

2009. The VOC emissions from such tanks at oil and gas production sites (especially emissions 

arising from flashed gases) have been found to be a significant source of VOC emissions and 

have previously not been reported. 

A new exemption 51 15.117(a)(9) has been added to specify that if an owner or operator can 

demonstrate that a condensate tank with throughput greater than 1,500 barrels per year would 

have emissions less than 25 tpy, then the tank would not be subject to the flash emission 

controls in 5 1 15.1 12(d)(4). 
Adopted 8 1 15.1 19(c) specifies that compliance with the requirements of 58 1 15.1 12(d), 

1 15.1 15(c), and 1 15.1 16(c) must occur by January 1, 2009, as part of the effort to address the 

eight-hour ozone standard for the HGB area. However, if compliance with the new 

requirements would necessitate emptying and degassing the tank, compliance would not be 

required until the next time the tank is emptied or degassed but not later than January 1, 201 7. 

Additional emissions that would arise from emptying and degassing a tank could negate the 

benefit of the emission controls and so would not be required solely for the purpose of installing 

controls. Because tanks are generally taken out of service at least once every ten years, the 

controls must be installed no later than ten years from the date these rules are adopted. The 

delay in compliance would apply only to the installation of equipment; monitoring and 

recordkeeping requirements must be observed beginning January 1, 2009. Regulated entities 

that use the delay of compliance provision should be prepared to justify why tank emptying and 

degassing was necessary to comply with the rules. Tanks with a nominal capacity less than 

210,000 gallons (794,850 liters) storing crude oil and condensate prior to custody transfer that 

were previously exempt must comply by January 1, 2009. Since proposal, wording has been 

added to clarify that these tanks must comply by January 1, 2009, regardless if compliance 

would require emptying and degassing the tank. 

Subchapter F, Miscellaneous Industrial Sources 

Division 3, Degassing or Cleaning of Stationary, Marine, and Transport Vessels 

The adopted change to 8 1 15.541 (a)(l) specifies that after January 1, 2009, the degassing 

control requirements will apply to storage tanks in the HGB area with a nominal capacity of 

75,000 gallons or greater storing materials with a true vapor pressure greater than 2.6 psia or to 

storage tanks with a nominal capacity of 250,000 gallons or more storing material with a true 

vapor pressure of 0.5 psia or greater. The current rule mandates degassing controls only to 
storage tanks with a nominal capacity of one million gallons or more. The EI database has 

records of more than 950 floating roof storage tanks with capacity between 75,000 and one 

million gallon capacity that could be required to employ vapor recovery during tank degassing 

under the adopted rule. There are also more than 3,000 fixed roof storage tanks in this sue 

range, but an unknown number of these storage tanks store materials with a vapor pressure less 

than 2.6 or 0.5 psia and will not be subject to the adopted degassing requirement. Degassing 

emissions from these smaller storage tanks can be abated with technology similar to that used 

for larger tanks. The sue and vapor pressure criteria for determining which storage tanks are 

subject to the degassing control requirements were changed since proposal in response to 

comments and subsequent cost effectiveness calculations by staff. 

The adopted change to $1 15.542(a)(5) specifies that the current control requirements apply in 

the HGB area only until January 1, 2009. Adopted §115.542(a)(6) specifies new criteria for 

control of degassing vapors from storage tanks and transport vessels in the HGB area. The 

change requires that vapors be vented to a control device until the VOC concentration of the 

vapors is reduced to less than 34,000 ppm by volume (ppmv) as methane or to less than 50% of 

the lower explosive limit (LEL). The current rules specify the 34,000 ppmv concentration as 

one criterion for determining when vapors can be vented to the atmosphere but also allow 

venting after a turnover of four vapor space volumes has occurred. If the storage tanks are 

drained dry and if the flow of displacement gases is measured properly, four turnovers would 

generally be sufficient to reduce VOC concentrations to less than 34,000 ppmv. If liquid 

remains in the bottom of the storage tank or transport vessel, as commonly occurs due to 

irregularities in the vessel surface, the remaining liquid would continue to be a source of VOC 

emissions after the four turnover criterion has been satisfied. The adopted rules remove the 

option to vent to atmosphere after a turnover of four vapor space volumes has occurred. 
Dilution from ventilation gas used to sweep the vapor space within the vessel could also cause a 

reading of 34,000 ppmv VOC to be reached temporarily, but if liquid remains in the storage 

tank the concentration could again rise when the flow of ventilation gas ceases. The adopted 

revision requires continued control of the vapors until the VOC concentration decreases to 

below 34,000 ppmv or a reading of less than 50% is obtained on an LEL meter. The 

concentration must be rechecked periodically while the tank is vented to the atmosphere to 

ensure that it remains below 34,000 ppmv or 50% LEL. If ventilation is continuous, the 

concentration must be measured at least once every 12 hours. If ventilation ceases for more 

than four hours, the concentration must be rechecked before the tank is reopened. The 50% 

LEL criterion was added in response to comments. The VOC concentration equivalent to 50% 

LEL is less than 34,000 ppmv and therefore is an acceptable criterion to determine when 

degassing vapors can be emitted to atmosphere. Also in response to comments, lqguage has 

been added to specify that the concentration measurements are no longer required after five 

consecutive readings less than 34,000 ppmv or less than 50% LEL have been obtained. 

The adopted change to $115.542(b)(4) specifies that the stated control requirements apply in the 

HGB area only until January 1, 2009. Adopted $115.542(b)(5) specifies new criteria for control 

of degassing vapors fiom marine vessels in the HGB area. The change requires vapors to be 

vented to a control device until the VOC concentration of the vapors is reduced to less than 

34,000 ppmv as methane or 50% LEL. The current rules specify this concentration as one 

criterion for determining when vapors may be vented to the atmosphere but also allow venting 

after a turnover of four vapor space volumes has occurred. The adopted rules remove the 

option to vent to atmosphere after a turnover of four vapor space volumes has occurred. This 

change is being adopted for degassing vapors fiom marine vessels for the same reasons 

discussed for the adopted §115.542(a)(6) for storage tanks and transport vessels. The 50% LEL 
criterion has been added to the rule because the commission has specified that an equivalent 

LEL percentage can be used to determine when degassing need no longer be controlled for 

storage tanks. The current rule in $1 15.542(b)(4) uses 20% of the LEL as one of the criteria for 

when marine vessels may be vented to the atmosphere. This requirement was not changed 

because it applies to sources in the Beaumont-Port Arthur area as well as (until January 1, 

2009) sources in the HGB area. The revised §115.542(b)(5) specifies 50% of the LEL to be 

consistent with the value used in $1 15.542(a)(6) for storage tanks and transport vessels. 

Because the LEL criterion is an option to allow flexibility in measurement methods, using 50 % 

instead of 20% in $1 15.142(b)(5) will not allow an increase in VOC emissions over those 

allowed under $1 15.542(b)(4). 

Adopted $1 15.545(11) specifies the methods that must be used to measure the VOC 

concentration of the storage vessels, transport vessels, or marine vessels to determine when the 

vapors can be vented to the atmosphere instead of to a control device. In response to comments, 

several additional analytical methods have been specified to allow flexibility for the 

concentration measurements. However, the large potential variability in chemical composition 

of stored liquids necessitates carefully selecting and implementing the analytical method 

according to the precise chemical and physical circumstances occurring at the time of the 

measurement. Thus, the commission requires that sufficient records and other information be 

maintained to show that the alternative method used completely meet the needs of the specific 

instance. Examples of such records are maintenance and calibration records of all equipment, 

training records of equipment operators, and a written sampling plan for each instance complete 

with data quality objectives and QAIQC measurement parameters. The measurement should be 

made at the head space of the vessel, as close as possible to the tank bottom to ensure that the 
concentration measurement is representative of actual conditions, but the measurements should 

be made at a safe location. 

Adopted $1 15.546(1)(D) specifies that records of the VOC concentration measurements 

required by §115.542(a)(6) and (b)(5) must be maintained. The records are necessary to 

document that degassing vapors are routed to a control device until they reach the criteria to be 

released to the atmosphere. 

A change to $1 15.547(2) is adopted to state that after January 1, 2009, storage tanks in the 

HGB area with a nominal capacity of less than one million gallons but greater than or equal to 

250,000 gallons or with a nominal capacity of greater than or equal to 75,000 gallons storing 

material with vapor pressure greater than 2.6 psia will no longer be exempt from the 

requirements to control degassing emissions. As discussed earlier in this preamble, degassing 

emissions from these smaller tanks can be controlled with technology similar to that used to 

control degassing emissions from the larger tanks. The commission revised the exemption level 

in response to public comments. 

The words "causes" and "prevents" are added to 81 15.547(4) so that the text more clearly 

expresses the intended meaning of the exemption. 

Adopted §115.549(d) specifies that compliance with the new and revised requirements must 

occur by January 1, 2009, as part of the effort to address the eight-hour ozone standard for the 

HGB area. 
FINAL REGULATORY IMPACT ANALYSIS DETERMINATION 

The commission reviewed the adopted rulemaking action in light of the regulatory analysis 

requirements of Texas Government Code, 5200 1.0225, and determined that the rulemaking 

action does not meet the definition of a "major environmental rule" as defined in that statute. A 

"major environmental rule" is a rule the specific intent of which is to protect the environment 

or reduce risks to human health from environmental exposure and that may adversely affect in a 

material way the economy, productivity, competition, jobs, the environment, or the public 

health and safety of the state or a sector of the state. The primary purpose of this adopted 

rulemaking action is to require owners or operators of VOC storage tanks, transport vessels, 

and marine vessels located in the HGB eight-hour ozone nonattainment area to better control 

their storage and degassing operations, thereby reducing VOC emissions. The adopted rules 

assist in identifying previously unreported emissions, and reducing them appropriately. It is 

anticipated that this adopted rulernaking will positively affect human health and the 

environment, and not adversely affect the economy or productivity in any material manner. 

Moreover, the adopted rules will improve air quality and make positive progress towards 

attainment of the HGB eight-hour ozone standard. Therefore, the adopted rulernaking does not 

constitute a major environmental rule, and thus is not subject to a formal regulatory analysis. 

In addition, this adopted rulemaking does not meet any of the four applicability criteria of a 

"major environmental rule" as defined in the Texas Government Code. Texas Government 

Code, 52001.0225 applies only to a major environmental rule the result of which is to: 1) 

exceed a standard set by federal law, unless the rule is specifically required by state law; 2) 

exceed an express requirement of state law, unless the rule is specifically required by federal 

law; 3) exceed a requirement of a delegation agreement or contract between the state and an 

agency or representative of the federal government to implement a state and federal program; 
or 4) adopt a rule solely under the general powers of the agency instead of under a specific state 

law. 

The rulemaking action, which is designed to reduce VOC emissions that have previously been 

underreported in EI, does not exceed an express requirement under federal or state law. 

