Bay Area Air Quality Management District 

939 Ellis Street 

San Francisco, CA 94109 

Proposed 

Regulation 12, Rule 11: 

Flare Monitoring at Petroleum Refineries 

Staff Report

May 2003 

(Revised 5/27/03) 

Prepared by: 

Alex Ezersky 

Compliance and Enforcement Division 

Bill Guy 

Planning and Research Division 

i 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY........................................................................................................................... 1

BACKGROUND ........................................................................................................................................... 3

FLARES AND SIMILAR DEVICES.................................................................................................................... 4

FLARE DESIGN AND OPERATION .................................................................................................................. 4

EMISSIONS FROM FLARES............................................................................................................................. 6

BAY AREA FLARES AND EXISTING MONITORING EQUIPMENT...................................................................... 7

FLOW MONITORING TECHNOLOGIES ..........................................................................................................11

GAS COMPOSITION MONITORING ...............................................................................................................14

HISTORY OF MONITORING..........................................................................................................................15

CALIFORNIA AIR DISTRICT REGULATIONS..................................................................................................16

PROPOSED RULE.....................................................................................................................................17

EXEMPTIONS..............................................................................................................................................18

DEFINITIONS...............................................................................................................................................19

ADMINISTRATIVE REQUIREMENTS .............................................................................................................20

MONITORING AND RECORDS......................................................................................................................22

MANUAL OF PROCEDURES .........................................................................................................................31

EMISSIONS REDUCTIONS.....................................................................................................................33

ECONOMIC IMPACTS ............................................................................................................................33

COSTS ........................................................................................................................................................33

SOCIOECONOMIC IMPACTS.........................................................................................................................35

INCREMENTAL COSTS ................................................................................................................................35

ENVIRONMENTAL IMPACTS...............................................................................................................35

REGULATORY IMPACTS.......................................................................................................................36

FEDERAL REQUIREMENTS ..........................................................................................................................36

DISTRICT REQUIREMENTS ..........................................................................................................................37

RULE DEVELOPMENT HISTORY ........................................................................................................37

DISTRICT STAFF IMPACTS...................................................................................................................38

CONCLUSION............................................................................................................................................38

REFERENCES............................................................................................................................................40

COMMENTS AND RESPONSES.............................................................................................................41
ii 

FIGURES 

FIGURE 1. TYPICAL FLARE SYSTEM ..................................................................................................... 5

FIGURE 2. ORIFICE PLATE .....................................................................................................................11

FIGURE 3. TYPICAL HOT-WIRE ANEMOMETER................................................................................12

FIGURE 4. ANEMOMETER HOT WIRE..................................................................................................12

FIGURE 5. TIME OF FLIGHT ULTRASONIC FLOW METER...............................................................13

TABLES 

TABLE 1: EXISTING FLARE MONITORING ........................................................................................... 7

TABLE 2: COMPARISON OF FLOW MEASUREMENT DEVICES......................................................... 9

TABLE 3: CALIFORNIA FLARE MONITORING RULES ......................................................................16

TABLE 4: FLOW AS A FUNCTION OF HEADER SIZE AND VELOCITY............................................26

TABLE 5. CAPITAL COST ITEMS...........................................................................................................33

TABLE 6. ANNUAL OPERATING COSTS ..............................................................................................34

TABLE 7: COMPARISON OF REGULATORY REQUIREMENTS ........................................................36
1 

EXECUTIVE SUMMARY 

Proposed District Regulation 12, Rule 11: Flare Monitoring at Petroleum Refineries is intended 

to implement control measure SS-15 from the Bay Area 2001 Ozone Attainment Plan. This new 

rule would require refineries to monitor the volume and composition of gases burned in refinery 

flares, to calculate flare emissions based on this data, to determine the reasons for flaring, to 

report all of this information to the District, and to provide video monitoring of flares. The rule 

will lead to much more accurate estimates of flare emissions, will allow the District to refine its 

emission inventory for flaring, and will provide information that is likely to lead to reductions in 

flaring. 

Flares are primarily intended as safety and pollution control devices. They burn gases that cannot 

be used by the refinery and prevent their direct release to the atmosphere. The proposed rule 

would require the monitoring of these gases. The primary parameters to be monitored are vent 

gas flow to the flare and vent gas composition. 

For monitoring of the volume of gas directed to flares, the rule establishes range and accuracy 

requirements that, at present, can be met only by ultrasonic flow monitors. These monitors are 

called time-of-flight (TOF) ultrasonic monitors. They determine flow velocity by measuring the 

time required for ultrasonic waves to travel in the flare gas from an "upstream" probe to a 

"downstream" probe and by comparing the time to that required for the slower "upstream" trip. 

This technology is the best available technology for measuring gas flow for flares. Two of the 

Bay Area refineries already have older ultrasonic monitors, but the rule would require all of the 

refineries to install newer, more sophisticated, and more accurate monitors. 

For monitoring of flare gas composition, the rule allows two primary options: (1) collection of 

samples for subsequent lab analysis, or (2) use of continuous analyzers that sample gas and 

analyze it automatically. For the first option, samples can be collected with an auto-sampler or 

manually. Manual sampling is expected to be limited to infrequently used flares. For the second 

option, a number of continuous analyzer technologies are available: flame ionization detectors 

(FID), non-dispersive infrared (NDIR) spectrophotometry, and gas chromatography (GC). These 

methods are widely used by industry and by regulators, but have never been used on flare 

headers. The rule establishes appropriate methods and procedures for each technology. 

The rule allows the two options, sampling and continuous analyzers, because each has 

advantages and disadvantages that may dictate one over the other for the specific flare in 

question. Sampling is a proven approach that will, over time, build a large set of data for each 

flare for which it is used. Continuous analyzers, though desirable because of the continuous data 

they can provide, have not yet been used to monitor flare vent gas, which is not as "clean" as 

most gas streams for which these analyzers are used. Use of continuous analyzers will require 

sample conditioning equipment that may be difficult to design and may require considerable 

maintenance. The rule represents a compromise, allowing a method that is known to work 

(sampling) while encouraging a method that the District would like to see proven in practice 

(continuous analyzers). This ensures that the rule will work and avoids the risk of rule failure 
2 

that would come from mandating only continuous analyzers and the missed opportunity that 

might come from mandating only sampling. District staff expects that the result may be the use 

of continuous analyzers on some flares and sampling on others. 

The proposed rule requires monitoring data to be submitted to the District in a monthly report 

that is due within 30 days after the end of each month. The report must include flow data, 

composition data, emissions estimates, descriptions of all flaring activity, and information on any 

downtime for the monitors, and the archive of video images recorded for the month. The rule 

also requires a semi-annual report comparing flow monitor data for a period of time with a set of 

data for the same period derived by other methods. The comparison data can come from 

methods approved by the monitor manufacturer, from flow volume or velocity measurements 

using tracer gases, from flow measurements with pitot tubes, or from data derived from other 

methods approved by the District. 

The proposed rule also requires video monitoring of flares. The flare image is required to be 

recorded, and the recorded images for each month must be submitted with the monthly report. 

This will allow the District to examine flare imagery to help explain any flaring, to respond to 

any community concerns or complaints, and to ensure that monitor data corresponds with the 

images. 

The rule requirements would be imposed in steps that are based upon the District's determination 

about the length of time required to install the necessary equipment. All refineries would have to 

start taking daily composition samples within 3 months (some are already doing so). Within 6 

months, each refinery will have to have continuous flow monitors in place. In 9 months, each 

refinery will be required to monitor composition at more frequent intervals using sampling or 

continuous analyzers. 

The proposed rule would apply to the 25 flares located at the five Bay Area refineries: 

ChevronTexaco in Richmond (9 flares), ConocoPhillips in Rodeo (2 flares), Valero in Benicia (3 

flares), Tesoro in Avon (6 flares), and Shell in Martinez (5 flares). Two of the twenty-five are 

not in service. All of the flares in service are currently monitored for some parameter, typically 

flow or vent gas heating value. The proposed rule would require that all of the refineries upgrade 

their current monitoring equipment, but the new equipment necessary and the costs involved 

would vary greatly, depending upon the sophistication of the currently-installed equipment. The 

District has estimated a range of costs for a refinery based on costs for the various options 

allowed under the proposed rule. The cost of the monitoring equipment for a single flare is 

roughly $200,000. The District has estimated the annual cost per flare, with equipment costs 

amortized over ten years and including operating and maintenance costs, to be $50,000 per flare 

per year. 

In developing this rule, the District relied on information and data gathered during the District's 

flare further study effort. In August 2002, District staff held a workshop in Martinez to discuss 

basic rule concepts. It began developing a draft rule in late 2002, and in March shared 

preliminary drafts with representatives from the five Bay Area refineries, the Western States 

Petroleum Association (WSPA), and Communities for a Better Environment (CBE). In late 
3 

March and early April, District staff held three community meetings to discuss detailed rule 

concepts. The meetings were held in Richmond, Martinez, and Rodeo. Rule drafts were also 

shared with ARB and EPA. 

After the proposed rule was developed for the May 21st Board hearing, the District convened the 

flare workgroup that has been working on the District’s flare further study (further study measure 

FS-8 from the Bay Area 2001 Ozone Attainment Plan) to discuss the proposed rule. Additional 

issues were identified, and a revised rule is now proposed for adoption by the Board. To avoid 

confusion, this staff report refers to the rule prepared and made available with the public notice 

for the May 21st hearing as the “proposed rule.” This is in keeping with standard terminology 

used by ARB, air districts, and the Health and Safety Code (§§40725, 40726). The revised 

version of the rule now proposed for adoption is called the “revised rule.” Earlier drafts of the 

rule are called “earlier drafts.” 

At the May 21st Board hearing, a number of additional changes in the revised rule were 

suggested in comments by WSPA, individual refineries, the Air Resources Board, CBE, and 

refinery labor unions. In response to those comments, additional changes have been made to the 

revised rule. These changes are reflected in double underline / double strikethrough format in the 

revised rule. The revisions are in Sections 12-11-401, 502, 506, and 507. Brief discussions of 

the changed rule sections have been added to this staff report and are underlined. These changes 

are not so substantial as to change the meaning of the rule and can be adopted at the June 4, 2003 

hearing. The most significant issue raised at the hearing was the issue of "webcasting." Staff is 

proposing that the webcasting issue be referred to the Stationary Source Committee of the Board 

because of its difficulty, because it was not included in the rule for which the CEQA document 

was prepared, and because resolution of webcasting issues could delay the rest of the rule 

substantially if not treated separately.

Pursuant to the California Environmental Quality Act (CEQA), the District prepared an initial 

study to determine the potential environmental impacts of proposed Regulation 12, Rule 11. The 

study identified the construction work required to install monitors as a source of potential 

environmental impacts. However, because of the safety requirements that govern this type of 

work, the regularity with which similar hot work is conducted in refineries, and the consequent 

familiarity with and preparedness for this type of work on the part of refinery workers and 

contractors, the study concluded that the proposed rule would not result in any significant 

environmental impacts. The document was circulated for comment, and no comments were 

received. 

BACKGROUND 

Flares provide a safety and emission control mechanism for refinery blowdown systems. 

Blowdown systems collect and separate both liquid and gaseous discharges from various refinery 

process units and equipment. The systems generally recover liquids and send gases to the fuel 

gas system for use in refinery combustion. However, when the heating value of the gas stream is 

insufficient, when the stream is intermittent, or when the stream exceeds what is necessary to 

satisfy refinery combustion needs, flares combust these gases and prevent their direct release to 
4 

the atmosphere. Flares are designed to handle large fluctuations in the flow rate and hydrocarbon 

content of gases. 

Flares and Similar Devices 

A number of different devices may be called flares. A flare, as defined in the proposed rule, is a 

combustion device that uses an open flame to burn combustible gases with combustion air 

provided by uncontrolled ambient air surrounding the flame. The term is most commonly 

applied to the open air flare. It is also commonly applied to ground flares, which are located at 

ground level and typically have an enclosure around the open flame. The term "enclosed flare" 

may also be applied to this type of flare, regardless whether it is located at ground level. Flares, 

whether "open air," "ground," or "enclosed," rely on surrounding air for combustion and do not 

have any mechanism for control of this combustion air. 

The term "thermal oxidizer" is sometimes used as a broad term to apply to many types of devices 

that oxidize combustible gases, including flares. However, the term is more properly applied to 

enclosed devices that, unlike flares, control the mixing of combustion air and fuel. As defined in 

the proposed rule, a thermal oxidizer is an enclosed or partially enclosed combustion device that 

is used to oxidize combustible gases, that generally comes with controls for combustion 

temperature and often with controls for air/fuel mixture, and that exhausts all combustion 

products through a vent, duct, or stack so that emissions can be measured directly. 

In general, flares are used to control units and operations from which gas flows may be 

intermittent and may range from very low flows to very high flows. They are accepted as the 

most reliable way to ensure that the potentially enormous flows that may result from an upset or 

shutdown of a large refinery unit, a large block of units, or an entire refinery can be controlled. 

Thermal oxidizers are generally used to control emissions from sources or operations for which 

flows are lower and more stable. These sources include wastewater systems, loading racks, 

storage vessels, pumps or compressors, and some relief systems on small process units. Because 

of the greater control over combustion afforded by temperature and mixture controls, thermal 

oxidizers typically have very high combustion efficiency. Thermal oxidizers are typically subject 

to permit conditions requiring combustion efficiency of 98% or higher. Because combustion 

products past through a vent, a duct, or a stack, the combustion efficiency of thermal oxidizers 

can be verified by source tests. 

Flare Design and Operation 

The open air flare is the predominant design type in the Bay Area. These flares are designed to 

handle large fluctuations in the flow rate and hydrocarbon content of gases. They are used to 

prevent releases of uncombusted materials generated during maintenance activities, emergency 

events such as power and equipment failures, and to a lesser extent as a control device for 

materials that cannot be recovered. 
5 

Figure 1. Typical Flare System 

The diagram above illustrates a typical general service flare system. The system is a component 

of the refinery blowdown system. The blowdown system is designed to collect gases and liquids 

released throughout the refinery and direct them to the refinery recovery system or, when there is 

insufficient capacity to recover them, to a flare. These gases and liquids may be released for 

many different reasons. They may be normal byproducts of a process unit or vessel, they may 

result from an upset in a process unit, or they may come from refinery process units during 

startup and shutdown when the balance between gas generation and the combustion of that gas 

for process heat is disrupted. 

The blowdown system delivers gases and liquids to a knockout drum that captures liquids and 

directs them to the oil recovery stream. The refinery flare gas compressors then direct gases to 

the fuel gas system. The extent to which these gases can be captured depends upon the capacity 

of the compressors. A refinery in good balance should be able to capture most of the gases 

delivered to the blowdown system during normal operations and use them to heat process units. 

This is not the case if a refinery has insufficient compressor capacity or when there is an upset or 

accident, and the volume of gases is too great for the compressors to handle. 
6 

Emissions from Flares 

Flares produce air pollutants through two primary mechanisms. The first mechanism is 

incomplete combustion. Like all combustion devices, flares do not combust all of the fuel 

directed to them. Combustion efficiency is the extent to which the oxidation reactions that occur 

in combustion are complete reactions converting the gases entering the flare into fully oxidized 

combustion products. Combustion efficiency may be stated in terms of the extent to which all 

gases entering the flare are combusted, typically called "overall combustion efficiency" or simply 

"combustion efficiency", or it may be stated as the efficiency of combustion for some constituent 

of the flare gas as, for example, "hydrocarbon destruction efficiency." 

The second mechanism of pollutant generation is through the oxidation of flare gases to form 

other pollutants. As an example, the gases that are burned in flares typically contain sulfur in 

varying amounts. Combustion oxidizes these sulfur compounds to form sulfur dioxide, a 

pollutant. In addition, combustion also produces relatively minor amounts of nitrogen oxides 

through oxidation of the nitrogen in flare gas or atmospheric nitrogen in combustion air. 

Unlike internal combustion devices like engines and turbines, flares combust fuel in the open air, 

and combustion products are not contained and emitted through a stack, a duct, or an exhaust 

pipe. As a result, emission measurement is difficult. 

Studies can be conducted on small flares under a hood or in a wind tunnel where all combustion 

products can be captured. Any results for these small flares must be adjusted with scaling factors 

if they are to be applied to full-size flares. For full-size operating industrial flares, which may 

have a diameter of four feet or more and a stack height of 200 feet or more, all combustion 

products cannot be captured and measured. To study emissions from these flares, emissions can 

be sampled with downwind test probes attached to the stack, a tower, or a crane. Emissions can 

also be studied using remote sensing technologies like open-path Fourier transform infrared 

technology (FTIR) or differential absorption lidar (DIAL). In applying the results of any 

particular study to a specific flare or flare type, it is important to note any differences in flare 

design and construction. For example, some flares are simply open pipes, while others, like most 

refinery flares, have flare tips that are engineered to promote mixing. In addition, studies suggest 

that composition and BTU content of gas burned, gas flow rates, flare operating conditions, and 

environmental factors like wind speed may affect, to varying extents, the efficiency of flare 

combustion. 

The question of flare combustion efficiency is one of the issues being explored by the Technical 

Committee of the BAAQMD Advisory Council. On April 1, 2003, District staff and 

representatives from Bay Area refineries made presentations to the Committee on various flare 

issues, including combustion efficiency. The Committee has indicated that it intends to examine 

the efficiency issue and may invite experts to appear before it. 
7 

Bay Area Flares and Existing Monitoring Equipment 

There are 25 flares at the five Bay Area refineries. Two of these flares are not in operation. All 

of these flares in service have some existing monitoring equipment to monitor one or more of the 

following parameters: (1) hydrogen sulfide content of the fuel gas used for the pilot, (2) status of 

the pilot light, (3) flame appearance to insure a smokeless operation, (4) heating value of the 

gases, (5) compliance with limits on the amount of material processed at the flare, (6) quantity of 

fuel gas, and (7) total reduced sulfur content. Table 2 on the following page lists flares that 

would be subject to the proposed rule. For each flare, the table lists the existing monitoring 

equipment and the reason or reasons that the equipment is installed. 

Table 1: Existing Flare Monitoring 

Site & 

Source # Service Parameter Monitored Monitor Type Basis1 

Chevron

6006 LSFO Low Level Flare N/A Disconnected 

6010 LSFO High Level Flare 

Pilot & purge gas, btu 

& HHV 

Flow transmitter & 

chart 

PC 

6012 South Isomax Pilot gas, btu & HHV Rotameter PC 

6013 North Isomax Purge gas, btu & HHV Field meter PC 

6015 D&R Flare 

Pilot & purge gas, btu 

& HHV 

Flow transmitter & 

chart 

PC, NSPS 

6016 FCC Flare 

Pilot & purge gas, btu 

& HHV 

Flow transmitter & 

chart 

PC 

6017 SRU Flare 

Pilot & purge gas, btu 

& HHV 

Flow transmitter & 

chart 

PC 

6019 Alky Flare 

Pilot & purge gas, btu 

& HHV 

Flow transmitter & 

chart 

PC 

6039 Lube Flare (RLOP) Pilot & purge, btu & 

HHV Rotameter PC 

Shell

1471 LOP Auxiliary Flare Flow, molecular wt. Ultrasonic PC 

1472 LOP Main Flare Flow, molecular wt. N/A Blinded Off 

1771 FXG Flare H2S, flow Venturi PC, NSPS 

1772 HC Flare H2S, flow Orifice PC, NSPS 

4201 Delayed Coking Flare 

Molecular wt., sulfur, 

btu/scf, fuel flow 

PC, NSPS 

ConocoPhillips

297 C-1 Flare Flow Ultrasonic, anemometer PC, NSPS 

398 C-602 Flare Flow Ultrasonic PC, NSPS 

Tesoro

854 East Air Flare Flow, sulfur Ultrasonic PC, NSPS 

944 North Coker Flare Flow, sulfur Ultrasonic PC, NSPS 

945 South Coker Flare Flow, sulfur Ultrasonic PC, NSPS 

992 Emergency Flare Flow, sulfur Ultrasonic PC, NSPS 

1012 West Air Flare Flow, sulfur Ultrasonic PC, NSPS 

1013 Ammonia Flare Flow 
8 

Site & 

Source # Service Parameter Monitored Monitor Type Basis1 

Valero

16 Acid Gas Flare Purge flow Orifice plate PC 

18 South Flare Oil, flow, hydrocarbon 

Venturi meter, 

anemometer 

EB 

19 North Flare 

Oil, flow, hydrocarbon, 

H2S 

Venturi meter, 

anemometer 

EB, NSPS 

1

PC - Permit Condition 

EB - Energy Balance 

NSPS - Federal New Source Performance Standards for flares used as a control device 

As shown in the table, a variety of technologies are used to quantify the volume of gases 

combusted. Each technology has advantages and limitations. Some of these have been identified 

by EPA in their Compliance Assurance Monitoring (CAM) Technical Guidance Document and 

are summarized in Table 3 on the following pages. 
9 

Table 2: Comparison of Flow Measurement Devices 

Type of Flow 

Meter 

Type of 

Measurement 

Liquid, Gas, or 

Both 

Applicable Pipe 

Diameter 

Applicable Flow Rate Straight Pipe 

Requirementsa

Net Pressure Loss Accuracy Restrictions 

Venturi Tube Volumetric Both 5 to 120 cm 

(2 to 48 in.) 

