During the course of environmental due diligence, Targus identified the presence of one used oil underground storage tank (UST) in the basement parking garage of the Williams Tower. The UST was reported to have previously been removed or filled in place; however, state regulatory listings indicated that the UST remained in place and was out-of-use. Upon further investigation, the presence of the UST was confirmed by direct examination. After required regulatory notifications, a licensed UST contractor exposed tank openings, emptied the contents, and cleaned the interior. Targus completed a Release Determination Assessment by sampling around the tank and augmented that with separate groundwater sampling conducted at nearby accessible locations. After characterization of liquid removed from the tank, the liquid was transported for off-site disposal. With concurrence from the Texas Commission on Environmental Quality (TCEQ) Petroleum Storage Tank group, based on the physical access limitations posed by low overhead and interference by building structural members, the UST was filled with a cement grout and the surface patched. A No Further Action Letter was subsequently issued by the TCEQ.