Furthermore, there is no contract or delegation agreement that covers the topic that is the 

subject of this action. Finally, this rulemaking action was not developed solely under the 

general powers of the agency, but is authorized by specific sections of Texas Health and Safety 

Code, Chapter 382 (also known as the Texas Clean Air Act), and the Texas Water Code, which 

are cited in the STATUTORY AUTHORITY section of this preamble, including Texas Health 

and Safety Code, $ $382.01 1, 382.012, and 382.017. Therefore, the adopted rulemaking does 

not exceed a standard set by federal law, exceed an express requirement of state law, exceed a 

requirement of a delegation agreement, nor is adopted solely under the general powers of the 

agency. 

Based upon the foregoing, this rulemaking action is not subject to the regulatory analysis 

provisions of Texas Government Code, $2001.0225. 

TAKINGS IMPACT ASSESSMENT 

Under Texas Government Code, §2007.002(5), "taking" means a governmental action that 

affects private real property, in whole or in part or temporarily or permanently, in a manner 

that requires the governmental entity to compensate the private real property owner as provided 

by the Fifth and Fourteenth Amendments to the United States Constitution or $17 or $19, 

Article I, Texas Constitution; or a governmental action that affects an owner's private real 

property that is the subject of the governmental action, in whole or in part or temporarily or 
permanently, in a manner that restricts or limits the owner's right to the property that would 

otherwise exist in the absence of the governmental action; and is the producing cause of a 

reduction of at least 25% in the market value of the affected private real property, determined 

by comparing the market value of the property as if the governmental action is not in effect and 

the market value of the property determined as if the governmental action is in effect. 

The commission completed a takings impact assessment for the adopted rules. The adopted 

rules will not affect private real property in a manner that would require compensation to 

private real property owners under the United States Constitution or the Texas Constitution. 

The adoption also will not affect private real property in a manner that restricts or limits an 

owner's right to the property that would otherwise exist in the absence of the governmental 

action. Therefore, the adopted rules will not cause a taking under Texas Government Code, 

Chapter 2007. 

CONSISTENCY WITH THE COASTAL MANAGEMENT PROGRAM 

The commission determined that this rulemaking action relates to an action or actions subject to 

the Texas Coastal Management Program (CMP) in accordance with the Coastal Coordination 

Act of 199 1, as amended (Texas Natural Resources Code, 5533.201 et seq.), and the 

commission rules in 30 TAC Chapter 281, Subchapter B, concerning Consistency with the 

Texas Coastal Management Program. As required by 5281.45(a)(3) and 31 TAC $505.1 l(b)(2), 

relating to Actions and Rules Subject to the Coastal Management Program, commission rules 

governing air pollutant emissions must be consistent with the applicable goals and policies of 

the CMP. The commission reviewed this action for consistency with the CMP goals and 

policies in accordance with the rules of the Coastal Coordination Council, and determined the 

action is consistent with the applicable CMP goals and policies. The CMP goal applicable to 
this rulemaking action is the goal to protect, preserve, and enhance the diversity, quality, 

quantity, functions, and values of coastal natural resource areas (31 TAC #501.12(1)). No new 

sources of air contaminants will be authorized and the adopted rules will maintain at least the 

same level of or increase the level of emissions control as the existing rules. The CMP policy 

applicable to this rulemaking action is the policy that commission rules comply with federal 

regulations in 40 CFR, to protect and enhance air quality in the coastal areas (3 1 TAC 

8501.32). This rulemaking action complies with 40 CFR Part 51, Requirements for 

Preparation, Adoption, and Submittal of Implementation Plans. Therefore, in accordance with 

31 TAC §505.22(e), the commission affirms this rulemaking action is consistent with CMP 

goals and policies. 

EFFECT ON SITES SUBJECT TO THE FEDERAL OPERATING PERMITS PROGRAM 

The requirements of Chapter 115 are applicable requirements of 30 TAC Chapter 122. Owners 

or operators of sites subject to the Federal Operating Permit Program will be required to obtain, 

revise, reopen, and renew their Federal Operating Permits, as appropriate, in order to include 

the requirements of this adopted rulernaking. 

PUBLIC COMMENT 

The commission held public hearings on this proposal at the following times and locations: 

January 29, 2007, 2:00 p.m. and 6:00 p.m., Houston-Galveston Area Council, 3555 Timmons 

Lane, Houston; January 3 1, 2007, 7:00 p.m., J. Erik Jonsson Central Library Auditorium, 

1515 Young Street, Dallas; February 1,2007,2:00 p.m., Arlington City Hall Council 

Chambers, 101 W. Abrarns Street, Arlington; February 1, 2007, 6:00 p.m., Midlothian 

Conference Center, 1 Community Circle, Midlothian; February 6, 2007, 2:00 p.m., Longview 
Public Library, 222 W. Cotton Street, Longview; and February 8, 2007, 2:00 p.m., Texas 

Commission on Environmental Quality, Building E, Room 201S, 12100 Park 35 Circle, Austin. 

The commission received comments from Baker Botts L.L.P. on behalf of the 8-Hour Ozone 

SIP Coalition (EOSIPC), Association of Electric Companies of Texas, Inc. (AECT), Celanese, 

Ltd., CEMA Solutions, Inc. (CEMA), Coalition of Manufacturers for Air Quality (COMAQ), 

Dow Chemical Company (Dow), Energy Business, Inc. (EBI), GEM Mobile Treatment 

Services, Inc. (GEM), Galveston-Houston Association for Smog Prevention (GHASP), Harris 

County Public Health & Environmental Services (HCPHES), Houston-Sierra Club (HSC), 

Marathon Pipe Line (MPL), Mothers for Clean Air (MFCA), Remediation Service, Int'l (RSI), 

Texas Chemical Council (TCC), Texas Oil & Gas Association (TxOGA), Baker Botts L.L.P. 

on behalf of Texas Terminal Operators Group (TTO), United States Environmental Protection 

Agency Region 6 (EPA), and one individual. State Representative AM E. Hernandez of District 

143, State Representative Jessica Farrar of District 148, and Mayor Bill White of Houston 

jointly with County Judge Robert Eckels of Harris County submitted comments on the SIP that 

did not have specific comments on the proposed rules. 

The comrnenters suggested modifications to the proposed rules as stated in the RESPONSE TO 

COMMENTS section of this preamble. 

RESPONSE TO COMMENTS 

The EPA requested that the commission provide a legend or explanation that clarifies the 

symbols used to identify changes that will be made to the rule. 
The commission used Texas Register format to indicate changes to the rule. In the 

proposal, new rule language was shown in underline, and rule language to be deleted was 

in brackets. 

Celanese endorsed the comments provided by the TCC. 

The commission acknowledges Celanese's endorsement of the comments provided by the 

TCC. 

The AECT and EOSIPC expressed support for the process the agency has used to select the 

proposed control strategies and the conclusions reached. The EOSIPC and TxOGA also 

expressed support for the proposal with the technical corrections submitted by its members 

comments, and AECT, Dow, EOSIPC, and TCC stated that these control strategies will result 

in additional progress towards attainment of the eight-hour ozone standard in the HGB area. 

The commission appreciates the support. 

The EPA and RSI expressed support for the agency's efforts to expand controls and reduce 

VOC emissions within the HGB area. EBI stated that accounting for storage and transport 

emissions sources is "very good stewardship. " 

The commission appreciates the support. 
The EOSIPC expressed support for the commission's ongoing work to incorporate the findings 

of the TexAQS I1 field study into the development of new modeling episodes that occurred in 

2005 and 2006. 

Both the TCC and Dow support the development of a new modeling episode that incorporates 

the TexAQS I1 field study results. Dow additionally suggested that the TCEQ should consider 

information resulting from industry-sponsored research projects that show point source 

emissions from the HGB perimeter counties have little effect on key air quality monitors in 

Harris County. 

The commission appreciates the support for the technical work completed to date. The 

TCEQ has, and will continue, to review and analyze other technical studies as it moves 

forward with development of a new modeling episode and development of appropriate 

control strategies for the HGB area. 

Both the AECT and COMAQ encouraged the agency to consider the primary reason the HGB 

area cannot attain the eight-hour ozone standard by the deadline is due to NOx and VOC 

emissions from on-road and off-road mobile sources, marine vessels, and other federally 

regulated sources. The COMAQ stated that NOx emissions from such sources are estimated to 

comprise about 54% of the 2009 NOx emissions inventory for the HGB area. The EOSIPC 

asserted that agency photochemical modeling demonstrates that on-road and non-road mobile 

source emissions reductions constitute the most effective path toward the HGB area achieving 

attainment. The COMAQ and EOSIPC stated that significant progress towards attainment in the 

HGB area cannot be realized before substantial reductions are made in mobile source emissions. 

COMAQ further noted the TCEQ does not have the authority to regulate emissions from 
federally regulated sources. The TCC and Dow encouraged the commission to continue 

promoting voluntary programs like TERP to accelerate mobile source emission reductions. 

AECT and COMAQ expressed support for additional legislative funding for the TERP 

program. COMAQ additionally commented that the agency should emphasize that TERP has 

resulted in about 22 tpd of NOx and VOC emission reductions from on-road and non-road 

sources in the HGB area. The AECT suggested the commission continue to encourage the EPA 

to take all appropriate measures to accelerate reductions of NOx and VOC emissions from onroad and non-road mobile sources, marine vessels, and other federally regulated emission 

sources in the HGB area. The AECT suggested the commission encourage and support 

programs and initiatives that will reduce NOx and VOC emissions from on-road and non-road 

mobile sources in the HGB area even if the measures cannot be used for emission reduction 

credits in the SIP. 

The issues brought up in these comments are beyond the scope of this rulemaking. The 

purpose of this rule project is to decrease VOC emissions from industrial point sources 

that have been previously unreported or underreported to the TCEQ and to provide better 

recordkeeping and reporting to formulate a more accurate inventory and enable more 

accurate modeling for future SIP development. 

The COMAQ encouraged the TCEQ to continue to emphasize the following facts and to use 

these facts in the development of the HGB eight-hour ozone SIP rules: (1) emissions of NOx 

and VOC (including HRVOC) from industrial point sources have been significantly reduced 

since 2001; and (2) TCEQ photochemical modeling indicates additional NOx and VOC 

(including HRVOC) emissions reductions from point and area sources in the HGB area will not 

bring the area into attainment with the eight-hour ozone standard. The EOSIPC stated that since 
2001, its member companies have invested over two billion dollars in state-of-the-art emissions 

controls that have reduced ozone precursor emissions; the results of these investments are 

evident in the ambient air. Additionally, the EOSIPC asserts that independent scientific studies 

show that the current control strategies are reducing ozone. These decreases have occurred 

before the full implementation of the current point source NOx and HRVOC emissions control 

strategy that was adopted in 2004 and will be fully implemented in 2007. 

The commission acknowledges the efforts that have been made by industrial point sources 

in the HGB area to reduce emissions. The purpose of this rule package is to reduce 

emissions of VOC that have been previously unreported or underreported in the EI and 

therefore not considered in modeling exercises to determine the most effective control 

measures to reduce ozone. Additional emission reductions from across the broad spectrum 

of sources may be needed to reduce ozone levels enough to meet the eight-hour standard. 

