Well, the plant is at the very end of the dirt road, right by the railroad tracks (see map / image). There's pavement between the tracks and SR-89 (although it's very damaged due to heavy traffic).
If you follow FS-492 / Yavapai Co Rd 71, then FR-354 and FR-318 you will end in Jerome (see previous posts). I have completed the full Drake-Jerome run once (when I was the Slow Sweep comms ridealong during the Prescott Rally.
http://maps.google.com/maps?f=q&source= ... 2&t=h&z=15The plant construction area is more or less within the blue lines, but the final plant should be smaller (right now they have the concrete plant, storage, deliveries, etc)

The plant is also at an excellent location, because it will be right by the BNSF railway, and so they can ship cement by train straight to Phoenix or to Ash Fork and then other places. And there is plenty of limestone in the area (there's a lot of quarries there, I feel like visiting again during a weekday to see the truck traffic.
As I said before, there used to be a couple of places in there, Cedar Glade, Drake and Putenney (I think Cedar Glade was later renamed Drake, but I'm not sure), and they existed because of the limestone extraction operations back in the 1900s. Back then these towns were right by what used to be the AT&SF Ash Fork - Prescott branch and that also made shipping easier.