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Subchapter 15. Petroleum Safety Orders--Refining, Transportation and Handling
Article 9. Tanks and Reservoirs
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§6803. Stationary Tanks and Reservoirs.

(a) The roofs of tanks and reservoirs in service shall be externally inspected by a qualified person at intervals not to exceed one year. Where a roof has been found to be unsafe or has not been inspected, substantial barriers shall be erected to block off the entire roof or that portion which is unsafe. Legible signs shall be posted at all approaches to the tank or reservoir roof if the entire roof is blocked off, or on the barrier facing all approaches to the defective area if only a portion of the tank or reservoir roof is barricaded. These signs shall read: "DANGER - UNSAFE ROOF - KEEP OFF", or equivalent wording in letters at least two inches (2") in height.

(b) Work shall not be performed upon the exterior of the roof or shell of a tank at a location where the employee may be exposed to a hazardous concentration of flammable or toxic gases or vapors. When there is reason to suspect the existence of any of the hazards above mentioned, jobsite atmospheric tests shall be made and employees shall be protected. This order shall not prohibit an employee, when protected by approved respiratory equipment, from entering such a hazardous atmosphere when necessary, provided that the work is not of a nature that tends to aggravate the hazard.

(c) When tank or reservoir roof plates or sheathing are suspected to be weak or defective and it is necessary for employees to go onto a roof to determine the extent of the weak and defective parts or to remove them, the following precautions or equally safe procedures shall be used;

(1) Employees shall work at least two rafters apart, be provided with and use an approved safety harness with safety line securely attached to safe supports;

(2) If rafters, girders or posts are known to be weak or defective over an area which cannot be spanned safely, temporary shoring or support shall be installed inside the tank or reservoir before employees are permitted to work on the defective roof area. If this is impractical, an adequate overhead lifeline shall be installed and the employees shall attach their harness to this lifeline;

(3) A standby employee shall be available within sight and sound to offer assistance should an emergency arise while duties are performed.

(d) The roofs of tanks shall be capable of safely supporting employees required to go on the roofs. Locations on tank roofs where work is performed shall be provided with safe platforms and safe access thereto. A walkway will be acceptable as a safe platform when the work is performed entirely from the walkway.

(e) Where the means of access, the walkways, or the platforms of a group of two or more tanks are connected, there shall be provided sufficient unobstructed stairways, ramps, fixed ladders, slides, walkways or crosswalks to permit an employee to escape from the roof, walkway or platform of any tank in the group in the event the walkway or platform of any other tank in the group becomes impassable due to fire or other emergency. Provided, however, that this order shall not apply to tanks containing water or tanks containing petroleum products having an open cup flash point above 3000 F. as determined by A.S.T.M. Designation D92, or in the case of fuel oils by the A.S.T.M. Designation D93, and where such tanks are isolated from tanks, pipelines and other equipment containing liquids at a temperature above 1500 F., gases, flammable liquids or corrosives.

(f) Within this subsection, tanks shall be classified as follows:

Class A--Tanks with fixed steel roofs but excluding steel water-seal roofs.

Class B--Tanks with nonmetal roofs.

Class C--Tanks with steel water-seal roofs.

Walkways and platforms on tank roofs required by subsections (b) and (c) of this Section, and the railings and toeboards, shall be provided as follows:

(1) The roofs of tanks in Class A shall have walkways as follows:

(A) Tank roofs having a thickness less than one-eighth inch (1/8") shall not be used as a walkway regardless of the slope of the roof. In measuring the thickness of metal roofs, allowance shall be made for manufacturers tolerances.

(B) Tank roofs having a slope of two inches (2") per foot or less may be used as a walkway. Such walkways shall be clearly defined by color contrast and if the slope of the tank roof is one inch (1") per foot or greater, the walkway shall have a nonskid surface.

(C) Tank roofs having a slope greater than two inches (2") per foot shall be provided with independent walkways of steel or wood construction.

(2) The roofs of tanks in Class B and C shall have independent walkways of metal or wood construction.

(3) No independent walkways on a tank roof of Class A or B shall have a slope greater than three inches (3") per foot.

(4) No walkway on a tank roof of Class A or B shall have a transverse slope greater than two inches (2") per foot.

(5) Walkways on tank roofs shall be not less than twenty-four inches (24") in width but it shall be permissible to install midrails and toeboards within this width provided, however, that a minimum clear width of twenty inches (20") shall be maintained. Walkways shall be designed to carry the load to the supporting structure of the tank roof and shall be securely attached to the tank. Walkways constructed of steel shall have a nominal thickness not less than one-eighth inch (1/8"). Walkways shall be of sufficient strength to safely support the loads imposed on them.

(6) Platforms on tanks of Class A, B and C shall be at least the equivalent in safety of the type of walkway required for the tank class.

(7) Tanks in Class A, B, and C, the roofs of which are five feet (5') or more above ground or floor level, shall have those portions of their walkway and platform edges that are within six feet (6') of the roof edge equipped with railings and toeboards, or, as an alternative, railings and toeboards shall be installed on the tank edges which are within six feet (6') of the walkways or platforms. Provided, however, that toeboards shall not be required on that side of a platform that faces the peak of the roof.

(g) When duties require an employee to travel on or over reservoir roofs, walkways shall be installed.

(h) Tank roofs, platforms, walkways and stairways shall be kept clear of loose material or equipment except that sampling and gaging equipment may be kept on tank roofs in special racks or containers. Oil spills shall be cleaned up to prevent fire and slipping hazards.

(i) When in the open position the covers of gage, sampling and manhole openings in tank roofs shall be securely attached to the roof or roof opening fixture to prevent their falling.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. New subsections (a)-(c)(3), subsection redesignation, amendment of subsections (d)-(f), (g) and (i) and new NOTE filed 9-6-94; operative 10-6-94 (Register 94, No. 36).

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