The TT0 requested that the commission make changes to the proposed rule to address market 

realities that for-hire terminals face. HSC noted that under "Potentially Controversial Matters" 

in the Executive Summary for the HGB VOC rules TCEQ stated, "Representatives of terminal 

operators oppose the prohibition of convenience tank landings." HSC expressed objection that 

TCEQ was allowing the regulated community to "call the shots" about rule development. 

The commission has made some changes to the proposed rule as a result of the TTO 

comments, as discussed in the Response to Comments section of this rulemaking. The 

reference to the opposition of terminal owners and operators to the prohibition of 

convenience landings was intended only to alert the commissioners to communications that 

had been received before the formal rule proposal. The prohibition was included in the 
proposed rule, but after further discussion and research, 5115.112(d)(2)(H)(v) and (vi) 

allow for convenience landings if emissions are authorized under a permit limit or emission 

cap in a permit issued under 30 TAC Chapter 116 or if site-wide emissions from tank roof 

landings are less than 25 tpy. 

Both GHASP and HSC requested that the VOC rules be made more stringent because TCEQ 

has not been able to document sufficient VOC emission reductions to show attainment of the 

ozone standard by 2010. Similarly, an individual commenter encouraged the commission to 

place more stringent controls on storage tank emissions. 

Photochemical modeling has shown that VOC reductions alone would not be sufficient to 

allow the HGB area to attain the eight-hour ozone standard by 2010. The commission's 

responses to the commenters' specific suggestions for making the VOC rules more 

stringent are detailed elsewhere in this document. 

GHASP asserted that the only new control measures in the &hour ozone SIP are enhancements 

to on-road and non-road NOx emissions controls and encouraged the agency to adopt additional 

control measures. GHASP specifically encouraged the agency to consider measures that would 

expand the monitoring network, track emissions events and predict future emissions event 

impacts, incorporate reactivity based strategies such as trading of HRVOC and/or other VOC 

emissions, and control wastewater and other industrial VOC sources. GHASP stated that the 

HGB area needs every possible emissions reduction to achieve attainment and generally favors 

industrial controls first, followed by diesel source controls. 
The commission appreciates the comment but the suggestions are outside the scope of this 

rulemaking and therefore no changes were made to the Chapter 115 rules as a result of 

this comment. The commission considered developing rules to require more stringent 

controls for wastewater facilities, but concluded that more information is needed to 

quantify potentially underreported emissions before effective rules can be developed. 

MFCA specifically suggested increasing VOC reductions from large industrial sources in the 

HGB area by 95 % or more, and both MFCA and GHASP suggested establishing controls on 

other VOC in addition to HRVOC in the HGB area. Additionally, GHASP encouraged the 

agency to consider measures that concomitantly reduce pollutants that pose additional risks, 

such as air toxics and particulates. 

The commission appreciates the comments but the suggestions are outside the scope of this 

rulemaking and therefore no changes were made to the Chapter 115 rules as a result of 

these comments. 

HCPHES expressed support for the amendments to Chapter 115 to reduce VOC emissions from 

storage and degassing operations in the HGB area. The HCPHES suggested adopting and/or 

implementing various rules adopted by other states to reduce VOC content in solvents, paints, 

~d various household and cosmetic products. The HCPHES also suggested expanding the 

HRVOC regulations beyond Harris County and adding to the list of chemicals subject to the 

HRVOC rules. 

The commission appreciates the comment in support of the Chapter 115 rules and the 

suggestions for additional control measures to reduce VOC emissions. The rule sections 
associated with the HCPHES suggestions are beyond the scope of this rulemaking and 

therefore no changes have been made to the rule based on the comments. Furthermore, 

the EPA is scheduled to adopt more stringent VOC content limits in paints and various 

household and cosmetic products in November 2007. 

HSC commented that the rule changes for storage tanks, degassing, and flash emissions should 

be applied statewide. 

Extending coverage of these rules to the entire state is beyond the scope of this 

rulemakiug. Because the proposal only applied the rule changes to the HGB area, affected 

parties in other areas of the state have not received proper notice of the changes and 

would not have an opportunity to comment. The commission may consider extending 

coverage of the rule amendments in a future rulemaking. 

EBI objected to the adoption of the rule language prior to determining the resolution of the 

Texas Petrochemical situation with the city of Houston. El31 recommended the commission 

expressly notify the city of Houston of the intended purpose of the regulations and suggested 

adding a qualifier to the rule language specifying the rule does not apply to the foregoing 

situation. 

The city of Houston is aware of the proposed rule language, as evidenced by comments 

made by the mayor of Houston on the SIP proposal. The commission has made no changes 

to the rule as a result of this comment. 
HSC expressed disagreement with the statements in the Executive Summary for the HGB VOC 

rules concerning enforcement responsibilities. HSC further expressed concern that new TCEQ 

regulations in the past have created greatly increased workloads for investigators and requested 

that the commission document how many more investigations and investigator hours will be 

required to implement these rules. EBI expressed concerns about the commission's lack of 

enforcement of the regulations the commission promulgates. 

The proposed increased stringency of rules for tanks does not require additional 

inspections, just changes in compliance criteria. The changes to the degassing rules would 

affect additional sources, but degassing is done infrequently. The requirements for control 

of flash emissions would impose new requirements at sites that are already subject to other 

commission rules for permitting and emissions inventory reporting but may not be 

complying with these requirements due to underestimation of flash emissions. The 

recordkeeping requirements of the new rules could aid investigators in determining 

whether facilities are in compliance with existii rules. 

GEM suggested clarifying whether the term "storage vesseln used in the proposed rule text 

refers to "storage tanks." 

The term "storage vessel" as used in the rule includes "storage tanks." Most instances of 

the term "storage vessel" in the adopted rule have been changed to "storage tank." 

EBI suggested the Chapter 115 rule language be revised to distinguish between VOC and 

NMVOC. EBI recommended clarifying that the rule applies to storage for VOC and NMVOC 
or limit the rule solely to crude and natural gas tanks and then propose a separate rule for 

NMVOC. 

The defdtion of VOC in 30 TAC $101.1 (relating to Definitions) excludes methane and 

other compounds determined by the EPA to have a negligible contribution to tropospheric 

ozone formation. Therefore, the suggested change is not necessary. 

COMAQ, TCC, ?TO, and Dow suggested including in $1 15.110 definitions of the following 

terms as they are defined by the EPA in 40 CFR $63.1061: pole float, pole sleeve, pole wiper, 

and slotted guidepole. The ?TO suggested also adding the following defmitions: deck cover, 

external floating roof tank cover, flexible enclosure system, internal sleeve emission control 

system. 

The commission has added definitions for the terms deck cover, pole float, pole sleeve, 

pole wiper, slotted guidepole, flexible enclosure system, and internal sleeve emission 

control system as requested. A definition for external floating roof tank cover was not 

added because it was not necessary. 

Dow suggested the TCEQ expand the definition of "incompatible liquid" in $1 15.110 to include 

(1) liquids that have different chemical mixtures and cannot be mixed due to product quality 

specifications and (2) different grades of liquid materials that cannot be mixed due to product 

quality specifications. In addition, Dow suggested that theses definition changes should be 

considered acceptable in $ 1 15.1 12(d)(2)(H)(ii). Dow also suggested that any liquid or fuel with 

a different specification should be considered as,an incompatible liquid for the purposes of the 

rule. The ?TO suggested the rule language in $1 15.1 lO(1) be revised to read "incompatible 
liquid--a liquid that is a different chemical compound, a fuel with different regulatory 

specifications, or any liquid that is otherwise compatible but for commercial contractual 

reasons." The TCC suggested the term "incompatible" should recognize the following 

additional scenarios: a liquid material that would contaminate or significantly change the quality 

of a future stored material, any liquid or fuel with different product specifications. 

The commission has revised the defmition to include different chemical mixtures or 

different grades of liquid material that would be unusable for its intended purpose due to 

contamination from the previously stored liquid. Mmor differences in product quality 

specifications or materials owned by different customers are not intended to be covered 

under the definition, or the definition of incompatible liquid would be so broad as to be 

practically unenforceable. The commission notes that facilities have the option to authorize 

landing emissions under a cap or emissions limit under a Chapter 116 permit or a 25 tpy 

exemption as allowed in 0115.112(6)(2)(H)(v) and (mi. 

The TxOGA expressed support for the definition of "incompatible liquid" in 5 1 15.1 lO(1). The 

TCC agreed with the concept of allowing floating roof landings to support a change in service 

to a liquid that is incompatible with the previously stored liquid. 

The commission appreciates the support. 

The TxOGA and TCC suggested the definition of "tank battery" in $1 15.1 lO(2) be changed to 

read "Exploration and Production Tank Battery--A collection of equipment at an exploration 

and production site used to separate, treat, store, and transfer crude oil, condensate, natural 

gas, and produced water." 
Instead of making the change as suggested, the commission is changing the definition to 

specify that a collection of tanks at a pipeline breakout station, petroleum refinery, or 

petrochemical plant is not considered to be a tank battery. The commission has also 

changed §115.112(d)(4) and (5) to specify that control of flash emissions is required only 

for crude oil or condensate storage prior to custody transfer or at a pipeline breakout 

station. With these changes, the flash emission control requirements would apply to 

individual tanks or the collection of tanks at an oil and gas exploration and production site 

and to individual tanks at a pipeline breakout station. The requirements would apply to 

upstream and midstream operations but not to downstream operations such as crude oil 

and condensate storage at pipeline terminals, petroleum refmeries, or petrochemical 

plants. The commission will continue to evaluate the extent of flash emissions at the 

downstream operations and may take action to regulate these sources at a later time. 

HSC requested that the minimum control efficiency in $1 15.112(a)(3) and (d)(3) be increased 

from 90% to 95%. 

The commission made no changes to the rule as a result of this comment. The focus of the 

rulemaking project was to effect real reductions in VOC emissions. Although the rule only 

requires a control efficiency of 90%, many of the control devices in use in fact reduce 

emissions by 95% or more. 

HSC requested that the rules in 51 15.112(b) and (c) for Gregg, Nueces, Victoria, Aransas, 

Bexar, Calhoun, Matagorda, San Patricia, and Travis Counties be changed to be as stringent as 

those for the HGB area. HSC also requested that all references in $1 15.1 12(c)(l), Table I(b), to 
1.5 psia be changed to 0.5 psia and that all references to 25,000 gallons be changed to 10,000 

gallons. 

Revising the rules for the listed counties is beyond the scope of this rulemaking. Because 

no changes were proposed to the referenced subsections, affected parties in these counties 

have not received proper notice of the changes and would not have an opportunity to 

comment. The commission may consider extending coverage of the rule amendments in a 

future rulemaking. 

HSC commented that rules in $1 15.112(d) should apply statewide. 

Extending coverage to the entire state is beyond the scope of this rulemaking. Because the 

proposed rule only applied the rule changes to the HGB area, affected parties in other 

areas of the state have not received proper notice of the changes and would not have an 

opportunity to comment. The commission may consider extending coverage of the rule 

amendments in a future rulemaking. 