Limited to ~ 4:1 flow range 6 to 20 D up 

2 to 40 D down 

10 to 20% of ∆P 

depending on β

± 0.75% flow rate w/o 

calibration 

Eliminate swirl and 

pulsations 

Flow nozzle Volumetric Both 7.6 to 60 cm 

(3 to 24 in.) 

Limited to ~ 4:1 flow range 6 to 20 D up 

2 to 4 D down 

30 to 8.5% of ∆P 

depending on β

± 1.0% flow rate w/o 

calibration 

Eliminate swirl and 

pulsations 

Orifice plate Volumetric Both 1.3 to 180 cm 

(1/2 to 72 in.) 

Limited to ~ 4:1 flow range 6 to 20 D up 

2 to 4 D down 

Slightly more than flow 

nozzle 

± 0.6% flow rate w/o 

calibration 

Eliminate swirl and 

pulsations 

Magnetic Velocity Liquid 

(not petroleum) 

0.25 to 250 cm 

(0.1 to 96 in.) 

0.0008 to 9,500 L/min 

(0.002 to 2,500 gal/min) 

None None ± 1% flow rate Conductive liquid, 

not for gas 

Nutating disk Volumetric Liquid 1.3 to 5 cm 

(1/2 to 2 in.) 

7.5 to 600 L/min 

(2 to 160 gal/min) 

None ± 0.5% flow rate Household water 

meter, low maximum 

flow rate 

Oscillating piston Volumetric Liquid 1.3 to 5 cm 

(1/2 to 2 in.) 

2.8 to 600 L/min 

(0.75 to 160 gal/min) 

Maximum of 4.3 to 480 

m

3

/hr (150 to 17,000 ft 3/hr) 

None ± 0.5% flow rate Household water 

meter, low maximum 

flow rate 

Bellows gas Volumetric Gas Maximum of 4.3 top 480 

m

3

/hr (150 to 17,000 ft3/hr) 

None Used for commercial 

and domestic gas 

service 

Lobed impeller Volumetric Both 3.8 to 60 cm 

(1-1/2 to 24 in.) 

30 to 68,000 L/min 

(8 to 18,000 gal/min) 

None Low ± 0.2% flow rate Best used at high flow 

rates 

Slide-vane rotary Volumetric Liquid Up to 40 cm 

(Up to 16 in.) 

None ± 0.1% to 0.2% flow 

rate 

Retracting-vane 

rotary 

Volumetric Liquid Up to 10 cm 

(Up to 4 in.) 

None ± 0.1% to 0.2% flow 

rate 

Helical Gear Volumetric Liquid 3.8 to 25 cm 

(1-1/2 to 10 in.) 

19 to 15000 L/min 

(5 to 4,000 gal/min) 

None Low ± 0.1% to 0.2% flow 

rate 

High viscous liquids 

only 

Turbine Volumetric Both 0.64 to 60 cm 

(1/4 to 24 in.) 

190,000 L/min 

(50,000 gal/min) 

65 scmm (230,000 scfm) 

10 D up 

5 D down 

34 to 41 kPa @ 6.1 m/sec. 

(5 to 6 psi @ 20 ft/sec) 

water flow 

± 0.5% flow rate Straightening vanes. 

Do not exceed 

maximum flow 

Vortex Shedding Velocity Both 2.5 to 30 cm 

(1 to 12 in.) 

0.30 to 6.1 m/sec 

(1 to 30 ft/sec) 

11 to 19,000 L/min 

(3 to 5,000 gal/min) 

10 to 20D up 

5 D down 

34 to 41 kPa @ 6.1 m/sec 

(5 to 6 psi @ 20 ft/sec) 

water flow 

± 1% flow rate 

(liquid) 

± 2% flow rate (gas) 

Straightening vanes 

Vortex Precession Velocity Gas 2.5 to 20 cm 

(1 to 8 in.) 

0.30 to 6.1 m/sec 

(1 to 20 ft/sec) 

10 to 20 D up 

5 D down 

5% more than shedder ± 2% flow rate Straightening vanes 

Fluidic oscillating Velocity Liquid 2.5 to 10 cm 

(1 to 4 in.) 

Up to 6.1 m/sec 

(20 ft/sec) 

6 D up 

2 D down 

34 to 41 kPa @ 6.1 m/sec. 

5 to 6 psi @ 20 ft/s water 

flow 

± 1.25 to 2% flow 

rate 

Carefully determine 

minimum flow rate 

TOF ultrasonic Velocity Both > 0.32 cm 

> 1/8 in.) 

Minimum 0.03 m/sec 

(0.1 ft/sec) 

10 to 30 D up 

5 to 10 D down 

None ± 0.5% to 10% full 

scale 

Need clean fluid 
10 

Type of Flow 

Meter 

Type of 

Measurement 

Liquid, Gas, or 

Both 

Applicable Pipe 

Diameter 

Applicable Flow Rate Straight Pipe 

Requirementsa

Net Pressure Loss Accuracy Restrictions 

Doppler Ultrasonic Velocity Liquid > 0.32 cm 

(> 1/8 in.) 

Minimum 0.15 m/s 

(0.5 ft/sec); 0.38 L/min 

(0.1 gal/min) 

Yes None As low as 1% flow 

rate 

Fluid must have 

sufficient particles or 

bubbles 

Thermoanemometer Velocity 

(mass) 

Gas > 5 cm 

(> 2 in.) 

8 to 10 D up 

3 D down 

Very low ± 2% flow rate Critically positioned 

probes 

Highly fluid 

composition 

dependent 

Colorimetric Velocity 

(mass) 

Gas > 5 cm 

(> 2 in.) 

8 to 10 D up 

3 D down 

Low ± 4% flow rate 

Coriolis mass Mass flow Both limited gas 0.16 to 15 cm 

(1/16 to 6 in.) 

Definitive max. + min. flow 

rate 

None High ± 0.2% to 0.4% flow 

rate 

Pressure drop across 

flow meter cannot 

exceed max. system 

pressure drop 

Rotameter Velocity Both 1.3 to 10 cm 

(1/2 to 4 in.) 

Up to 750 L/min 

(200 gal/min for liquid); 

unlimited for gas 

None Low ± 1 to 2% full scale Must be mounted 

vertically 
11 

Flow Monitoring Technologies 

The following discussions of flow monitoring technologies are taken from EPA's CAM 

Guidance. Discussion is limited to those technologies most common in the Bay Area refineries. 

Orifice Plates and Venturis 

Orifice plates can be used to measure fluid flow in pipes with diameters of approximately 1.3 to 

180 cm (0.5 to 72 in.). Orifice plates operate on Bernoulli's principle, which says that pressure 

decreases with increased flow velocity. An orifice plate consists of a square-edged or sharpedged, thin opening in a metallic plate perpendicular to the flow. The opening is of a 

predetermined size and shape and is machined to tight tolerances. The flow velocity must 

increase through the orifice. The result is a higher pressure upstream of the plate and a lower 

pressure downstream. The pressure differential increases with flow velocity. The pressure 

readings for an orifice plate are obtained from a pair of pressure taps, one on either side of the 

plate: 

Figure 2. Orifice Plate 

Venturi meters operate on the same principle. The pressure differential for a venturi is obtained 

from two taps: one at the full pipe diameter and one at the throat of the venturi. 

Hot Wire Anemometer 

The hot wire anemometer (figure 3) works by measuring the current drawn through the hot wire 

as a result of the cooling effect of the air flow extracting heat from the wire. The instrument 

maintains the wire at a fixed temperature so that as it is cooled by the air flow the current 

increases to maintain the temperature of the wire. The core of the anemometer is an exposed hot 

wire either heated up by a constant current or maintained at a constant temperature (figure 4). In 

either case, the heat lost to fluid convection is a function of the fluid velocity. 
12 

Figure 3. Typical Hot-Wire Anemometer 

By measuring the change in wire temperature under constant current or the current required to 

maintain a constant wire temperature, the heat lost can be obtained. The heat lost can then be 

converted into a fluid velocity in accordance with convective theory. 

Figure 4. Anemometer Hot Wire 
13 

Ultrasonic Flow Meters 

Two types of ultrasonic flow meters are available: time-of-flight (TOF) and Doppler. Doppler 

meters are suitable only for liquids and are not discussed here. In TOF ultrasonic flow meters, 

sound waves are introduced into the flowing fluid, one wave traveling with the flow and one 

wave traveling against the flow. The difference in transit time of the waves is proportional to the 

fluid flow rate, because the sound wave is accelerated when traveling with the flow and slowed 

when traveling against the flow. If the sound wave velocity of the fluid (speed of sound) is 

known, the transit distance is known, and time difference is known, then the fluid flow rate can 

be determined. Time-of-flight ultrasonic flow meters can be classified as one of the following: 

axial transmission, multi-beam (transverse or longitudinal) contra-propagating, cross beam, sing 

around, and reflected beam. Figure 5 depicts a TOF ultrasonic flow meter. 

Figure 5. Time of flight ultrasonic flow meter 

Ultrasonic flow meters are comprised of the following basic parts: the transducer, receiver, timer, 

and temperature sensor. Ultrasonic flow meters can be used to measure fluid flow in pipes with a 

diameter greater than 0.32 cm (0.125 in.) with a minimum flow rate of approximately 0.38 L/min 

(0.1 gal/min). Time-of-flight ultrasonic flow meters are applicable to liquids and gases flowing at 

velocities greater than 0.03 m/sec (0.1 ft/sec). 
14 

Gas Composition Monitoring 

The type of composition monitoring currently in use at a refinery depends upon the applicable 

regulatory requirements, as shown in Table 2. Regulatory requirements are specified in the 

District imposed permit conditions or in Federal requirements. The most common requirement is 

that a flare be monitored for emissions of sulfur oxides to meet New Source Performance 

Standards for flares used as a control device. For some flares, the District has imposed 

conditions on flares for purposes of controlling odors or to meet offset requirements. Typically 

these conditions place limits on the quantity and composition of fuel gas that can be burned, 

impose design criteria for tip velocity, and specify analytical protocols. Some composition 

monitoring may be done to meet other needs of the facility. For example, some facilities analyze 

for composition to “energy balance” the consumption of fuel gas within individual process units. 

All of the composition monitoring being done at the Bay Area refineries at present is through 

sampling and subsequent lab analysis. 

Composition can also be monitored by continuous analyzers. Several technologies are available: 

the flame ionization detector (FID), the non-dispersive infrared (NDIR) spectrophotometer, and 

gas chromatography (GC). 

A flame ionization detector (FID) burns sampled gas in a hydrogen flame. Organic compounds 

produce positive ions, which are collected at an electrode above the flame. The generated current 

is then measured. The FID is useful for measuring concentrations of organic compounds and is 

very sensitive and accurate over many orders of magnitude. Because the FID responds to any 

molecule with a carbon-hydrogen bond, but not at all, or poorly to other compounds, it is not 

useful for measuring concentrations of hydrogen sulfide or sulfur dioxide. 

A non-dispersive infrared (NDIR) spectrophotometer measures the amount of infrared radiation 

that is absorbed by a sample. Infrared radiation from a hot wire is directed through two parallel 

cells: a reference cell filled with nitrogen, and a cell through which the sample flows. The gas in 

the sample cell absorbs an amount of energy proportional to its concentration. This is converted 

into an electrical output by the detector. The NDIR is commonly used to measure carbon 

monoxide, carbon dioxide, methane, and total hydrocarbon concentrations. 

A gas chromatograph, or GC, consists of a column, oven, and detector. The column separates the 

gas sample into its various components. GC columns are available in different sizes, and 

packing for the columns depends upon the composition of the gas stream to be analyzed. The 

oven provides a controlled temperature enclosure for the column. The detector has to be chosen 

based on the type of gases being analyzed. A thermal conductivity detector or a FID can be used 

as the detector on a gas chromatograph. 

In the gas chromatograph, a sample goes to the column, separates into individual compounds and 

proceeds through the hydrogen flame ionization detector, generating a response called a 

chromatogram. The various chemical components contained within the sample travel through 

the column at different speeds, depending on their respective solubility in or adsorption on the 

packing material (liquid or solid). The height of the peak on the chromatogram is related to the 
15 

concentration and the time it takes to go through the column, which helps identify the 

component. 

History of Monitoring 

In 1984, Citizens for a Better Environment (CBE) petitioned the California Air Resources Board 

(CARB) to evaluate the feasibility of continuous emission monitors for refinery flares. CARB 

determined that no refinery in California accurately monitored flow rates to its flares. Several 

types of flow meters had been installed on refinery flares, but the instrumentation could only 

provide relative flow information because gas density varies and gas composition data is 

necessary to calculate flow accurately. CARB concluded that continuous monitoring of flow 

rates and composition and remote monitoring of flare plumes would require substantial 

development before it would be available. CARB determined that monitoring devices were 

available for limited applications to identify and record continuously the on/off status of flares. 

CARB also encouraged local air pollution control districts to adopt rules requiring refineries to 

install on/off status monitors and collect flare gas composition data so that a suggested control 

measure for the control of emissions from refinery flares could be developed. 

In response to the CARB findings, the District conducted a flare monitoring study in 1988 and 

1989 using the tools that were then available (BAAQMD 1990). Instantaneous flow information 

was obtained using pitot tubes. Composition was analyzed by taking grab samples at the same 

time that the flow measurement was made. All of the data simply gave the District a series of 

"snapshot" data. Conclusions had to be extrapolated from this limited data by assuming that it 

was representative of refinery operations, but there was no way to determine whether this was a 

valid assumption. Nevertheless, it remained the only flare flow and composition data set 

available for Bay Area refineries. The data collected was used as a basis for adjustments to the 

emission inventory used for the Bay Area 2001 Ozone Attainment Plan. 

By the 1990's, ultrasonic flow meters were coming to be regarded as a reliable way to measure 

flare flows. Recognizing that the ultrasonic meters provided a reliable means of monitoring flare 

gas, the South Coast Air Quality Management District adopted its Rule 1118 requiring refinery 

flare monitoring. The rule was adopted in 1998, but there were numerous delays, and monitors 

were finally installed and operational by late 2000. 
16 

California Air District Regulations 

The following table summarizes existing flare regulations within California. 

Table 3: California Flare Monitoring Rules 

Regulation Control/Performance 

Requirements 

Monitoring 

Requirements 

Minimization 

Plan 

Emission Limitations 

SCAQMD 

Rule 1118 

None Gas flow, heating 

value and sulfur 

content 

No No 

SJVAPCD 

Rule 4311 

Open Air Flares 

<5psig must meet 40 

CFR section 60.18 

For flares used during 

an emergency, record 

of the duration of flare 

operation, amount of 

gas burned, and the 

nature of the 

emergency situation. 

No Ground level enclosed flares only 

SBAPCD 

Rule 359 

Heating value, exit 

velocity, automatic 

ignition system 

Presence of a flame Yes Sulfur compounds may not exceed 

15 grains per 100 cubic feet (239 

ppmv) in the Southern Zone of 

Santa Barbara County or 50 grains 

per 100 cubic feet (796 ppmv) in the 

Northern Zone of Santa Barbara 

County; smokeless 

In 1994, the Santa Barbara Air Pollution Control District (SBAPCD) adopted Rule 359, Flares 

and Thermal Oxidizers. This rule applies to flares and thermal oxidizers used in oil and gas 

production, petroleum refineries and related sources, natural gas supply and transportation 

sources, and in distribution petroleum/petroleum products. Rule 359 specifies sulfur content 

limits for flare gas, technology-based standards for flares and thermal oxidizers, emission limits 

for nitrogen oxides and reactive organic compounds, and operational limits. The rule also 

requires plans to minimize use of flares. 

In 1998, the South Coast Air Quality Management District adopted Rule 1118 (Emissions from 

Refinery Flares), which requires refinery flare monitoring. Monitors were installed and 

operational by late 2000. 

In 2002, the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) adopted 

Rule 4311, Flares. This rule requires all open air flares to comply with federal limitations on 

sulfur in fuel gas. The federal requirement (40 CFR section 60.18) is found in New Source 

Performance Standards and, in the absence of the SJVUAPCD rule, would apply only to new 

flares. The rule does not impose extensive monitoring requirements like those in the proposed 

District rule or in SCAQMD Rule 1118. 
17 

PROPOSED RULE 

Proposed Regulation 12, Rule 11 would require refiners to: 

• Continuously monitor vent gas flow for each flare; 

• Monitor vent gas composition either by (1) taking samples manually or with an auto 

sampler, or by (2) using continuous analyzers; 

• Submit monthly reports that include vent gas flow and composition, pilot and purge gas 

flow, estimates of hydrocarbon and sulfur emissions, descriptions of all flaring of more 

than 1 million standard cubic feet of vent gas (duration, time, cause, measures to reduce 

or eliminate), and monitor downtime; 

• Monitor flare operation by video camera and record and retain recordings of flare images. 

These requirements would be imposed in steps that are based upon the District's determination 

about the length of time required to install the necessary equipment: 

• Effective in 90 days, each refinery would be required to begin daily sampling for 

composition when there is flaring activity. (Some refiners already have this capability 

and are reporting this data to the District pursuant to an agreement entered into pursuant 

to the flare further study effort described in the introduction; others will have to install 

necessary sampling ports.) 

• Effective in 180 days, each refinery will have to have continuous flow monitors in place. 

This effective data is based upon the expectation that the manufacturer of ultrasonic flow 

monitors will be able to supply, and the refiners will be able to install, these monitors 

within this time. 

• Effective in 270 days, each refinery will be required to have in place the equipment 

necessary to monitor composition at more frequent intervals or continuously. If sampling 

is chosen, the refineries will have to determine how to take more frequent samples, either 

through installation of auto-samplers or additional staffing, and how to process these 

samples, either in their own labs or through outside labs. If continuous analyzers are 

chosen, the refineries will have to design and install sample conditioning systems and 

analyzers, or arrange to have this work done by outside vendors. 

The following sections of the staff report discuss the provisions of the proposed rule in the order 

in which they appear in the rule. In this discussion, the rule prepared and made available with the 

public notice for the May 21st hearing is called the “proposed rule.” This is in keeping with 

standard terminology used by ARB, air districts, and the Health and Safety Code (§§40725, 

40726). The revised version of the rule now proposed for adoption is called the “revised rule.” 

Earlier drafts of the rule are called “earlier drafts.” 
18 

Exemptions 

The exemptions are intended to make it clear that the rule applies to flares and not other types of 

abatement devices used to control small sources and operations such as storage tanks or loading 

racks. These sources are subject to other BAAQMD rules and permit conditions. In particular, 

the exemptions make it clear that the rule is not intended to apply to thermal oxidizers, which 

differ from flares in numerous respects but most importantly in having emissions that can be 

directly measured and verified by source tests. For a discussion of this issue, see the discussion 

of the definition section of the rule below. 

Section 12-11-110 Exemption, Organic Liquid Storage and Distribution 

This exemption would exempt flares or thermal oxidizers controlling emissions exclusively from 

storage tanks or loading racks. The exemption would apply to six sources in the District. The 

first is a backup safety flare that serves a vapor recovery system for a propane tank at the Tesoro 

refinery. This flare is designed to control emissions from the propane tank if the tank’s vapor 

recovery system fails or is taken out of service for maintenance. The second is also a backup 

safety flare that serves a vapor recovery system for a butane tank at the Valero refinery. This 

flare serves the same purpose as the flare at Tesoro. The other four sources are located at the 

Shell refinery. Three of the flares are backup safety flares for three vapor recovery systems that 

serve fixed roof storage tanks. The other Shell flare serves a liquefied petroleum gas (LPG) 

railcar loading operation at the Shell refinery. Railcars are unloaded using natural gas to push the 

LPG (propane and butane) out of the railcar. When railcars arrive at the refinery for loading, 

propane and butane displace the natural gas to the flare. So this flare combusts natural gas and 

small amounts of LPG that vaporizes during the loading. For 2002, Shell loaded 971 tank cars. 

Total annual non-methane hydrocarbon emissions from the flare were approximately 1000 

pounds. All of the flares exempted by this provision, with the exception of Shell’s railcar 

loading flare, are backup safety flares and are not primary control devices. At 3 pounds per day, 

emissions from Shell’s railcar loading flare are not significant. 

Section 12-11-111 Exemption, Marine Vessel Loading Terminals 

Marine vessel loading terminals are located at all five Bay Area petroleum refineries. All 

terminals are subject to Regulation 8, Rule 44, which requires that emissions from the loading of 

specified cargos by reduced by 95% or to 2 pounds per thousand barrels of cargo loaded. 

Thermal oxidizers are used at the Chevron, ConocoPhillips, and Shell refineries to meet the 

rule’s control requirements. No terminal uses a flare for control. The thermal oxidizers at the 

three marine terminals have high efficiencies that are mandated by the rule and by permit 

conditions and can be directly verified by source tests. Because these devices are, by definition, 

thermal oxidizers, they are not subject to the rule. This exemption is therefore included merely 

to clarify that this is the case. 

Section 12-11-112 Exemption, Wastewater Treatment Systems 

The Valero and Tesoro refineries each use a thermal oxidizer to control components of the 

refinery wastewater treatment system. As discussed above, properly operated thermal oxidizers 
19 

have high control efficiencies that can be verified by source tests. Like all thermal oxidizers, 

these thermal oxidizers are, by definition, not subject to the rule, and the exemption is included 

to make this clear. 

