GR translation: under the tanks snailing whitely to heaven

[Mike Jing]

V524.30-34   They ride on up to where Pavel’s sniffing synthetic gasoline
on the side of the lampless beige hill, under the tanks snailing whitely to
heaven, here he is, one of the IG’s happiest customers. . . .
       Does Pavel know something the rest of us don’t? If the IG wanted
this to be a cover-up for something else, why not the breath of Mukuru?

What does "snailing whitely to heaven" mean here?
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