(Adopted December 4, 1987)(Amended April 1, 1988)(Amended July 14, 1995) 

(Amended May 2, 2008) 

RULE 1149. STORAGE TANK AND PIPELINE CLEANING AND 

DEGASSING 

(a) Purpose and Applicability 

The purpose of this rule is to reduce Volatile Organic Compounds (VOCs) and 

toxics emissions from roof landings, cleaning, maintenance, testing, repair and 

removal of storage tanks and pipelines. This rule applies to the cleaning and 

degassing of a pipeline opened to atmosphere outside the boundaries of a facility, 

stationary tank, reservoir, or other container, storing or last used to store VOCs. 

(b) Definitions 

(1) CLEANING is the process of washing or rinsing a stationary tank, 

reservoir, pipelines, or other container or removing vapor, sludge, or 

rinsing liquid from a stationary tank, reservoir, or other container. 

(2) DEGASSING is the process of removing organic gases from a stationary 

tank, reservoir, pipelines, or other container. 

(3) 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. 

(4) EXEMPT COMPOUNDS are defined in Rule 102 -- Definition of Terms. 

(5) FACILITY means any source or group of sources or other air 

contaminant-emitting activities that are located on one or more contiguous 

properties within the District, in actual physical contact or separated solely 

by a public roadway or other public right of way, and are owned by the 

same person (or by persons under common control). 

(6) LIQUID BALANCING is a process in which an organic liquid having a 

Reid vapor pressure subject to this rule is replaced in a floating roof 

storage tank by an organic liquid with a Reid vapor pressure that is not 

subject to this rule without landing the floating roof on its internal 

supports. 

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Rule 1149 (Cont.) (Amended May 2, 2008) 

(7) LIQUID LEAK is the dripping of liquid VOC at the rate of more than 

three drops per minute. 

(8) NATURAL GAS is a mixture of hydrocarbons, with at least 80 percent 

methane by volume and less than 10 percent by weight VOC, determined 

according to the test method specified in paragraph (d)(3).

(9) REID VAPOR PRESSURE (RVP) is the vapor pressure of a product 

determined in a volume of air four times greater than the liquid volume at 

100° F. 

(10) VAPOR LEAK is the detection of gaseous volatile organic compounds in 

excess of 5,000 ppmv, measured as methane. 

(11) VAPOR TIGHT CONDITION is a condition that exists when the reading 

on a portable hydrocarbon analyzer is less than 500 parts per million 

(ppm), measured as methane, above background, measured using EPA 

Reference Method 21. 

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

(c) Requirements 

(1) A stationary tank, reservoir, or container of equal or greater capacity and 

containing or last containing any organic liquid with a vapor pressure 

equal or greater than in Table 1 shall not be opened to the atmosphere 

unless the emissions are controlled by one of the following: 

(A) Liquid balancing; or 

(B) Other control techniques such that the gaseous VOC concentration 

within the tank, reservoir or other container is reduced to less than 

5,000 ppmv, measured as methane, for at least one hour after 

degassing operations have ceased. 

Table 1 

Capacity and Vapor Pressure Rule Applicability 

Capacity 

gallons 

(liters) Vapor Pressure (RVP) 

500 (1,893) 3.9 psia 

26,420 (100,000) 2.6 psia 

100,000 (378,500) 0.5 psia 

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Rule 1149 (Cont.) (Amended May 2, 2008) 

(2) The roof of a floating storage tank containing or last containing a VOC 

liquid with a Reid vapor pressure greater than 25 mm Hg (0.5 psi) may not 

rest upon its support legs after it has been emptied unless emissions are 

controlled by one of the following: 

(A) The vapor space created is vented to a control device approved by 

the Executive Officer; or 

(B) The gaseous VOC concentration within the tank, reservoir or other 

container is reduced to less than 5,000 ppmv, measured as 

methane, for at least one hour after degassing operations have 

ceased. 

(3) In lieu of meeting the requirements of paragraph (c)(2), drain-dry breakout 

tanks shall be maintained in a vapor tight condition outside the tank shell 

while the roof is resting upon its support legs and shall be monitored 

monthly. Records shall be maintained pursuant to paragraph (c)(11). 

Owners or operators of facilities requiring tank modifications to meet the 

drain-dry breakout tank definition and utilize this compliance option shall 

make the modifications according to the following schedule: 

(A) At least 1/4 of the tanks subject to this provision by August 1, 

2009; 

(B) At least 1/2 of the tanks subject to this provision by August 1, 

2010; 

(C) At least 3/4 of the tanks subject to this provision by August 1, 

2011; and 

(D) All tanks subject to this provision by August 1, 2012. 

By August 1, 2008, an owner or operator shall submit to the District a 

compliance plan identifying the applicable tanks and the schedule for 

modification completion. Applicable tanks shall be maintained in a vapor 

tight condition outside the tank shell while resting upon its support legs 

and monitored monthly. 

(4) Effective June 1, 2008, pipelines with a diameter of 6 inches or greater 

containing or last containing a VOC liquid with a Reid vapor pressure 

greater than 134 mm Hg (2.6 psi) shall not be opened to the atmosphere 

unless emissions are controlled by one of the following: 

(A) The vapor space created is vented to a control device approved by 

the Executive Officer; or 

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Rule 1149 (Cont.) (Amended May 2, 2008) 

(B) The gaseous VOC concentration within the pipeline is reduced to 

less than 5,000 ppmv, measured as methane, for at least one hour 

after degassing operations have ceased; or 

(C) The gaseous VOC concentration outside the pipeline, as measured 

pursuant to paragraph (d)(1) while the pipeline is open, is less 

than 5,000 ppmv, measured as methane. 

