SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT

463 - 1 

(Adopted August 15, 1977)(Amended June 1, 1984)(Amended December 7, 1990) 

(Amended March 11, 1994)(Amended May 6, 2005) 

(Amended November 4, 2011) 

RULE 463. ORGANIC LIQUID STORAGE 

(a) Purpose and Applicability 

The purpose of this rule is to reduce emissions of volatile organic compounds 

(VOC) from the storage of organic liquids in stationary above-ground tanks. This 

rule applies to any above-ground stationary tank with a capacity of 75,000 liters 

(19,815 gallons) or greater used for storage of organic liquids, and any aboveground tank with a capacity between 950 liters (251 gallons) and 75,000 liters 

(19,815 gallons) used for storage of gasoline. 

(b) Definitions 

For purposes of this rule, the following definitions apply: 

(1) ACTUAL STORAGE CONDITIONS means the temperature at which a 

product is stored in an above ground stationary tank. 

(2) AMBIENT TEMPERATURE is the temperature of an organic liquid 

within a storage tank that has been influenced by atmospheric conditions 

only and is not elevated by a non-atmospheric means of heating at the tank 

which includes but is not limited to steam, hot water, heaters, heat 

exchangers, tank insulation, or tank jacketing. 

(3) CERTIFIED PERSON is an individual who has successfully completed 

the District tank self-inspection program, and who holds a certificate 

issued by the Executive Officer evidencing that such individual is in good 

standing in this program. 

(4) DRAIN-DRY BREAKOUT TANK is an above-ground storage tank 

designed such that the floating roof rests on support legs no higher than 

one foot along the tank shell with a bottom sloped to a sump or sumps 

such that no product or sludge remains on the tank bottom and walls after 

emptying except clingage and is primarily used to receive product from 

pipelines and to distribute product back into pipelines. 

(5) EXEMPT COMPOUND is as defined in Rule 102. 

(6) GASOLINE means any petroleum distillate having a Reid vapor pressure 

of 200 mm Hg (3.9 pounds per square inch), or greater. 

(7) HEAVY CRUDE OIL means a crude oil with American Petroleum 

Institute (API) gravity 20 degrees or less. 
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(8) ORGANIC LIQUID is any liquid containing VOC. 

(9) PRESSURE RELIEF VALVE (PRV) is a valve which is automatically 

actuated by upstream static pressure, and used for safety or emergency 

purposes. 

(10) SEAL is a closure device between the tank wall and the floating roof edge 

that controls emissions of VOCs. Approved floating roof tank seals are 

categorized as follows: 

(A) Category "A" seals are seals approved by the Executive Officer as 

most effective in the control of VOCs and are deemed Best 

Available Control Technology (BACT) according to the criteria set 

forth in Attachment A - "Floating Roof Tank Seal Categories." 

(B) Category "B" seals are seals approved by the Executive Officer 

that are considered more effective than Category "C" seals based 

on the criteria set forth in Attachment A - "Floating Roof Tank 

Seal Categories." 

(C) Category "C" seals are seals approved by the Executive Officer 

which are currently in service but are considered least effective in 

the control of VOCs. 

(11) TANK is any stationary above-ground reservoir or any other stationary 

above-ground container used for storage of an organic liquid. 

(12) VAPOR TIGHT is a condition that exists when the reading on a portable 

hydrocarbon meter is less than 500 parts per million (ppm), expressed as 

methane, above background. 

(13) VOLATILE ORGANIC COMPOUND (VOC) is as defined in Rule 102. 

(14) WORKING DAY is Monday through Friday and includes holidays that 

fall on any of the days Monday through Friday. 

(c) Tank Roof Requirements 

No person shall place, store or hold in any tank with a capacity of 150,000 liters 

(39,630 gallons) or greater, any organic liquid having a true vapor pressure of 25.8 

mm Hg (0.5 psi) absolute or greater under actual storage conditions, and in any 

tank of more than 75,000 liters (19,815 gallons) capacity, any organic liquid 

having a true vapor pressure of 77.5 mm Hg (1.5 psi) absolute or greater under 

actual storage conditions, unless such tank is a pressure tank maintaining working 

pressures sufficient at all times to prevent organic vapor loss to the atmosphere, or 

is designed and equipped with one of the following vapor control devices, or other 
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vapor control device that has been determined to be equivalent after review by the 

staffs of the District, the Air Resources Board (ARB), and the United States 

Environmental Protection Agency (U.S. EPA), and approved in writing by the 

District Executive Officer, ARB, and U.S. EPA, which is properly installed and 

continuously maintained in good operating condition: 

(1) External Floating Roof 

An external floating roof shall consist of a pontoon-type or double decktype cover that continuously rests on the surface of the organic liquid and 

is equipped with a closure device between the tank shell and roof edge. 

The closure device shall consist of two seals, with one seal placed above 

the other. The seal below shall be designated as the primary seal, and the 

seal above shall be designated as the secondary seal. A seal which is not 

identified on the current list of seals approved by the Executive Officer 

shall not be installed or used unless the Executive Officer determines that 

such seal meets the applicable criteria of subparagraphs (c)(1)(A) through 

(c)(1)(C). 

