173-490-200  <<  173-490-201 >>   173-490-202

WAC 173-490-201

Petroleum liquid storage in external floating roof tanks.

(1) Specific applicability.
(a) This section shall apply to all petroleum liquid storage vessels equipped with external floating roofs, having capacities greater than 150,000 liters (40,000 gallons), and as qualified in WAC 173-490-025.
(b) This section does not apply to petroleum liquid storage vessels that:
(i) Are used to store waxy, heavy pour crude oil; or
(ii) Have capacities less than 1,600,000 liters (420,000 gallons) and are used to store produced crude oil and condensate prior to lease custody transfer; or
(iii) Contain a petroleum liquid with a true vapor pressure of less than 10.5 kPa (1.5 psia); or
(iv) Contain a petroleum liquid with a true vapor pressure less than 27.6 kPa (4.0 psia); are of welded construction; and presently possess a metallic-type shoe seal, a liquid-mounted foam seal, a liquid-mounted liquid filled type seal, or other closure device of demonstrated equivalence approved by ecology; or
(v) Are of welded construction, equipped with a metallic-type shoe primary seal and have secondary seal from the top of the shoe seal to the tank wall (shoe-mounted secondary seal).
(2) Provisions for specific processes.
(a) No owner(s) or operator(s) of a petroleum liquid storage vessel shall store a petroleum liquid in that vessel unless:
(i) The vessel has been fitted with:
(A) A continuous secondary seal extending from the floating roof to the tank wall (rim-mounted secondary seal); or
(B) A closure or other device which controls VOC emissions with an effectiveness equal to or greater than a seal required under WAC 173-490-201 (2)(a)(i)(A) and approved by ecology.
(ii) All seal closure devices meet the following requirements:
(A) There are no visible holes, tears, or other openings in the seal or seal fabric;
(B) The seal is intact and uniformly in place around the circumference of the floating roof between the floating roof and the tank wall; and
(C) For vapor mounted primary seals, the accumulated area of gaps exceeding 0.32 cm (1/8 inch) in width between the secondary seal and the tank wall shall not exceed 21.2 cm2 per meter of tank diameter (1.0 in.2 per foot of tank diameter), as determined by the method in WAC 173-490-201(3).
(iii) All openings in the external floating roof, except for automatic bleeder vents, rim space vents, and leg sleeves, are:
(A) Equipped with covers, seals, or lids in the closed position except when the openings are in actual use; and
(B) Equipped with projections into the tank which remain below the liquid surface at all times.
(iv) Automatic bleeder vents are closed at all times except when the roof is floated off or landed on the roof leg supports;
(v) Rim vents are set to open when the roof is being floated off the leg supports or at the manufacturer's recommended setting; and
(vi) Emergency roof drains are provided with slotted membrane fabric covers or equivalent covers which cover at least ninety percent of the area of the opening.
(b) The owner(s) or operator(s) of a petroleum liquid storage vessel with an external floating roof subject to this chapter shall:
(i) Perform routine inspections annually in order to insure compliance with WAC 173-490-201 (2)(a) and the inspection shall include a visual inspection of the secondary seal gap;
(ii) Measure the secondary seal gap annually in accordance with WAC 173-490-201(3) when the floating roof is equipped with a vapor-mounted primary seal; and
(iii) Maintain records of the types of volatile petroleum liquids stored, the maximum true vapor pressure of the liquid as stored, and the results of the inspections performed in WAC 173-490-201 (2)(b)(i) and (ii).
(c) The owner(s) or operator(s) of a petroleum liquid storage vessel with an external floating roof exempted from this chapter by WAC 173-490-201 (1)(b)(iii), but containing a petroleum liquid with a true vapor pressure greater than 7.0 kPa (1.0 psi), shall maintain records of the average monthly storage temperature, the type of liquid, and the maximum true vapor pressure for all petroleum liquids with a true vapor pressure greater than 7.0 kPa.
(d) Copies of all records under WAC 173-490-201 (2)(b) and (c) shall be retained by the owner(s) or operator(s) for a minimum of two years after the date on which the record was made.
(e) Copies of all records required under WAC 173-490-201 shall immediately be made available to the director, upon verbal or written request, at any reasonable time.
(3) Testing and monitoring.
(a) The owner or operator of a storage vessel covered under WAC 173-490-201 shall demonstrate compliance by the methods of this subsection or an alternative method approved by ecology.
(b) A person proposing to measure the seal fit of a storage vessel in order to comply with this section shall notify ecology of the intent to measure not less than five working days before the measurement so the director or a representative may observe the measurement if desired.
(c) Compliance with WAC 173-490-201 (2)(a)(ii)(C) shall be determined by physically measuring the length and width of all gaps around the circumference of the secondary seal in each place where a 0.32 cm (1/8 in.) diameter probe passes freely (without forcing or binding against the seal) between the seal and the tank wall and summing the area of the individual gaps.
[Statutory Authority: Chapter 70.94 RCW. WSR 91-05-064 (Order 90-06), § 173-490-201, filed 2/19/91, effective 3/22/91. Statutory Authority: RCW 70.94.331 and 70.94.395. WSR 80-11-062 (Order DE 80-18), § 173-490-201, filed 8/20/80.]
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