Section 12-11-113 Exemption, Pumps 

Pumps are subject to the District's equipment leak rule, Regulation 8, Rule 18. The rule imposes 

the most stringent equipment leak limits in California, and one way of complying is by installing 

containment around a pump seal and directing emissions to an abatement device. Both the 

Chevron and Tesoro refineries use thermal oxidizers to control emissions from some pump seals. 

These thermal oxidizers are, by definition, exempt from the rule, and the exemption is intended 

to make this clear. If fugitive emissions from pumps are directed to the refinery's general 

blowdown and relief system, additional language makes it clear that the exemption would not 

apply to exempt a flare that might combust these emissions. 

Section 12-11-114 Limited Exemption, Total Hydrocarbon and Methane 

Composition Monitoring and Reporting 

This section does not appear in the proposed rule. Earlier drafts of the rule included a broader 

exemption from hydrocarbon reporting for flares that exclusively serve sulfur plants and 

ammonia plants or exclusively burn flexicoker gas. This broad exemption was dropped from the 

proposed rule. 

Staff are now recommending a more limited exemption for flares that exclusively burn flexicoker 

gas with or without supplemental natural gas. Coking is a final refining stage that separates light 

products from the heavy coke byproducts of refining. The process converts feed with a very high 

carbon/hydrogen ratio into distillate products. Flexicoking is a continuous coking process that 

minimizes coke production and maximizes the production of useful products. It uses a gasifier in 

which steam and air are combined with the coke to produce gas. After hydrogen sulfide is 

removed from the gas, it is used as a fuel within the refinery. The process leaves very little coke. 

Flexicoker gas has very consistent composition. Gas from the flexicoker at the Shell refinery is 

primarily nitrogen, carbon monoxide, hydrogen, and carbon dioxide. It typically has a methane 

content of less than 2%, a non-methane hydrocarbon content of much less than 1%, and very low 

sulfur content. A flare is used to burn flexicoker gas that cannot be used by the refinery. Under 

this exemption, Shell's flexicoker flare would be exempt from hydrocarbon monitoring 

requirements provided it meets the conditions in the exemption that limit methane content to less 

than 2% and non-methane hydrocarbon content to less than 1%. Monitoring for flow and sulfur 

composition would still be required. 

Definitions 

As with all District rules, the proposed flare monitoring rule defines key terms used in the rule. 

There are two things to note about the definitions. First, the terms "flare" and "thermal oxidizer" 
20 

are defined (Sections 12-11-201 and 209) to make it clear that the rule applies to the flares that 

are listed in this staff report and not to thermal oxidizers and other abatement devices. The 

distinction drawn between flares and thermal oxidizers is that the latter term describes an 

enclosed combustion device that exhausts all combustion products through a vent, duct, or stack 

so that emissions can be measured directly. The intent of this rule is to require monitoring of 

open-flame devices – flares – from which emissions cannot be measured in the conventional 

manner. For a flare, there is no stack or duct in which probes can be located and emissions 

measured. The rule therefore requires the monitoring of gases directed to flares. The rule is not 

intended to impose these same requirements on thermal oxidizers, from which emissions can be 

measured directly, and the definitions are intended to draw this distinction. Thermal oxidizers 

typically have VOC destruction efficiencies that range from 98 to 99.99% and above. 

A second important aspect of the definitions is that the term "vent gas" is defined (Section 12-11-

210) to include all gas directed to a flare, excluding steam or air used to aid combustion and 

excluding pilot and continuous purge gas. This definition is then used in the definition of 

"flaring" (Section 12-11-203). The result is that "flaring" is any time the flare has a flame other 

than the pilot flame. The term is used in the interim sampling provisions in Section 12-11-502.2 

to ensure that samples are taken while active flaring is occurring. 

Administrative Requirements 

The Administrative Requirements set forth reporting requirements. 

Section 12-11-401 Flare Data Reporting Requirements 

In the proposed rule, this section requires a monthly report that must include the following: 

• Upon rule adoption, total flow for each day and for the month. The Bay Area refineries 

currently have various means of determining flow and are reporting this data to the 

District pursuant to an agreement developed for flare further study measure FS-8. The 

rule will require continued reporting of this data. After the flow monitors required by 

Section 12-11-501 are installed, the report would also have to include flow for each hour 

of the month (ultrasonic flow monitors are capable of providing much greater flow detail 

than the means currently employed by most of the refineries). 

• Methane, total hydrocarbon and sulfur content for every vent gas sample, and if 

continuous analyzers are used, for every hour of the month. 

• If the flow monitor measures molecular weight (as ultrasonic monitors do), the average 

molecular weight of vent gas for each hour of the month. 

• Type and quantity of pilot gas and purge gas used for each day and for the month. Where 

these flows are constant because of flare design, the parameters that dictate flow and the 

resultant flow are sufficient. 
21 

• For any 24-hour period during which more than 1 million standard cubic feet of vent gas 

are flared, a descriptions of the flaring, including time, duration, cause, the source of the 

vent gas, and any measures taken to reduce or eliminate flaring. 

• Flare monitoring downtime. 

• The archive of video images required by Section 12-11-507. 

The revised rule adds a requirement for calculated emissions that was included in earlier drafts 

but dropped from the proposed rule. At the request of WSPA and the Unions at the May 8th 

flare workgroup meeting, the revised rule re-incorporates a requirement for emission 

calculations. The Unions suggested using the efficiencies specified in the Texas rule (98% for 

most flares, 93% for low-BTU gases). While WSPA has argued for higher efficiency, the revised 

rule includes the Unions’ suggestion. 

The reasoning behind specifying an efficiency figure, as articulated by the Unions and WSPA, 

seems to be that it is better to provide the public with some estimate of total emissions, even if 

the estimate employs some assumptions that are open to debate. District staff was persuaded by 

this reasoning, and so has incorporated assumed efficiencies in the proposed rule. However, it is 

important to note that these efficiencies are set for the narrow purpose of emissions estimates to 

be made in reports submitted by refineries pursuant to the rule. The revised rule does not restrict 

the District or anyone else from using a different efficiency figure in any other context. If the 

District does use a different efficiency figure, it will of course explain it’s reasoning for doing so. 

If more reliable information regarding flare efficiency becomes available, the District will 

consider revising the rule to reflect that information. 

The revised rule also adds language to this section to require the submission of additional 

composition data that is not required by the section but is available from sampling analyzers or 

continuous analyzers. 

On May 21, 2003 following the initial hearing on the rule, the District convened a meeting of the 

flare workgroup to discuss issues raised at the hearing. The meeting was attended by 

representatives for WSPA, the individual refineries, refinery trade unions, and CBE. In response 

to concerns raised by the unions and CBE, a minor change to the revised rule is proposed in 

Section 12-11-401.9. The revised rule incorporated the concept of specifying an efficiency of 

98% except for low-BTU flexicoker gas, for which 93% was the default value. Staff are now 

proposing a change that requires the use of 93% for any vent gas with a lower heating value less 

than 300 British Thermal Units/Standard Cubic Feet (BTU/SCF). This is a minor change 

because data gathered during the flare study shows that most flare gas, with the exception of 

flexicoker gas, exceeds this BTU threshold.

Section 12-11-402 Flow Verification Report 

This section requires a semi-annual report on alternative means of determining flow to serve as a 

check on the data being provided by the flow monitors. Ultrasonic flow monitors provide the 
22 

most accurate and reliable means available to determine flare header flow. No currently 

available alternative method can provide similar precision or accuracy. If the ultrasonic monitor 

has been installed and calibrated properly and the data logger has been programmed properly, the 

data should be reliable. In one case during the flare study recently conducted by the District, a 

refinery submitted data from an ultrasonic monitor and mistakenly assumed that the ultrasonic 

monitor range setting was 10 times the actual set range (for example, a value was assumed to be 

5 million when it was actually 500,000). The required semi-annual report will provide a means 

of detecting such errors through a comparison of other data to the reported data. There are 

several alternative ways of determining flow that can be used as a "reality check" on the monitor. 

These alternatives are listed in Section 12-11-602 (see the discussion of that section for an 

explanation of each alternative). If a semi-annual report suggests that there may be a problem 

with a monitor, the District will be able to investigate further to determine whether the monitor 

still meets the requirements of Section 12-11-501 (requiring the monitor to accurately measure 

flow rate). 

No other flare monitoring rule includes a flow verification requirement. This is true of both the 

South Coast AQMD petroleum refinery flare and the Texas chemical plant flare rule. This is 

primarily because it is difficult to know whether differences between ultrasonic flow meter 

measurements and measurements through alternate means should be attributed to inaccuracy in 

the meter or in the alternate method. (For more information on this issue, see the discussion of 

Section 12-11-501.) 

For these reasons, it is difficult to specify how close the meter measurement must be to the 

expected measurement as derived from the flow verification. In the revised rule (Section 12-11-

501), staff is including language that would specify that the difference be no greater than ±20%. 

Monitoring and Records 

The Monitoring and Records requirements are central to the rule and impose the various 

monitoring and recordkeeping requirements. 

Section 12-11-501 Vent Gas Flow Monitoring 

This section requires continuous monitoring of vent gas flow. The proposed rule specifies that 

the device used to do this monitoring (1) must be capable of detecting a minimum flow velocity 

of 0.1 feet per second, (2) must continuously measure the range of flow rates corresponding to 

flow velocities from 0.5 to 275 feet per second, and (3) must be installed on the flare header in a 

location that ensures that the device measures all flow. Three additional requirements are 

recommended by staff and are included in the revised rule. These additional requirements would 

specify that the device (1) must have a manufacturer's specified accuracy of ±5% over the range 

from 1 to 275 feet per second, (2) must be maintained to be accurate to within ±20% as 

demonstrated by the flow verification report specified in Section 12-11-402 (effective 12 months 

after installation), and (3) must be accessible to the APCO to verify proper installation and 

operation. 
23 

Section 12-11-501.1 requires the use of a device having a limit of detection of 0.1 feet per 

second. The “limit of detection” of an instrument is the lowest value of a parameter being 

measured that an instrument can reliably distinguish from zero. The limit of detection in the rule 

comes from ultrasonic flow meter product literature, and the value is from laboratory testing. 

Product literature from two manufacturers of ultrasonic flow meters (Panametrics and Roxar) 

both specify minimum detectible velocities in this range. 

The primary criterion for any device installed pursuant to this section is that it be able to measure 

flow velocities over the range from 0.5 to 275 feet per second (Section 12-11-501.2). This range 

is taken from product literature for ultrasonic flow meters and is the general range over which the 

manufacturers claim the meters to be accurate. The revised rule now includes the manufacturer’s 

specified accuracy based on laboratory testing (Section 12-11-501.3 in the revised rule). 

“Accuracy” is used in EPA and District regulations and in metrology, the science of 

measurement, to mean closeness to the truth. Although the ultimate true value of any parameter 

being measured cannot be known, accuracy is treated as the difference between a value measured 

by an instrument and an accepted true value or standard. These accepted values or standards are 

established by the National Institute of Science and Technology (NIST) or other nationally 

recognized measurement standards bodies. NIST was formerly the National Bureau of Standards 

and is responsible for developing, maintaining, and retaining custody of U.S. national standards 

of measurement. For example, a carton of milk is filled based on a NIST standard for measuring 

volume. Time throughout the U.S. is based on the official NIST time as maintained by NIST’s 

atomic clock in Boulder, Colorado. 

For fluid flow, there are no standard measurement artifacts like those for length or volume. 

Instead, NIST has established flow measurement standards based on devices that deliver a 

measured volume of fluid over a measured time interval, with these measurements referenced to 

established NIST standards for volume and time. NIST provides calibration services for gas flow 

meters, thus allowing testing laboratories to calibrate master flow instruments that can be used to 

verify the accuracy of meters for field use. Accuracy for ultrasonic flow meters therefore 

generally refers to the closeness to the NIST-established “truth” under laboratory conditions. 

Although many laboratories can test liquid flow meters, there only a few testing laboratories in 

the United States that can test ultrasonic gas flow meters against standards traceable to the NIST 

standards. 

Though ultrasonic flow monitors can be calibrated at a flow laboratory prior to installation and 

can be determined to measure known flows accurately, unless the calibration facility can 

replicate the pipe size and likely conditions under which the meter will operate in a particular 

flare header, one simply can't say with certainty what the accuracy of field measurements will be. 

However, because these meters are extremely accurate under laboratory conditions, it is 

reasonable to assume that properly installed meters are accurate in the field. For any method 

used to check meter accuracy in the field, it is difficult to know whether differences between the 

meter measurement and the measurement derived using some alternate method should be 

attributed to inaccuracy in the meter or in the alternate method. 
24 

Staff recommend, and the revised rule includes in Section 12-11-501.6, an accuracy specification 

based on the flow verification required by Section 12-11-402. The revised rule states that 

effective 12 months after installation of the ultrasonic meters, the flow verification shall 

demonstrate a meter accuracy of ±20%. This will allow a year of experience with the meters and 

with various flow verification methods. District staff expect that through this experience it will 

become clear whether the accuracy requirement can be met. District staff is proposing to report 

back to the Board 18 months after rule adoption. If it appears that the specification should be 

changed, staff can recommend appropriate changes at that time. 

Section 12-11-501.4 requires that the meter be installed at a location that ensures that the device 

measures all flow. An early draft of the rule specified that the meter must be installed at a 

location after the knockout pot, after all locations at which supplementary fuel is introduced, and 

after the water seal. This more prescriptive language was derived from a recently adopted Texas 

rule that applies to flares that combust certain highly-reactive VOCs. (Because refinery flare gas 

does not typically contain significant amounts of these highly-reactive VOCs, the Texas rule 

would not apply to most refinery flares and is instead intended to apply to chemical plants.) 

District staff determined that using the prescriptive approach of the Texas flare rule in this 

context would have required the installation of meters within the radiation zone for some Bay 

Area flares. Less prescriptive language is proposed to allow discretion to locate a meter where it 

would still measure all significant flows while avoiding damage to the meter. 

Section 12-11-501.5 specifies, effective 180 days after adoption of the rule, that the APCO is to 

have access to the flow monitoring system to verify proper installation and operation. 

Section 12-11-502 Vent Gas Composition Monitoring 

This section requires composition monitoring of vent gas. At present, some of the Bay Area 

refineries are taking daily samples of vent gas for lab analysis. Within 90 days after rule 

adoption and until more stringent requirements in the section take effect, all Bay Area refineries 

are required to take and analyze a grab sample for each day on which there is flaring activity 

(Section 12-11-502.2). These samples are required to be taken within 30 minutes after flaring 

begins. 

Effective nine months after rule adoption, more stringent composition monitoring requirements 

take effect. Refiners will have two primary options: (1) sampling and subsequent lab analysis, or 

(2) the use of continuous analyzers. There are then alternatives with each of the primary options. 

The various options are discussed below. 

Sampling 

Sampling is proposed as an option because the technology is proven, is robust, and is already in 

widespread use. Sampling can be more economical because sampling equipment will not require 

sample conditioning trains as complex as those required for continuous analyzers. However, 

sample processing in a lab can be labor and time intensive, and, with a short sampling interval, 
25 

can become as expensive as other options. Both manual sampling and auto-sampling are proven 

in practice. A number of refineries in Southern California are using auto-samplers to take vent 

gas samples as required by the South Coast AQMD flare monitoring rule. With manual 

sampling, great care must be taken to ensure the safety of refinery workers involved in sampling. 

In some cases, the available sampling locations may have potential to expose workers to 

dangerous high temperatures if the vent gas flow rate is high. 

The proposed rule allows only integrated sampling, which relies upon automated sampling 

equipment. Integrated sampling produces a composite sample out of individual aliquots taken 

over time. An aliquot is a fractional part of the sample that is an exact divisor of the whole 

sample. For example, ten aliquots of 100 milliliters each could compose a 1 liter sample. 

Because the aliquots are taken over time, the sample reflects variation in composition that may 

occur over time. Integrated sampling was included as the only sampling option in the proposed 

rule because of its potential to reflect composition variation with time. 

District staff now recommend that two alternative sampling options be available: manual 

sampling and integrated sampling. The revised rule reflects this recommendation. The reason 

for including a manual sampling option is that a number of flares in the District are very rarely 

used: some less than once in a year and others less than once in several years. For these flares, a 

requirement to use integrated sampling or continuous analyzers would dictate the installation and 

maintenance of expensive and sensitive equipment that would rarely be used. This equipment 

would require regular attention to ensure that it remains in a state of readiness. As a result, 

Section 12-11-502.3.1 sets forth a manual sampling option. 

This manual sampling option is probably not practical for flares that are used with some 

regularity. The need to continually take samples would be burdensome, and would likely result 

in missed samples. The likely outcome of the inclusion of this option is that its use will be 

restricted to these low usage flares. 

On May 21, 2003 following the initial hearing on the rule, the District convened a meeting of the 

flare workgroup to discuss issues raised at the hearing. The meeting was attended by 

representatives for WSPA, the individual refineries, refinery trade unions, and CBE. In response 

to concerns raised by WSPA and individual refineries, a minor change to the revised rule is 

proposed in Section 12-11-502.3.1.a. The revised rule allowed up to one hour to take the first 

sample for a flare serving a sulfur plant. The reason for the proposal was that taking a sample at 

such a flare could expose workers to extremely dangerous concentrations of hydrogen sulfide. 

Safety procedures would require the use of extensive safety equipment including self-contained 

breathing gear. Because preparation for taking such a sample would require a significant amount 

of time, the allowance was one hour rather than 15 minutes to take the first sample. At the flare 

workgroup meeting, the refiners pointed out that the same risks applied at ammonia plant flares. 

Staff are now proposing a minor change that would extend the same allowance to these flares and 

also give refiners an additional option of submitting worst-case composition data in lieu of 

undertaking sampling that could be extremely hazardous under some circumstances. The data 

would have to be verified by the APCO as properly representing worst-case composition.
26 

As noted, the only sampling option included in the proposed rule was integrated sampling. 

District staff are recommending retention of this option with modifications to the sampling 

trigger and additional language to ensure that sample containers are not left in service for more 

than a day. 

Sampling Trigger

Staff recommend adoption of the South AQMD trigger for sampling. The revised rule states that 

if the flow rate in any consecutive 15-minute period continuously exceeds 330 standard cubic 

feet per minute, sampling must begin within 15 minutes. Sampling must continue until flow rate 

in any consecutive 15-minute period is continuously 330 standard cubic feet per minute or less. 

The proposed rule set the sample trigger for integrated sampling at 6,000 standard cubic feet in a 

15-minute period. An earlier version of the rule proposed 50,000 standard cubic feet in one hour 

as the trigger for sampling. 

All efforts to set the sampling trigger have been based on setting the trigger at the lowest flow 

velocity at which (1) the flow meter is accurate and (2) the measured flow would represent real 

flow to the flare. The earlier draft’s proposed trigger of 50,000 standard cubic feet in an hour 

was based on a flow velocity of 1 foot per second. In response to comments from community 

and labor groups, the triggers in both the proposed rule and the revised rule are based on a flow 

velocity of approximately 0.5 foot per second. The recommended trigger included in the revised 

rule is identical to the trigger in the South Coast AQMD flare monitoring rule. 

The flow velocity for a given volumetric flow rate depends upon the size of the flare header. The 

table below lists volumetric flow rates for flow velocities of 1 foot per second and 0.5 foot per 

second in various sized flare headers. 

Table 4: Flow as a Function of Header Size and Velocity 

Volumetric Flow Rate for Given Flow Velocities (ft3/hr) 

Flow Velocity 

(feet/sec.) 

Diameter of Flare Header (inches) 

24" 30" 42" 48" 

1.0 11,310 17,671 34,636 45,239 

0.5 5655 8836 17,318 22,619 

Because most of the refineries have one or more large (42 inch or 48 inch) flare headers, using 

flow above 50,000 standard cubic feet per hour as a trigger ensures that sampling is triggered 

only when flow velocity is more than 1 foot per second in flare headers. Using an hourly trigger 

of 20,000 standard feet per hour (or about 330 standard cubic feet per minute over 15 minutes) 

ensures that sampling is triggered only when flow velocity is approximately 0.5 foot per second. 

Several reasons support setting the trigger for sampling at a flow velocity of approximately 0.5 

feet per second or higher. First, ultrasonic flow meters are not considered by manufacturers and 

users to be as accurate at flow velocities below about 0.5 feet per second. 
27 

Second, large flare headers are subject to various effects that produce low velocity currents 

within the header that do not represent flow to the flare. Such effects include the differential 

heating of a header by the sun producing stratification and circulation of gases and the suction of 

a compressor producing a surging effect on gas in the header. As a result, eddies can form and 

move within a header. As a result of these effects, gas can move past the sensors of the flow 

meter when no flaring is occurring. With a lower trigger, flow may be indicated where none 

exists (i.e., a false positive flow). Under such circumstances, samples would not represent actual 

vent gas but would instead represent still gas in the header and could bias results. 

A third reason for choosing the recommended trigger level is that an analysis of data collected 

during the District's flare study shows that use of this level would capture most of the flaring 

events of significance. Even if some events are missed, the larger events caught by this trigger 

will yield an extensive collection of data that will vastly expand understanding of the 

composition of flare gas. 

A fourth reason for choosing this trigger level is that the data loggers used to record flare flow 

can be easily programmed to compare gas volume flared for the current minute against the trigger 

and to recognize when there are 15 consecutive minutes of flow about the trigger level. This will 

provide a clear signal for triggering sampling and can be easily enforced. 