MFCA suggested requiring the installation of control measures for storage tanks with VOC 

vapor pressure equal to or greater than 0.5 pounds per square inch absolute. GHASP 

commented that the Chapter 115 rules should be changed to reflect the best available control 

technology requirements that dictate storage tanks operating with a vapor pressure greater than 

0.5 psia and a capacity of more than 25,000 gallons have a floating roof or vent to control 

device. HSC commented that all references to 1.5 psia in Tables I(a) and II(a) should be 

changed to 0.5 psia and that all references to 25,000 gallons and 40,000 gallons in Tables I(a) 

and II(a) should be changed to 10,000 gallons. 
The commission considered lowering the vapor pressure that would trigger control 

requirements during the development of the rule proposal. After reviewing data available 

in the EI, the commission concluded that emissions from fmed-roof tanks storing materials 

with vapor pressures between 0.5 and 1.5 psia represented a small portion of the total 

VOC emissions from fmed roof tanks and that requiring additional controls for these 

tanks would not provide a meaningful reduction in VOC emissions. 

Controls for smaller tanks are less cost effective than controls for larger tanks. According 

to data in the EI, there are a total of 3,451 fmed roof tanks with a total capacity of 52.8 

million gallons that have capacities greater than or equal to 10,000 gallons but less than 

25,000 gallons in the HGB area. There are 1,073 tanks with total capacity of 32.6 million 

gallons that have capacities between 25,000 and 40,000 gallons. For comparison, there are 

5,498 fured roof tanks with a total capacity of over 14 billion gallons that have capacities of 

40,000 gallons or more. There are an additional 2,259 floating roof tanks with combined 

capacity over 24 billion gallons. The relative capacity of tanks that would be affected by 

the requested change represent less than 1% of the total fmed roof tank capacity in the 

HGB and less than 0.3% of the total fmed and floating roof capacity. The commission 

decided not to pursue additional controls for tanks that represent such a small percentage 

of the total tank capacity. Controls for these small tanks would not result in meaningful 

emission reductions. 

The EPA requested confirmation that § 1 15.112(d) specifying additional requirements for 

storage vessels in the HGB area will begin January 1, 2009. The EPA also noted that although 

the preamble makes this clear, a start date of January 1, 2009, may need to be added to the 

rule. 
The commission has added the start date of January 1,2009, to 5115.112(d) as suggested. 

The TCC suggested incorporating the language in 40 CFR §63.1063(b)(l), (2), (3), and (5) into 

$1 15.112(d)(2) to address the operational requirements of floating roof tanks. 

The commission has revised 5115.112(d)(2)(H) to include the language in 40 CFR 

563.1063(b)(l) regarding support of a floating roof by other devices (e.g., hangers from 

the fixed roof). Language in 40 CFR 563.1063(b)(3) requiring that cavers be closed at all 

times except when they must be opened for access has been incorporated into 

91 15.112(d)(2)(A). The commission declines to add the language in 40 CFR §63.1063(b)(2) 

and (5). The language in 40 CFR §63.1063(b)(2) would require that when the liquid depth 

is insufficient to float the floating roof, the process of filling to refloat the roof must be 

continuous and be performed as soon as practical. The restrictions on tank landings in 

§115.112(d)(2)0 adequately address emissions from landed floating roofs. The 

requirement in 40 CFR §63.1063(b)(5) for each unslotted guidepole cap to be closed at all 

times except when gauging the liquid level or taking liquid samples is addressed in 

§115.112(d)(2)(A). 

The COMAQ and TCC suggested the rule language in $1 15.1 12(d)(2)(A) be revised to replace 

the phrase "no visible gapn with the phrase "no gap of more than 118 inch." The requested 

change would make the TCEQ language consistent with the language in the EPA MACT 

standard 40 CFR §63.1063(d)(l)(v). 

The commission has made the suggested change. 
The TCC encouraged the agency to incorporate the language used in 40 CFR Part 63, Subpart 

WW and revise 51 15.112(d)(2)(A) to allow exemption for leg sleeves from the requirement to 

have a cover. 

The commission has made the suggested changes. 

TxOGA suggested the word "emergency " be added before "roof drains" in $1 15.1 12(d)(2)(A) 

and (D). 

The commission has not made the suggested change. The wording of 6115.112(d)(2)@) 

specifies that the requirement applies to roof drains that empty into the stored liquid. A 

roof drain system that uses a hose or piping to drain water from the roof to the side of the 

tank shell does not empty into the stored liquid and so would not be subject to the control 

requirement. 

Dow, COMAQ, and the TCC suggested replacing the phrase "working gasket" in 

$1 15.112(d)(2)(A)-(C) (and elsewhere in the proposed document) with the phrase "gasket in 

good operating condition" for clarity. Additionally, the TCC and COMAQ suggested revising 

$1 15.112(d)(2)(A) and (C) by changing the term "rim vent" to "rim space vent." 

The commission has made the suggested changes. 

TTO suggested the rule language in $1 15.112(d)(2)(A) be deleted and replaced with language 

from 40 CFR §63.1063(a)(2)(i) and (ii) to read "each opening except for those for automatic 

bleeder vents (vacuum breaker vents) and rim space vents shall have its lower edge below the 
surface of the stored liquid. Each opening except for automatic bleeder vents (vacuum breaker 

vents), rim space vents, leg sleeves, and deck (roof) drains shall be equipped with a deck 

cover. The deck cover shall be equipped with a gasket between the cover and the deck." 

The commission has made the suggested changes, with slight differences in wording to 

correspond to the format of the existing rule as well as agency guidelines, Texas Register 

guidelines, and Texas Legislative DmfCing Manual, August 2006. 

TTO suggested the rule language in $1 15.112(d)(2)(B) be deleted and replaced with language 

from 40 CFR $63.1063(b)(4) to read "each automatic bleeder vent (vacuum breaker vent) and 

rim space vent shall be closed at all times, except when required to be open to relieve excess 

pressure or vacuv, in accordance with the manufacturer's design." TCC suggested revising 

$1 15.112(d)(2)(B) by adding the phrase "or at the manufacturer's recommended setting" so that 

9 1 15.1 12(d)(2)(B) will be consistent with 41 15.1 12(d)(2)(C) and with 40 CFR §63.1063(b)(4). 

The commission has made the suggested changes. 

TxOGA suggested the rule language in $1 15.1 12(d)(2)(C) be clarified concerning the placement 

of gaskets on rim vents. TxOGA suggested that the language read "rim vent valves, if flanged, 

must be equipped with a working gasket and the valve be set to open only when the roof is 

being floated off the roof leg supports or at the manufacturer's recommended setting." 

The commission has revised the language in §115.112(d)(2) to be consistent with language 

in 40 CFR §63.1063(a)(2)(iii). The new language applicable to rim vents is in 

§115.112(d)(2)(B). It specifes that rim space vents must be equipped with a gasketed lid, 
pallet, flapper, or other closure device instead of specifying that each rim vent be 

equipped with a gasket. 

TTO expressed support for exempting stub drains from the requirements of $1 15.112(d)(2)(D) 

and agreed with the commission's assessment that controls on stub drains would provide 

minimal VOC reductions. 

The commission appreciates the support. 

TxOGA suggested the rule language in 5 1 15.1 12(d)(2)(E) be clarified to read "there must be no 

visible holes, tears, or other openings in a primary or secondary seal or seal fabric." TxOGA 

expressed the opinion that the envelope on a mechanical shoe seal system is not part of the 

primary or secondary seal, and that the "no tear or hole" requirement should not be construed 

to apply to the envelope on a mechanical shoe seal system. 

The commission has not made the suggested change in the rule language because the 

language applies to fabrics used to seal deck fittings as well as primary and secondary 

seals. The commission acknowledges that inspecting the envelope would be diff~cult in a 

tank equipped with a secondary seal. The inspection requirements in 8115.114 do not 

require moving the secondary seal to inspect the primary seal. If a hole or tear in the 

envelope of a mechanical shoe seal is found, it must be repaired if it would cause an 

increase in VOC emissions. Information available to commission staff indicates that the 

envelope is part of the vapor barrier and thus any holes or tears found in the envelope 

must be repaired. 
TxOGA suggested the rule language in $1 15.112(d)(2)(F) be clarified to read "for external 

floating roof storage tanks, secondary seals must be the rim-mounted type (the seal must be 

continuous from the floating roof to the tank wall with the exception of gaps that do not exceed 

the following specifications). The accumulated area of gaps that exceed 118 inch (0.32 

centimeters) in width between the secondary seal and the tank wall must be no greater than 1.0 

square inch per foot (2 1 square centimeters per meter) of tank diameter. " 

The commission has made the requested change. 

COMAQ, Dow, MPL, and TxOGA suggested that the TCEQ allow the use of a pole sleeve 

option, similar to the EPA option in 40 CFR $60.1063(a)(2)(viii), to control VOC emissions 

from slotted guidepoles as an alternative to a gasketed float as specified in $ 1 15.1 12(d)(2)(G). 

TTO suggested the rule language in $1 15.112(d)(2)(G) be deleted and replaced with language 

from both the EPA Storage Tank Emission Reduction Partnership Program (STERPP) (65 FR 

19891, April 13, 2000) and 40 CFR §63.1063(a)(2)(viii) to read "each opening for a slotted 

guidepole shall be equipped with one of the following control device configurations: (i) a pole 

wiper and a pole float. The wiper or seal of the pole float shall be at or above the height of the 

pole wiper, (ii) a pole wiper and a pole sleeve, (iii) an internal sleeve emission control system, 

(iv) a flexible enclosure system, or (v) an external floating roof tank cover." TCC and TxOGA 

suggested revising $1 15.1 12(d)(2)(G) to adopt the language of 40 CFR $63.1063 as well as all 

other control options provided in the EPA STERPP (65 FR 19891, April 13, 2000). 

The commission has revised 81 15.112(d) (2) (6) to include the suggested options. 
TTO suggested the language in $1 15.112(d)(2)(H) be revised to read "the floating roof must be 

floating on the liquid surface at all times except when the floating roof is supported by the leg 

supports during the initial fill of a new floating roof storage tank or an existing floating roof 

storage tank that has been degassed and/or cleaned pursuant to Subchapter F of this chapter, or 

as allowed under the following circumstances." TTO additionally requested clarification in 

preamble language concerning under which, if any, circumstances uncontrolled landing 

emissions would not be required to be routed to a control device in order to comply with 

proposed 30 TAC 5 1 15.1 12(d)(2)(H). 

The commission has revised the language in 0115.112(d)(2) (H) to allow refi of a tank that 

has been degassed and cleaned according to the requirements of Chapter 115, Subchapter 

F, Division 3. The commission has also modified preamble language to clarify that 

uncoritrolled landing emissions would be allowed under an emissions cap as specified in 

0115.112(d)(2)(I-l)(v) or when total landing emissions at a site are less than 25 tpy as 

specified in the new 0115.112(d)(2)0(vi). 

Dow suggested that $1 15.112(d)(2)(H)(i) be clarified so that the phrase "when necessary for 

required maintenance or inspection" includes maintenance and inspection activities required by 

both environmental regulations and by company/individual site programs. COMAQ and TCC 

suggested removing the term "required" from $ 1 15.1 12(d)(2)(H)(i) since the term could be 

interpreted to mean the maintenance that is required by a particular rule. 

