The Block 37 development in downtown Chicago involved construction of a high rise building, two tunnel connections and a new platform. During excavation of the tunnel connections, cracks were noted in the freight tunnel underlying one of the excavation zones. The tunnels at that location were horseshoe-shaped, approximately 7.7-foot wide and 9.7-foot high and were instrumented. The freight tunnels house sensitive utilities vital to the City of Chicago. The objective of this paper is to evaluate the instrumentation program employed for freight tunnels at Block 37, analyze the data and help design more effective instrumentation plans for Chicago freight tunnels for future projects.