A fifth reason for choosing the proposed trigger level is that alternative forms appear to be more 

problematic. One alternative trigger that would still rely on the ultrasonic flow meter might be a 

sustained flow velocity exceeding 1 foot per second over some period of time. The disadvantage 

is that the sampling trigger would then vary with header size, which seems inequitable. In a 

small header the flow volume would be relatively inconsequential while significant in a large 

header. Use of a trigger other than the ultrasonic flow meter was also considered. A visual 

trigger tied to video monitor images could be used but would be subjective and difficult to 

enforce. Use of a trigger based upon flare header pressures that exceed the flare water seal 

pressure for some period of time would require instrumentation of water seals, and there is little 

District or industry experience with this data and its correlation to flow. 

Continuous Analyzers 

The other option for determining vent gas composition is the use of continuous analyzers 

pursuant to Sections 12-11-502.3.2 and 502.3.3. Several technologies are available: (1) flame 

ionization detectors (FID), (2) non dispersive infrared (NDIR), and (3) gas chromatography. 

These technologies were described above under "Background." 

Continuous analyzers are widely used to monitor gas composition in the chemical and petroleum 

industry. However, District staff have been unable to identify any refinery in California or Texas 

using a continuous analyzer to monitor flare vent gas composition. One of the difficulties of 

monitoring vent gas is that it can include water, oil, rust and other particles, a very wide range of 

organic compounds, and high sulfur levels. In general, continuous analyzers need to be carefully 

tailored to a relatively predictable gas stream. In addition, samples need to be carefully 

conditioned to remove water and particles. Use of continuous analyzers will therefore require 
28 

design and installation of a sample conditioning system. There is no off-the-shelf system 

available for this service. While District staff believe that such a system can be made to work, 

the technological challenges are not fully known. Until these systems are designed and installed, 

the maintenance needs for such a system are unknown. Because of the nature of the vent gas 

stream, it seems likely that these sample conditioning systems will require more maintenance 

than those in more conventional service. 

Rationale for Options 

The rule allows the two primary options, sampling and continuous analyzers, because each has 

advantages and disadvantages that may dictate one over the other for the specific flare in 

question. Sampling is a proven approach. Though continuous data is desirable, continuous 

analyzers have not yet been proven as a technology to monitor flare vent gas, which is not as 

"clean" as most gas streams for which these analyzers are used. Use of continuous analyzers will 

require sample conditioning equipment that may be more difficult to design than those required 

for sampling and may require considerable maintenance. The rule represents a compromise, 

allowing a method that is known to work (sampling) while encouraging a method that the 

District would like to see proven in practice (continuous analyzers). This ensures that the rule 

will work and avoids the risk of rule failure that would come from mandating only continuous 

analyzers and the missed opportunity that might come from mandating only sampling. District 

staff expects that the result may be the use of continuous analyzers on some flares and sampling 

on others. District staff expects that either approach will provide sufficient data to support the 

accurate characterization of flare gas composition. 

General Requirements 

Section 12-11-502.1 specifies requirements that apply to all composition monitoring. Vent gas 

monitored for composition must be taken from a location that is representative of vent gas 

composition. Where flares share a common header, a sample from the header is sufficient for all 

flares served by the header. The composition monitoring system must provide a means for the 

District to take samples to verify the composition analyses required by the rule. 

Section 12-11-503 Pilot Monitoring 

This section requires each pilot to have a properly functioning ignition system. Most flares have 

pilot lights and most have an electric arc backup in case the pilot is lost. 

Section 12-11-504 Pilot and Purge Gas Monitoring 

This section requires monitoring of pilot and purge gas either by a flow measuring device or by 

the monitoring of other parameters. Most of the refineries rely on water seals rather than purge 

gas, and volumetric flow of pilot gas is constant and dictated by pilot design. Under these 

circumstances, the monthly report can simply state the parameters that dictate flow and repeat the 

flow data each month (see discussion of Section 12-11- 401). 
29 

Section 12-11-505 Recordkeeping Requirements 

Pursuant to this section, monitoring records, except for video monitoring, must be kept for 5 

years. The section repeats existing requirements contained in federal law for Title V facilities. 

Section 12-11-506 General Monitoring Requirements 

General monitoring requirements that apply to all monitors are included in this section. The 

section limits hours of monitor inoperation and requires reporting when monitors go out of 

service. Monitors are allowed 15 consecutive days of inoperation, with proof of expeditious 

repair required after the 15 days and with a limit of 30 days total in one year. During periods 

when monitors are out of service, flows must be calculated and composition must be determined 

by sampling. Monitors are required to be maintained and calibrated in accordance with 

manufacturer's requirements. Finally, the section specifies that the electronic data loggers used 

to record data must be capable of one-minute averages and must record flow data as one-minute 

averages. Continuous composition analyzers do not produce one-minute averages, as the cycle 

for such an analyzer may take 15 minutes or more. 

The revised rule includes amendments to the monitor downtime provisions that are intended to 

encourage the use of integrated sampling and continuous analyzers. Though these approaches 

have not yet been used on flare headers, several Bay Area refineries are interested in trying one or 

more of these options, but are concerned that the downtime provisions are too stringent for new 

equipment with which they have no experience. The changes to this section allow a 6 month 

grace period for integrated sampling, continuous analyzers, and gas chromatography during 

which the downtime limits will not apply. This will give the refineries time to work out any 

problems and acquire experience with the new equipment. 

In response to comments from the Air Resources Board received just before the May 21, 2003 

hearing on the revised rule, District staff are proposing two minor changes to Section 12-11-

506.1 of the revised rule. The first change would delete an allowance of monitoring downtime 

for purely manual sampling, for which a downtime allowance is inappropriate (see response #127 

in Comments and Responses). The second change would correct a typographical error in the 

same section (see response #128).

Section 12-11-507 Video Monitoring 

This section requires the installation within 90 days of recording equipment for flares currently 

equipped with video monitoring equipment. Effective in 6 months, video monitors and recording 

equipment must be installed on each flare that currently lacks video monitoring equipment and 

that has a significant release (1 million standard cubic feet of vent gas in 24-hour period) as 

measured by the ultrasonic flow monitors. 

The video monitoring requirements are intended to provide a backup to the extensive data that 

will be available after the rule's other monitoring requirements go into effect. Recorded video 

will serve as a broad scale verification on the operation of flow monitors. For instance, if 

recorded video shows a significant flaring event that is not indicated in monitoring data, this 
30 

would be indicative of monitor equipment failure. In this way, recorded video data will provide 

an additional benefit in linking actual flaring events with emissions data and will thereby further 

the District compliance and enforcement capabilities. Though recorded video is not nearly as 

useful as other forms of monitoring for determining the quantity or character of flare emissions, 

its low cost and utility as a gross verification method justifies its inclusion in the rule. 

Community members originally asked for video monitoring so that the District would have the 

means to verify complaints about flaring. In the past, flaring complaints occasionally came to the 

District on weekends or at other times when a District inspector was unable to verify the 

complaint. In the past, however, inspectors did not have the flow and composition data that will 

now routinely be available. It is possible, but uncertain, that video data will assist the District in 

responding more effectively to community complaints. The District believes this possibility, 

combined with the usefulness of video data as a broad scale verification on monitor function, 

justifies imposition of the requirement. With the proposed rule, video data will be redundant, but 

the recordings will provide an additional check on flaring. 

At the District's August 2002 conceptual workshop for the proposed rule, community members 

asked for video monitoring with retention of images for a period sufficient to allow verification. 

The District's original proposal was to require recording of images and retention of the images 

for 72 hours. At community meetings, many participants requested retention for a greater length 

of time. The proposed rule therefore requires retention and submission of the images recorded 

during a particular month with the monthly report required by Section 12-11-401. This 

requirement ensures that images will be available to answer questions raised by neighbors or by 

District staff after reviewing the report. 

This section specifies certain minimum requirements for the images and recording. The flare 

image must be of sufficient size, contrast, and resolution to be readily apparent in the overall 

image or frame and it must include an embedded date and time stamp. 

The image of the flare must be recorded at a frame rate of no less than 1 frame per minute. This 

frame rate was selected to ensure that the resulting size of the electronic file was no bigger than 

could be recorded on one DVD per flare per month. In arriving at this frame rate, the District 

assumed that the individual image file for each image of the flare would be 40 kilobytes. This 

file size was selected based on the size of a typical JPEG image file of reasonable size. Images 

for one month would then produce a file of 1.7 gigabytes (40 Kb * 60 min/hr * 24 hrs/day * 30 

days). A single-sided single-layer DVD is capable of holding 4.7 gigabytes of data. Though this 

file size is reasonable for a DVD, it is an extremely large file by internet standards and could not 

be sent as a typical e-mail attachment or over anything but the fastest internet connections in any 

reasonable amount of time. 

Comments on earlier versions of the rule have suggested that much higher frame rates could be 

required for the image recordings. But there are tradeoffs. The basic determinants of the size of 

an electronic image file are its size in pixels, the bit depth for each pixel (the number of bits used 

to represent colors for each pixel), the number of images included in the file (determined by the 
31 

frame rate and length of time), and the compression used (various different approaches are used 

to reduce file size, but generally at the expense of resolution). 

As an example, a typical image size is 320 pixels by 240 pixels. Producing a black and white 

image requires a bit depth of 1 bit. To produce a good grayscale image or an image with a 

limited range of color requires a bit depth of 8 bits. With limited color, the file size for each 

frame is already 75 kilobytes (320 pixels * 240 pixels * 8 bits/pixel * 1 byte/8bits * 1 

kilobyte/1024 bytes). At a frame rate of 30 frames per second (the standard video frame rate), 

the file size for 1 minute of video is 132 megabytes. A DVD could store 36 minutes of these 

uncompressed video images. This is why compression is used. The standard compression used 

for video was developed by the Moving Pictures Experts Group and is called MPEG. MPEG 

achieves good results at compression ratios up to 20:1 for video, with visual artifacts and 

distortion appearing at higher compression ratios. With the current example and a compression 

ratio of 20:1, a DVD could store about 12 hours of video images. Video images of the example 

size at 30 frames per second for a single flare for a month would therefore require 60 DVDs. 

One participant in the August 2002 conceptual workshop also suggested requiring flare operators 

to put flare images on the internet. The proposed rule does not require posting of images on the 

internet. The District believes that the current video monitoring requirement will sufficiently 

provide the information the District seeks to carry out its responsibilities. Web posting, as 

proposed by some workshop participants and commenters, would not provide any additional 

benefit in determining emissions, enforcing applicable regulations, or investigating incidents. If 

the District receives complaints as a result of a flaring incident, an on-site investigation by an 

inspector would normally follow. 

On May 21, 2003 following the initial hearing on the rule, which included a discussion of 

"webcasting" by the Board, the District convened a meeting of the flare workgroup to discuss 

webcasting and other issues raised at the hearing. The meeting was attended by representatives 

for WSPA, the individual refineries, refinery trade unions, and CBE. The consensus of all 

present was that webcasting raises a number of difficult issues and should be separated from the 

remainder of the rule and referred to the Stationary Source Committee. The staff proposal for the 

June 4, 2003 Board meeting reflects this consensus. To avoid imposing video recording and 

storage requirements that would require immediate decisions about technology that might prove 

to be inconsistent with later direction by the Stationary Source Committee, the District is 

proposing to push back the effective date of Section 12-11-507 to allow further study of 

webcasting and related issues. The section would be effective 180 days after rule adoption rather 

than 90 days to allow the necessary time for this effort.

Manual of Procedures 

Provisions in the Manual of Procedures section of the rule specify test methods to be used to 

carry out the monitoring required by the rule. 
32 

Section 12-11-601 Testing, Sampling, and Analytical Methods 

This section lists the methods that are allowed for the various approaches to composition 

monitoring. Section 12-11-601.1 specifies methods to be used for laboratory analysis of samples 

taken manually or with an auto-sampler. Section 12-11-601.2 specifies methods to be used with 

flame ionization detectors or non-dispersive infrared spectrophotometry. Section 12-11-601.3 

specifies methods for gas chromatography. For gas chromatography, although equipment may be 

capable of completing cycles in 15 minutes, the allowed sampling frequency is 30 minutes, both 

because some refiners may want to analyze for additional compounds beyond those required by 

the rule, which increases the cycle time, or because some may want to use one gas 

chromatograph to analyze samples from more than one flare header. 

The revised rule makes a minor change to this section to allow use of subsequent revised 

versions of the listed methods. 

Section 12-11-602 Flow Verification Test Methods 

Section 12-11-402 requires a semi-annual flow verification for the flow monitors required by the 

rule. As noted in the discussion of that section, this requirement simply provides a check on the 

flow meters. Section 12-11-602 specifies 6 methods that can be used to measure or estimate 

flow for a particular period of time. Pursuant to Section 402, the measure or estimate will then 

be compared to flow monitor data for the same period. If there is a difference between the data 

produced by the monitor and that produced by the verification method, it is difficult to know 

whether the error lies with the meter or with alternative. The verification is primarily intended to 

flag any major differences for further investigation. The verification would catch, for example, 

any error in the range setting for the ultrasonic flow meter (see discussion under Section 12-11-

402). If there is a reason to suspect a problem in the flow meter, a flow meter can be removed 

and bench tested with controlled flows. 

The revised rule includes a requirement that measurement from the meter and the flow 

verification agree to within ±20%. 

Sections 12-11-602.1 and 602.2 allow pitot tube traverses as a check on flow and specify District 

and EPA methods respectively for conducting these traverses. These methods involve inserting a 

pitot tube into a port in a flare header and measuring flow. Though the methods have been 

included, they are not likely to be used very often because of the risks involved with inserting 

probes into a live flare header. Their use is also limited to velocities greater than 10 to 20 feet 

per second. 

Section 12-11-602.3 would allow the use of flow monitors or process monitors that can provide 

comparison flow rate data for a vent stream that is flowing past the ultrasonic flow meter. 

Section 12-11-602.4 would allow the use of any method recommended by the manufacturer of 

the ultrasonic flow meter. 
33 

Section 12-11-602.5 would allow the use of a tracer gas to determine flow. A tracer gas can be 

introduced into a flare header through a port upstream of a second port at which vent gas is 

sampled for presence of the tracer gas. By timing how long it takes the tracer gas to move from 

the port where it is introduced to the port where it is detected or by measuring the tracer gas 

concentration, flow velocity can be determined. 

Section 12-11-602.6 would allow any alternative method if approved by the District and EPA. 

EMISSIONS REDUCTIONS 

The purpose of Regulation 12, Rule 11, Flare Monitoring at Petroleum Refineries is to gather 

information on flaring including flow, composition, and cause. The proposed rule does not 

mandate reductions. Nevertheless, District staff have found that because refiners have looked 

more closely both at monitoring and the feasibility of flaring reductions, flaring at the five Bay 

Area refineries has dropped dramatically over the past year. One refinery has installed new 

compressors that have allowed it to go from flaring an average of 5 million standard cubic feet of 

vent gas per day to virtually zero routine flaring. The result has been a significant emission 

reduction that cannot be directly attributed to this rule, but will ultimately be reflected in the 

emissions inventory. 

ECONOMIC IMPACTS 

Costs 

The proposed rule requires the installation of 3 types of monitoring equipment: (1) flow 

monitoring equipment, (2) composition monitoring equipment, and (3) video monitoring 

equipment. Because the rule allows each refinery options, particularly in determining how to 

monitor vent gas composition, it is difficult to predict cost for each refinery. Cost will also vary 

because the number of flares at each refinery varies. Costs are divided into two main categories: 

(1) initial capital and installation costs for equipment, and (2) annual operating and maintenance 

costs. 

Table 5. Capital Cost Items 

Cost Item Cost1 Comment 

Flow monitor 

Ultrasonic meter w/ 

installation 

Annual amortized cost2

$50,000 

$6164 

Continuous analyzer (NDIR) 

Hydrocarbon analyzer 

 H2S analyzer 

Sample conditioning 

AutoCal system 

Installation 

$9,000 

$15,000 

$40,000 

$25,000 

$50,000 

2 analyzers: (1) dual channelmethane and total 

hydrocarbon, (2) H2S 
34 

Cost Item Cost1 Comment 

Total 

Annual amortized cost2

$139,000 

$17,137 

Continuous analyzer (FID) 

Hydrocarbon analyzer 

 H2S analyzer 

Sample conditioning 

AutoCal system 

Installation 

Total 

Annual amortized cost2

$12,000 

$15,000 

$40,000 

$25,000 

$50,000 

$142,000 

$17,507 

2 analyzers: (1) dual channelmethane and total 

hydrocarbon, (2) H2S 

Continuous analyzer (GC) 

GC 

Sample conditioning 

Installation 

Total 

Annual amortized cost2

$50,000 

$40,000 

$50,000 

$140,000 

$17,261 

Auto-sampling system 

Auto-sampler 

Installation 

Total 

Annual amortized cost2

$15,000 

$15,000 

$30,000

$3,699 

Manual sampling station 

Installation 

Annual amortized cost2

$10,000 

$1233 

Video monitoring 

Equipment w/installation 

Annual amortized cost2

$5,000 

$616 

1 Costs based on vendor estimates or quotes to ARB or District staff 

2 Costs amortized over 10 years @ 4% real interest rate

Table 6. Annual Operating Costs 

Cost Item Cost Comment 

Maintenance for all monitors 

(per flare) 

$20,000 District estimate 

Sample analysis $500/sample Vendor quote 

Report preparation per flare1$4,000 Costs based on 1 day of labor 

@$50/hr/flare/month 

Based on the above cost estimates, the annual cost per flare will depend upon the flare 

monitoring technologies chosen, but the cost is expected to be about $50,000 per flare. For flares 

for which composition is monitored by sampling, equipment costs are lower but sample analysis 

costs bring total cost up to a level comparable to that for flares using continuous analyzers. 
35 

At an annual cost of $50,000 per flare, the total cost for the Bay Area refineries together is 

expected to be about $1.15 million per year. The cost per refinery will depend upon the number 

of flares at the refinery. 

Socioeconomic Impacts 

Section 40728.5 of the Health and Safety Code requires an air district to assess the 

socioeconomic impacts of the adoption, amendment, or repeal of a rule if the rule is one that 

“will significantly affect air quality or emissions limitations.” The proposed rule is intended to 

provide the tools necessary to analyze refinery flaring. It would impose monitoring requirements 

for refinery flares but would not impose emission limitations. As a result, these limits cannot be 

said to “significantly affect air quality or emission limitations,” within the meaning of Section 

40728.5, and the District will not prepare the socioeconomic analysis that would otherwise be 

required under Section 40728.5 of the Health and Safety Code. However, the District has 

attempted to minimize the costs imposed by the proposed rule. 

Incremental Costs 

Under Health and Safety Code Section 40920.6, the District is required to perform an 

incremental cost analysis for a proposed rule under certain circumstances. To perform this 

analysis, the District must (1) identify one or more control options achieving the emission 

reduction objectives for the proposed rule, (2) determine the cost effectiveness for each option, 

and (3) calculate the incremental cost effectiveness for each option. To determine incremental 

costs, the District must “calculate the difference in the dollar costs divided by the difference in 

the emission reduction potentials between each progressively more stringent potential control 

option as compared to the next less expensive control option.” Because the proposed rule does 

not impose control requirements, no incremental cost analysis will be prepared. 

ENVIRONMENTAL IMPACTS 

Pursuant to the California Environmental Quality Act, the District prepared an initial study for 

the proposed rule to determine whether rule adoption would result in any significant 

environmental impacts. The rule is intended to allow the District to collect data on refinery 

flaring through the imposition of monitoring requirements. Because the rule would not impose 

emission control requirements, which always have some potential to alter emissions or transfer 

them from one media to another, and because any necessary construction would take place within 

existing refineries, no adverse environmental impacts are expected. The study did identify the 

construction work required to install monitors as a source of potential environmental impacts. 

However, because of the safety requirements that govern this type of work, the regularity with 

which similar hot work is conducted in refineries, and the consequent familiarity with and 

preparedness for this type of work on the part of refinery workers and contractors, the study 

concluded that the proposed rule would not result in any significant environmental impacts 

through this mechanism. 
36 

A CEQA Negative Declaration is proposed for adoption by the Board in connection with the 

adoption of the revised rule. The CEQA document was circulated for public comment during the 

period from April 21, 2003 to May 12, 2003. No comments on the document were received. 

REGULATORY IMPACTS 

California Health and Safety Code Section 40727.2 require the District to identify existing 

federal air pollution control requirements for the equipment or source type affected by the 

proposed rule or regulation. The District must then note any differences between these existing 

requirements and the requirements imposed by the proposed rule. Table 7 is a matrix of the 

proposed rule, existing Bay Area regulations, and federal requirements for flares. 

Table 7: Comparison of Regulatory Requirements 

Agency Regulation Control/Performance 

Requirements 

Monitoring 

Requirements 

Emission 

Limitations 

BAAQMD Reg. 2, Rule 6 

(Title V 

permit) 

Specific to facility and source Specific to facility 

and source 

Throughput 

limits, visible 

emission 

BAAQMD Proposed 

Reg. 12, Rule 

11 

No Volumetric flow 

and composition 

No 

EPA 40 CFR 60.18 

(applies to 

flares subject 

to NSPS) 

Pilot flame present at all times, 

heat content, maximum tip 

velocity, sulfur content 

Presence of flame, 

heating value 

Smokeless 

capacity 

Federal Requirements 

Federal New Source Performance Standards (NSPS) in 40 CFR Part 60, Subpart A, Section 

60.18 apply to flares that are used as general control devices. They specify design and 

operational criteria for new and modified flares. The requirements include monitoring to ensure 

that flares are operated and maintained in conformance with their designs. Flares are required to 

be monitored for the presence of a pilot flame using a thermocouple or equivalent device. Other 

parameters to be monitored include visible emissions, exit velocity and net heat content of the 

gas being combusted by the flare. 