(A) A closure device on a welded or a riveted tank shell which uses a 

metallic shoe-type seal as its primary seal shall comply with the 

following requirements: 

(i) Gaps between the tank shell and the primary seal shall not 

exceed 1.3 centimeters (1/2 inch) for a cumulative length of 

30 percent of the circumference of the tank, and 0.32 

centimeter (1/8 inch) for 60 percent of the circumference of 

the tank. No gap between the tank shell and the primary 

seal shall exceed 3.8 centimeters (1-1/2 inches). No 

continuous gap between the tank shell and the primary seal 

greater than 0.32 centimeter (1/8 inch) shall exceed 10 

percent of the circumference of the tank. 

(ii) Gaps between the tank shell and the secondary seal shall 

not exceed 0.32 centimeter (1/8 inch) for a cumulative 

length of 95 percent of the circumference of the tank. No 

gap between the tank shell and the secondary seal shall 

exceed 1.3 centimeters (1/2 inch). 

(iii) Metallic shoe-type seals installed on or after August 1, 

1977 shall be installed so that one end of the shoe extends 

into the stored organic liquid and the other end extends a 
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minimum vertical distance of 61 centimeters (24 inches) 

above the stored organic liquid surface. 

(iv) The geometry of the shoe shall be such that the maximum 

gap between the shoe and the tank shell is no greater than 

double the gap allowed by the seal gap criteria specified in 

clause (c)(1)(A)(i) for a length of at least 46 centimeters (18 

inches) in the vertical plane above the liquid surface. 

(B) A closure device which uses a resilient toroid-type seal as its 

primary seal shall comply with the applicable requirements of 

subparagraph (c)(1)(A). 

(C) The primary and secondary seals shall comply with the following 

requirements: 

(i) The primary seal envelope shall be made available for 

unobstructed inspection by the Executive Officer along its 

circumference. In the case of riveted tanks with resilient 

toroid-type seals, at least eight such locations shall be made 

available; for all other types of seals, at least four such 

locations shall be made available. If the Executive Officer 

deems it necessary, further unobstructed inspection of the 

primary seal may be required to determine the seal's 

condition along its entire circumference. 

(ii) The secondary seal shall be installed in a way that permits 

the Executive Officer to insert probes up to 3.8 centimeters 

(1-1/2 inches) in width to measure gaps in the primary seal. 

(iii) The secondary seal shall extend from the roof to the tank 

shell and shall not be attached to the primary seal. 

(iv) Notwithstanding the secondary and the primary seal 

requirements of paragraph (c)(1), a secondary or primary 

seal may be loosened or removed for preventive 

maintenance, inspection or repair for a period not 

exceeding 72 hours with prior notification to the Executive 

Officer. 

(D) All openings in the roof except pressure-vacuum valves, shall 

provide a projection below the liquid surface to prevent belching, 

escape, or entrainment of organic liquid, and shall be equipped 

with a cover, seal or lid. The cover, seal, or lid shall at all times be 
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in a closed position, with no visible gaps, except when the device 

or appurtenance is in use. Pressure vacuum valves shall be set to 

within 10 percent of the maximum allowable working pressure of 

the roof. 

(E) There shall be no holes, tears or openings in the secondary seal or 

in the primary seal envelope surrounding the annular vapor space 

enclosed by the roof edge, seal fabric, and secondary seal. 

(F) Any emergency roof drain shall be provided with a slotted 

membrane fabric cover, or equivalent device, that covers at least 

nine-tenths (9/10) of the area of the opening. 

(2) Internal Floating-Type Cover 

A fixed roof tank equipped with an internal floating-type cover shall 

comply with the following requirements: 

(A) A fixed roof tank with an existing internal floating-type cover 

approved by the Executive Officer on or before June 1, 1984, shall 

comply with the requirements applicable at the time such approval 

was given. 

(B) A fixed roof tank which has an internal floating-type cover 

installed, modified, or replaced after June 1, 1984, shall have a 

closure device which consists of either a single liquid mounted 

primary seal or a primary and a secondary seal. All openings and 

fittings shall be fully gasketed or controlled in a manner specified 

by the Executive Officer. The closure device shall control vapor 

loss with an effectiveness equivalent to a closure device which 

meets the requirements of subparagraph (c)(1)(A). Seal designs 

not identified on the current list of seals approved by the Executive 

Officer shall not be installed or used unless the Executive Officer 

has given his prior written approval to its installation or use. For 

purposes of this paragraph, modification includes an identical 

replacement. 

(C) The concentration of organic vapor in the vapor space above the 

internal floating-type cover shall not exceed 50 percent of its lower 

explosive limit (LEL) for those installed prior to June 1, 1984 and 

30 percent of its LEL for those installed after June 1, 1984. 

