In NFPA-58 3-2.4.1 (c) it states: "Where physical damage to LP-Gas cylinder, or systems of which they are a part, from vehicles is a possibility, precautions shall be taken against such damage." . What if anything covers falling objects from above.???There is a ~ 200 gal propane cylender actually built into the bottom of a cliff of granite , boulders, and vegetation held soil. Large rocks could easily fall over 20 ft onto or into the cylinder . My home is directly above the cylinder at the top of the cliff. Lack of mention of falling objects: Is that an oversight?, deliberate?, or is the provision covered somewhere else? If somewhere else, where? Help!