In addition, the NSPS limit sulfur oxides in vent gases combusted in a flare installed after June 

11, 1973 (40 CFR Part 60, Subpart J, Section 60.104). Upset gases or fuel gas that is released to 

the flare as a result of relief valve leakage, startup/shutdown, or other emergency malfunctions is 

exempt from the standard. 
37 

District Requirements 

Within the District, a new emission source or a modified existing source must meet the District’s 

New Source Review (NSR) requirements. The NSR program requires the use of Best Available 

Control Technology (BACT) for new or modified sources that have the potential to emit 10 

pounds per day or more of VOC, carbon monoxide, oxides of nitrogen, particulate matter, or 

sulfur dioxide. For flares, BACT requires a control efficiency of 98% for elevated flares and 

98.5% for ground flares. Other permit conditions are imposed on some flares. These conditions 

may include throughput limits and record keeping to document compliance. 

The proposed rule would require continuous monitoring for volume and sampling or the use of 

continuous analyzers for vent gas composition. Recording of video images of flares would be 

required. Monthly reports of flow, composition, and other data would be required. For larger 

releases (over 1 million standard cubic feet per day), a report on the time, cause, duration, and 

reason for the flaring would be required. 

RULE DEVELOPMENT HISTORY 

The District has been carrying out a complex study of flares and flaring at the Bay Area refineries 

since January 2002. The study implements further study measure FS-8 from the 2001 Bay Area 

Ozone Attainment Plan. In the course of the study, District staff have visited all five Bay Area 

refineries numerous times, have met with refinery staff, ARB and EPA staff, and with 

community groups in over 50 meetings to discuss issues related to flaring. 

A work group was formed to carry out the further study. The workgroup included representatives 

from California Air Resources Board, Industry, Communities for a Better Environment, and 

District Staff. The Environmental Protection Agency and other air districts, including the South 

Coast AQMD and the San Joaquin Valley Unified APCD participated at various levels 

throughout the project. The workgroup has met periodically since January 2002 to discuss 

technical issues. Among those issues have been flare monitoring issues such as flow monitoring 

and available technologies and composition monitoring methods. 

In May 2002, the District conducted an informational public meeting to gather input on the 

District’s plans to implement the commitments in the ozone attainment plan. In August 2002, 

District staff held a workshop in Martinez to discuss flare monitoring concepts. At this 

workshop, community members indicated that they would like to see a rule that required flow 

monitoring, composition monitoring, reporting requirements, and video monitoring. 

Three community meetings were held in March and April 2003. After the community meetings, 

a draft rule was circulated for a short comment period ending April 17, 2003. Extensive 

comments were received from WSPA, Communities for a Better Environment, and refinery trade 

unions. On April 16, 2003, the proposed rule was discussed before the Stationary Source 

Committee. A flare workgroup meeting was then held on April 18, 2003. The meeting was 

attended by representatives for various refineries, WSPA, CBE, the refinery trade unions, 

monitoring equipment vendors, ARB, and District staff. Based on the draft and these further 
38 

discussions, the proposed rule was developed and sent to the Air Resources Board on April 21, 

2003. Discussions continued on May 8, 2003 with a second flare workgroup meeting. After the 

second meeting, modifications to the proposed rule were developed and circulated among all 

who participated in the meeting. After discussion with members of the workgroup, staff 

prepared the revised rule. 

DISTRICT STAFF IMPACTS 

Implementation of the proposed regulation will have a significant impact on the District’s 

resources. However, these changes are essential and necessary in order to satisfy the 

commitments in the Bay Area 2001 Ozone Attainment Plan. 

The proposed regulation will require the installation of monitors. The District will have to 

exercise oversight for these monitors in a manner similar to that used to oversee continuous 

emission monitors (CEM). The resources required are similar, and will require District staff to 

verify the installation of monitoring equipment, conduct accuracy tests or ensure that they are 

conducted, review monthly reports, perform compliance inspections, and investigate flaring 

incidents. 

Monthly reports on flaring will be required. These reports will have to be reviewed by District 

staff. The District expects to continue to investigate significant flaring events. This would not 

represent a change from the model used in the further study measure for flares. A flaring event 

was defined for the study as any flow over 1,000,000 standard cubic feet per day to a flare. The 

rule requires an investigation that is included in the monthly report from the refinery whenever 

daily volume exceeds 1,000,000 standard cubic feet. During the further study period, the time 

required to investigate events varied, was dependant on the complexity of operations, and ranged 

from less than an hour to hundreds of hours. This workload will diminish as flaring decreases (as 

it is currently) and as more data becomes available with new monitors in place. 

CONCLUSION 

Proposed Regulation 12, Rule 11, Flare Monitoring at Petroleum Refineries, will implement 

control measure SS-15 from the Bay Area 2001 Ozone Attainment Plan. The rule is intended to 

gather data on flaring operations at petroleum refineries. 

Pursuant to the Health and Safety Code Section 40727, new regulations must meet necessity, 

authority, clarity, consistency, non-duplicity and reference. The proposed regulation is: 

• Necessary to implement control measure SS-15 in the Bay Area 2001 Ozone Attainment 

Plan; 

• Authorized by California Health and Safety Code Section 40702; 

• Clear, in that the new regulation specifically delineates the affected industry, compliance 

options and administrative requirements for industry subject to this rule; 

• Consistent with other District rules, and not in conflict with state or federal law; 
39 

• Non-duplicative of other statutes, rules or regulations; and 

• The proposed regulation properly references the applicable District rules and test methods 

and does not reference other existing law. 
40 

REFERENCES 

Bay Area Air Quality Management District. 2001. Bay Area 2001 Ozone Attainment Plan, 

adopted October 24, 2001. San Francisco, CA. 

. 1990. BAAQMD Flare Gas Monitoring: March 1988 through December 1989. San 

Francisco, CA. 

California Air Resources Board (CARB). CARB Board Resolution No. 86-80. Sacramento, CA. 

San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD). 2002. Rule 4311, 

Flares, adopted on June 20, 2002. Fresno, CA. 

Santa Barbara Air Pollution Control District (SBAPCD). 1994. Rule 359, Flares and Thermal 

Oxidizers, adopted on June 28, 1994. Santa Barbara, CA. 

South Coast Air Quality Management District Rule. 1998. Rule 1118 Board Package, February 

13, 1998. Los Angeles, CA. 

U.S. Environmental Protection Agency. 1998. Draft Compliance Assurance Monitoring Rule, 

Technical Reference For Monitoring Equipment And Instruments, Section 4.0, August 

17, 1998. Washington, D.C. (available on the web at 

http://www.epa.gov/ttnemc01/cam/sec4-5.pdf)

. Air Pollution Technology Factsheet: Flare. Washington, D.C. (available on the web at 

http://www.epa.gov/ttn/catc/dir1/fflare.pdf)

. Air Pollution Technology Factsheet: Thermal Incinerator. Washington, D.C. (available 

on the web at http://www.epa.gov/ttn/catc/dir1/fthermal.pdf)
41 

COMMENTS AND RESPONSES 

The following written comments were received during the rule development process for the 

proposed flare monitoring rule. These comments and responses refer to the rule prepared and 

made available with the public notice for the May 21st hearing as the “proposed rule.” This is in 

keeping with standard terminology used by ARB, air districts, and the Health and Safety Code 

(§§40725, 40726). The revised version of the rule now proposed for adoption is called the 

“revised rule.” Earlier drafts of the rule are called “earlier drafts.” These comments were made 

on an earlier draft that preceded the proposed rule. Many of the comments were addressed in the 

proposed rule or in the revised rule that staff is recommending for adoption by the Board. 

Written Comments Received During Community Meetings 

The District held three community meetings in March and April 2003 to discuss rule concepts. 

During or after these meetings, the District received the following written comments related to an 

earlier rule draft. 

1. The draft rule allows refineries to choose once per day sampling and skip 

monitoring gas composition for the rest of the day. Refineries are only 

required to sample gas composition during 60 minute periods exceeding 

50,000 cubic feet of gases flowing to the flare. This loophole allows each 

flare to skip monitoring the gas composition of over a million cubic feet per 

day of gases (49,000 cubic feet X 23 hours). <May, Communities for a 

Better Environment (CBE). E-mail. 3/27/03> 

For the sampling option to which the comment refers, the earlier draft rule set a 

trigger that required sampling when the volume of vent gas measured during a 

60-minute period exceeded 50,000 standard cubic feet of gas. Based in part on 

a concern expressed in earlier comments, the trigger was revised downward in 

the proposed rule and subsequently in the revised rule now recommended for 

adoption. The revised trigger that staff recommend is identical to the trigger in 

the South Coast AQMD rule (which requires sampling when flows continuously 

exceed 330 cubic feet per minute for 15 minutes). 

Note that all vent gas must be monitored for flow volume regardless of the 

means used to determine composition. If sampling is used for monitoring vent 

gas composition, it is important that the trigger be set at some minimum flow that 

represents actual flow to the flare so that false positive readings are avoided. 

The earlier draft rule to which this comment was directed set a trigger that was 

based on an assumption that ultrasonic flow meters could not reliably measure 

flare flows at below 1 foot per second. The revised trigger is based on an 

assumption that there is adequate reliability even at approximately 0.5 foot per 

second. 
42 

As discussed in the staff report (see discussion of Section 12-11-502), large flare 

headers are subject to various effects that produce low velocity currents within 

the header that do not represent flow to the flare. With a trigger lower than 

approximately 0.5 foot per second, meter accuracy is lower, and low-velocity 

flows that do not represent flow to the flare may be encountered. The result is 

that flow may be indicated where none exists (i.e., a false positive flow). If 

samples are then taken, these “no flow” samples will bias results. 

2. The draft rule allows huge flows of gases to go unmonitored because the 

refineries are allowed to skip measuring flows below 0.5 ft./sec. <May, 

CBE. 3/27/03> 

The rule requires all flows to be measured and reported (see Section 12-11-401). 

The comment is a response to Section 12-11-501, which specifies a series of 

requirements for any device used to measure flow. One of the specifications is 

that the meter must measure the range of flow corresponding to velocities from 

0.5 to 275 feet per second. This is a device specification and not a limitation on 

the reporting otherwise required by Section 12-11-401. An ultrasonic meter that 

meets the specification is capable of reporting data on flow down to its limit of 

detection. The specification is derived from literature from Panametrics. The 

Panametrics meter is capable of detecting flow down to 0.1 feet per second. As 

noted above, however, these low velocity flows may not represent flow to the 

flare. 

3. The draft rule allows poor quality assurance procedures, such as 

“engineering calculations” or “other flow monitoring devices or process 

monitors” for determining whether [flow] monitoring equipment is working 

right. <May, CBE. 3/27/03> 

Ultrasonic flow meters are state-of-the-art devices for measuring flow. They are 

extremely accurate over a wide range of flows, are robust with no moving parts, 

and are proven in service. They are widely used as custody transfer meters to 

price large volumes of natural gas at sale. Section 12-11-506.3 already requires 

proper calibration and maintenance. The verification procedures included in the 

rule are inevitably less accurate means of measuring flow, but are included in the 

rule as a check on the meters to avoid gross errors such as might come from 

misinterpreting the range setting or units represented by the meter display or 

output. 

Written Comments Received During Written Comment Period 

Following the completion of the community meetings, the District prepared a revised draft and 

made it, a draft staff report, and a draft CEQA initial study available for public comment. The 

comment period ran from April 7 – 17, 2003. The following comments were received. 
43 

4. What data/monitoring is needed for proposing rule-making? <Partnership 

for Public Health, Environmental Health Committee (PPH). 4/16/03> 

For any rulemaking, the District must make a number of findings required by 

California Health and Safety Code section 40727. Findings of necessity and 

authority are among the required findings. For this rulemaking (flare monitoring), 

this staff report serves as the basis for the necessary findings. 

5. What is the nature of the discrepancies between the Air District 

assessment and the assessment from the refineries? How will these 

discrepancies be addressed? What is the avenue for meaningful public 

participation in this process? <PPH. 4/16/03> 

The major differences between the District's Draft Technical Assessment 

Document and data submitted by the refineries are in the hydrocarbon content 

and volume of gases flared. These differences will be addressed through the 

ongoing technical assessment process for flares. The public can participate 

through the flare work group or by commenting on the technical assessment 

document as revised. 

6. Is routine flaring legal? If not, what does the Air District plan to do about 

these flares (i.e.; fines, cease and desist orders, control measures). <PPH. 

4/16/03> 

Under certain circumstances routine flaring may result in a violation of Federal 

standards (40 C.F. R. Section 60.104(a)(1)). Such a determination is based 

upon the factual circumstances in any given flaring event. Because the purpose 

of the current regulation is to gather data and monitor emissions, this question 

may be better answered in another forum. 

7. What monitoring technology is currently available? What is the best way to 

monitor? <PPH. 4/16/03> 

For flare gas flow rate (cubic feet per minute of gas vented to the flare), the 

current state-of-the-art monitoring technology is ultrasonic flow meters. For flare 

gas composition, there are various methods, including taking grab samples to be 

analyzed in a laboratory, continuous gas chromatographs that collect and 

analyze a sample every 15 minutes, and continuous monitors that measure 

methane, total hydrocarbons, and sulfur compounds. There are advantages and 

disadvantages for each monitoring method. Grab sampling and subsequent lab 

analysis is simple but labor intensive, provides a “snapshot” of composition for 

the instant when it was taken, but is not available until hours after the sample 

was taken. Continuous gas chromatographs are complicated, require complex 

sample conditioning systems, may need much maintenance, but provide very 

detailed composition information every 15 minutes. Continuous monitors for 

methane, total hydrocarbons, and sulfur compounds also require complex 
44 

sample conditioning systems but provide continuous composition information for 

these compounds. 

8. What does monitoring tell us from an exposure standpoint and from a 

health effects standpoint? That is, how much exposure is the community 

getting and is this harmful to the health of the community members? Is 

there any additional concern for those who are chronically ill, are 

chemically sensitive, the young and the elderly? <PPH. 4/16/03> 

Flare monitoring for flow rate and flare gas composition will provide data that can 

be used to calculate emissions. Dispersion models can be used to calculate the 

air quality impact of the flare emissions. These air quality impacts can then be 

used to estimate exposure. Health professionals can evaluate the health 

impacts. Generally speaking, young children, the elderly, and those with 

respiratory illness are more sensitive to air pollution than healthy adults. 

9. Are all flares monitored? For instance, are there records of specific dates 

and times of flaring incidents over the last few months? <PPH. 4/16/03> 

The information available today is limited. The District has been conducting a 

study of flaring with the available data and has posted on its website 

(www.baaqmd.gov) preliminary flaring data covering the period from January 

2001 to August 2002. This data is preliminary and in many cases relies upon 

assumptions that may be revised. With new flare monitoring technology, much 

more reliable information will be available. 

10. When flares are monitored, how quickly is the monitoring information 

available to residents? What is the Air District plan for public notification? 

<PPH. 4/16/03> 

Refineries will be required to provide the District with a monthly report for each 

flare that will include flow and composition data. The District has not yet 

determined how best to provide this information to the public, but is considering 

the use of its website and perhaps other means. 

11. What is the breakdown of the emissions? What specific chemicals are 

monitored and what chemicals that are emitted are not monitored? Why 

aren’t all chemicals monitored? <PPH. 4/16/03> 

Emissions come from two primary mechanisms: oxidation of flare gases to other 

compounds and incomplete combustion that allows a small portion of the flare 

gas to pass through the flare uncombusted. Flare gas is generally composed 

primarily of methane, non-methane hydrocarbons, nitrogen, and hydrogen with 

small amounts of other compounds, including sulfur compounds. The primary 

combustion products are carbon dioxide and water, but sulfur compounds are 

oxidized to oxides of sulfur. The flare monitoring rule focuses on composition 

monitoring for methane, total hydrocarbons, and sulfur compounds because 
45 

these compounds form ozone and sulfur dioxide, and health-based ambient air 

standards have been established for both pollutants. 

12. How long will it be before the Air District implements measures that will 

reduce the amount of pollution being discharged by flares? <PPH. 

4/16/03> 

The District is currently completing its study of flares and expects to determine by 

summer how it will move forward to reduce flaring. The refineries have already 

significantly reduced flaring from 2001 and 2002 levels. 

13. How will the information and input be gathered from this and other 

meetings and from monitoring be used in rule-making regarding flaring? 

What is the timeline for rule-making? How can residents be involved in 

this process? <PPH. 4/16/03> 

Information provided from the public through the comment period, public 

hearings and other submittals and meetings have been considered in drafting the 

District's final monitoring proposal. We are still working on the flare study that 

will determine the next steps regarding potential controls on flares. Though the 

data we have developed through the study may not have the precision of the 

data that will come from the new monitors, it should be adequate to guide the 

District's decision about controls. The District expects that, if the study 

concludes that controls are available, the rule development effort to impose 

controls would be concluded by the end of 2003. The District will again consider 

comments that have already been received regarding controls, and residents will 

again be invited to participate and comment in the flare control rulemaking 

process. 

14. Are you documenting each of our questions? How are you going to 

respond to the community concerns? <Asthma Community Advocate 

(ACA). 4/16/03> 

The District is considering all comments and responding to all written comments. 

The proposed rule incorporates many community suggestions. 

15. Will there be a timeline for creating and implementing the rule? <ACA. 

4/16/03> 

The District Board of Directors will conduct a public hearing on May 21, 2003 at 

which it will consider adoption of the rule. 

16. Are there any consequences for the refineries if the designated timeline is 

not maintained? (fines, etc.) <ACA. 4/16/03> 

Yes. Failure to meet rule requirements would be a violation of the rule subject to 

potential enforcement action and penalties. 
46 

17. Are the refineries going to be allowed to continue to use flares for planned 

and routine use? <ACA. 4/16/03> 

The proposed flare monitoring rule does not impose restrictions on flare use. 

Consideration of flare controls is a separate process. See response to comment 

#13. 

18. How will non-accidental uses of flares be regulated and monitored? <ACA. 

4/16/03> 

The proposed rule would require monitoring of all flaring events from flares 

subject to the rule, accidental or not. Also see response #17. 

19. How will the public know what measures refineries are taking to implement 

technologies to reduce the need for flares in the first place? <ACA. 

4/16/03> 

Section 12-11-401 of the proposed rule requires that monthly reports on flaring 

include a description of any measures taken to reduce or eliminate flaring. 

20. How will this information be provided to the community? <ACA. 4/16/03> 

See response #10. 

21. Do the refineries have to wait to implement pollution controls until this 

flare rule is developed? <ACA. 4/16/03> 

No. One refinery has installed new compressors that allowed it to virtually 

eliminate routine flaring. Most of the refineries now have compressors that 

should allow them to avoid routine flaring. Nothing in this rule prevents refineries 

from moving forward with flare controls. 

22. Why isn’t the Air Board monitoring for hydrogen and nitrogen? <ACA. 

4/16/03> 

Hydrogen and nitrogen in the flare gas do not contribute directly to air pollution. 

When hydrogen is burned in a flare, it is converted to water. Flares use 

surrounding air to provide the oxygen for combustion. Air is about 20% oxygen 

and 80% nitrogen by volume. While a small amount of nitrogen in the air is 

converted to nitrogen oxides, which can contribute to ozone formation, nitrogen 

in flare gas would not increase emissions of nitrogen oxides. 

23. Don’t wait to implement pollution controls to reduce the need for flaresplanned, routine or accidental! <ACA. 4/16/03> 

See responses #13 and #21. 
47 

24. How is the public going to be notified about the findings of the flares? In 

real time? In plain English? What about the findings of the report? <ACA. 

4/16/03> 

Information about major flaring events is posted on the District's website. The 

monthly reports on flaring that are required by the proposed rule will be available 

to the public (see response #10). The flare study as revised will be available on 

the District website. 

25. We feel that someone from the West County Asthma Coalition should be 

kept updated on a routine basis by the Air Board about the flare issue. 

<ACA. 4/16/03> 

See response #24. We are happy to discuss flaring issues with the West County 

Asthma Coalition. 

26. We recommend requiring continuous analyzers for vent gas monitoring. If 

there is a malfunction of that equipment then manual sampling should be 

used. <ACA. 4/16/03> 

Continuous analyzers are an allowed option. Other options are allowed because 

continuous analyzers have never been installed on refinery flare headers, and 

the feasibility of this approach is not yet known. 

27. What are penalties or consequences if the monitoring requirements are not 

met? <ACA. 4/16/03> 

Failure to comply with the monitoring requirements would be a rule violation 

subject to potential enforcement action and penalties. 

