Sub-terrain Detection: The DHS TED is currently evaluating technologies to detect, predict, map, and remediate cross-border tunnels. The large number of variables and conditions, variety of detection technologies, sparsity of geologic data, and lack of test tunnels or standardized test procedures creates a complex challenge for the T&E community to predict the efficacy of one of these systems before acquisition and deployment. The S&T Directorate is supporting ongoing research and development activities associated with tunnel detection in collaboration with Customs & Border Protection, Department of Defense, and international partners. A current gap in DHS is the T&E impacts of numerous variables. Also, to assist in subterranean detection, the DHS T&E community needs modeling and simulation tools along with a reach back source to provide acoustic, seismic, and geologic expertise.