The commission has deleted the word "required" as requested. The intent of the rule 

language is to allow landings when needed for maintenance and inspection whether the 
activities are needed in order to comply with environmental regulations or to satisfy 

company or individual site programs. 

COMAQ, TCC, and TTO suggested adding the phrase "but not limited to" after "including" in 

5 1 15.11 2(d)(2)(H)(ii). 

The commission has not made the requested change. Legally, the term "including" is 

understood to mean "but not limited to." The commission has changed the wording to use 

the definition of incompatible liquid in 5115.110, so the wording no longer contains the 

word "including." 

TTO requested that 51 15.112(d)(2)(H)(ii) be revised to read "when necessary for supporting a 

change in service to a liquid that is not compatible with the previously stored liquid, including 

but not limited to gasoline with a different RVP to comply with applicable requirements; a 

termination of a contract for the storage of a liquid; a new customer or owner of a liquid 

coming into a storage tank; or off-spec products." 

The commission has revised the definition of "incompatible liquid" in 5115.110 and has 

changed the wording of 5115.112(d)(2)(H)(iii to use the definition. Landings to replace offspec products could be allowed under the revised definition if the product to be loaded into 

the tank would be contaminated with the previously stored off-spec product to the extent 

that the newly-loaded product would be unusable for its intended purpose. The 

commission declines to allow landings for commercial reasons such as termination of a 

contract or a new customer or owner of a liquid but notes that facilities have the option to 
authorize landing emissions under an emission limit or cap or a 25 tpy exemption as 

specified in 51 15.1 12(d) (2) (H)(v) and (vi) . 

HSC requested that the proposed $1 15.112(d)(2)(H)(iii) be revised to change the reference to 

25,000 gallons to 10,000 gallons and from 1.5 psia to 0.5 psia. 

The purpose of the proposed $115.112(d)(2)(H)(iii) was to exempt floating roof tanks that 

store materials that could be stored in fured-roof tanks without controls under 

h115.112(d)(l) from the prohibition on tank landings. When a floating roof is landed, the 

tank functions essentially as a fued roof tank, negating the emission reduction benefits of 

the floating roof. Because $115.112(d)(l) allows materials with a vapor pressure less than 

1.5 psia to be stored in f~ed roof tanks, restricting landings when the materials are stored 

in floating roof tanks would hold owners and operators who go beyond the requirements 

of the rule by storing such materials in floating roof tanks to an unnecessarily restrictive 

standard. As discussed in response to other comments, the commission has chosen not to 

require materials with a vapor pressure of less than 1.5 psia to be stored in a floating roof 

tank or a fmed roof tank with controls. 

TxOGA and TTO suggested the rule language in $1 15.112(d)(2)(H)(iv) be clarified to read 

"(H) The floating roof must be floating on the liquid surface at all times except when the 

floating roof is supported by the leg supports during the initial fill or as allowed under the 

following circumstances: (iv) when the vapors are routed to a control device from the time the 

roof is landed until it is within 10% of being refloated. " The cornmenters expressed concern 

that vapor abatement equipment may experience problems if liquids are accidentally injected. 
The commission has made the requested change. 

Dow expressed support for a floating roof storage tank emissions cap in $1 15.112(d)(2)(H)(v) 

and suggested that the cap does not have to be sitewide in order to be effective. Dow suggested 

a structure similar to the TCEQ flexible air permitting program, where the regulated entity 

defines the universe of the storage tanks at a given site that can be included in the emissions 

cap. Dow also suggested allowing a single plant site to have multiple caps to address floating 

roof tanks in different geographical areas of the site. 

The commission has removed the term "sitewide" from 0115.112(d)(2)(H)(v) as requested. 

COMAQ suggested clarifying $1 15.112(d)(2)(H)(v) to indicate that emissions from the landing 

of floating roof tanks can be authorized by an emission limit in a permit or permit by rule 

(PBR), or included in an emissions cap approved under 30 TAC Chapter 116. TCC suggested 

removing the term "sitewide" from the preamble language and from $1 15.112(d)(2)(H)(v) and 

revising the rule language to read "tank landings that comply with established Chapter 116 

emission limits or caps." Both Dow and TCC suggested the rule include PBR 106.263 (which 

can be used for tank landings due to scheduled maintenance, startups, or shutdowns) as an 

authorization option for the landing of the floating roof tanks for a single tank. 

The commission has removed the term "sitewide" from 0115.112(d) (2)(H)(v) and added 

language to clarify that landing emissions can be authorized by an emission limit or a cap 

under a Chapter 116 permit, as long as the limit expressly includes landing loss emissions. 

The commission does not agree to allow the use of a PBR to comply with the provisions of 

#115.112(d)(2)(H). Allowing use of PBR 0106.263 to authorize emissions from convenience 
landings could allow a site to add up to 25 tpy of VOC emissions in addition to landing loss 

emissions that have been authorized under an express permit limit or permit cap. The 

provisions of §115.112(d)(2)(H) would not prevent an owner or operator from authorizing 

a new tank or change of service to an existing tank under an applicable PBR, but floating 

roof tank landings from any such tanks would have to either meet the requirements of 

§115.112(d)(2)(H)(i) - (iv) or (vi) or be incorporated into an emission cap as referenced in 

5115.115(d)(2)(H)(v). 

TTO expressed support for the compliance option authorizing the approval of sitewide floating 

roof storage tank emission caps in permits issued under Chapter 116 but objected to the 

language that excludes an increase in caps from "otherwise prohibited roof landing emissions. 

TTO stated the language was vague, could be read to conflict with several existing cap 

agreements with the Executive Director, and the cap is more appropriately left to the 

commission's permitting staff. TTO suggested the language "and the cap value is not increased 

to account for emission from landings that would otherwise be prohibited" be deleted from 

5 115.112(d)(2)(H)(v). 

The purpose of rules in Chapter 115 requiring emission reductions or controls from 

specific types of sources is to reduce emissions of VOC that are contributing to ozone 

formation in ozone nonattainment areas. Requirements in Chapter 115 may thus be more 

stringent than would be required by the commission's permitting staff. The requirements 

for monitoring and control of HRVOC in Chapter 115, Subchapter H, are an example. 

For the current rulemaking, however, the commission has deleted the suggested language. 
HSC requested that $1 15.112(d)(2)(H)(v) be deleted. HSC objects to the use of an emission cap 

in lieu of a prohibition on convenience landings. 

For-hie terminals may have difticulty~complying with a strict prohibition on convenience 

landings, since the terminals do not own the liquid in the tanks. Complying with individual 

emission limits or caps will require tank owners and operators to miniie landing loss 

emissions while allowing them operational flexibility. 

TTO suggested adding a new $1 15.112(d)(2)(H)(vi) and (vii) to read "(vi) when aggregate 

sitewide uncontrolled VOC emissions from all floating roof tank landings are less than 25 tons 

per year on a rolling 12-month basis using the methodology for landing emissions in the United 

Stated Environmental Protection Agency AP-42 "Compilation of Air Pollutant Emission 

Factors" (revised November 2006); (vii) when landing emissions are authorized under an 

applicable permit by rule in Chapter 106 of this title." 

The commission agrees that an exemption from the prohibition on roof landings is 

appropriate for facilities with low landing loss emissions and has therefore added 

5 115.112(d)(2) (H) (vi) to provide an exemption for facilities with sitewide emissions less 

than 25 tpy. As noted in response to a previous comment, the commission does not agree 

to allow the use of a PBR to comply with the provisions of $115.112(d)(2)(H). 

GHASP suggested that the vapor recovery system control efficiency requirements in 

$ 115.112(d)(3) be changed from 90% to 95 % citing that the New Source Performance 

Standards specify a minimum control efficiency of 95%. 
The commission made no changes to the rule in response to this comment. The focus of the 

rulemaking project was to effect real reductions in VOC emissions. Although the rule only 

requires a control efficiency of 90%, many of the control devices in use in fact reduce 

emissions by 95% or more. 

HSC requested that $1 15.112(d)(4) be made more stringent by requiring control of flash 

emissions for tanks with emissions of greater than or equal to 10 tpy instead of the proposed 

level of 25 tpy . 

The cost effectiveness of controls decreases proportionally to a source's emissions rate. If 

no pipeline is available to transport recovered vapors, emissions and energy use from 

tanker trucks would counter some of the benefits from vapor recovery. Other states that 

explicitly require control of flash emissions include Wyoming and Colorado. Wyoming 

requires control if uncontrolled emissions are greater than or equal to 40 tpy. The statewide Colorado rule requires control if uncontrolled emissions are greater than or equal to 

20 tpy. The commenter gave no specific justification for the proposed level of 10 tpy. 

Furthermore, the EPA expressed support for the 25 tpy threshold. 

EPA endorsed the 25 tpy threshold for control because it defines the major source level for 

severe ozone nonattainment areas. 

The commission appreciates the support. 

The TCC commented that the vapor pressure of certain liquid streams at oil and gas exploration 

and production sites may be greater than 11 psia because of the presence of entrained gas. TCC 
further requested the commission clarify that tanks containing crude oil and condensate streams 

that have a true vapor pressure less than 11 psia and meet the control requirements of §115.112 

Table l(a), including storage in an external floating roof with a primary and secondary seal, are 

adequately controlled for the purposes of this rule. 

The commission does not agree that crude oil and condensate streams with a reported true 

vapor pressure less than 11 psia do not have flash emissions nor that storage in an external 

floating roof tank with primary and secondary seals provides adequate control if flash 

emissions are occurring. The commission acknowledges that the highest flash emissions 

would be expected to occur at upstream oil and gas exploration and production sites when 

the stream is fust exposed to atmospheric pressure. Tanks at midstream pipeline breakout 

stations would also be expected to have higher potential for flash emissions than tanks at 

downstream petroleum refineries or petrochemical plants. For these reasons, the 

commission has revised the rule to require control of flash emissions only at the upstream 

oil and gas exploration and production sites and at midstream pipeline breakout stations. 

The TCC suggested the preamble (specifically pages 17 and 18) be revised to remove 

references to crude oil and condensate storage at all locations other than exploration and 

production facilities. Additionally, the TCC requested the commission clarify that the term 

"condensaten applies to the liquids produced from natural gas rather than those tanks at a 

petroleum plant that may receive condensate from a natural gas production site. TxOGA 

requested that the term "tanksn in $1 15.112(d)(4) be revised to the phrase "exploration and 

production tanks. " 
The commission has changed 5115.112(d)(4) and (5) to specify that control of flash 

emissions is required only for crude oil or condensate storage at upstream oil and gas 

exploration and production sites prior to custody transfer or at pipeline breakout stations. 

The requirements would not apply to downstream operations such as crude oil and 

condensate storage at petroleum refineries or petrochemical plants. Remote sensing 

projects carried out under TexAQS II found plumes from crude oil storage tanks at 

refineries. Crude oil and condensate transferred downstream may stiU contain dissolved 

gases; thus, flash emissions could still be occurring at these downstream locations. 

