The four-day Cascadia Rising exercise of 2016, which simulated a magnitude 9+ rupture of the almost 700 miles long Cascadian subduction zone with up to 5 min of violent shaking followed by a 20 to 30 feet-high tsunami in the Northwestern United States, was one of the largest response exercises of a catastrophic incident ever conducted in the United States. It involved 23,000 professional responders in three states in the Pacific Northwest. In reality, the simulated catastrophe would likely carry a five-digit number of fatalities and send the entire region on a decades-long course of recovery to a “new” normal, in which nothing would be close to what it once had been. The study investigated the numerous managerial challenges that responders faced. Communication and coordination challenges were found the most prevalent among other challenges. The research also uncovered the lack of standardization of response structures, processes, and procedures as major inhibitors of a more effective response besides other inhibiting factors. While the “containment” and “effective mitigation” of a truly catastrophic incident is illusory, the study provides recommendations regarding preparation and problem mitigation in the management of the response.