Compliance shall be verified by the use of an explosimeter. 
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(3) Vapor Recovery System 

A fixed roof tank equipped with a vapor recovery system shall comply 

with the following requirements: 

(A) Any tank gauging or sampling device on a tank vented to the vapor 

recovery system shall be equipped with a vapor-tight cover which 

shall be closed at all times except during gauging or sampling. The 

roof of such tank shall be properly maintained in a vapor tight 

condition with no holes, tears or uncovered openings. 

(B) All piping, valves and fittings shall be constructed and maintained 

in a vapor-tight condition, in accordance with requirements of 

other District rules for such equipment. 

(C) For purposes of this paragraph, the efficiency of a vapor recovery 

system shall be determined by making a comparison of controlled 

emissions to those emissions which would occur from a fixed cone 

roof tank holding the same organic liquid without a vapor control 

or vapor recovery system. The vapor recovery system shall have 

an efficiency of at least 95 percent by weight, or vent tank 

emissions to a fuel gas system. 

(d) Other Performance Requirements 

(1) A person shall not place, store or hold gasoline in any tank, with a capacity 

of between 950 liters (251 gallons) and 75,000 liters (19,815 gallons) 

unless such tank is equipped with a pressure-vacuum valve which is set to 

within 10 percent of the maximum allowable working pressure of the 

container, or is equipped with a vapor loss control device which complies 

with the requirements set forth in subdivision (c).

(2) The roof of any internal or external floating roof tank shall float on the 

organic liquid at all times (i.e., free of the roof leg supports) except when 

the tank is being completely emptied for cleaning, or repair. The process 

of emptying or refilling, when the roof is resting on leg supports, shall be 

continuous. 

(3) If a tank has been gas-freed and is to be refilled with gasoline, the roof 

shall be refloated with water or by an equivalent procedure approved by 

the Executive Officer. Paragraphs (d)(2) and (d)(3) shall be inapplicable 

to gasoline storage tanks at bulk gasoline distribution terminals which do 

not have: 
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(A) existing facilities for treatment of waste water used to refloat the 

tank roof; or 

(B) facilities for equivalent emission control when refloating the roof 

with organic liquid. 

(4) A fixed roof tank with an internal floating-type cover or a tank with an 

external floating roof cover shall not be used for storing organic liquids 

having a true vapor pressure of 11 psia (569 mm Hg) or greater under 

actual storage conditions. 

(5) Replacement of a seal on a floating roof tank shall be allowed only if the 

replacement seal is chosen from the current list of seals approved by the 

Executive Officer. Category "A" seals shall be replaced only by Category 

"A" seals. Category "B" seals shall be replaced only by Category "A" or 

Category "B" seals. Category "C" seals shall be replaced only by Category 

"A" or Category "B" seals. 

(6) Organic liquids listed on the addendum to this rule shall be deemed to be 

in compliance with the appropriate vapor pressure limits for the tank in 

which it is stored provided the actual storage temperature does not exceed 

the corresponding maximum temperature listed. 

(e) Self-Inspection of Floating Roof Tanks 

Any owner or operator of a floating roof tank(s) shall conduct self-inspections of 

its tank(s) according to the following procedures: 

(1) Inspection and Maintenance Plan 

(A) Each owner or operator shall maintain a current or revised 

Inspection and Maintenance Plan approved by the Executive 

Officer. Each owner or operator constructing floating roof tank(s) 

subject to this rule shall submit an Inspection and Maintenance 

Plan, or a revision of its current Inspection and Maintenance Plan, 

to the Executive Officer prior to the completion of construction. 

The Inspection and Maintenance Plan shall include an inventory of 

floating roof tanks subject to this rule, the proposed self-inspection 

schedule, the number of certified persons to be dedicated to the 

program, any self-inspection procedures proposed in addition to 

those required by the District, and a copy of the owner or operator's 

safety procedures used for floating roof tanks. The tank inventory 

shall include tank identification number, maximum design 
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capacity, product, shell type, dimensions, seal type and 

manufacturer, floating roof type, date of construction and location. 

(2) Identification Requirements 

(A) All floating roof tanks subject to this rule shall be clearly and 

visibly identified by a sign on the outside wall for inventory, 

inspection and recordkeeping purposes. 

(B) Any change(s) in floating roof tank identification shall require 

prior written approval by the Executive Officer. 

(3) Owner or Operator Inspection Requirements 

(A) All floating roof tanks subject to this rule shall be inspected by a 

certified person twice per year at 4 to 8 months intervals according 

to the procedures and guidelines set forth in Attachment B - 

"Inspection Procedures and Compliance Report Form."

(B) The primary and secondary seals shall be inspected by a certified 

person each time a floating roof tank is emptied and degassed. 

Gap measurements shall be performed on an external floating roof 

tank when the liquid surface is still but not more than 24 hours 

after the tank roof is refloated. 

(C) The Executive Officer shall be notified in writing at least 2 weeks 

prior to the start of any tank-emptying or roof-refloating operation 

for planned maintenance of a tank. 

