Dirt is about to turn for another downtown Austin high-rise.

Construction will begin immediately on another office tower in downtown Austin. Co., in association with Principal Real Estate Investors, formally purchased a parcel at the former Green Water Treatment Plant downtown from the city of Austin in the last few days and is proceeding with a speculative office tower.

The office tower at the northwest corner of Cesar Chavez and San Antonio streets will complement a 440-unit apartment tower that is already going vertical at the so-called Green Water site. See .

“We are pleased to officially kick off the second phase of the Green Water Treatment Plant redevelopment with our partner Principal Real Estate Investors and the city of Austin,” said principal with Trammell Crow Austin, in a statement released to the Austin Business Journal Wednesday.