However, the H51C study that was used to determine default emission factors for crude oil 

and condensate storage tested tanks at upstream sites only, and the test methods that were 

used to measure the emissions would not be applicable to large external floating roof 

storage tanks such as those typically used at refineries. Tanks at midstream pipeline 

breakout stations are also regulated under the rule as adopted. Crude oil and condensate 

that have been transferred through pressurized pipelines are likely to flash when 

transferred to atmospheric storage tanks. The commission will continue to evaluate the 

extent of flash emissions at the downstream operations and may take action to regulate 

these sources at a later time. 

The TCC suggested consistency between the actual rule language in $1 15.112(d)(4) and the 

preamble for the rule with regards to estimating flash emissions using the method that yields the 

higher emission rate. 

The commission has moved the requirements that were proposed as §115.112(d)(4) to 

5115.112(d)(5) and has revised the language to state that if emissions determined using 

direct measurements or other metbods approved by the executive director under 
§115.112(d)(5)(A) or (D) are higher than emissions estimated using the default factors or 

charts in §115.112(d)(5)(B) or (C), the higher values must be used. The intent of allowing 

the use of default emission factors is to enable regulated entities to avoid the cost of 

performing measurements or complex computer simulations. However, if the regulated 

entity chooses to use one of the more accurate, site-specific emission determination 

methods, this information should be used in determining whether emissions exceed the 25 

tpy threshold. 

The TCC requested clarification that simulation methods acceptable for use to estimate flash 

emissions include API E&P Tank Model and any other model as listed in the TCEQ EI 

guidance document (Technical Supplement 6, January, 2007). 

The EI guidance document lists a number of methods for estimating flash emissions and 

ranks them according to expected accuracy. These methods are used state-wide. Flash 

emissions have traditionally been under reported, and one goal of the current rulemaking 

is to obtain a better accounting of these emissions in the HGB area. Thus, some of the 

methods that may be acceptable for estimating flash emissions in ozone attainment areas 

in West Texas may not be accurate for sources in the HGB area. The use of any 

simulation method is problematic, because the model must be run correctly using proper 

input data in order to get accurate results. Because of these problems, the commission has 

revised $1 15.112(d)(5) to delete the proposed §115.112(d)(4) (D) that would have allowed 

the use of computer simulations. The new §115.112(d)(5)@) allows the use of other test 

methods or computer simulations pre-approved by the executive director to estimate flash 

emissions. Computer simulations can still be used, but must be pre-approved by the 

executive director to make sure the simulation is used properly. 
HSC requested that 81 15.116(a)(l) and (b)(l) be ma& more stringent by changing the 

referenced vapor pressure from 1.0 psia to 0.5 psia. 

The requested change would affect tanks in other nonattainment areas than HGB. Because 

notice for the proposed rule indicated that the proposed changes would only apply to tanks 

in the HGB area, affected owners and operators in other areas of the state have not 

received proper notice of any changes that would affect their operations. Thus, the 

requested change is beyond the scope of the current rulemaking. . 

Dow and COMAQ suggested the removal of the word "reportable" from 51 15.1 16(a)(2) since 

the term "reportable" has other meanings in other portions of Texas air pollution regulations. 

The removal of the word "reportable" will clarify that the additional emissions must be 

included in the emissions inventory report and then either recorded or reported per the 

applicable existing provisions in 30 TAC Chapter 101 (General Rules). TCC suggested revising 

§ 115.116(a)(2) to change the term "reportable" to "emission inventory reportable" to clarify 

that emissions from secondary seal gaps are not necessarily a reportable emission event as 

defined in Chapter 10 1, Subchapter F. 

The commission has changed the term "reportable" to "emissions inventory reportable" 

as suggested. 

CEMA suggested that language be added to the rule that acknowledges the option for facility 

operators to use internal combustion engine (ICE) based VOC oxidation systems to prevent an 

unfair market advantage for the control technologies listed in Chapter 115 despite equal or 

better performance by ICE-based equipment. CEMA suggested revising the rule language in 
5 1 15.1 16(a)(3) and (b)(3) and 5 115.546(2) to include a section that reads "the output voltage of 

the engine exhaust oxygen sensor and the inlet and outlet gas temperature of the catalytic 

converter on an internal combustion engine." 

The language in the rules does not specify nor exclude the use of any particular control 

technology as long as it achieves the required 90% reduction. The referenced rule sections 

do not list monitoring requirements for all possible types of control. Moreover, the 

suggested monitoring language for ICE equipment would not be sufficient to insure that 

the ICE system is functioning properly. For example, PBR 5106.533(g)(4) for remediation 

requires that owners or operators of ICE systems conduct an evaluation of engine 

effectiveness initially and at least weekly, using a photo ionization detector (PID) or flame 

ionization detector (FID) in conjunction with a flow meter to determine the quantity of 

carbon compounds in the inlet gas stream and the engine exhaust. The FID or PID 

instrument chosen must be capable of properly detecting the types of contaminants 

present. For these reasons, no changes have been made to the rule language in response to 

the comment, but the absence of specific mention in the rule does not exclude the use of 

ICEbased equipment. 

GHASP suggested that the owners and operators of facilities subject to the monitoring and 

recordkeeping requirements in 5 115.1 16 be required to report their performance parameters 

and efficiency calculations because the public needs the opportunity to monitor these facilities. 

Facilities with Title V operating permits under 30 TAC Chapter 122 are required to 

submit annual reports stating whether they are in compliance with all applicable 

requirements, which would include rules in Chapter 115. Owners or operators must also 
submit deviation reports for each six-month period if there have been deviations in permit 

terms or conditions during the period. The public can obtain copies of these reports 

(minus any confidential data) from TCEQ. TCEQ investigators can also request that 

monitored data or calculations be reported. 

EPA recommended that each requirement for a two-year record retention time, including those 

in $1 15.116(a)(S) and (b)(5), be changed to require a five-year record retention time, consistent 

with Title V and 30 TAC Chapter 122 requirements. 

The commission has not made the suggested change. Facilities with Title V permits are 

required to retain records for five years under Title V and 30 TAC Chapter 122, 

regardless of the specified retention time in a specific rule. The requirements ip 

§115.116(a)(5) and (b)(5) apply to sources outside the HGB nonattainment area. Thus, no 

changes can be made to these requirements at this time because public notice for the 

rulemaking indicated that the rule changes would apply only to sources in the HGB area. 

HSC requested that $115.116(c)(l) be made more stringent by changing 40,000 gallons and 

25,000 gallons to 10,000. 

The purpose of the recordkeeping requirement in §115.116(~)(1) is to require owners and 

operators to maintain records documenting that the materials stored in tanks that are not 

equipped with controls as specified in Table I(a) or Table II(a) of §115.112(a)(l) have 

vapor pressures low enough to be stored without controls. As noted in response to other 

comments, the commission has chosen not to change the size threshold at which tanks 

would be subject to controls to 10,000 gallons. 
Dow and TCC suggested deleting the recordkeeping requirements in $1 15.116(c)(l) since the 

regulated entity is already required to report this information through the Title V Operating 

Permits program. The TCC also suggested that if $1 15.116(c)(l) is not deleted, then the 

commission should clarify the phrase "length of time the material is stored" to indicate if the 

phrase refers to the date the tank is placed into service, the period of time it takes the tank to 

turnover, or the period of time that the liquid material lies in the tank while the roof is resting 

on its legs. 

The commission has maintained the referenced recordkeeping requirement to ensure that 

owners and operators have appropriate, current, readily available records to allow 

investigators to verify that materials stored in uncontrolled tanks have vapor pressures low 

enough to be stored without controls. Records in Title V operating permits may only refer 

to material safety data sheets that list a range of vapor pressures for an ill-defmed 

material (such as bunker oil). The actual vapor pressure of such materials can vary with 

different suppliers, different shipments, or different production runs. Results of remote 

sensing studies have shown unexpected VOC emissions from fmed-roof storage tanks that 

store materials with reportedly low vapor pressures. The commission has revised the 

language in $115.116(c)(l) to specify that the "length of time the material is stored" refers 

to the starting and ending dates that a material is or has been in the tank. 

HSC requested that $1 15.116(~)(2) be made more stringent by changing the referenced 

emission level from 25 tpy to 10 tpy. 

The purpose of the recordkeeping requirement in $115.116(~)(2) is to document that 

emissions from tanks not equipped with controls for flash emissions are below the level at 
which control is required. As discussed in response to other comments, the commission has 

chosen not to change the level from 25 tpy to 10 tpy. Since the level has not changed, it 

would be inappropriate to revise this recordkeeping requirement. 

The TCC suggested revising 5 1 15.1 16(c)(2) to read "the owner or operator of any Exploration 

and Production storage vessel ... shall maintain records ... The records must be updated 

annually and must be made available for review as soon as possible upon request." The TCC 

suggested the commission use the "maximum authorized emission rate" to satisfy the "projected 

emissions" requirement, rather than requiring the owner or operator of an Exploration and 

Production storage vessel to speculate within the context of the rule on the projected tank 

emissions for the next year of operations. 

The commission has revised §115.116(~)(2) to specify that the recordkeeping requirement 

applies only to crude oil and condensate stored prior to custody transfer or at midstream 

pipeline breakout stations. The commission agrees that the maximum authorized emission 

rate, if calculated to correctly account for flash emissions, can be used to document that 

emissions are less than the 25 tpy threshold for control and has deleted the requirement to 

project emissions for the next year. 

HSC requested that the rule be made more stringent by changing 1.5 psia to 0.5 psia in 

51 15.117(a)(l) and by changing 25,000 gallons to 10,000 gallons in 51 15.117(a)(3). 

As noted in response to earlier comments, the commission has decided to maintain the 

exemption levels at 1.5 psia and 25,000 gallons. 
HSC requested that the rule be made more stringent by changing 1.5 psia to 0.5 psia in 

$1 15.117(b)(l) and (c)(l), by eliminating the exemption in $115.117(b)(2), by changing 25,000 

gallons to 10,000 gallons in $1 15.1 17(b)(3) and (c)(3), and changing 420,000 gallons to 10,000 

gallons in @ 1 15.1 17(c)(4). 

The requested changes affect subsections that were not opened in the current rulemaking. 

These subsections affect sources outside the HGB eight-hour ozone nonattainment area. 

Owners and operators of these sources have not been given proper notice of proposed 

changes and would not have an opportunity to comment. Thus, making the suggested 

changes is beyond the scope of the current rulemaking. 

GHASP suggested eliminating the exemptions for tanks constructed prior to 1980 and 1982 and 

requiring the installation of appropriate rim mounted secondary seals for external floating roof 

tanks. In instances where upgrading the tanks is not technologically feasible, GHASP 

suggested that those tanks should be relegated to service with liquids with vapor pressures less 

than 0.5 psia, or service exempt from NSPS Subpart Kb. 

The commission did not propose substantive changes to the referenced exemptions in 

§115.117(4), (6), or (7). Making changes at this time is thus beyond the scope of the 

current rulemaking because it would impose controls on owners or operators who have not 

received proper notice of additional regulatory requirements and would not have an 

opportunity to comment. The commission may consider eliminating these exemptions in a 

future rulemaking. 
The EPA requested confirmation that credit for this rule has been appropriately prorated to 

reflect the extended time period allowed for compliance. 