(4) Maintenance Requirements 

Any floating roof tank which does not comply with any provision of this 

rule shall be brought into compliance within 72 hours of the determination 

of non-compliance. 

(f) Reporting and Recordkeeping Requirements 

(1) The following shall apply to activities subject to the provisions of 

subdivision (e): 

(A) All inspections shall be recorded on compliance inspection report 

forms approved by the Executive Officer as described in 

Attachment B - "Inspection Procedures and Compliance Report 

Form." 

(B) All compliance inspection reports and documents shall be 

submitted to the Executive Officer either electronically or by hard 

copy within 5 working days of completion of the self-inspection. 
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(C) If a tank is determined to be in violation of the requirements of this 

rule, a written report shall be submitted to the Executive Officer 

within 120 hours of the determination of non-compliance, 

indicating corrective actions taken to achieve compliance. 

(D) All records of owner or operator inspection and repair shall be 

maintained at the facility for a period of 3 years and shall be made 

available to the Executive Officer upon request. 

(2) Emissions Reporting 

(A) An owner or operator shall provide emissions information, to the 

Executive Officer upon request, based on the parameters listed in 

Attachment C using AQMD’s Annual Emissions Reporting 

Program or U.S. EPA’s most recent version of TANKS 4.0 

Program. The requirement shall apply to all organic liquid storage 

tanks without regard to exemptions specified in subdivision (g). 

(B) An owner or operator shall provide all upset emissions information 

associated with product change, repair, and turnover or any other 

excess emission incidents. 

(C) An owner or operator shall maintain records of emissions data for 

all organic liquid storage tanks for the most recent two (2) year 

period. 

(3) A person whose tanks are subject to this rule shall keep an accurate record 

of liquids stored in such containers, the vapor pressure ranges, the API 

gravity, the temperature, and the initial boiling points referenced. 

(g) Exemptions 

(1) The provisions of this rule shall not apply to the following tanks, provided 

the person seeking the exemption supplies proof of the applicable criteria 

sufficient to satisfy the Executive Officer: 

(A) Oil production tanks with a capacity of between 75,000 liters 

(19,815 gallons) and 159,000 liters (42,008 gallons) which have a 

properly maintained vapor-tight roof and are equipped with a 

pressure-vacuum valve which is set within 10 percent of the 

maximum allowable working pressure of the tank, are exempt from 

the control requirements of this rule when: 

(i) The organic liquid contents fail to comply with subdivision 

(c) only when heated for shipment, and such heating occurs 
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for not more than 48 hours and not more than once in any 

20-day period; or 

(ii) The tank has a monthly average throughput of not more 

than 30 barrels of oil per day and was constructed prior to 

June 1, 1984. 

(B) Tanks being brought into compliance within the time period 

specified in paragraph (e)(4). 

(2) The provisions of (d)(2) shall not apply to drain-dry breakout tanks that are 

subject to the provisions of Rule 1149 - Storage Tank And Pipeline 

Cleaning And Degassing. 

(h) Test Methods 

The following test methods and procedures shall be used to determine compliance 

with this rule. Other test methods determined to be equivalent after review by the 

staffs of the District, the Air Resources Board, and the U.S. EPA, and approved in 

writing by the District Executive Officer may also be used. 

(1) Efficiency of a vapor recovery system specified in subparagraph (c)(3)(C) 

shall be determined according to SCAQMD Method 501.1 for the 

determination of total organic compound emissions. EPA Reference 

Methods 25 or 25A may be used, as applicable, in place of SCAQMD 

Method 25.1 specified in Method 501.1. An efficiency determined to be 

less than established by this rule through the use of any of the abovereferenced test methods shall constitute a violation of the rule. Baseline 

emissions shall be calculated by using the criteria outlined in American 

Petroleum Institute Bulletin 2518. 

(2) Exempt compounds shall be determined according to SCAQMD Method 

303. For the purpose of testing the efficiency of a vapor recovery system, 

exempt compounds shall be determined according to EPA Reference 

Method 18 or ARB Method 422. Any test method(s) for exempt 

compounds which cannot be identified through these referenced test 

methods shall be specified by the owner or operator seeking an exemption 

and shall be subject to approval in accordance with the procedures set 

forth above in this subdivision. 

(3) The Reid vapor pressure specified in paragraph (b)(6) and the Reid vapor 

pressure used in determining the true vapor pressure limit specified in 

paragraph (d)(4) shall be determined according to ASTM D-323-82 
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Vapor Pressure of Petroleum Products (Reid Method) or California Code 

of Regulations, Title 13, Section 2297, and converted to true vapor 

pressure using applicable nomographs in U.S. EPA AP-42, Fifth Edition, 

Volume 1, Chapter 7, or nomographs approved by the Executive Officer 

and U.S. EPA. 