The process of removing liquid from pipelines shall be continuous and the 

liquid shall be immediately transferred into a container that meets the 

requirements of paragraph (c)(9). During the liquid removal process, the 

gaseous VOC concentration standard stated in paragraph (c)(4) will not 

apply. 

(5) Equipment used in the cleaning or degassing process shall be free of liquid 

and vapor leaks. This includes, but is not limited to: the degassing 

equipment, vacuum truck, pumps, hoses, and connections. 

(6) Effective June 1, 2008, vacuum trucks used to remove liquid, sludge or 

vapors from tanks or pipelines subject to this rule shall not exhaust vapors 

to the atmosphere greater than 500 ppmv, measured as methane. Until 

January 1, 2009, this provision will not apply after the tank or pipeline has 

met the requirements of paragraphs (c)(1), (c)(3) or (c)(4). 

(7) The District shall be notified of the intent to degas any tank or pipeline 

subject to the rule. Initial notifications shall be submitted in a written 

format approved by the Executive Officer at least two (2) hours and no 

more than two (2) days prior to the start of the degassing operation. The 

initial notification shall include: 

(A) Start date and time; 

(B) Tank or pipeline owner, address, tank location and applicable tank 

permit numbers; 

(C) Degassing operator’s name, contact person, telephone number and 

applicable control equipment permit numbers; and 

(D) Tank or pipeline capacity, volume of space degassed and materials 

stored. 

A follow-up notification, using a form approved by the Executive Officer 

which is fully completed, including associated notification fees, as set 

forth in Rule 301 – Permitting and Associated Fees, must be submitted to 

the District postmarked, received or delivered no later than three business 

days following the degassing activity. 

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Rule 1149 (Cont.) (Amended May 2, 2008) 

(8) The VOC concentration in the exhaust stream of any control device shall 

be less than 500 ppmv, measured as methane. When carbon adsorption is 

used for degassing: 

(A) An organic vapor monitor/analyzer approved by the Executive 

Officer or designee shall be installed and operated at any exit of 

the carbon adsorption device to determine the concentration of 

hydrocarbon discharged to the atmosphere. 

(B) An owner or operator shall not regenerate any spent carbon from a 

carbon adsorber unless the regeneration is conducted using 

equipment operating under a valid permit to operate issued by the 

Executive Officer or designee. 

(9) Any liquids or sludge removed from the tank or pipeline prior to the tank 

meeting the requirements of paragraphs (c)(1), (c)(3) or (c)(4), shall be 

handled or disposed of in closed containers that are free of liquid and 

vapor leaks or in a manner previously approved by the Executive Officer. 

(10) A person engaged in the off-site cleaning or degassing of stationary 

storage tanks shall complete the cleaning and degassing operations in 

accordance with the requirements of subdivision (c) within 14 days of 

receiving the tanks. 

(11) Records shall be maintained by the owner and operator for two (2) years, 

or five (5) years if the facility is a Title V facility, and be made available 

to the Executive Officer or designee upon request. The records shall 

include, but are not limited to: 

(A) All notification requirements under paragraph (c)(7); 

(B) Tank or pipeline owner, address and applicable tank permit 

numbers; 

(C) Tank or pipeline degassing operator’s name, contact person, 

telephone number and applicable control equipment permit 

numbers; 

(D) Tank or pipeline capacity, volume of vapor space degassed and 

materials stored; 

(E) The flow rate and gaseous VOC concentration vented to the 

degassing equipment, if applicable; 

(F) The gaseous VOC concentration of the degassing equipment 

exhaust, if applicable; 

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Rule 1149 (Cont.) (Amended May 2, 2008) 

(G) The total amount of VOC processed in the degassing equipment, if 

applicable; and 

(H) All readings measured according to EPA Reference Test Method 

21, as specified in subdivision (d). 

(d) Test Methods 

For the purpose of this rule, the following test methods shall be used. 

(1) Measurement of gaseous VOC concentrations shall be conducted 

according to EPA Reference Method 21 using an appropriate analyzer 

calibrated with methane at a distance of 1 cm (0.4 inch) or less from the 

source. For pipelines, the probe inlet shall be located one foot away from 

the opening in the pipeline. When determining compliance with 

subparagraphs (c)(1)(B) or (c)(2)(B), the probe inlet of the monitoring 

instrument shall be located no more than 1 foot above the bottom of the 

tank or no more than 1 foot above the surface of the sludge material on the 

bottom of the tank. For upright, cylindrical aboveground tanks, the probe 

inlet shall be located at least 2 feet away from the inner surface of the tank 

wall. 

(2) Reid vapor pressure is determined by ASTM D 323-90. 

(3) The VOC content of gases shall be determined according to ASTM 

Method D 1945. 

(e) Exemptions 

(1) The provisions of this rule shall not apply to the degassing of less than 100 

feet of a pipeline. 

(2) The provisions of this rule shall not apply to the degassing of less than 

0.25 miles of a pipeline that contained or previously contained any organic 

liquid having a Reid vapor pressure less than 202 mm Hg (3.9 psi). 

(3) The provisions of subdivision (c) shall not apply to natural gas pipelines. 

(4) The provisions of subdivision (c) shall not apply while connecting or 

disconnecting degassing equipment, sampling emissions, purging inert gas 

from pipelines when reintroducing product or while connecting or 

disconnecting pipelines and associated control techniques or control 

equipment. 

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