This document provides an update on EPA's vapor intrusion and TCE potential source investigation at the former NAS Moffett Field. It summarizes that TCE is a solvent that can migrate from contaminated groundwater into overlying buildings through vapor intrusion. EPA sampled over 90 residences in 2013-2014 and found TCE levels exceeding indoor air cleanup levels in only two homes, where vapor intrusion systems were installed. EPA is continuing to investigate potential TCE source areas and groundwater in order to better understand the vapor intrusion risk.