(4) Notwithstanding the provisions of paragraph (h)(3), if a permit condition 

or District rule requires a demonstration of true vapor pressure of less than 

5 mm Hg (0.1 psi) absolute, either of the following test methods may be 

used: 

(A) Organic liquids that are stored at ambient temperatures with a true 

vapor pressure of greater than 5 mm Hg (0.1 psi) absolute under 

actual storage conditions shall be determined as those with a flash 

point of less than 100 °F as determined by ASTM Method D-93 – 

10a - Flash Point by Pensky-Martens Closed Cup Tester. 

(B) Organic liquids that are stored at above ambient temperatures with 

a true vapor pressure greater than 5 mm Hg (0.1 psi) absolute under 

actual storage conditions shall be determined as those whose 

volume percent evaporated is greater than ten percent at an 

adjusted temperature TAdj as determined by ASTM Method D-86 – 

11a - Distillation of Petroleum Products at Atmospheric Pressure 

of: 

TAdj = 300 °F + T1 - Ta

Where: 

T1 = Liquid Storage Temperature (°F) 

Ta = Ambient Temperature (°F) = 70 °F 

(5) Notwithstanding the provisions of paragraph (h)(3), the true vapor 

pressure of crude oils and distillates shall be determined, at actual storage 

conditions, by converting Reid vapor pressure using the appropriate API 

nomograph found in U.S. EPA AP-42, Fifth Edition, Volume 1, Chapter 7, 

or API nomograph found in API Publication 2517, Second Edition, 

February 1980. The true vapor pressure of crude oils with an API gravity 

of 26.0 or less, may be measured using the Lawrence Berkeley National 

Laboratory “Test Method for Vapor Pressure of Reactive Organic 
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Compounds in Heavy Crude Oil Using Gas Chromatography.”, May 28, 

2002. 

(6) Vapor tight condition specified in subparagraphs (c)(3)(A) and (c)(3)(B) 

shall be determined according to U.S. EPA's Reference Method 21 using 

an appropriate analyzer calibrated with methane. 

(7) API gravity is determined using the following: 

(A) ASTM D-1298-99e2 Standard Test Method for Density, Relative 

Density (Specific Gravity), or API Gravity of Crude Petroleum 

Products by Hydrometer Method; or 

(B) ASTM D-6822-02 Standard Test Method for Density, Relative 

Density, and API Gravity of Crude Petroleum and Liquid 

Petroleum Products by Thermohydrometer Method; or 

(C) ASTM D-287-92(2000)e1 Standard Test Method for API Gravity 

of Crude Petroleum and Petroleum Products (Hydrometer Method). 
Rule 463 (Cont.) (Amended November 4, 2011) 

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SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT 

RULE 463 - ADDENDUM 

Storage Temperatures Versus Actual Vapor Pressure 

(Gravity/Initial Boiling Points Referenced) 

Reference 

Property Temperature, oF 

A - oAPI Not to Exceed Vapor 

 B - IBP, oF Pressure 

 

Organic Liquids A B 0.5 psia 1.5 psia 

Crude Oils 12 -- -- -- 

 13 -- 120 180 

 14 -- 85 145 

 16 -- 60 107 

 18 -- 55 93 

 20 -- 52 84 

 22 -- 49 77 

 24 -- 45 73 

 26 -- 42 70 

 28 -- 40 67 

 30 -- 38 64 

Middle Distillates 

 Kerosene 42.5 350 195 250 

 Diesel 36.4 372 230 290 

 Gas Oil 26.2 390 249 310 

 Stove Oil 23 421 275 340 

Jet Fuels 

 JP-1 43.1 330 165 230 

 JP-3 54.7 110 -- 25 

 JP-4 51.5 150 20 68 

 JP-5 39.6 355 205 260 

 JP-7 44-50 360 205 260 

Fuel Oil 

 No. 1 42.5 350 195 250 

 No. 2 36.4 372 230 290 

 No. 3 26.2 390 249 310 

 No. 4 23 421 275 340 

 No. 5 19.9 560 380 465 

 No. 6 16.2 625 450 -- 
Rule 463 (Cont.) (Amended November 4, 2011) 

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RULE 463 - ADDENDUM (Cont.) 

Reference 

Property Temperature, oF 

A - oAPI Not to Exceed Vapor 

 B - IBP, oF Pressure 

 

Organic Liquids A B 0.5 psia 1.5 psia 

Asphalts 

 60 - 100 pen. -- -- 490 550 

 120 - 150 pen. -- -- 450 500 

 200 - 300 pen. -- -- 360 420 

Acetone 47.0 133 -- 35 

Acrylonitrile 41.8 173 30 60 

Benzene 27.7 176 35 70 

Carbon Disulfide 10.6 116 -- 10 

 (lb/gal) 

Carbon Tetrachloride 13.4 170 30 60 

Chloroform 12.5 142 -- 40 

 (lb/gal) 

Cylohexane 49.7 177 35 70 

1,2 Dichloroethane 10.5 180 35 77 

 (lb/gal) 

Ethyl Acetate 23.6 171 35 70 

Ethyl Alcohol 47.0 173 45 83 

Isopropyl Alcohol 47.0 181 45 87 

Methyl Alcohol 47.0 148 -- 50 

Methylene Chloride 11.1 104 -- 70 

 (lb/gal) 

