Residential areas, persistence

Location. The fictional River City is located on a major transportation corridor, serves as an inland port, and is a centralized hub of industrial production. The city abuts a major fresh waterway that serves as a source of drinking water for millions of people in the city and downstream from it. River City s terrain is moderately hilly and a majority of the population resides in low-lying areas, increasing the potential for a persistent toxic cloud to develop over a large residential area at a concentration hazardous to life and health. Limited evacuation routes are available to the community. River City has a population density greater than 8,000 people per square mile. 

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