28. We understand that the positioning of the camera could influence the 

reading of the emissions from refineries. So, is it possible to have more 

than one video recording device monitoring flares? There should be a time 

and date stamp. <ACA. 4/16/03> 

Cameras cannot be used to read emissions from flares. The rule requires 

monitoring of flow and composition using flow meters and other means that 

provide more reliable information than cameras. Cameras provide secondary 

information about the size and shape of the flame that cannot be used to 

determine the nature and quantity of emissions. The rule specifies minimum 

requirements for video monitoring. More than one camera would be allowed but 

not required. The proposed rule requires a time and date stamp. 

29. Flare images should be retained for at least 7 days, as opposed to a 

minimum of 72 hours. We understand that storage has come up as an 

issue, but how big an inconvenience is too big an inconvenience to store 

small video digital tapes? <ACA. 4/16/03> 
48 

The proposed rule now requires that the flare images for each month be 

recorded and submitted to the District. Tapes are not a reliable storage means. 

It is expected that video information would be converted to digital files and 

archived on DVDs or other storage media. 

30. Are video tapes going to be fully accessible to the public? Since this is 

public information, can it be available at public libraries or other public 

places, so the public won’t have to necessarily go through a government 

agency for access to the videos. <ACA. 4/16/03> 

It is unlikely that tapes will be used. It is more likely that images will be digitally 

recorded on DVDs or other media that can be read by computers. The District 

has not yet decided how to make the data available. 

31. Periodically, will public sharing of flaring videos be scheduled and 

presented in plain English? We recommend that if the Air Board is given 

24 hours notice, than any member of the public should be allowed to see 

any video. <ACA. 4/16/03> 

See response #30. 

32. How many years are you going to collect data before you require changes 

in industrial practices leading to a reduction in flares? <ACA. 4/16/03> 

See responses #12 and #13. 

33. What is your proof or data, that flare emissions are not impacting the 

health of the local community? <ACA. 4/16/03> 

All air pollutants have the potential to affect health, particularly for the young, the 

elderly, and those with respiratory illness. Flares are just one of many 

contributors to air pollution. Many other sources, including cars and trucks, 

contribute emissions, including sulfur emissions, that are similar to those from 

flares. Given that these flare emissions are not unique and that the causes of 

asthma, cancer, and many other illnesses are not well understood, it is unlikely 

that flare emissions can be identified as being responsible for a particular health 

problem. Nor can it be proved that they are not responsible. In general, it is well 

known that ozone and sulfur dioxide can, for example, trigger asthma attacks. 

As a result, the District works to reduce these pollutants, regardless of the 

source. 

34. Is there any proof that sulfur emissions from flares have no harmful health 

effects? <ACA. 4/16/03> 

See response #33. 
49 

35. In general, sulfur components trigger asthma, what proof do you have that 

sulfur emissions from flares have no harmful health effects? <ACA. 

4/16/03> 

See response #33. 

36. The short comment period has hampered our ability to thoroughly review 

the proposed rule. We strongly support a thorough and vigilant flare 

monitoring rule. We also support the detailed comments on this rule 

submitted by Communities for a Better Environment. <Holtzclaw, Sierra 

Club. E-mail. 4/17/03> 

The District understands the difficulty. The District is moving quickly to establish 

a flare monitoring rule that is thorough and responsive. Given the District's 

desire for an expeditious and efficient process, the additional comment period 

was necessarily short. 

37. We believe that web-posted video monitoring on real-time basis is 

necessary to establish and maintain a common tool for community, 

regulators and regulatees to reference in their communications. We urge 

the District to require that real time flare images be posted so that nearby 

folks can monitor the flares along with regulators and refinery personnel. 

With 24 hour real time video monitoring that is accessible, it may be 

possible to identify which wind and release conditions result in troubling 

air quality. <Holtzclaw, Sierra Club. 4/17/03> 

The proposed rule does not require web posting for the reasons discussed in the 

staff report (see discussion of Section 12-11-507). The flow and composition 

monitoring requirements of the rule are a much more reliable source of the 

information that would be necessary to assess air quality impacts. 

38. The exemption of Section 12-11-111 should include thermal oxidizers. 

Thermal oxidizers are highly efficient control devices, therefore all thermal 

oxidizer applications should be exempt from this rule. < Buchan, Western 

States Petroleum Association (WSPA). E-mail. 4/17/03> 

Thermal oxidizers are by definition exempt from the rule, but the exemptions of 

Sections 12-11-110, 112, 113, and 114 have been modified to make this clear. 

39. Modify the definition of "flare" to clarify the difference between flares and 

other combustion equipment. <Buchan, WSPA. 4/17/03> 

The definitions of "flare" and “thermal oxidizer” have been modified to accomplish 

this. 

40. A definition for “flare monitoring systems” is needed to identify all 

monitoring equipment that could fail and, therefore, come under the 
50 

equipment malfunction requirements of section 506.1. <Buchan, WSPA. 

4/17/03> 

The District has added a definition and clarified the monitor downtime provisions 

of Section 12-11-506.1. 

41. A definition for “day” is needed to clarify its usage throughout the 

regulation. We believe that a calendar day would simplify various 

recordkeeping requirements and is appropriate. <Buchan, WSPA. 4/17/03> 

The rule does not include the definition. Section 12-11-401.6 requires a "root 

cause" analysis if more than 1 million standard cubic feet of gas are flared in a 

24-hour period. This analysis would be required when flaring begins in the 

evening, and the 1 million standard cubic foot threshold is reached after 

midnight. Use of "day" instead of "24-hour period" would mean no analysis 

would be required under these circumstances. 

42. Changing the report due date to the end of the following month aligns the 

deadline for the flare reporting with several other monthly report deadlines 

so the reports can be submitted together. <Buchan, WSPA. 4/17/03> 

Section 12-11-401 has been modified to include this deadline. 

43. Adding an “(s)” to the reference [in Section 12-11-401] to flare headers 

clarifies the reporting requirements for flare systems with one or more 

headers feeding the same cascading or staged flare system. <Buchan, 

WSPA. 4/17/03> 

Section 12-11-401 has been modified to make it clear that only one report is 

required for such a system rather than individual reports for each flare in the 

system. 

44. Deletion of requirements for hourly data in section 401.1 and 401.3 is 

proposed because we believe that hourly data is overly burdensome and is 

not needed to determine emissions from the flares. <Buchan, WSPA. 

4/17/03> 

Hourly data will be generated by the monitors and can be easily provided in 

electronic format. During large flaring events, emissions can change significantly 

from hour to hour. 

45. Changes to section 401.4 are proposed to simplify the wording regarding 

purge gas data in the monthly report. <Buchan, WSPA. 4/17/03> 

The District believes the proposed language is clear. The suggested language 

would allow submission of daily averages under circumstances where more 
51 

detailed data is available. Where purge gas use is at a fixed rate, it would be 

permissible with our language to submit the daily average. 

46. Changes are proposed in section 401.6 to clarify the accumulation time for 

the 1.2 million standard cubic feet of vent gas and a requirement for hourly 

flow during such periods was added to ensure adequate data is collected 

for such flaring events. <Buchan, WSPA. 4/17/03> 

See response #41. 

47. The use of a 24-hr period unnecessarily compounds the data capture and 

reporting task. Instrument data is normally archived and presented in a 

simplified midnight to midnight basis. The use of another 24-hr period will 

require the execution of additional manual tasks that may result in a loss of 

the data automation accuracy from flow recording systems. Additionally, 

routine duties such as monitoring of flare event periods should match as 

closely as possible, the normal work routines and schedule of refinery 

personnel. The introduction of a task that is triggered by an unpredictable 

monitoring activity will require additional task execution by the operators. 

<Buchan, WSPA. 4/17/03> 

See response #44. Flow monitor data loggers can be easily programmed to 

recognize when the threshold has been reached. With either the proposed 

language or the WSPA language, the threshold could be reached at any hour of 

the day. 

48. We are willing to provide emissions calculations on using the 98% control 

efficiency basis. However, we wish to note that there are several studies 

that indicate that the flare hydrocarbon destruction efficiencies are 

typically higher than 98%. Therefore, the emission calculations will very 

likely be overestimating the actual flare hydrocarbon emissions. This fact 

should be taken into account when considering possible uses for these 

emission numbers. <Buchan, WSPA. 4/17/03> 

Comment noted. 

49. [In Section 12-11-501,] the minimum velocity should be 0.5 feet per 

second(fps) or 0.34 MPH. Based on our experience and the experience in 

the SCAQMD, a 0.5 fps zero cutoff will create false vent gas flow readings. 

These false readings are primarily caused by eddy currents and 

temperature changes within the flare stack. Due to the sensitivity of the 

flow meter at this very low flow setting, gas expansion due to daily 

changes in ambient temperature will result in signals of non-existent vent 

gas flows. Upon receiving these false signals, the operator must then 

monitor and report these “ghost” flows per 12-11-401 on a daily basis. To 

avoid this unnecessary low flow indication and subsequent reporting of 
52 

these miniscule false flows and false emissions, we request that the 

minimum velocity be 0.5 fps. <Buchan, WSPA. 4/17/03> 

The rule specifies that the flow monitoring device must continuously measure 

flow velocity from 0.5 to 275 feet per second because this is the range over 

which ultrasonic flow meter manufacturers (Panametrics and Roxar) guarantee 

highest accuracy. But Section 12-11-401 requires continuous flow monitoring 

and reporting of all flow data, not just flows above 0.5 foot per second. 

50. The requirement in Section 501.3 that the flow monitoring device 

continuously measure molecular weight should be to allow maximum 

flexibility in the type of flow meter used. Currently, the most likely type of 

flare flow meter does allow a continuous measurement of molecular 

weight. However, other acceptable flow monitoring instruments may 

become available and the molecular weight requirement may prevent use 

of any other flow instruments, limiting the flow monitoring to a single 

supplier. <Buchan, WSPA. 4/17/03> 

This requirement has been removed from Section 12-11-501. Section 12-11-

401.4 now specifies that this information must be reported if available from the 

meter. 

51. Section 502.2 does not allow enough time to properly design, review, order, 

and construct a safe sampling system. The section should be changed to 

allow 90 days. <Buchan, WSPA. 4/17/03> 

The section now allows 90 days rather than 60. 

52. The minimum sampling frequency of once per day [in Sections 502.2 and 

502.3] does not make sense if there is no flow. <Buchan, WSPA. 4/17/03> 

We have eliminated the requirement for daily sampling in favor of a trigger that 

would require sampling only when there is flow to the flare. 

53. The rate [of 50,000 standard cubic feet in one hour] triggering sampling 

and the frequency of sampling required [every 3 hours] seems excessive. 

We propose increasing the trigger for frequent sampling to a 100,000 

standard cubic feet event in one hour. This would still identify very small 

events (less than 50 pounds of hydrocarbon using typical vent gas 

composition). Sampling even smaller events would not provide any 

significant information and would significantly increase the cost for 

sampling and analysis. In addition, it would allow operators to focus on 

stopping even small flaring events rather than concentrate on verifying that 

samples have been taken for insignificant events. Also, we propose that 

the frequency for sampling such events should be reduced to once every 8 

hours. Generally, the vent gas composition during a flaring event does not 

change significantly over a period of 8 hours. Therefore, a sampling 
53 

frequency of once every 8 hours should be adequate. <Buchan, WSPA. 

4/17/03> 

In the proposed rule, the trigger for sampling was set at 6,000 standard cubic 

feet in 15 minutes. However, staff is now recommending that the trigger be 

modified to be identical to the trigger used in the South Coast AQMD rule (330 

standard cubic feet per minute continuously for 15 minutes). This change is 

included in the revised rule. 

To address community concerns that a sampling interval measured in hours 

would mean that composition would go unmonitored for too long during flaring 

events, the proposed rule specified integrated sampling at 15 minute intervals. 

Integrated sampling produces a composite sample out of aliquots (portions of the 

total sample size). Because the aliquots are taken over time, the sample reflects 

variation in composition that may occur over time. However, because this 

eliminated conventional sampling and meant that expensive sampling equipment 

or continuous analyzers would be required for numerous flares that are rarely 

used, recommended changes are included in the revised rule to add back a 

conventional sampling option with a sampling interval of three hours. Integrated 

sampling provisions are also retained. 

54. Section 506.1 changes are made to clarify that all monitoring equipment 

(see added definition for “flare monitoring system”) come under this 

section. Flare monitoring will require a significant amount of equipment. 

Since much of this monitoring will be new installations and will involve 

monitoring that has not typically been done in this application, it is likely 

that there will be more instrument downtime than an old, existing 

monitoring requirement. Therefore, we recommend that the wording in this 

section be made consistent with the continuous emission monitoring 

requirements found in Regulation 1-522.4. To accomplish this, the last 

sentence in 12-11-506.1 should be deleted. <Buchan, WSPA. 4/17/03> 

Rather than eliminate the sentence that limits downtime to 30 days in a calendar 

year, staff is recommending changes to the proposed rule to allow a 6-month 

delay in this requirement for integrated sampling, gas chromatography, and other 

continuous analyzers to allow time to identify and correct problems in the 

systems before the requirements come into effect. 

55. Section 506.2 requires manual sampling during periods of inoperation of 

continuous analyzers. This should extend to auto-samplers. We believe 

this was the District’s intent. <Buchan, WSPA. 4/17/03> 

This was our intent, but the change was not included in the proposed rule. The 

revised rule includes this change. 

56. Section 506.4 changes clarify that many in-line analyzers cannot provide 

one-minute averages since the analytical sampling period is greater than 
54 

once per minute. For example, most if not all hydrogen sulfide analyzers 

have a response time of 3 minutes or longer. Gas chromatography 

analyzers take 30 minutes or more for a complete analysis. Therefore, 

since many analyzers are incapable of providing one minute data, let alone 

averages, that portion of the section should be removed. <Buchan, WSPA. 

4/17/03> 

The section indicates that the data logger must be capable of recording oneminute averages. The District recognizes that composition data will not be one 

minute averages and need not be recorded as such. 

57. The requirement to archive video images for each 24-hour period should be 

changed to a requirement to archive the images for each day to clarify daily 

archiving of daily video monitoring. <Buchan, WSPA. 4/17/03> 

The proposed language change would not change the requirement. The “24-

hour” language was used to allow flexibility to produce a daily archive that runs 

from, for example 12 noon to 12 noon, rather than limiting it to a 12 am to 12 am 

day. 

58. EPA commonly allows an Equivalent Voluntary Consensus Standards Body 

to determine the most appropriate methods for analyses. Examples of this 

are ASTM, API and others. In this way, the rule need not be opened each 

time a more accurate, sensitive, or appropriate method is deemed more 

suitable for the analysis. <Buchan, WSPA. 4/17/03> 

The text of the proposed rule, in Section 12-11-601, did not address this issue. 

The revised rule addresses the issue, and allows subsequent revisions to 

methods to be used. 

59. Initial Studies with proposed Negative Declarations or Mitigated Negative 

Declarations require at least 20 days for public comment (30 days if 

submitted to the State Clearinghouse). See California’s Environmental 

Quality Act (CEQA) Guidelines, Sec. 15073(a). The BAAQMD published its 

Request for Comments online on April 7, 2003. Since comments are due 

today, April 17, 2003, the District has provided merely 10 days for public 

comment. Accordingly, OCE request that the District provide an 

explanation for the abbreviated comment period. <Costa, Our Children’s 

Earth Foundation (OCE). E-mail. 4/17/03> 

The document on which comments were requested was a draft initial study. No 

public review of a draft initial study is required by CEQA. Initial studies typically 

serve as the basis for an agency's conclusion about the appropriate CEQA 

document required for a project. If an agency decides that a negative declaration 

is the appropriate document, it must, at that point, indicate that it intends to adopt 

a negative declaration (which includes the initial study) and provide for the 

review period required by CEQA Guidelines section 15073. The District has now 
55 

made the negative declaration for this rule development project available for a 

review period exceeding 20 days. In asking for any comments on the draft initial 

study, the District was providing an opportunity for comment beyond those 

required by CEQA. 

60. The BAAQMD’s flare monitoring rule should require that the District take 

stack samples during flaring incidences, in normal weather conditions, to 

determine the amount of chemicals released into the atmosphere. <Costa, 

OCE. 4/17/03> 

Refinery and District safety requirements preclude sampling in the flare 

combustion zone. Remote sensing can be used to study combustion emissions. 

The District is following such a study being conducted under contract to the 

Texas Commission on Environmental Quality (TCEQ). 

61. The flare monitoring rule should require that the BAAQMD include all the 

emissions reported pursuant to the proposed rule in the emissions 

inventory to assess whether the Bay Area is making Reasonable Further 

Progress in the direction of compliance with NAAQS <Costa, OCE. 

4/17/03> 

The BAAQMD emissions inventory already includes flare emissions of 13 tons 

per day based on data from an earlier BAAQMD flare study (see the discussion 

regarding inventory issues in the Bay Area 2001 Ozone Attainment Plan on pp. 

6-7). Although the District's preliminary estimate in the current flare study was 

higher than 13 tons, the estimate was based in part on assumptions that will 

need to be revised to reflect data received after the estimate was made. 

Although the current study has not been finalized, emissions estimates will likely 

be lower than indicated in the draft study, and may be no higher for the study 

period than the 13 tons already included in the inventory. Data gathered through 

monitoring installed pursuant to the monitoring rule should provide a basis for 

estimating flare emissions that is far superior to the bases underlying previous 

estimates, and can be used to refine the inventory. 

62. The 98-99% destruction efficiency rate assumes that certain meteorological 

conditions are also being met. EPA studies conducted in the early 1980’s 

do not take into account environmental factors that may affect flare 

efficiency. “There is no suggestion [in the EPA study] that combustion 

efficiencies may depend on parameters that influence flame size, and 

consequently heat releases, such as stack velocities and wind speeds.” 

[Douglas M. Leahey, Katherine Preston and Mel Strosher, Theoretical and 

Observational Assessment of Flare Efficiency, 51 J. Air & Waste Mgmt. 

1610, 1616 (2001).] More studies should be done to determine the correct 

destruction efficiency rate. <Costa, OCE. 4/17/03> 

Most arguments about flare efficiency that have been made to the District are 

based on a selective reading of technical scientific and technical literature on the 
56 

subject, and much of that literature is not analytically robust. The Technical 

Committee of the BAAQMD Advisory Council is currently exploring the question 

of efficiency. In addition, an interesting flare efficiency study is currently being 

conducted by the Texas Commission on Environmental Quality (TCEQ). The 

study is expected to be completed in 2003, and the District will follow this effort 

and other relevant studies closely. The District agrees that a better 

understanding of flare efficiency is desirable, and expects that studies currently 

underway will promote a better understanding. 

63. Bay Area residents deserve to know about the pollution released in their 

own backyard; the BAAQMD should publish the flare monitoring reports 

online. <Costa, OCE. 4/17/03> 

See response #10. 

64. The flare monitoring rule should ensure that the monitoring data will 

disclose the amount of pollution that is actually released and ensure that 

the information is transparent so that Bay Area residents can interpret the 

data. <Costa, OCE. 4/17/03> 

This is the intent of the flare monitoring rule. 

65. BAAQMD should conduct further investigations to ensure that flare 

technology is satisfactorily destroying pollutants emitted through waste 

streams at these facilities in the Bay Area and to take an active role in 

requiring facilities to reduce the level of emissions produced through 

upsets, startup, shutdown, and maintenance events. <Costa, OCE. 

4/17/03> 

The District is following the TCEQ study on flare efficiency and other studies on 

flare efficiency. The flare monitoring rule requires monitoring but does not 

impose controls. See responses #13, #17, and #21. 

66. Reports of smoke are entirely dependent on visual observations made by 

workers at these facilities who may miss many events. BAAQMD must 

require accurate reporting of emission discharges from flare operating 

systems and improved reporting requirements so as to better distinguish 

between reporting of smoking flare events and opacity events which are 

not related to flares. <Costa, OCE. 4/17/03> 

Enforcement of smoking and opacity restrictions requires visual observation, and 

reporting is insufficient for enforcement purposes. Opacity monitoring required 

by 40 CFR §60.18 is based on Method 22, a visual observation method. The 

District uses visual observation methods to enforce a three-minute-per-hour 

smoke limit on all flares, whether they are subject to the NSPS or not. 
57 

67. Reports of VOCs, H2S, and other emissions should be based on much 

more accurate estimates of flare performance that take into account factors 

which diminish combustion efficiency. <Costa, OCE. 4/17/03> 

See response #62. 

68. Sources are required under state and federal law to ensure that flares will 

not smoke for more than five minutes in a consecutive two hour period. 

Yet, many sources report repeated violations of flares which smoke beyond 

five minutes in their upset reports. BAAQMD must enforce violations of the 

smoking flare requirements and ensure that sources are abiding by state 

and federal law. <Costa, OCE. 4/17/03> 

This statement is a direct quotation from a report by a New York environmental 

group on smoking flares in Port Arthur, Texas. It is not correct as a statement of 

California conditions or law. The BAAQMD enforces California and BAAQMD 

requirements that are more stringent than the cited standards. 

69. Recent studies indicate that flare combustion technology is not performing 

at expected levels of efficiency when conditions such as high wind speed 

are present. BAAQMD must require companies to improve current 

technology and enhance flare design to rectify the affects of 

meteorological conditions on flare combustion. <Costa, OCE. 4/17/03> 

This is also a direct quote from the Port Arthur, Texas report. See response #68. 

Regarding efficiency, see response #62. 

70. Notes need to be taken at ALL meetings- whether they are community 

meetings, public workshops, public hearings or work group meetings. 

