4.3.8.3.(4)

Intent 1:

To remove the requirement in Sentence 4.3.8.3.(1) for underground tanks to be totally below adjacent ground level if certain conditions exist [subsurface conditions make it impracticable and adequate ground cover is provided over the portion of the tank above adjacent ground level].

This is to limit the probability of tank fire exposure and mechanical damage, which could lead to the escape and spread of liquid, which could lead to the ignition of vapour from a nearby ignition source, which could lead to harm to persons.

Intent 2:

To limit the probability that excessive external loading will lead to tank stress, which could lead to tank damage and failure, which could lead to the escape and spread of liquid, which could lead to the ignition of vapour from a nearby ignition source, which could lead to harm to persons.

Intent 3:

This also permits an unburied [aboveground] tank to be treated as an underground tank.