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Threat Ensemble Vulnerability Assessment: Sensor Placement Software

Homeland Security Research News
The figure shows sensor locations (dots) recommended by TEVA SPOT to be added to a water utility distribution system (lines).
Water distribution networks deliver drinking water to consumers through systems of pipes, valves, pumps, and tanks. Within these systems, sensors that can detect contaminants can be placed at various locations, such as fire stations, schools, hospitals, public buildings, publicly owned infrastructure, and even private homes. While many utilities are able to identify locations to help monitor daily water quality, it is more difficult to identify locations for monitoring water security. Determining water security monitoring locations is difficult because there are no applicable government regulations.

Studies have shown that optimization methods and models outperform experts in selecting sensor locations. For this reason, EPA developed the Threat Ensemble Vulnerability Assessment and Sensor Placement Optimization Toolkit (TEVA-SPOT) software, which can be used to:

  • Recommend sensor placement in water distribution systems for the detection of contamination incidents
  • Quantitatively compare the benefits of different sensor designs
  • Assess the consequences of contamination incidents
  • Improve water distribution system network models

Development of TEVA-SPOT Software

In 2003, EPA’s TEVA Research Program partnered with the University of Cincinnati, Sandia National Laboratories, and Argonne National Laboratory to investigate sensor placement issues. Research has focused on questions such as:

  • How can effective placement of sensors within a large water distribution system be identified quickly (i.e., within minutes to hours) using typical desktop computers?
  • Can multiple performance objectives be optimized at the same time (e.g., a sensor network that minimizes both detection time and the public health impacts of a contamination incident)?
  • Should the sensor network be designed to detect only very high consequence scenarios, or should it also be designed to be capable of detecting localized, small-impact scenarios?
  • Is there one generic approach to sensor placement that can be recommended to most water utilities?

This research has resulted in the development of the TEVA-SPOT software, which has been described in several conference proceedings papers and presentations, as well as in journal articles. The TEVA-SPOT software was developed through an ongoing collaboration between EPA, the American Water Works Association, and more than 20 participating water utilities, and is in the testing and development phase. In addition, the research will yield a technical report that provides recommendations on designing contamination warning systems for improving the security of drinking water distribution systems. This report is expected to be available in 2008.

Use of TEVA-SPOT Software

TEVA-SPOT software can be used to determine the number and location of sensors needed to support a contamination warning system. The location of these online sensors is optimized to detect contamination incidents in time to mitigate both economic and public health consequences. The software allows the user to specify a wide range of performance objectives, determining:

  • Population-based health measures
  • Time to detection
  • Extent of contamination
  • Volume of contaminated water consumed
  • Number of contamination events detected

TEVA-SPOT facilitates interactive design and allows the user to specify constraints to ensure that multiple performance objectives are simultaneously satisfied. For example, a TEVA-SPOT user can integrate expert knowledge during the design process by identifying either existing or unfeasible sensor locations. Installation and maintenance costs for sensor placement can also be factored into the analysis. A particular strength of the TEVA-SPOT software is that it determines optimal sensor locations for large water distribution systems. TEVA-SPOT also provides methods (heuristic and exact solvers) for solving the optimization problem quickly.

In order to use TEVA-SPOT, it is necessary to have utility-specific input (e.g., a water distribution system network model). Through the application of TEVA‑SPOT, improvements to the distribution system models have been made, which in turn have benefited the water utility’s understanding and management of the distribution system. It should be noted that the software can also be used to demonstrate the importance of a rapid response to a detected contamination incident.

Availability of TEVA-SPOT Software

TEVA-SPOT software is available to water utilities participating in EPA’s Water Security Initiative. It is anticipated that the software will become available to a larger group of water utilities in 2008.

TEVA-SPOT is not intended to replace any commercial software, but rather to supplement existing software or serve to motivate further commercial development of similar products. In addition, it is hoped that the release of TEVA-SPOT will motivate additional research and development in this field.

See Also
Threat Ensemble Vulnerability Assessment Research Program


Contact: Regan Murray

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