<Cosentino, Communities for a Better Environment (CBE). E-mail. 

4/17/03> 

The District generally makes sound recordings of workshops but did not do so for 

the community meetings on the flare monitoring rule. It is important to note that 

the meetings were conducted in addition to, not in lieu of, an opportunity to 

submit comment. 

71. Notes from community and industry meetings need to be posted on the 

District’s website and distributed to all participants. Transparency in the 

rule making process is of benefit to everyone involved. <Cosentino, CBE. 

4/17/03> 

The District regularly meets with community members and with the industries it 

regulates. Many of these meetings are informal, and notes are not taken. 

District resources available to record these informal discussions are limited. At 

some point, commitment of resources to transcription of discussions takes away 

from the District’s ability to conduct outreach and solicit views. 
58 

72. Facilitation needs to be improved. The District should have both a 

facilitator and a “stacker” (to keep track of who raises their hand first and 

call on people) at all meetings. Also the stacker should help bring around a 

microphone which would ensure everyone can hear the public’s questions 

and comments as well as the Districts (the microphone would also record 

people’s comments). Everyone should be allowed to speak, and open 

discussion about issues should be encouraged. <Cosentino, CBE. 

4/17/03> 

Comment noted. These appear to be reasonable suggestions for conducting 

some formal meetings. 

73. Develop a follow up plan with the community. The District does not need 

to answer everyone’s questions in the meeting, but should develop a 

follow-up plan with the community as to how issues will be addressed by 

the District. <Cosentino, CBE. 4/17/03> 

Comment noted. This also appears to be reasonable for certain processes. 

74. An agenda needs to be provided ahead of time and should be posted and 

followed in the meeting. I understand the District intended to move quickly 

to adopt a flare monitoring rule. However, this should not be at the 

expense of a meaningful public process. I remind you that a false process 

such as this violates Environmental Justice Principles. Environmental 

Justice Principle #7 Environmental Justice demands the right to participate 

as equal partners at every level of decision-making, including needs 

assessment, planning, implementation, enforcement and evaluation. 

<Cosentino, CBE. 4/17/03> 

The District disagrees with the view that the process for developing this 

proposed rule was somehow a "false process." The meetings that were 

conducted provided a forum for discussion of a great many issues and concerns, 

and many members of the communities thanked us for the effort. We have also 

provided extensive opportunity for comment since the meetings. The District 

acknowledges that more productive feedback and discussion could have 

occurred if there were more time to complete the process. As you know, the 

2001 Ozone Plan as approved by the three regional agencies allowed to the end 

of 2003 to complete the further study measures. At the request of CBE and 

others, the District agreed to complete drafts of the further studies by the end of 

2002. This has left us with fewer resources to devote to the control measures in 

the Plan. 

75. I believe it would be of great benefit to the District in administering this 

rule, if the requirement was added for submittal of a Flare Monitoring Plan 

from each affected refinery. The required plan would include: 

Description of all flare monitoring and video monitoring equipment 
59 

proposed for compliance with the rule; 

Detailed description of manufacturer's specifications, including type, 

manufacturer, model, range, precision, accuracy, calibration and 

maintenance requirements, and recommended quality assurance 

procedures; 

Description of proposed sampling locations for each flare at the facility; 

Description of proposed type of gas composition sampling and analytical 

methods to be used for each flare at the facility; 

Description of selected flow verification test methods to be used; 

Description of data collection and management systems; 

Proposal for alternative sampling methods/protocols. 

I think that adding this level of structure to the new rule would benefit both 

the refineries and the District in overall execution of the new rule, 

especially considering individual system modifications over time. Wileen 

Sweet-Dodge, Environmental Manager, Emerald Hills, CA. E-mail. 4/17/03. 

The District considered this approach. The South Coast AQMD rule requires 

submission of monitoring plans that include these elements. However, 

incorporating a process for plan submission, review, and approval would 

substantially delay effectiveness of the rule. District staff ultimately decided that 

requirements for flare monitoring could be adequately put into effect and 

enforced through generic rule provisions. The District believes the proposed 

rule, in conjunction with other information-gathering tools, will allow it to obtain 

necessary facility-specific information, and to track changes that occur over time. 

76. Once a day gas composition sampling allowed by the rule completely 

invalidates its usefulness, and legally allows 11 or more tons per day of 

unmonitored hydrocarbon emissions, resulting in little or no progress 

toward monitoring and determining Bay Area flare emissions. <May, 

Communities for a Better Environment (CBE). E-mail. 4/17/03> 

This comment was based on the sampling trigger proposed in an earlier draft. 

The trigger level has since been modified and made more stringent relative to 

that earlier draft. Even with the trigger level in the earlier draft, all flows would be 

monitored for volume, and so it was not the case that 11 tons of emissions would 

go unmonitored. See response #1. 

77. Sampling should be required every 15 minutes rather than once per day. 

<May, CBE. 4/17/03> 

The current proposal allows four different approaches to sampling. Three of the 

four methods require sampling every 15 minutes or continuously. Manual 

sampling, which is also allowed, is likely to be used for flares that are used 

infrequently. Manual sampling would not be practical for flares used regularly 

because it would become cumbersome with regular use and would involve 
60 

unnecessary risks to workers. Even this manual sampling method is more 

stringent than the South Coast AQMD rule. 

78. Readily available and cheap autosampling should be required to protect 

workers from hazards and to facilitate more frequent sampling. <May, 

CBE. 4/17/03> 

Autosampling is one of the methods allowed in the rule. The rule continues to 

allow manual sampling because some flares have not been used in years, and 

imposing a requirement to install auto-samplers or continuous analyzers for 

these flares would not be reasonable. See response #77. All equipment, 

whether manual sampling equipment, auto samplers, or continuous analyzers 

require attention and maintenance and therefore some risk to workers. 

79. Available flow monitoring equipment has the capability to detect flows ten 

times lower than the 50,000 cu ft/hour threshold, making unnecessary the 

exemptions for lower flows where efficiency may be lower. <May, CBE. 

4/17/03> 

No version of the rule has included such an exemption. See response #2. 

80. The lax “flow verification” section (12-11-602) allows the choice between 

vague and undefined methods for quality control of flow measuring 

equipment and should be narrowed and defined. <May, CBE. 4/17/03> 

Section 12-11-602 has been revised to delete less well defined verification 

methods. Also see response #3. 

81. The flare efficiency is defined as 98% in the regulation, which does not 

account for conditions known to cause efficiency to go far below this 

number. <May, CBE. 4/17/03> 

Most arguments about flare efficiency that have been made to the District are 

based on selective readings of scientific and technical literature, and much of 

that literature is not analytically robust. The District expects that progress will be 

made in the near future towards understanding flare efficiency. For instance, the 

Technical Committee of the BAAQMD Advisory Council is currently exploring the 

question of efficiency. In addition, an interesting flare efficiency study is currently 

being conducted by the Texas Commission on Environmental Quality (TCEQ). 

The study is expected to be completed in 2003. 

The proposed rule did not require calculation of emissions by flare operators, 

and the specification in earlier drafts of the efficiency to be used was deleted. At 

the request of WSPA and the Unions at the May 8th flare workgroup meeting, 

the revised rule re-incorporates a requirement for emission calculations. The 

Unions suggested using the efficiencies specified in the Texas rule (98% for 
61 

most flares, 93% for low-BTU gases). While WSPA has argued for higher 

efficiency, the proposed rule includes the Unions’ suggestion. 

The reasoning behind specifying an efficiency figure, as articulated by the 

Unions and WSPA, seems to be that it is better to provide the public with some 

estimate of total emissions, even if the estimate employs some assumptions that 

are open to debate. District staff was persuaded by this reasoning, and so has 

incorporated assumed efficiencies in the revised rule. However, it is important to 

note that these efficiencies are set for the narrow purpose of emissions 

estimates to be made in reports submitted by refineries pursuant to the rule. The 

proposed rule does not restrict the District or anyone else from using a different 

efficiency figure in any other context. If the District does use a different efficiency 

figure, it will of course explain its reasoning for doing so. If more reliable 

information regarding flare efficiency becomes available, the District will consider 

revising the rule to reflect that information. 

82. The District should explore and report on available methods for 

determining flare efficiency and emissions in the atmosphere. <May, CBE. 

4/17/03> 

The Advisory Council Technical Committee is examining the question of flare 

efficiency. The District is also monitoring progress on the TCEQ study 

mentioned in response #62. 

83. Putting video monitoring of flaring on the web would allow District staff to 

instantly view in real-time the same incidents neighbors are reporting, and 

allow them to discuss flaring with refinery personnel as events are 

occurring. <May, CBE. 4/17/03> 

The proposed rule does not require web posting for the reasons discussed in the 

staff report (see discussion of Section 12-11-507). Video monitoring records 

must be submitted to the District each month. 

84. Video monitoring records should also be electronically stored at the 

District. <May, CBE. 4/17/03> 

See response #82. 

85. The current version of the rule actually neglects to require that the refiners 

submit the video image archives to the District with the monthly report. 

<May, CBE. 4/17/03> 

Section 12-11-401 has been revised to require submission to the District. 

86. The rule unnecessarily limits the requirement for storage of video 

monitoring to one frame per second, effectively reducing the video 
62 

monitoring to a bunch of snapshots that don’t show the full effect of flame 

characteristics. <May, CBE. 4/17/03> 

The video frame rate of the proposal is intended to ensure that electronic video 

files are of reasonable size so that they can be easily stored and distributed. 

This requires a frame rate of one frame per minute, the frame rate found in the 

proposed rule. At higher frame rates, files cannot be sent electronically and 

would require multiple DVDs per month to store the images for each flare. 

87. The recently added blanket exemptions for monitoring sulfur recovery 

plants and flexicoker gas ignore hydrocarbons present in these streams 

which can significantly add to flare emissions. <May, CBE. 4/17/03> 

The exemption in the earlier draft rule was not a “blanket exemption;” the 

exemption only exempted these flares from composition monitoring for 

hydrocarbons. Monitoring for flow and sulfur content was required. The 

proposed rule entirely deleted this exemption. District staff is now 

recommending in the revised rule to add back a more limited exemption for flares 

burning gas from a flexicoker. For these flares, the operator would have to 

monitor for flow and sulfur content. The limited exemption would allow an 

operator to avoid monitoring for hydrocarbons provided methane concentration 

was demonstrated to be less than 2% and non-methane hydrocarbon content 

was demonstrated to be less than 1%. 

88. Exemptions for monitoring flaring of operations of wastewater ponds, 

marine vessels, and storage tanks could represent huge emissions and 

should be removed. <May, CBE. 4/17/03> 

These exemptions are limited to thermal oxidizers for which emissions can be 

measured directly and to several small flares that serve as backup to vapor 

recovery systems. The one flare that is neither a thermal oxidizer nor a safety 

backup flare is one that controls emissions from a railcar loading operation at the 

Shell refinery. The staff report now includes a more detailed discussion of the 

exemptions and the sources to which they would apply. 

89. Equipment downtime less than 24 hours is exempt from reporting. <May, 

CBE. 4/17/03> 

The proposed Section 12-11-401.7 requires reporting of downtime exceeding 24 

hours. District staff are recommending in the revised rule to require that monthly 

reports include all downtime. This data for shorter downtime periods would 

generally be available in the monthly reports even without this explicit 

requirement because monitoring data from flow meters and continuous analyzers 

should be continuous data; all monitor downtime would then appear as data 

gaps. For CEMs, the refineries typically note data gaps due to meter downtime. 

Note that the rule requires calculation of flows if flow monitors are down, and 

sampling if continuous analyzers are down. 
63 

90. Both H2S and total sulfur need to be monitored (not total reduced sulfur 

which misses oxidized sulfur compounds-section 502.3 3.2). If only total 

sulfur is measured, then for purposes of compliance with federal Subpart J 

H2S limits, all of total sulfur must be considered as H2S. <May, CBE. 

4/17/03> 

Flare gas does not contain significant amounts of oxidized sulfur compounds. 

Monitoring of total reduced sulfur is appropriate for determining compliance with 

the Subpart J limits, which apply to flares that were subject to New Source 

Review and are used as control devices. 

91. Continuous monitoring is feasible, and monitoring “dirty” streams of fuel 

gas and sulfur recovery plants is common in Bay Area refineries. <May, 

CBE. 4/17/03> 

Continuous analyzers are used at refineries to monitor sulfur compounds in fuel 

gas and after sulfur recovery. Fuel gas is quite clean compared to flare gas, and 

any monitoring at sulfur recovery plants using sensitive equipment is 

downstream of sulfur recovery and required tail gas control units. No refinery in 

California or Texas has used continuous analyzers on flare vent gas. The rule is 

structured to encourage this approach, but other methods must be allowed to 

ensure that the rule will be workable. 

92. The public review process for this rulemaking had severe problems which 

can be avoided in the future. <May, CBE. 4/17/03> 

At the direction of the APCO/Executive Officer, the staff put the development of 

this rule on a fast track. As the commenter is aware, the 2001 Ozone Plan as 

approved by the three regional agencies allowed to the end of 2003 to put into 

effect control measures anticipated in the Plan. At the request of CBE and 

others, the District agreed to complete drafts by the end of 2002. It was 

foreseeable and perhaps inevitable that we would have to expedite this 

rulemaking effort and that other control measures will be similarly expedited. 

The District has tried to balance the need for an expedited process, as driven by 

Plan deadlines, with the desire expressed by many for a more thorough and 

deliberate rule development process. 

93. The rule proposed by the District would fail to detect up to 93% of flaring 

events, based on actual flaring data submitted by the Shell refinery, and 

would fail to detect up to 80% of flaring events at the ChevronTexaco 

refinery. Because of inadequate detection limits, the proposed rule would 

allow the flares to release over 28 million cubic feet per day of gases, or a 

total of 11 tons per day, without any monitoring. <Drury and Fox, Refinery 

Trade Unions - PSU Local 302, IBEW Local 549, Laborers Local 324, 

Insulators Local 16 (Unions). E-mail and messenger. 4/17/03> 
64 

None of this flow would be missed by flow meters. The comment is misleading in 

failing to state that the commenters are claiming that composition sampling 

would not be required for these flows because, in their opinion, the sampling 

trigger in the earlier draft was not sufficiently stringent (note that the revised rule 

includes the trigger level advocated by the Unions in their comments). The Shell 

and Chevron data is not "actual flaring data" and does not come from flow 

meters. It is based on calculations and estimates and therefore on average 

flows. Because averages would miss the variability that is found in actual flow 

meter measurements, the Shell and Chevron estimates provide no information 

that can be used to determine whether sampling would have been required 

under any proposed trigger. It can be said, however, that most of the Shell 

flaring events were of such short duration that no sampling would have been 

possible, regardless of the sampling trigger used. It is also important to note that 

the Shell and Chevron estimates indicate that these two refineries were together 

responsible for about 9% of all vent gas flared during the study period (excluding 

Shell's flexi-gas flare for which sampling or continuous analysis would clearly be 

required under either the earlier or current trigger proposal). 

94. The proposed rule is inadequate because it only requires once per day 

monitoring for most flaring events (Rule Section 502.3.3. I.a) except when 

the flow to the flares exceeds 50,000 cubic feet in any 60 minute period. 

The Bay Area's rule should be at least as stringent as the rules in Texas, 

Utah and Los Angeles. The rule should require automatic sampling or 

continuous composition monitoring every 15 minutes after any flow is 

detected above 0. 1 feet per second, and the sampling should continue 

every 15 minutes until the flaring ceases. <Drury and Fox, Unions. 

4/17/03> 

The composition monitoring trigger level in the revised rule is identical to that in 

the South Coast AQMD flare monitoring rule. However, the sampling frequency 

requirement is far more stringent than the South Coast rule because it requires 

samples every 15 minutes after the trigger level is reached if integrated sampling 

is used and every 3 hours if manual sampling is used. Note that manual 

sampling is not likely to be used if a flare is in regular use. See response #77. 

The South Coast rule only requires one sample per week once sampling is 

triggered. 

The Texas rule applies to flares that receive gas streams containing at least 5% 

highly-reactive VOCs (defined as 1,3 butadiene, butenes, ethylene, and 

propylene – see Title 30, Texas Administrative Code §115.10). Refinery flare 

gas typically contains less than 5% of these highly-reactive VOCs. The Texas 

rule was written for chemical plant flares and is not an appropriate comparator. 

The Utah rule applies to landfill gas collection systems and requires that flow rate

(not composition) be monitored every 15 minutes "to identify periods when the 

gas flow has been diverted from the control device or periods of no flow from the 
65 

collection system." The Utah rule therefore does not support the commenter’s 

assertion regarding frequency of composition monitoring. Regarding flow rate 

monitoring, the Utah rule is clearly less stringent than the proposed rule, which 

requires continuous monitoring of flow rate. 

95. The detection limits required by the rule will fall to detect many flaring 

events, despite the fact that much more accurate technology is readily 

available. <Drury and Fox, Unions. 4/17/03> 

The rule requires all flows to be measured and reported (see Section 12-11-401). 

The comment is based on a misinterpretation of Section 12-11-501, which 

specifies a series of requirements for any device used to measure flow. These 

requirements can, at present, be met only by ultrasonic flow meters. A major 

manufacturer guarantees these meters to be accurate to within 5% over the 

range from 1 to 275 feet per second. Specifying this flow velocity range does not 

mean that the meter does not measure lower flows; it just does so with reduced 

accuracy. 

96. The proposed rule only requires monitoring of what goes into the flare, not 

what comes out and assumes that 98% of flare gas is destroyed. An 

estimated efficiency of 98% should only be allowed when the requirements 

of 40 CFR §60.18 are met. At all other times, an estimated efficiency of 80% 

should be used, which is the lowest reported efficiency in studies relied 

upon by the District for a large flare. The BAAQMD should conduct a flare 

destruction efficiency study to analyze actual efficiency in the field, and the 

results of that study may be used to refine the rule. <Drury and Fox, 

Unions. 4/17/03> 

See response #81. 

97. The exemptions for marine vessel loading, sulfur recovery plant flares, 

flexicoker flares, thermal oxidizers, and organic liquid storage should be 

removed from the rule. <Drury and Fox, Unions. 4/17/03> 

The exemption for sulfur recovery plants and flexicoker flares was removed from 

the proposed rule. Staff is now recommending and has included in the revised 

rule a limited exemption for flexicoker flares. The staff report provides 

justifications for the other exemptions included in the rule. All of the exempted 

devices, except for flares exempted by Section 12-11-110, are thermal oxidizers, 

which, unlike flares, are enclosed combustion devices that exhaust combustion 

products through a duct or stack where they can be directly measured. The 

proposed rule requires monitoring of the gas input to flares because there is no 

readily-available means to directly measure flare emissions (though some 

remote sensing devices are being used in research). There is no useful purpose 

in imposing flare monitoring requirements on devices from which emissions can 

be directly measured. For a discussion of the flares exempted by Section 12-11-

110, see response #99. 
66 

98. The staff report provides no justification for the distinction between flares 

and thermal oxidizers or the assumed de minimus [sic] emissions. <Drury 

and Fox, Unions. 4/17/03> 

This comment was made on an earlier draft of the staff report. The staff report 

discussion of this issue has been expanded. As noted in response #92, thermal 

oxidizers and flares are different devices. The thermal oxidizer definition in the 

proposed rule (Section 12-11-209) clarifies this distinction. The Fox comments 

are incorrect in claiming that “a thermal oxidizer is a flare.” The distinction drawn 

between the two in most air pollution control literature is the same as that drawn 

by the added language: a thermal oxidizer exhausts combustion products 

through a duct or stack where emissions can be directly measured. For that 

reason, it would serve no useful purpose to impose requirements to monitor gas 

going to a thermal oxidizer when the combustion products can be directly 

measured in the stack. 

99. The exemption for organic liquid storage and distribution [in Section 12-11-

110] is not justified because emissions are high enough to warrant 

concern. <Drury and Fox, Unions. 4/17/03> 

The staff report states that this exemption would apply to six sources in the 

District: a backup safety flare for a propane tank at the Tesoro refinery, a similar 

flare for a butane sphere at the Valero refinery, three backup flares for vapor 

recovery systems on tanks at the Shell refinery, and a flare for the LPG railcar 

loading operation at the Shell refinery. All but the LPG loading flare are 

secondary control devices that are used when a vapor recovery system fails or is 

being maintained. The Fox comments claim that “the emissions from the Shell 

tank flares were 1.2 tons per year of VOCs and 0.1 ton/yr of SO2” as the basis 

for an argument that the flares should not be exempt from the rule. The VOC 

emissions are 6.6 pounds per day. From the perspective of the proposed rule, 

these emissions are de minimis and do not warrant the kind of monitoring that 

the rule requires for flares, which can potentially emit VOCs at a rate three or 

four orders of magnitude higher. In addition, all of these sources are control 

devices used to comply with other District regulations. 

100. The exemption for flares and thermal oxidizers used to control marine 

vessel loading should be eliminated because there is no data to confirm 

that they have negligible emissions. <Drury and Fox, Unions. 4/17/03> 

Thermal oxidizers are used at the Chevron, ConocoPhillips, and Shell refineries 

to meet Regulation 8, Rule 44 control requirements. No marine loading terminal 

uses a flare for control. The thermal oxidizers at the three marine terminals have 

high efficiencies that are mandated by the rule and by permit conditions and can 

be directly verified by source tests. Because these devices are, by definition, 

thermal oxidizers, they are not subject to the rule. This exemption is therefore 

included merely to clarify their exempt status. In any case, it would serve no 

useful purpose to impose the flare monitoring rule requirements on these devices 
67 

because emissions can be directly determined through a source test of the 

thermal oxidizer stack. 

