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Every storage container installed underground shall be buried not less than 6 inches below the surface of the natural grade level except where the container might be subject to abrasive action or physical damage due to vehicular traffic or other causes in which case it shall be:
Installed not less than 2 feet below the surface of the natural grade level; or otherwise protected against physical damage.
Every such vessel shall be set on a 6-inch thick bedding of water-washed sand (beach sand shall not be used) free from soil, rock, or gravel. Before any back filling is done, the position of the vessel and the sand bedding shall be approved by the Chief. After such approval, the excavation shall be back filled with the same quality water-washed sand in such a manner that the sand back fill on the sides, ends, and the top of such vessel shall be at least 6 inches thick.
Every opening for the attachment of piping and appurtenant equipment shall be in the top of such vessel. No pipe or equipment connection to any such vessel shall be buried underground, but shall be aboveground, connected to a dome or passageway which is an integral part of the vessel, or shall be in a valve pit constructed as provided in Section 57.5003.2.4.3.2.6.
A collision barrier and a security fence, constructed as provided in Section 57.312, shall be installed and maintained to provide a minimum clearance of 5 feet from the outer portion of every pit, vaporizer, pump, valve, or pipe riser.
All buried containers shall be completely uncovered for an inspection of all external surfaces at least once every three years. The intervals may be changed at the discretion of the Chief if a test plate is buried adjacent to the container and shows no appreciable corrosion on inspection by the Department after three years of service; provided, however, that every container shall be uncovered at least every 15 years. The test plates shall be of the same material as the shell of the tank and shall be at least 1/4 of the container diameter in length and 6 inches wide, and shall be buried in the water-washed sand at least as deep as the lowest surface of the container and shall not be coated. Test plates shall be provided in accordance with the following:
1. Containers 10 feet or less in length, one test plate.
2. Containers more than 10 feet but less than 20 feet in length, two test plates, one on each side near opposite ends.
3. Containers 20 feet or more in length, one test plate for each 10 feet of length, placed on alternate sides at 10-foot intervals.
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