Planning for the Unthinkable Risk Assessment and Emergency Response Planning for Catastrophic Events District of Columbia Water and Sewer Authority (DC WASA)

Manager’s decision capabilities can be improved through a better understanding of a system’s inter-dependability. Communication and planning during non-emergency periods enable managers and engineers to review the impacts that would be expected during several scenarios, and what system improvements could be made to minimize those impacts. The plan that DC WASA developed helped managers achieve their Strategic Goal for improving their Technical Performance and meeting their objective of developing a Crises Communication Plan.

Redundant electrical supply is commonly used and often required as a typical risk avoidance investment. However, catastrophic loss of electrical power service, from natural disasters or man made events has impacted the assumptions made for redundant electrical supplies. DC WASA managers took the initiative during a Strategic Planning session to evaluate the impacts of a catastrophic loss of their infrastructure facilities, using scenario planning techniques, hydraulic modeling tools, and their Geographic Information System (GIS) maps.

The DC WASA provides regional wastewater conveyance and treatment service for nearly 2 million citizens. The sewer system is comprised of both combined sewers and separate sanitary sewers, with approximately one-third of the District served by combined sewers. The collection system has grown from the original foundations laid in the 1830’s, through a natural expansion and growth utilizing a number of pumping stations, regulator structures, inflatable dams, and treatment facilities. The system has a number of flexible operations strategies. Figures No. 1, attached, highlights the system configuration and complexity.

When making strategic decisions, DC WASA managers recognized that the organization is made up of interrelated and interdependent parts; decisions that impact on one part have repercussions on the operations of another part. Given that the collection system is highly complex system, decisions made during emergencies by one department may adversely impact other services that may not be aware what was occurring.

An Emergency Operations Plan was prepared based on a series of events that appeared unlikely. New tools, such as the collection system hydraulic model and GIS maps were now available to helped DC WASA managers with their planning and decision-making. At the same time, communication between various Departments during non-emergency periods allowed for a more complete review and input on any proposed action. The scenarios also provided managers the opportunity to look at issues strategically so that any risk exposure could be addressed in their long range planning.

Below is detailed information and comparison of conditions that were considered. These scenarios included:

  • Loss of pumping at the regional treatment plant
  • Loss of pumping at a combination of pumping stations
  • Comparison of impacts of these impacts during dry-weather and wet-weather conditions
  • Effect of tidal changes on the capacity of the discharge outfalls of the combined sewer system

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