101. The exemption for thermal oxidizers used to control emissions from 

wastewater treatment systems should be eliminated because emissions 

from wastewater systems are significant. <Drury and Fox, Unions. 

4/17/03> 

The Fox comment suggests that because wastewater treatment systems as a 

category may have significant emissions, thermal oxidizers that control 

wastewater sources should be subject to the flare monitoring rule. But emissions 

from thermal oxidizers are directly verifiable; imposing requirements to monitor 

gas flow to an oxidizer would be unnecessary. In any case, these devices are 

exempt by definition. See responses #98 and #100. 

102. Sulfur recovery plant flares should not be exempt because of the potential 

for organic emissions. <Drury and Fox, Unions. 4/17/03> 

This exemption has been dropped. 

103. Flexicoker flares should not be exempt from monitoring for hydrocarbon 

and methane composition because flexicoker gases may contain elevated 

concentrations of methane and other hydrocarbons. <Drury and Fox, 

Unions. 4/17/03> 

This exemption was dropped from the proposed rule. Staff are recommending 

and have included in the revised rule a limited exemption from hydrocarbon and 

methane monitoring (Section 12-11-114). The exemption is conditioned upon a 

weekly lab analysis showing that methane and non-methane hydrocarbons are 

not found in elevated concentrations (methane content must be less than 2% 

and non-methane hydrocarbon content must be less than 1%). 

104. The definitions of flare and thermal oxidizer are inadequate. <Drury and 

Fox, Unions. 4/17/03> 

These definitions have been clarified. Language in the definition of thermal 

oxidizer makes it clear that a thermal oxidizer exhausts combustion products 

through a vent, duct, or stack that allows direct measurement of combustion 

products. See response #98. 

105. The vent gas definitions should not exclude purge and pilot gases because 

only vent gas is monitored for composition, and these gases may contain 

hydrocarbons. <Drury and Fox, Unions. 4/17/03> 

Most of the flares at refineries in the District use water seals and do not use 

purge gas at all. For those that do, natural gas is used. Requiring composition 

monitoring would be pointless. If there were a reason to require this monitoring, 
68 

changing the definition of vent gas would not be the appropriate way to 

accomplish this purpose. 

106. The rule should be modified to require posting of monthly reports on the 

District website within 24 hours, placing copies in libraries, and 

preparation and distribution of CDs containing all supporting data. <Drury 

and Fox, Unions. 4/17/03> 

The District will consider use of the District website. See response #10. 

107. The reporting requirements allow emission calculations to assume a flare 

control efficiency of 98%. The studies do not support this assumption, and 

we recommend that the section be amended to adopt the TNRCC approach. 

<Drury and Fox, Unions. 4/17/03> 

See response #81. 

108. The language in Section 12-11-501.2 should be modified to read: “The 

device shall continuously measure velocity over the full potential range of 

operation of each covered flare, from a minimum velocity of 0.1 ft/sec to the 

maximum expected for each individual flare, but no lower than 275 ft/ sec. 

<Drury and Fox, Unions. 4/17/03> 

This comment reflects a concern that the specification (in Section 12-11-501.2) 

that the flow measurement device measures the velocity range from 0.5 to 275 

feet per second is a limitation on the requirement in Section 12-11-401 to report 

all flows. Section 12-11-501 is intended as a device specification that effectively 

dictates ultrasonic meters. The velocity specification does not mean that the 

meter is incapable of measuring lower flows; it just does so with reduced 

accuracy. 

109. We recommend that the rule be revised to require a minimum accuracy of 

5% over the entire flow range. <Drury and Fox, Unions. 4/17/03> 

The proposed rule did not include an accuracy specification for the flow 

monitoring device. The revised rule now includes an accuracy specification in 

Section 12-11-501. 

110. Section 501.4 should be modified to require that the monitor be located 'on 

the main flare header, after the knock-out pot and addition of any 

supplementary fuel' to assure that it measures the flow that is actually 

combusted. <Drury and Fox, Unions. 4/17/03> 

The suggested language is too prescriptive and, in some cases, would dictate 

the installation of a flow meter within the radiation zone of a flare. The heat 

would destroy the meter. 
69 

111. We recommend that Section 501.3 be modified to require molecular weight, 

temperature, and pressure to be continuously measured. <Drury and Fox, 

Unions. 4/17/03> 

Time of flight ultrasonic meters automatically make these measurements in order 

to produce volumetric flow outputs in standard cubic feet. Including these 

requirements in the device specification would preclude competing technologies 

that might offer superior performance without relying on these measurements. 

The proposed rule adds a requirement that molecular weight data be reported if 

available from the flow meter (Section 12-11-401). 

112. We recommend that Section 501.3 be modified to require that the monitors 

be maintained according to vendor specifications and annually calibrated 

to specifications. <Drury and Fox, Unions. 4/17/03> 

All drafts of the rule have included a requirement (in Section 12-11-506.3) that 

meters be maintained and calibrated in accordance with the manufacturer's 

specifications. 

113. Because of worker safety issues, we suggest that the rule state that 

manual sampling may be not be used. <Drury and Fox, Unions. 4/17/03> 

The proposed rule does not include a provision for manual sampling. However, 

District staff have concluded that manual sampling is an appropriate option for 

flares that are used infrequently. For these flares, which may combust vent gas 

less than once per year, installation of auto-samplers or continuous analyzers 

would be unreasonable. In addition, the maintenance necessary to keep this 

equipment in a state of readiness would involve greater worker exposure to risk 

than would an occasional need to sample manually. The revised rule therefore 

includes a manual sampling option. This option uses the stringent South Coast 

AQMD trigger for sampling. 

This manual sampling option would probably not be practical for flares that are 

used with some regularity. The need to continually take samples would be 

burdensome, and would likely result in missed samples. Because of these 

considerations, the District expects that the use of manual sampling will be 

restricted to low usage flares. 

114. The draft rule's trigger of 50,000 standard cubic feet in an hour with 

samples required within 15 minutes for auto-samplers and 30 minutes for 

manual sampling and with subsequent samples every three hours 

thereafter means that samples are taken at flows that are too high, too long 

after flaring starts, and too infrequently thereafter. The rule should be 

modified to require that sampling commence within 15 minutes of the 

detection of flow and to reduce the sampling frequency to every 15 

minutes. <Drury and Fox, Unions. 4/17/03> 
70 

At the flare workgroup meeting on April 18th, significant time was spent 

discussing the trigger level for composition sampling. Based on these 

discussions, the proposed rule specified a composition sampling trigger level of 

6,000 standard cubic feet in 15 minutes, which represented a flow velocity of 

approximately 0.5 feet per second, the lowest velocity that District staff felt would 

represent real flows to the flare (see response #1). At the May 8th workgroup 

meeting, refinery representatives suggested that the trigger was too sensitive, 

and the Unions proposed use of the South Coast AQMD trigger. The revised 

rule incorporates the South Coast sampling trigger, with sampling to begin within 

15 minutes. Sampling would then be required every 3 hours with the manual 

sampling option, every 15 minutes with integrated sampling, and continuously 

with continuous analyzers. These requirements for sampling frequency are far 

more stringent than the South Coast AQMD requirements (which specify one 

sample after the trigger is reached and a weekly sample thereafter). 

115. Section 12-1-502 should be revised to require that both total sulfur and H2S 

be measured because oxidized sulfur compounds are included in vent gas 

streams. <Drury and Fox, Unions. 4/17/03> 

Oxidized sulfur would not typically be found in flare vent gas in significant 

quantities. 

116. Section 502 should be modified to require that opacity and net heat content 

be monitored using the methods in 40 CFR 60.18 to ensure that the control 

efficiency is met. <Drury and Fox, Unions. 4/17/03> 

Opacity monitoring required by 40 CFR §60.18 is based on Method 22, a visual 

observation method. The District already uses visual observation methods to 

enforce a three-minute-per-hour limit on all flares, whether they are subject to the 

NSPS or not. The District standard is more stringent than the NSPS standard. 

Sampling, integrated sampling, and GC analysis already specified in the rule 

would provide composition data that would allow the heat content to be 

calculated. 

117. We recommend that Regulation 12, Rule 11 be expanded to require that 

each refinery use an optical, remote-sensing instrument capable of 

measuring both S02 and hydrocarbons in flare exhaust gases. <Drury and 

Fox, Unions. 4/17/03> 

Optical remote sensing equipment is currently used in flare efficiency research. 

This equipment is large, complicated, extremely costly, and requires highlytrained operators. Open-path passive FTIR systems rely on radiation differences 

between hot flare combustion gases and background and have higher limits of 

detection than active FTIR systems which use a radiation source. FTIR 

measurements depend upon keeping the plume within the instrument’s field of 

detection. Passive FTIR is not suitable for flare monitoring because the flare 

plume varies in size and shape with flaring rate and moves with wind. Flare 
71 

studies require skilled operators to ensure that the plume remains within the 

instrument’s window. 

118. We recommend that Section 506.1 be modified to require recordkeeping of 

all periods of monitor inoperation and monthly reporting of the 

accumulated downtime for each monitor. <Drury and Fox, Unions. 

4/17/03> 

District staff are recommending in Section 12-11-401.7 of the revised rule that all 

periods of monitor inoperation be reported. 

119. We recommend that Section 506.2 be modified to require that any facility 

electing to use a continuous analyzer must also obtain equipment to allow 

manual or auto-sampling when the continuous analyzer is down and use it 

to collect a minimum of one sample every three hours. <Drury and Fox, 

Unions. 4/17/03> 

In the revised rule, the sampling interval for manual sampling is three hours (see 

Section 12-11-502.3. When a continuous analyzer is down, this would be the 

default sampling interval. 

120. A new section should be added to Section 506 that requires that flow rate 

be estimated when the flow meter is out of service using either the 

methods in Section 602 and/or flame length as recorded by the video. 

<Drury and Fox, Unions. 4/17/03> 

This section in the revised rule now requires that flow be estimated using good 

engineering practices, which would allow use of the methods in Section 602, a 

flame length method, or other methods as available. 

121. We recommend that Section 506.3 be modified to require annual 

maintenance and field zeroing of ultrasonic velocity meters. <Drury and 

Fox, Unions. 4/17/03> 

All drafts of the rule have included a requirement (in Section 12-11-506.3) that 

meters be maintained and calibrated in accordance with the manufacturer's 

specifications. 

Written Comments Received in Connection with May 21st Hearing 

The public hearing notice for the May 21st hearing on the revised rule indicated that comments 

would be accepted during the period from April 21st to May 12th. No comments were received 

during that period, but the following comments were received just prior to the May 21st hearing. 

122. Section 401.7 waives reporting requirements during monitoring system 

breakdowns less than 24 hours. BAAQMD should consider revising this 
72 

section to assure that the 24-hour reporting exemption due to monitoring 

system breakdowns is reduced or eliminated. <EPA. E-mail. 5/20/03> 

EPA examined the proposed rule. The revised rule requires reporting of all 

monitor downtime. 

123. Section 506 waives monitoring requirements during breakdown conditions. 

BAAQMD should consider revising this section consistent with more 

stringent requirements in South Coast Rule 1118 and to assure that 

breakdown exemptions are as short as possible. <EPA. 5/20/03> 

Section 12-11-506 does not waive monitoring requirements during breakdown. 

Unlike the South Coast rule, Section 12-11-506 would require alternative 

monitoring during periods of monitor inoperation. In addition, the composition 

monitoring required during downtime of automated composition analyzers is 

more stringent than any composition monitoring required by the South Coast 

rule. 

124. ASTM Method UOP 539-97, referenced in Section 601, has not been 

reviewed by EPA for use in SIP-approved rules. BAAQMD should submit 

this method for EPA review. <EPA. 5/20/03> 

The proposed rule specifies ASTM Method UOP 539-97 as one of three methods 

that may be used for the required analysis of vent gas samples. UOP 539-97 is 

the only ASTM method developed specifically for the analysis of the composition 

of refinery fuel gas, which may include up to 25% hydrogen sulfide. The 

proposed rule is a monitoring rule only, and as such, does not include any 

emission limitations. ASTM Method UOP 539-97, if used, would not be used to 

determine compliance. Therefore the District does not believe that it must be 

submitted to EPA for review. 

125. Section 602, Flow Verification Test Methods, provides broad discretion for 

establishing methods to verify vent gas flow. Since this parameter is so 

critical to the rule, paragraphs 602.3, 602.4 and 602.5 should be revised to 

provide greater specificity on the verification methods that may be used. 

We are also concerned that the limit of detection for the methods in 

paragraphs 602.1 and 602.2 (4-6 feet per second) is not sensitive enough 

given the requirement in paragraph 501.1(0.1 feet per second). <EPA. 

5/20/03> 

Section 12-11-506.3 requires ultrasonic flow meters to be maintained and 

calibrated in accordance with manufacturer’s specifications. Properly maintained 

and calibrated ultrasonic flow meters are extremely accurate. No test method 

has been developed to test these meters in place once they have been 

calibrated and installed. To get a rough check on accuracy requires the use of 

existing less-accurate approaches such as pitot tube traverses, tracer gas 

methods, or other flow or process meters. The meters are more accurate than 
73 

any of these alternative approaches. No other flare monitoring rule even 

includes provisions that attempt to make this check (see South Coast Rule 

1118). The BAAQMD provision was developed to provide a means to identify 

large errors that might result from misinterpretation of the meter’s specified range 

and calibration factor. The District is proposing to revisit the rule in 18 months, 

review the data developed from the use of various alternatives, and make any 

appropriate changes in these provisions. 

126. Section 502.3.1: The last sentence in Section 502.3.1.a states “In no case 

shall a sample be required more frequently than once every 3 hours.” We 

do not believe it is appropriate to relieve a facility from the requirement to 

initiate sampling within 15 minutes of exceeding the flow rate threshold 

specified if one “threshold event” is followed by another within two hours 

of the final sample taken during the initial event. It is unclear why this 

change was made or how it would be implemented. We recommend the 

following modification: “In no case shall a sample be required more 

frequently than once every 3 hours during periods of flaring that 

continuously exceed the sampling threshold.” <ARB. E-mail. 5/20/02> 

The District proposal is far more stringent than South Coast sampling provisions 

(which require one sample near the beginning of a flaring event and once per 

day thereafter during the event). The District provisions are intended to ensure 

that sampling is not required more frequently than is reasonably necessary for 

adequate data while ensuring feasibility and personnel safety. The District 

believes the proposed sampling requirements will provide the data necessary to 

adequately characterize the flare activity. 

127. Section 506.1: We do not believe it appropriate to provide for “periods of 

inoperation” for purely manual sampling operations as proposed in Section 

506.1. We recommend the following change: “Periods of inoperation of the

vent gas auto-samplers installed pursuant to composition monitoring 

specified in Section 12-11-502.3.1 (grab sampling) shall not exceed 30 days 

per calendar year.” <ARB. 5/20/02> 

The District agrees that downtime for purely manual sampling is not appropriate. 

This section has been changed. 

128. Section 506.1: This section states: “Effective 450 days after the adoption 

of this rule, periods of inoperation of the vent gas composition monitoring 

specified in Section 12-11-503.3.3 (continuous analyzers) shall not exceed 

30 days per calendar year per analyzer.” We believe the appropriate 

reference section is “Section 12-11-5032.3.3”. <ARB. 5/20/02> 

The District agrees. This section has been changed. 

129. Section 506.2: During periods of inoperation of continuous analyzers or 

auto-samplers installed pursuant to Section 12-11- 502.3, we believe 
74 

persons responsible for monitoring should be required to take samples as 

specified in Section 12-11-502.2. We recommend the following changes in 

the sections referenced in 506.2: “During periods of inoperation of 

continuous analyzers or auto-samplers installed pursuant to Section 12-11-

502.3, persons responsible for monitoring shall take manual samples as 

required by Section 12-11-502.32.1.” <ARB. 5/20/02> 

The District believes the sampling provisions for downtime are adequate to 

provide data necessary to characterize flaring during these periods. Staff 

reviewed its database for existing monitors in sulfur plants and fuel gas service 

(a service that is most similar to flare gas service) that were reported out of 

service pursuant to the CEM downtime provisions. These periods were 

infrequent, and it is anticipated that this will be the case for flare monitoring. 

130. Section 507: We believe the one frame per minute video recording 

specification in Section 507 should be increased such that the recorded 

image is more representative of a real time recording and that each facility 

be required to archive their captured video data on a hard drive, and make 

specific portions of the archived data available to the district upon request. 

Due to the ability of current technology to store large volumes of digital 

data on one large hard drive (80 gig), we believe this approach will enable 

capture rates in excess of one frame per minute while still providing for a 

reasonable archive retention time (at least two weeks, possibly one month). 

<ARB. 5/20/02> 

The District is now proposing to refer the issue of webcasting to the Stationary 

Source Committee of the Board. To avoid imposing video recording and storage 

requirements that would require immediate decisions about technology that 

might prove to be inconsistent with later recommendations of the Stationary 

Source Committee, the District is proposing to push back the effective date of 

this provision to allow further study of webcasting and related issues. Section 

12-11-507 has been modified to be effective 180 days after rule adoption rather 

than 90 days to allow the necessary time for this effort. 

131. Section 602: Due to the flexibility provided in the flow verification 

requirements of Section 602, we recommend each facility be required to 

submit a proposed flow verification plan that must be approved by the 

district prior to its implementation. <ARB. 5/20/02> 

The District considered this option in the early stages of the workgroup meetings. 

South Coast Rule 1118 includes plan submittal requirements for flare monitoring. 

(Note that the South Coast rule has no flow verification requirements like those 

to which this comment refers.) The District believes that including plan submittal 

requirements for flow verification would add unnecessary delay in implementing 

the flow and composition monitoring requirements of the rule. The District is 

proposing to revisit the rule in 18 months, review the data developed from the 
75 

use of various verification methods, and propose any necessary changes to 

these provisions. 

132. The BAAQMD should adopt the Texas Rule under which an estimated 

efficiency of 98% should be allowed only when the requirements of 40 CFR 

§60.18 are met. At all other times, an estimated efficiency of 93% should be 

used. <Drury, Refinery Trade Unions - PSU Local 302, IBEW Local 549, 

Laborers Local 324, Insulators Local 16 (Unions). E-mail. 5/20/03> 

The Texas rule does not apply to refinery flares (see response #94). District staff 

contacted TCEQ and confirmed this point. Nevertheless, the revised rule 

incorporated the concept of specifying an efficiency of 98% except for low-BTU 

gas. In the reviseed rule, 98% was specified except for the flexicoker flare, for 

which 93% was the default value. This flare handles flexicoker gas that has a 

low heating value. Staff are now proposing a change that requires the use of 

93% for any vent gas with a lower heating value less than 300 British Thermal 

Units/Standard Cubic Feet (BTU/SCF)and therefore would not meet the 

requirements of 40 CFR §60.18. This is a minor change because data gathered 

during the flare study shows that most flare gas, with the exception of flexicoker 

gas, exceeds this BTU threshold. 

133. The BAAQMD should conduct a flare destruction efficiency study to 

analyze actual efficiency in the field, and the results of that study may be 

used to refine the rule. <Drury, Unions. 5/20/03> 

See responses #81 and #96. 

134. Webcasting: The rule would be greatly improved by requiring 

“webcasting” of flare video-monitoring. Webcasting would allow any 

interested member of the public, including Air District staff and Board 

members, to see what is happening with refinery flares in “real time” 

simply by clicking on a page on the BAAQMD’s website. Air District staff 

could verify public complaints of refinery flaring instantly simply by 

clicking on the website. Webcasting is a low-cost and widely available 

technology. <Drury, Unions. 5/20/03> 

To discuss webcasting and other issues, the District convened a meeting of the 

flare workgroup immediately following the May 21, 2003 Board meeting. 

Representative from WSPA, the individual refineries, refinery labor unions, and 

CBE attended this meeting. The consensus of all present was that the 

webcasting issue should be separated from the proposed rule and that the 

proposed rule should be adopted and implemented. District staff is 

recommending that the webcasting issue be referred to the Board’s Stationary 

Source Committee. 

135. As you are well aware, the rate of asthma has climbed dramatically in the 

past decade, and ozone has been documented to have a direct connection. 
76 

Of course, we are also concerned about particulate matter in release of 

emissions, as well as other chemicals. We agree that the videotaped 

footage of flaring required by the rule be placed on the web so that 

BAAQMD can view the same images that the public is seeing. And we also 

ask that the rulemaking begin soon to control flare emissions, not simply 

to monitor. <Weiner, American Lung Association of San Francisco and San 

Mateo Counties (ALA). E-mail. 5/20/03> 

Ozone exposure in the Bay Area has declined at the same times that asthma 

rates have increased. The weight of the evidence suggests that ozone is not 

responsible for increases in Bay Area asthma rates. While it is true that high 

ozone levels can trigger asthma attacks, high levels are uncommon in the Bay 

Area. 

Regarding webcasting, see response #134. The District's flare workgroup is still 

working on the flare study that will determine the next steps regarding potential 

controls on flares. The District expects that if the study concludes that controls 

are available, the rule development effort to impose controls could be concluded 

by the end of 2003.