§ 14.2. Physical requirements of vaults.
(a) Vaults for retail distribution shall be constructed below grade. Vaults for nonretail distribution may be constructed either above or below grade.
(b) The vault shall completely enclose each tank. There may not be openings in the vault enclosure except those necessary for access to, inspection of, and filling, emptying and venting of the tank. The walls and floor of the vault shall be constructed of reinforced concrete at least 6 inches thick. The top of an above grade vault shall be constructed of noncombustible material constructed to be weaker than the walls to assure that in the event of an explosion inside the vault, the thrust of the explosion will be inside the vault. The top, floor and tank foundation shall be designed to withstand the anticipated loading. The walls and floor of a vault installed below grade shall be designed to withstand anticipated soil and hydrostatic loading. The vault shall be substantially liquid tight and there may be no backfill around the tank. There shall be sufficient space between the tank and the vault to allow for inspection of the tank and appurtenances.
(c) Each vault and its tank shall be suitably anchored to withstand uplifting by groundwater or flooding, including when the tank is empty.
(d) The vault shall be designed to be wind and earthquake resistant, in accordance with sound engineering practice. The vault shall be resistant to damage from the impact of a motor vehicle, or suitable collision barriers shall be provided.
(e) Each tank shall be in its own vault. Adjacent vaults may share a common wall if the top of each vault is constructed to conform to the requirements of subsection (b). The top of each vault shall be constructed of noncombustible material constructed to be weaker than the walls to assure that in the event of an explosion inside the vault, the thrust of the explosion will be directed upward before a significantly high pressure can develop inside the vault.
(f) Connections shall be provided to permit venting of each vault to dilute, disperse and remove vapors prior to personnel entering the vault.
(g) Vaults shall be provided with continuous ventilation at a rate of not less than 1 cubic foot per minute per square foot of floor area, but not less than 150 cubic feet per minute. Failure of the exhaust air flow shall automatically shut down the dispensing system. The exhaust system shall be designed to provide air movement across all parts of the vault floor. Supply and exhaust ducts shall extend to within 3 inches, but not more than 12 inches of the floor. The exhaust system shall be installed in accordance with NFPA 91, Standard For Exhaust Systems For Air Conveying of Materials. A means shall be provided to automatically detect flammable vapors and to automatically shut down the dispensing system upon detection of the flammable vapors in the exhaust duct at a concentration of 25% of the lower flammable limit.
(h) Each vault shall be equipped with a detection system capable of detecting liquids, including water, and of activating an alarm upon detection.
(i) A means to recover liquid from the vault shall be provided. If a pump is used to meet this requirement, the pump may not be permanently installed in the vault. Electric powered portable pumps used to recover liquid shall be suitable for use in Class I, Division I locations, as defined in NFPA 70, National Electric Code.
(j) Vent pipes that are provided for normal tank venting shall extend at least 12 feet above ground level.
(k) Emergency vents shall be vapor tight and shall be permitted to discharge inside the vault. Long-bolt manhole covers will not be permitted for this purpose.
(l) Each vault shall be provided with a means for personnel entry. At each entry point, a warning sign indicating the need for procedures for safe entry into confined spaces shall be posted. Employees and other persons who anticipate entering the vault shall be made aware of and each entry shall conform to applicable Federal regulations regarding confined space entry. Each entry point shall be secured against unauthorized entry and vandalism.
(m) Each vault shall be provided with a suitable means to admit a fire suppression agent. The connection shall be at least 25 feet from the nearest wall of the vault and shall be compatible with standard couplings used by fire departments in that area.
(n) The interior of a vault shall be designated a Class I, Division I location as defined in NFPA 70, National Electric Code.
(o) Each vault shall be equipped with adequate lighting. The lighting shall be explosion proof and conform with NFPA 70, National Electric Code.
(p) Tanks within vaults shall be approved for aboveground use and shall have been tested in accordance with UL 142, Standard for Steel Aboveground Tanks For Flammable Or Combustible Liquids, or an equivalent test procedure. Individual tanks shall be limited to a maximum capacity of 12,000 gallons.
(q) Tanks within above grade vaults shall be at least 25 feet from buildings on the same property, 25 feet from the nearest side of a public way and 50 feet from a property line that may be built upon. Tanks within below grade vaults shall be at least 5 feet from buildings on the same property, 5 feet from the nearest side of a public way and 5 feet from property lines.
Cross References This section cited in 37 Pa. Code § 14.1 (relating to installation of vaults for the storage of flammable and combustible liquids).
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