I searched for projects on Nueces Street. I came up with this one from 2014. It has the same address. They're calling it "2211 ATX" on the permit. It was approved. The elevations are files 22 and 23.
https://www.austintexas.gov/devrevie...erRSN=11190450
There's a 1.8 foot drop off below the 0 feet line. If you measure from that point, the main roof comes to 176.47 feet. The elevations didn't show the height for the mechanical penthouse, but I measured it as 185 feet above the main roof slab. This also shows it with 20 floors instead of 18. Maybe we'll get an updated site plan released this week that will show if they've changed it. They are working on a new site plan according to the link above.
There is also an Austin American-Statesman article about an effort to move the historic house that is on the site. The house is called the Dabney Horne House. There are several articles on it if you Google it.
http://www.mystatesman.com/news/news...istoric/nZQTK/