As a prerequisite to this item dropping, you must have completed the quest 'As The Crow Flies', given by Ysiel Windsinger in the Cenarion Refuge in Zangarmarsh.
This quest given by this item ultimately leads to one of the quests available for the Coilfang Reservoir Instance Hub.
This item drops from Bloodscale Nagas and the Steam Pump Overseer Nagas in Zangarmarsh.
Drain Schematics as a quest objective
Turn this item in to Ysiel Windsinger at the Cenarion Refuge in Zangarmarsh.