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EPA Floating Roof Regulations

The objective of floating-roof regulations is to control vapor pressure from liquid hazardous waste stored in tanks. There are two types of floating roofs, an internal floating roof contained within a fixed-roof tank and an external floating roof, which is placed upon a free-standing storage tank, both of which float upon liquid hazardous waste to prevent the buildup of vapor pressure that can lead to catastrophic or minor air pollutant emission releases. The Environmental Protection Agency's hazardous waste storage tank regulations cover seals and acceptable openings under 40 CFR 264.1084; tank controls for venting and pressure monitoring are covered with other regulations.

  1. Tanks

    • Floating roofs are required for liquid hazardous materials stored in tanks that range in capacity from 75 cubic meters, with 11.1 pounds per square inch of pressure to 151 cubic meters of stored material, with .75 pounds per square inch of pressure.

    Seals

    • Each floating foam roof must have a continuous seals, either liquid-mounted or metallic shoe, between the circular wall of the tank and the floating roof edge. A liquid-mounted seal is encapsulated foam or liquid mounted to the wall and encircling the roof. Metallic shoe seals are metal sheets spring-mounted to the tank and connected to the roof with braces, extending into the liquid and at least 61 centimeters above the surface.

    Openings and Gaps

    • The gaps between the tank wall, seals and roof cannot exceed 21.2 square centimeters per meter of tank diameter. The width of any gap cannot exceed 3.8 centimeters. Floating roofs have to provide access to below liquid surface for venting tubes, sampling and monitoring; ladders, perforated tubes and gasketed columns will all project below the surface. Each access opening must be 90 percent covered with sliding covers when not in use.

    Inspections

    • Visual inspections are required every 12 months after the initial filling of the tanks. Inspections should identify any defects that release air pollutant emissions to the air. Significant releases may be occurring if the roof is not floating on the surface, there is liquid accumulation on top of the roof, the roof is detached from the seals, there are tears in the foam roof, the gaskets are not closed or if slotted membrane covers are more than 10% open. Any necessary repairs must be initiated no later than five days after identification and must be completed no later than 45 days after initial identification.

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