Abstract: After large-scale disasters, diverse partner agencies rely heavily on an information-sharing environment that supports collaborative work. In the U.S., this occurs under the Incident Command System (ICS), a structured organizational framework for coordinated action. We explore obstacles to information sharing and coordinationobserved at a county-level Emergency Operations Center (EOC) operating under ICS during the response phase of a large-scale regional disaster exercise. Textual observations collected in situ are analyzed for both the effect/manifestation and cause/source of barriers to information sharing. Two-thirds of barriers that manifest as computational issues are not caused by technology breakdowns, and a third caused by unclear processes manifest as computational issues. Overall, obstacles to collaborative work that appear to be related to computational issues are generally attributable to non-technical causes. This indicates that resources directed at improving collaborative management of disasters by enhancing technological capabilities are likely to be misdirected.