Multiple container installations with a total water storage capacity of more than 180,000 gallons (681 300 L) [150,000-gallon (567 750 L) LP-gas capacity] shall be subdivided into groups containing not more than 180,000 gallons (681 300 L) in each group. Such groups shall be separated by a distance of not less than 50 feet (15 240 mm), unless the containers are protected in accordance with one of the following:
- Mounded in an approved manner.
- Protected with approved insulation on areas that are subject to impingement of ignited gas from pipelines or other leakage.
- Protected by firewalls of approved construction.
- Protected by an approved system for application of water as specified in NFPA 58, Table 6.4.2.
- Protected by other approved means.
Where one of these forms of protection is provided, the separation shall not be less than 25 feet (7620 mm) between container groups.