Methylethyl Ketone 44.3 175 30 70 

1,1,1-Trichloroethane 11.2 165 60 100 

 (lb/gal) 

Trichloroethylene 12.3 188 50 91 

 (lb/gal) 

Toluene 30.0 231 73 115 

Vinyl Acetate 19.6 163 -- 60 
Rule 463 (Cont.) (Amended November 4, 2011) 

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ATTACHMENT A

FLOATING ROOF TANK SEAL CATEGORIES 

PRIMARY SEALS 

Category A Category B Category C

1. Liquid mounted multiple 

wipers with drip curtain 

and weight

1. Liquid mounted single 

wiper with drip curtain 

and weight

1. Liquid mounted single 

wiper

2. Liquid mounted 

mechanical shoe

2. Liquid mounted double 

foam wipers with vapor 

curtain

2. Liquid mounted foam 

log

3. Vapor mounted primary 

wiper

3. Liquid mounted foam 

log with vapor curtain

4. Vapor mounted E wiper 4. Liquid mounted resilient 

toroid type liquid filled 

log

5. Vapor mounted double 

wipers

5. Vapor mounted foam 

log/bag

6. Vapor mounted double 

foam wipers

6. Vapor mounted foam 

wiper

7. Vapor mounted multiple 

wipers

SECONDARY SEALS 

Category A Category B Category C

1. Multiple wipers 1. Single wiper 1. Liquid mounted wiper

 2. Foam log/bag

 3. Maloney

Criteria used for categorization of floating roof tank seals: 

1. Emission control effectiveness design 

2. Ability to maintain contact with tank wall 

3. Longevity in service 
Rule 463 (Cont.) (Amended November 4, 2011) 

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ATTACHMENT B 

INSPECTION PROCEDURES AND COMPLIANCE REPORT FORM 

Equipment Needed:

Explosimeter (for internal floating roof tanks), liquid resistant measuring tape or 

device, tank probe (to measure gaps in tank seals - 1/8 inch, 1/2 inch, 1-1/2 inch), 

flashlight. 

Inspection Procedures: 

1. The findings of all tank self-inspections, whether completed or not, shall be recorded 

on the Rule 463 Compliance Report form prescribed by the Executive Officer and 

submitted to the District's Refinery Section in accordance with the rule's 

requirements. If an inspection is stopped before completion, indicate the reason for 

this action in the Comments section of the compliance report form. 

2. During compliance inspection, the person(s) conducting the inspection must have a 

copy of the Permit to Operate or Permit to Construct pertinent to the tank being 

inspected. Any discrepancies between the permit equipment description and the 

existing tank or the permit conditions and the actual operating conditions of the tank 

as verified during inspection must be recorded in the Comments section of the 

compliance report form. 

3. Inspect the ground level periphery of each tank for possible leaks in the tank shell. 

Complete the tank information section (D) on the report. 

4. For floating roof tanks containing organic liquid not subject to the provisions of 

subdivision (c) of Rule 463, conduct only steps 1 through 3 of this attachment. For all 

other floating roof tanks, conduct steps 5 through 7 as applicable. 

5. For external floating roof tanks: 

o From the platform, conduct an overall visual inspection of the roof and check 

for obvious permit or rule violations. Record the information as shown under 

section F of the compliance report form. 

o During visual inspection of the roof, check for unsealed roof legs, open 

hatches, open emergency roof drains or vacuum breakers and record the 

findings on the report accordingly. Indicate presence of any tears in the fabric 

of both seals. 

o After the visual inspection, conduct an inspection of the entire secondary seal 

using the 1/8" and 1/2" probes. Record the gap data in section F(4) of the 

report. 

o Conduct an inspection of the entire primary seal using the 1/8", 1/2", and 1 

1/2" probes. Inspect the primary seal by holding back the secondary seal. 

Record the gap data in section F(5) of the report. 
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463 - 17 

o Record all cumulative gaps between 1/8 inch and 1/2 inch; between 1/2 inch 

and 1-1/2 inch; and in excess of 1-1/2 inches, for both primary and secondary 

seals in section G of the report. Secondary seal gaps greater than 1/2 inch 

should be measured for length and width, and recorded in Comments under 

section (J) of the report. 

6. For internal floating roof tanks: 

o Using an explosimeter, measure the concentration of the vapor space above 

the internal floating roof in terms of lower explosive limit (LEL), and record 

the reading in section (E) of the report. 

o Conduct a visual inspection of the roof openings and the secondary seal, if 

applicable, and record findings on the report. 

7. Complete all necessary calculations and record all required data accordingly on the 

report. 
Rule 463 (Cont.) ATTACHMENT B (Cont.) 

