I also wonder if the planners actually realise it is there btw. There is almost next to no detail on it, and in all the 98 documents and drawings, the only place i've seen that actually notes it is the landscape layout. And even then it gives no detail on what it is clad in, the height, what it looks like etc. Unless the planners have inserted a condition that requires further detail for it (can't be arsed reading back through all 57 of them), they could literally make it anything they want to. Not an insignificant little thing either, on many sites it might well be a contentious wee item.
Edit, couldnt resist, checked back through the conditions, nothing specifically covering the tank enclosure. You could argue it could be covered being part of the general materials condidion, but that has been discharged already without any mention of the tank room. They could as well clad that enclosure in marshmallows for all anyone would be able to know!