Possible for a valve pit - but why enclose it without banking (assuming for blast protection) or damp proof it? Seems small for a pump house but without details of the former tank farm it would be difficult to tell. Above-ground tankage would provide some static head to prime pumps, but if they were centrifugal then I'm not sure how effective they would be situated that far from the fuel.
Perhaps an electrical distribution station to power the BFI?
It would be interesting to have a gander inside.
Edited: Ignore my last - just read the previous post. That makes a lot of sense.