(Amended November 4, 2011) 

463-18 

SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT 

RULE 463 COMPLIANCE REPORT 

**PLEASE COMPLETE FORM LEGIBLY IN BLACK INK** 

Tank No. SCAQMD Permit No. Inspection Date Time 

Is This a Follow-up Inspection? No  Yes  If yes, Date of Previous Inspection 

A. COMPANY INFORMATION: 

 Company Name 

 Location Address City Zip 

Mailing Address City Zip

 Contact Person Title 

Phone

B. INSPECTION CONDUCTED BY: 

 Name Title 

Company Name Phone

Mailing Address City Zip

C. TANK INFORMATION: 

 Capacity (bbls) Installation Date Tank Diameter (ft) Tank Height (ft) 

Product Type Product RVP

 Type of Tank: Riveted  Welded  Other  (describe) 

Color of Shell Color of Roof

 Roof Type: Pontoon  Double Deck  Other(describe) 

 External floating roof  Internal floating roof 

D. GROUND LEVEL INSPECTION: 

 1) Product Temperature ° F 2) Product level (ft) 

 3) List type and location of leaks found in tank shell. 

 

 4) List any discrepancies between the existing equipment and the equipment description on the Permit.

 

 5) Is tank in compliance with Permit conditions? No  Yes  If no, explain 

 

E. INTERNAL FLOATING ROOF TANK: 

1) Check vapor space between floating roof and fixed roof with expiosimeter. % LEL

 2) Conduct visual inspection of roofs and secondary seals, if applicable. 

3) Are all roof openings covered? No  Yes  If no, explain in Comments section (J) and proceed to part (H)(6).
Rule 463 (Cont.) ATTACHMENT B (Cont.) 

(Amended November 4, 2011) 

463-19 

F. EXTERNAL FLOATING ROOF TANK: Page 2 of 4

1) On the diagram (below) indicate the location of the ladder, roof drain(s), anti-rotation device(s), platform, gauge well, and vents or other 

appurtenances. Note information in relation to North (to the top of the worksheet).

2) Describe any uncovered openings found on the roof in the Comments section (J). 

3) Identify any tears in the seal fabric. Describe and indicate on diagram (below):

 

 

4) Secondary Seal Inspection 

 a) Type of Secondary Seal: 

 b) Does 1/2” probe drop past seal? No  Yes  if yes, measure length(s) and show on diagram 

 c) Does 1/8” probe drop past seal? No  Yes  if yes, measure length(s) and show on diagram. 

d) Record dimensions of gap for gaps > 1/8” >1/2”

NOTE: Record the actual width and cumulative length of gaps in feet and inches.

(Do not include gaps > 1/2” in 1/8” measurements)

5) Primary Seal Inspection 

a) Type of Primary Seal:  Shoe;  Tube;  Other

 b) (shoe seal) does 1-1/2” probe drop past seal? No  Yes ; if yes, measure length(s) and show on diagram. 

c) (shoe seal) does 1/2” probe drop past seal? No ; Yes ; if yes, measure length(s) and show on diagram.

 d) (tube seal) does 1/2” probe drop past seal? No  Yes  if yes, measure (length(s) and show on diagram. 

e) (all seal types) does 1/8” probe drop past seal? No  Yes  if yes, measure (length(s) and show on diagram.

 f) Record dimensions of gaps for gaps >1/8” > 1/2” 

>1-1/2” NOTE: Record the actual width and cumulative length of gaps in feet and inches.

 (Do not include gaps > 1/2” in 1/8” measurements, or gaps > 1-1/2” in 1/2” measurements)

NOTE: Show defects using symbols. Show seal gaps and lengths.

LEGEND: 

Equipment: 

 Antirotational device 

O Gauge well 

┬ Leg stand 

⊗ Roof drain 

* Emergency roof drain 

∞ Vacuum breaker 

▲ Vent 

 Platform & ladder 

Defects: 

Ө Leg top 

╫ Leg pin 

ơ Open hatch 

\/\ Torn seal 

|-P-| Primary seal gap 

|-S-| Secondary seal gap 

N
Rule 463 (Cont.) ATTACHMENT B (Cont.) 

(Amended November 4, 2011) 

463-20 

SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT 

RULE 463 COMPLIANCE REPORT 

**PLEASE COMPLETE FORM LEGIBLY IN BLACK INK** 

Tank No. SCAQMD Permit No. 

 Page 3 of 4

IF INTERNAL FLOATING ROOF TANK, PROCEED TO PART H(6). 

G. CALCULATIONS - complete all applicable portions of the following: 

 Record dimensions of indicated gaps [from F(4)(d), F(5)(b), and F(5)(f)]. Record in feet and inches.

