REVISED PROPOSED December 15, 2011 

Revised Proposed 

Amendments to Rule 4625

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RULE 4625 WASTEWATER SEPARATORS (Adopted April 11, 1991; Amended May 21, 

1992; Amended December 17, 1992, Amended [Rule adoption date]) 

1.0 Purpose 

 The purpose of this rule is to limit VOC emissions from wastewater separators by 

requiring a vapor loss control devices, recordkeeping, inspection and test methods. 

2.0 Applicability 

 This rule applies to wastewater separators including air flotation units as defined in this 

rule. The requirements of this rule are not intended to applyonly apply to the 

separation of crude oil and water prior to after custody transfer. 

3.0 Definitions 

 3.1 Air flotation unit: equipment used to remove suspended matter, both oil and 

solid, from water by dissolving air under pressure and then releasing the air at 

atmospheric pressure in a tank or basin. 

3.2 APCO: the Air Pollution Control Officer of the San Joaquin Valley Unified Air 

Pollution Control District, or any person authorized to act on behalf of the APCO. 

3.3 ARB: California Air Resources Board as established by the California Health and 

Safety Code Section 39510, or any person authorized to act on its behalf. 

3.4 Custody transfer: the physical and contractual ownership transfer of produced 

fluids from an oil producer to another entity. 

 3.5 District: San Joaquin Valley Unified Air Pollution Control District. 

3.6 EPA: United States Environmental Protection Agency. 

3.7 Operator: includes but is not limited to any person who owns, leases, 

supervises, or operates a facility and/or equipment. 

3.8 Volatile Organic Compound (VOC): as defined in Rule 1020 (Definitions). 

 3.93.2 Wastewater Separator: any device or piece of equipment that is used to remove 

oil and associated chemicals from water, or any device, such as a flocculation 

tank, clarifier, etc. that removes petroleum-derived compounds from 

wastewater. 
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 3.103.3 Wastewater Separator Forbay: that section of a gravity-type wastewater 

separator which receives the untreated, oil-water waste from the preseparator 

flume; and acts as a header which distributes the influent to the separator 

channels. 

4.0 [Reserved]Exemptions 

 4.1 This rule shall not apply to any wastewater separator for which: 

 A 

 f x V exceeds 420, 

 where: 

 A = the area to be covered in square feet 

 V = the oil recovery rate in gallons/day on a annual basis 

 f = the estimated fractional volume loss 

of oil and is computed as: 

 -0.0663 + 0.000319 x 

(annual mean ambient temperature F) - [0.000286 x 

(10% true boiling point, F)]+ [0.00215 x (annual 

average influent temperature, F)] 

 4.2 Air Flotation Units 

 4.3 For existing facilities, if an incineration device is added or modified for the sole 

purpose of complying with the requirements of this rule, such a device shall be 

exempt from the Best Available Control Technology and the Offset requirements 

of Rule 2201 (New and Modified Stationary Source Review Rule). 

5.0 Requirements 

 5.1 A person shall not use any compartment of any vessel or device operated for the 

recovery of oil or tar from effluent water, from any equipment which processes, 

refines, stores or handles petroleum or coal tar products unless such 

compartments are equipped with one of the following vapor loss control devices, 

except when gauging or sampling is taking place: 

 5.1.1 A solid cover with all openings sealed and totally enclosing the liquid 

contents of the compartment, except for such breathing vents as are 

structurally necessary; or 

 

 
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 5.1.2 A floating pontoon or double-deck type cover, equipped with closure 

seals that have no holes or tears, installed and maintained so that gaps 

between the compartment wall and seal shall not exceed one-eighth (1/8) 

inch for an accumulative length of 97 percent of the perimeter of the 

tank, and shall not exceed one-half (1/2) inch for an accumulative length 

of the remaining three (3) percent of the perimeter of the tank. No gap 

between the compartment wall and the seal shall exceed one-half (1/2) 

inch; or 

 5.1.3 A vapor recovery system with a combined collection and control 

efficiency of at least 9095 percent by weight. 

 5.2 Any gauging and sampling device in the compartment cover shall be equipped 

with a cover or lid. The cover shall be in a closed position at all times, except 

when the device is in actual use. 

 5.3 All wastewater separator forbays shall be covered. 

 

 5.4 Skimmed oil or tar removed from wastewater separating devices shall be either 

charged to process units with feed or transferred to a container with a control 

system with at least 90 percent control efficiency by weight. A control device 

must be under District permit. 

 5.5 Inspection 

 On and after January 1, 2013: 

5.5.1 An operator complying with Section 5.1.1 shall visually inspect, the 

manholes, roof hatches, or other openings on the fixed roof, at least once 

every twelve (12) months after the tank is initially filled with an organic 

liquid. No holes, tears, or other openings are allowed that would permit 

the escape of hydrocarbon vapors. Any defects found are violations of 

this rule. 

5.5.2 An operator complying with Section 5.1.2 shall visually inspect, the 

internal floating roof and its appurtenant parts, fittings, etc., and the 

primary seal and/or secondary seal at least once every twelve (12) 

months after the tank is initially filled with an organic liquid. Other than 

the gap criteria specified by this rule, no holes, tears, or other openings 

are allowed that would permit the escape of hydrocarbon vapors. Any 

defects found are violations of this rule. 
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5.5.3 An operator complying with Section 5.1.3 shall visually inspect the 

manholes, roof hatches, other openings, fittings, etc., at least once every 

twelve (12) months after the tank is initially filled with an organic liquid. 

No holes, tears, or other openings are allowed that would permit the 

escape of hydrocarbon vapors. Any defects found are violations of this 

rule. 

6.0 Administrative Requirements 

 6.1 Test Methods 

Compliance with the requirements of Section 5.0 shall be determined in accordance 

with the following test methods or their equivalents as approved by the EPA and the 

APCO:

 6.1.1 Efficiency of VOC control device shall be determined by EPA Test 

Method 25 and analysis of halogenated exempt compounds shall be by 

ARB Method 422. 

 6.1.2 Analysis of halogenated exempt compounds shall be by ARB Method 

432. 

 6.1.32 Where add-on control equipment is utilized, collection efficiency shall be 

determined by the EPA document "Model Regulatory Language for 

Capture Efficiency Testing," August 3, 1990. 

 6.2 Recordkeeping 

 Any operator subject to Section 5.0 of this rule shall: 

 6.2.1 Maintain records of the type and location of each wastewater separator. 

 

 6.2.2 Record the date of inspections pursuant to Section 5.5. 

 

 6.2.3 Maintain required records for at least five (5) years and make available 

upon request. 

7.0. Compliance Schedule 

 7.1 The owner or operator of any existing wastewater separator, not previously 

subject to the requirements of this rule, which requires modification to comply 

with this rule must meet the following compliance schedule: 

 7.1.1 Submit applications for Authority to Construct by January 1, 1992. 
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 7.1.2 Complete on site construction and achieve final compliance by 

 July 1, 1993.