The purpose of the rule was to reduce VOC emissions that have been previously 

unreported or underreported in the EI. For this reason, the commission has not taken 

credit for emissions reductions from this rule. 

The EPA requested confinnation that the new rule includes all components needed for 

enforcement purposes. In particular, the EPA noted that if compliance with the rule would 

necessitate emptying and degassing the tank, compliance would not be required until the next 

time the tank is emptied and degassed but not later than January 1, 2017. The EPA asked the 

commission to consider whether existing reporting requirements are sufficient to allow 

inspectors to verify the most recent date a tank was emptied and degassed and to add reporting 

requirements if necessary to provide for enforceability of the rule. 

Commission general air quality rules in 30 TAC $101.201(b) require owners or operators 

to maintain records of scheduled maintenance activities, which would include tank 

degassing and cleaning. No changes were made to the rule as a result of this comment. 

COMAQ suggested that TCEQ reconsider its position in §115.119(c) that the required control 

equipment could be put into place without tanks having to be taken out of service, citing that 

COMAQ members' experience has been that any significant work on tank roof fittings and seal 

systems requires tank de-inventory and degassing in order to prevent unacceptable LEL 

readings and personnel safety concerns. 
The commission maintains that certain types of roof fittings and controls for slotted 

guidepoles can be installed without taking the tank out of service. However, the rule 

language in 0115.119(c) states that compliance can be delayed beyond January 1, 2009, 

until the next time the tank is emptied and degassed if compliant equipment cannot be 

installed without taking the tank out of service. The decision whether equipment can be 

safely installed without taking the tank out of service will be made by the owner or 

operator. The rule does not give specific requirements for proving that the installation 

cannot be safely performed while the tank is in service, but the owner or operator should 

document and maintain for inspection purposes the rationale for delayed compliance. 

Dow supports the TCEQ's consideration that storage vessels will have to be degassed and 

emptied to comply with 4 1 15.1 12(d) requirements, and suggested editing 5 1 15.1 19(c) to clarify 

that compliance with 44 1 15.112(d), 115.115(c), and 115.116(c) is not required until the next 

scheduled emptying and degassing activity after January 1,2009. 

The commission appreciates the support, but does not agree that compliance is not 

required until the next scheduled emptying and degassing activity after January 1,2009. 

The reason for allowing the delay of compliance is to avoid requiring that a tank be taken 

out of service and degassed solely for the purpose of complying with the new 

requirements. In some cases, the emissions that would occur from the degassing activity 

(even when complying with the revised requirements for degassing in Chapter 115, 

Subchapter F) would be greater than emissions that would be reduced by installing 

compliant equipment. For tanks that will be emptied and degassed after the date the rule 

becomes effective but prior to January 1, 2009, the commission expects that equipment 

required to comply with the revised rules can be installed at that time, even though 
compliance is not required until January 1, 2009. Owners and operators who are planning 

tank emptying and degassing activities should plan ahead to install compliant equipment at 

the next opportunity. 

EPA noted that the preamble discussion for 5 115.119(c) states, "The commission anticipates 

that most, if not all, of the required control equipment can be put into place without taking the 

tank out of service," and requested that the commission consider modifying the rule to require 

that most, if not all, of the components in the rules be met by January 1, 2009. 

Industry commenters disagree with the commission's statement that most required control 

equipment can be put into place without taking a tank out of service. The rule language 

states that compliance must be achieved by January 1,2009, unless compliance would 

require emptying and degassing the storage tank. A further requirement that "most" of 

the components in the rules be met by January 1,2009, would be unenforceable. 

HSC objected to delayed compliance for tanks that must be emptied and degassed to install 

controls, since degassing is controlled, and stated that exceptions to not emptying a tank for 

installation of controls should only be allowed based on a petition from a regulated entity that 

demonstrates that emissions from emptying and degassing cannot be controlled and that the tank 

must be emptied to install the controls. GHASP commented that the storage tank regulations in 

Chapter 115 should mandate compliance by all affected facilities by January 1, 2009. GHASP 

stated that operating practices can be modified to eliminate convenience landings and that if a 

facility chooses to install controls that require emptying the tank, operating practices can be 

modified until the tank maintenance is undertaken. 
In some cases, the emissions that would occur from the degassing activity (even when 

complying with the revised requirements for degassing in Chapter 115, Subchapter F) 

would be greater than emissions that would be reduced by installing compliant equipment. 

Due to the high cost effectiveness of requiring degassing controls on small tanks, the 

commission has revised the new degassing control requirements to apply only to tanks with 

nominal capacity greater than or equal to 250,000 gallons or to tanks with nominal 

capacity greater than or equal to 75,000 gallons storing material with vapor pressure 

greater than 2.6 psia. If degassing is not controlled, emissions from taking the tank out of 

service to install controls could negate the environmental benefit of the controls. The 

provision for delayed compliance is not anticipated to affect the compliance date for tank 

landings, since facilities can comply with the requirements by changes in operational 

practices, as noted by the commenter. 

HSC requested that the control requirements for VOC loading operations in 5115.212 be 

revised to require a control efficiency of 95 % rather than 90%. 

The requested change is beyond the scope of the current rulemaking, since no changes 

were proposed to 5115.212. Staff considered this change to loading requirements as the 

rule proposal was being developed. According to available data in the EI, most of the 

control devices in use were already reducing emissions by 95% or more. Also, emissions 

from controlled loading operations represent a small fraction of the total VOC from point 

sources in the HGB area. Thus, making this change would result in only minimal 

emissions reductions. 
RSI suggested the commission examine the upcoming South Coast Air Quality Management 

District (SCAQMD) tank degassing regulations. 

The commission has reviewed the existing SCAQMD regulations on tank degassing and 

commission staff has discussed upcoming changes with SCAQMD staff. 

GEM suggested degassing companies be required to provide notification of degassing activities 

if onsite inspections of tank degassing is going to be implemented. 

The commission requires notification of scheduled maintenance activities such as tank 

degassing if expected emissions will exceed a reportable quantity as defined in 30 TAC 

$101.1. A specific notification requirement may be considered in a future rulemaking. 

The TCC suggested the commission confirm in $115.541 that if a covered tank is flooded with 

a diluent that has a true vapor pressure of less than 0.50 psia then the control requirements of 

this subchapter are no longer applicable. 

The commission does not agree that flooding a tank with a low vapor pressure diluent 

automatically negates the applicability of control requirements of Subchapter F. Pockets of 

material with a higher vapor pressure may be present in sludge on the tank bottom and be 

unaffected by the use of the diluent. Use of a diluent would also create a mixture that 

would presumably be a waste that could cause additional VOC emissions when disposed. 

COMAQ suggested the emission specifications and control requirements for the degassing of 

storage tanks with a nominal capacity between 40,000 and 1 million gallons should not be 
included in 51 15.54,1(a)(l) and $115.547(2). COMAQ states that the 40,000 gallon threshold 

was arbitrarily chosen by the commission and does not take into account the quantity of 

emissions from the degassing process or the economic feasibility of installing the controls. TCC 

commented that the minimum cost for complying with the degassing requirements would be 

$5,000 and suggested revising the degassing emission specifications applicability threshold in 

$ 1 15.54 1 from 40,000 gallons to 250,000 gallons. HSC requested that the rule be made more 

stringent by changing 40,000 gallons to 10,000 gallons in $115.541(a)(l) and $1 15.547(2). 

Emission reductions that can be realized by requiring controlled degassing decrease as the 

size of the tank (and, thus, the amount of vapor space saturated with VOC) decreases. 

Control of degassing emissions is generally carried out by outside contractors who bring 

equipment to the site. The charge for bringing in and operating the equipment is generally 

the same regardless of the size of the tank to be degassed. Thus, the cost effectiveness for 

controlling degassing emissions for tanks as small as 10,000 gallons is much higher than 

for larger tanks. The commission does not believe that the cost for controlling degassing 

emissions from these smaller tanks is justified. As noted by TCC, the cost effectiveness for 

controlling degassing emissions from a 40,000 gallon tank storing a material with a vapor 

pressure of 0.5 psia would be greater than $60,000 per ton of VOC removed. The 

commission has estimated that the cost effectiveness of controlling degassing emissions 

from tanks with tapacity of 250,000 gallons storing materials with a vapor pressure of 0.5 

psia or higher would be less than $12,000 per ton. The cost effectiveness for requiring 

degassing controls increases for smaller tanks and would exceed the $12,000 per ton value 

that is used in evaluating BACT. Thus, the commission has revised the applicability 

threshold to 250,000 gallons for tanks storing materials with vapor pressures down to 0.5 

psia. However, smaller tanks storing more volatile materials would have higher emissions 
and lower cost effectiveness. Regulations applicable in the SCAQMD take the higher 

emission potential into account by requiring degassing controls for tanks as small as 

19,815 gallons storing materials with a vapor pressure greater than 3.9 psia, and for tanks 

as small as 39,630 gallons storing materials with a vapor pressure greater than 2.6 psia. 

Commission staff estimated the cost effectiveness to control degassing emissions from 

tanks with a range of sizes and vapor pressures of stored liquid, and concluded that the 

cost effectiveness to control degassing emissions from tanks 75,000 gallons or larger 

storing materials with vapor pressure greater than 2.6 psia was appreximately $20,000 per 

ton or less. The commission has revised the rule to require degassing control for tanks 

with a capacity of 250,000 gallons or more, and for tanks with capacity of 75,000 gallons 

to 250,000 gallons storing material with vapor pressure greater than 2.6 psia. 

HSC additionally requested that the rule be made more stringent by changing 8,000 gallons to 

5,000 gallons in $1 15.541(a)(2) and by changing 420,000 gallons to 10,000 gallons in 

$115.541(b) and $115.547(2). 

The commenter gives no basis to support the requested changes. The rule proposal did not 

include a change in the size of transport or marine vessel that would be required to control 

degassing emissions. Thus, the requested change is beyond the scope of the current 

rulemaking. 

HSC requested that the rule be made more stringent by changing 90% to 95 % in 

$ 115.541(a)(l)(B) and (a)(2)(B) and in $ 115.541(b)(2). 
The commission made no changes to the rule in response to this comment. The focus of the 

rulemaking project was to effect real reductions in VOC emissions. Although the rule only 

requires a control efficiency of 90%, many of the control devices in use in fact reduce 

emissions by 95% or more. 

GEM suggested if the four vapor space turnover requirement remains part of the degassing rule 

then the commission should require that approved inlet vapor flow meters be installed at the 

inlet of the control device to help standardize the flow volume measurement. 

The commission has deleted the turnover requirement for affected sources in the HGB 

after January 1,2009. The four vapor space turnover provision remains in effect for 

sources in the BPA nonattainment area, but changes that would affect sources in this area 

are beyond the scope of the current rulemaking since public notice indicated that rule 

changes were only being made for sources in the HGB area. 

HSC requested that the rule be made more stringent by changing 34,000 ppmv to 10,000 ppmv 

in 0 1 15.542(a)(2) and (b)(5). 

