Take Onin's Report back to Hulfdan in Ironforge.
The Quarry? Yap, I see those monstrous armored steam tanks come by this post near every day.
My contacts to the east tell me that the tank starts off at Ironforge, makes a pickup at the Gol'Bolar Quarry, stops over at Kharanos to refuel and then for some blasted reason, it takes the long way around past Gnomeregan, before reaching Ironforge to drop off the shipment.
It's all in the report, <race>. Take it back to Hulfdan so he can plan the next step.