Tunnel inspection is a challenging problem since they typically service high volume traffic and operate in aggressive environments. Keeping tunnels open during inspection and minimizing tunnel closures and user delays must be carefully balanced with the need to conduct detailed inspections to ensure the safety of drivers. This paper describes tunnel lining impairment detection and evaluation that is performed in the Hanging Lake Tunnel near Glenwood Springs, Colorado, using air-coupled ground penetrating radar (GPR) and ultrasonic tomography (UST). Potential regions of interest to monitor are first identified using high-speed air-coupled GPR and visual inspection, and then the UST technique is used manually. This study shows that this particular combination of NDE techniques is a powerful tool for monitoring and assessing the condition of tunnel linings and can detect potential anomalies such as delamination, depth of surface cracks, reinforcement depth and layout, and lining thickness. Since typical tunnel lining evaluations only involve visual inspection and monitoring, distress observed is often the result of underlying damage that has gone undetected by the human eye. For this reason, structural impairment detection is needed to complement visual inspection in order to detect the beginning stages of damage before it inhibits serviceability requirements, or worse, becomes a public safety issue. When these early stages are identified by NDE methods before significant damage has taken place, preventive actions can be recommended that will arrest the development of further damage.