The purpose of the proposed rule was to change the method for demonstrating when 

sufficient degassing had occurred, not changing the required level. The 34,000 ppmv level 

is based on requiring degassing control down to an equivalent partial pressure of 0.5 psia: 

0.5/14.7*1,000,000 = 34,000 ppmv. Because no change to this level was proposed, 

lowering it is beyond the scope of this rulemaking. 
HSC requested that the rule be made more stringent by changing 34,000 ppmv to 10,000 ppmv 

in $1 15.542(b)(4) and by eliminating the words "a turnover of at least four vapor space 

volumes has occurred, the partial vapor pressure is less than 0.5 psia (19,000 ppmw) ... or the 

concentration of VOC is less than 20% of the lower explosive limit." 

The requirements in §115.542(b)(4) apply to sources in the Beaumont-Port Arthur (BPA) 

and until January 1,2009, in the HGB area. No changes affecting sources in BPA were 

proposed; thus, making the requested change is beyond the scope of the current 

rulemaking. The regulated community must have time to implement new rule 

requirements; thus, the current wording is necessary to maintain the applicability of the 

erdsting requirements in HGB until the compliance date for the new requirements. 

COMAQ requests that the TCEQ clarify whether "ventilated, " "ventilation," and "vented" 

mean forced ventilation only, or both forced and passive ventilation as used in §115.542(a)(6). 

In this same section, the TCC suggested clarifying the intent of the phrase "before dilution." 

The commission has revised the rule language to use the term "vented to the atmosphere" 

for clarity. The commission has removed the word "before dilution" from the rule 

language as requested. The intent of the phrase "before dilution" was to emphasize that 

vapors are not to be released to the atmosphere untreated because an excessive volume of 

ventilation gas is used. Depending on the type of control technology used to abate the 

degassing emissions, dilution gas is sometimes necessary to maintain safe conditions in the 

abatement device. The concentration measurement should be made before the dilution gas 

is added. 
TxOGA expressed general support for $1 15.542 stating that the use of vapor concentration 

rather than turnover volume for determination of sufficient processing of vapors provides 

operational consistency during tank degassing. TxOGA suggested that the LEL is a better 

threshold for determining compliance than the ppmv or ppmw determination and suggested that 

$115.542(a)(5) and (6) be changed to add "50% LEL" as a criteria for determining when 

vapors can be released to atmosphere instead of the 34,000 ppmv concentration limit. 

The commission agrees that a VOC concentration equivalent to 50% LEL will be lower 

than the 34,000 ppmv concentration criteria and so has made the requested change in 

§115.542(6). The commission has not made the suggested change in §115.542(a)(5) because 

this provision applies to sources in the BPA nonattainment area as well as to the HGB area 

until January 1,2009. Because notice for the current rulemaking indicated that changes 

were being made only for the HGB area, changing the provision applicable to BPA is 

beyond the scope of the current rulemaking. 

Dow, TCC, and COMAQ suggested revising the periodic measurements required to confirm 

that the VOC concentration is less that 34,000 ppmv in $ 1 15.542(a)(6) and (b)(5). The 

commenters suggested that three consecutive readings, each taken at a 12-hour interval, with a 

VOC concentration less than 34,000 ppmv during ventilation is adequate to confirm that the 

VOC concentration is not varying significantly and that further checks every 12 hours are not 

warranted. 

The commission agrees that concentration measurements can be ceased at some point in 

the degassing and cleaning process but is concerned that if sludge remains in the tank after 

the initial degassing, VOC concentrations could decrease to less than 34,000 ppmv but 
later increase when the sludge is disturbed during the cleaning process. The commission 

has changed the rule to specify that concentration measurements can be discontinued after 

five consecutive readings less than 34,000 ppmv. With readings taken every 12 hours, the 

five readings would provide that the concentration would remain below 34,000 ppmv for 

at least 48 hours. VOC emissions associated with the removal of sludge from the tank may 

need to be recorded and reported under the maintenance rules in 30 TAC Chapter 101. 

The TCC suggested revising $1 15.541(a)(l) and $115.542(a)(5) to allow a delay in compliance 

until the next time the vessel is emptied but no later than January 1, 2017, if compliance would 

require the installation of degassing nozzles or connections. However, if appropriate degassing 

nozzles can be added by changing out a rnanway, the TCC suggested the commission should 

consider revising $1 15.542(a)(5) to allow a rnanway to be opened for the short period of time 

necessary to change-out the manway to one with the appropriate nozzles. 

The commission does not agree that a delay in compliance is necessary for tanks that must 

have degassing nozzles or connections installed. Hatches with nozzles installed can be 

obtained for newly-affected tanks. The commission has not revised $115.542(a)(5) to 

specificaUy allow the manway opening. Maintenance activities such as manway opening 

are subject to an affirmative defense as long as they comply with the general rules for 

maintenance in 30 TAC Chapter 101. 

The TCC suggested that $1 15.542(b)(5) be revised by adding the phrase "of the degassing 

operation. " 

The commission has made the suggested change. 

70 
TTO expressed support for the 34,000 ppmv trigger for controlling vapors during tank 

degassing but requested clarification that sampling to obtain VOC concentration measurements 

during degassing does not require tank entry and VOC concentration measurements can be 

taken from a tank's rnanway. TxOGA suggested that the preamble language regarding the 

frequency and method for measurement of VOC concentrations in $1 15.545(11) be modified to 

read "the measurement should be made at the head space of the vessel, as close as possible to 

the tank bottom to ensure that the concentration measurement is representative of actual 

conditions. However, these measurements are to be taken at locations that do not endanger the 

safety of sampling personnel. " 

The commission did not intend that VOC measurements be made inside the tank or other 

location that would endanger the safety of sampling personnd. 

COMAQ, Dow, GEM, TCC, TTO, and TxOGA suggested the agency allow acceptable 

alternate test methods for VOC concentration measurements specified in $1 15.545(11). The 

suggested methods include EPA Method 25A; EPA Method 18, adjusted to allow for one bag 

sample to be collected; bag sampling; portable hydrocarbon gas analyzer; PID; chemical 

specific detection tubes; and LEL meters. COMAQ commented that FIDs are not appropriate 

for testing VOC in nitrogen-rich, oxygen-poor atmospheres because the FID will "flame out. " 

Dow suggested that measurement of the total organic carbon (TOC) content of the condensate 

stream be allowed for vessels that are degassed and cleaned via steam. 

The commission agrees that additional methods for measuring the VOC concentration 

would be acceptable and has revised the rule accordingly. The commission does not agree 

that chemical specific detection tubes are appropriate because they are usually compound 

71 
specific and could result in false negatives. Also, the detection tubes might be diflicult to 

operate in the tank degassing environment. The commission does not agree that 

measurement of the TOC content of the condensate stream would be an appropriate 

indication of the VOC concentration of the vapor space. Even if an accurate correlation 

between the TOC concentration of the condensate and the VOC in the vapor space could 

be determined, use of this method would require the TCEQ staff to review and approve 

the correlation before it could be used. Tank degassing events are episodic and of short 

duration; approval of a correlation might not be possible in time for it to be used. 

Dow and TCC suggested that the TCEQ clarify that the instrument response factor criteria in 

$8.1 of EPA Method 21 be for the average composition of the liquid in the tank, transport 

vessel, or marine vessel and not for each individual VOC in the liquid. Dow noted that this 

approach is consistent with EPA's HON regulation in 40 CFR $63.180(b)(2)(i). 

The commission agrees that use of the average composition of the tank contents to 

determine the instrument response factor is appropriate and has revised the rule 

accordingly. 

RSI suggested that the protocol for sampling and analyzing must be clearly defined so that 

enforcement does not have to merely assume that measurements are being done correctly. 

The commission has listed approved testing methods in 3115.545(11) in order to ensure 

that measurements are being performed correctly. 
COMAQ suggested including an exemption from the emissions specifications and control 

requirements if the tank owner or operator can demonstrate compliance would be economically 

unreasonable by revising $115.547(2) to read "degassing and cleaning .. . any stationary VOC 

storage tank with a nominal storage capacity of less than one million gallons, or any marine 

vessel, with a nominal storage capacity of less than 10,000 barrels (420,000 gallons), is exempt 

from the requirements of this division. In addition, a tank is exempt from the requirements of 

this division if its owner or operator can demonstrate to the satisfaction of the executive director 

that compliance with the requirements of this division would be economically unreasonable." 

The commission does not agree that an exemption should be allowed for individual tanks 

based on whether control is "economically unreasonable." The rules in Chapter 115 must 

meet the standards that the EPA has set for reasonably available control technology 

(RACT). The EPA definition of RACT is "the lowest emission limitation that a particular 

source can meet by applying a control technique that is reasonably available considering 

technological and economic feasibility." The standard is economic feasibility, not economic 

reasonableness. With the revised applicability levels in the adopted rule based on tank size 

and vapor pressure of stored material, the commission maintains that control of degassing 

emissions from all affected tanks is economically reasonable as well as technically and 

economically feasible. 

RSI commented that calculating the destruction rate efficiency of abatement devices used to 

control emissions from the tank degassing process is not easily defined. Knowing the influent 

concentration in ppmv makes logical sense for determining when a tank degassing event is 

finished but in order to determine the allowable emissions it is necessary to also know the flow 

rate of the effluent in cubic feet per minute. 
The degassing rules do not require a calculation of allowable emissions from abatement 

devices. Thus, no changes have been made tothe rule in response to this comment. 

RSI expressed concern that their ICE technology, with destruction efficiency greater than 

99.9%, will be priced out of the market in Texas because these rules only require a destruction 

efficiency of 90 % . 

The commission has made no change to the rules as a result of this comment. Even though 

the rule only specifies 90% destruction efficiency, other concerns may drive regulated 

entities to use more efficient control equipment. When degassing operations are carried 

out as part of maintenance activities, emissions must be minimized under the requirements 

of the general air quality rules in 30 TAC Chapter 101. Emissions from planned 

maintenance activities must be authorized under 30 TAC Chapters 106 or 116 according to 

the schedule in 30 TAC 5101.222. Authorization will require use of BACT, which could 

require more stringent control than the minimum specified in 30 TAC 0115.541. 

TxOGA expressed support for a portable equipment registration or certification program for 

vendors or contractors who provide degassing equipment that would certify that the vendor 

degassing equipment meets TCEQ emission standards and ensure that contractor providing the 

portable equipment understands TCEQ rules and documentation requirements. 

Establishing a registration or certification program for degassing vendors or contractors is 

beyond the scope of the current rulemaking, but the commission may consider such a 

program in the future. 
HSC requested that the exemption for oceangoing, self-propelled marine vessels in 5 1 15.547(5) 

be removed so that these vessels must be degassed and cleaned when they have emptied their 

VOC cargo. 

The commission did not provide notice of any change to the referenced exemption for 

oceangoing, self-propelled marine vessels. Thus, proper notice to the owners and operators 

of such vessels has not been given and making the requested change is beyond the scope of 

the current rulemaking. The commission may consider a change to this exemption in 

future rulemaking.