 Gaps in primary seal between 1/8 and 1/2 inch: 

 Gaps in primary seal between 1/2 and 1-1/2 inch: 

Gaps in primary seal greater than 1-1/2 inches:

 Gaps in secondary seal between 1/8 and 1/2 inch: 

Gaps in secondary seal greater than 1/2 inch:

 Multiply diameter (ft) of tank to determine appropriate gap limits: 

5% circumference = diameter X 0.157 = 60% circ. = diam. X 1.88 =

 10% circumference = diameter X 0.314 = 90% circ. = diam. X 2.83 = 

 30% circumference = diameter X 0.942 = 95% circ. = diam. X 2.98 = 

H. DETERMINE COMPLIANCE STATUS OF TANK: 

 1) Were any openings found on the roof? No  Yes 

2) Were any tears in the seals found: No  Yes 

 3) Is the product level lower than the level at which the roof would be floating? No  Yes 

 4) Secondary Seal: 

Did 1/2” probe drop between shell and seal? No  Yes 

 Did cumulative 1/8” - 1/2” gap exceed 95% circumference length? No  Yes 

5) Primary Seal

 Shoe Did 1-1/2” probe drop between shell and seal? No  Yes 

Did cumulative 1/2” - 1-1/2” gap exceed 30% circumference length, and

 Did cumulative 1/8 - 1/2” gap exceed 60% circumference length? No  Yes 

Did any single continuous 1/8” - 1-1/2” gap exceed 10% circ. length? No  Yes 

 Tube Did 1/2” probe drop between shell and seal No  Yes 

 Did cumulative 1/8” - 1/2” gap exceed 95% circumference length? No  Yes 

6) Internal floating roof (installed before 6/1/84) did LEL exceed 50% No  Yes 

 (installed after 6/1/84) did LEL exceed 30%? No  Yes 

7) Does tank have permit conditions? No  Yes 

 Does tank comply with these conditions? No  Yes 

I. IF INSPECTION WAS TERMINATED PRIOR TO COMPLETION FOR ANY REASON, PLEASE EXPLAIN: 

 
Rule 463 (Cont.) ATTACHMENT B (Cont.) 

(Amended November 4, 2011) 

463-21 

J. COMMENTS: Page 4 of 4 

Use this section to complete answers to above listed items and to describe repairs made to the tank; include date and time repairs were made.

K. I(We) certify the foregoing information to be correct and complete to the best of my(our) knowledge. 

Inspection completed by: Date: 

(signature) (Certification ID #)

Compliance status by: Date: 

(signature) (Certification ID #)

 

Company Representative: Date: 

(signature) (Certification ID #)

 

SEND COMPLETED REPORT (Both Sheets) TO: 

 SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT 

21865 Copley Drive 

 FAX: (909) 396-3341 

Diamond Bar, CA 91765 

Attn: Rule 463 Program Supervisor 

FOR SCAQMD USE ONLY: Date received 

Reviewed by: Date reviewed 

 (signature) (Certification ID #) 

Tank Status: [ ] in compliance [ ] in violation, Rule(s) 

Comments: 

 
Rule 463 ATTACHMENT C 

DATA REPORTING REQUIREMENT FOR ROOF TANKS 

463-22 

The data items shall include, but not be limited to, the following: 

A. External Floating Roof Tank B. Internal Floating Roof Tank C. Fixed R

1. Tank I.D. 1. Tank I.D. 1. Tank I

2. Product Code 2. Product Code 2. Produc

3. Type of Floating Roof Seal 3. Type of Floating Roof Seal 3. Vent T

4. Shell Construction 4. Shell Construction *4. Averag5. Reid Vapor Pressure 5. Reid Vapor Pressure 5. True V

*6. Average Stock Storage Temperature *6. Average Stock Storage Temperature 6. Tank D

7. True Vapor pressure 7. True Vapor Pressure *7. Vapor 8. Tank Diameter 8. Tank Diameter 8. Averag

*9. Wind Speed Exponent *9. Wind Speed Exponent *9. Averag

*10. Average Wind Velocity *10. Average Wind Velocity 10. Throug*11. Seal Factor *11. Seal Factor 11. Turnov*12. Product Factor *12. Product Factor *12. Turnov

*13. Vapor Molecular Weight *13. Vapor Molecular Weight *13. Adjust

*14. Clingage Factor *14. Clingage Factor *14. Paint F

15. Throughput 15. Throughput *15. Crude-

*16. Density of Liquid Stock *16. Density of Liquid Stock *16. Crude-

17. Total Number of Different Type of Fitting *17. Number of Columns 17. Breath18. Total Roof Fitting Loss Factor *18. Effective Column Diameter 18. Workin19. Vapor Pressure Function 19. Total Number of Different Types of Fittings 19. Total L20. Roof Fitting Loss *20. Total Deck Fitting Loss Factor *20. Vapor 21. Standing Loss 21. Vapor Pressure Function 21. Total L

22. Withdrawal Loss *22. Deck Seam Length Factor 22. Numbe

23. Total Loss *23. Deck Seam Loss per Unit 23. Total E

24 Number of Excess Upset Emissions Incidents 24. Deck Seam Loss 

25. Total excess Upset Emissions 25. Deck Fitting Loss 

26. Standing Loss 

27. Withdrawal Loss 

28. Total Loss 

29. Number of Excess Upset Emissions Incidents 30. Total Excess Upset Emissions 

* Default values are available from the District 

The Data format and order shall be specified and approved by the Executive Officer.