Program of Attack

The terrorist attack on September 11, 2001, raised global awareness of the vulnerability of any society's infrastructure, including water supply, treatment and distribution utilities. Water utilities have always made the protection of public health their primary objective. Contingency planning for natural events, such as floods and earthquakes, as well as human-caused disasters, including spills and fires has been an integral part of water utility management.

The renewed interest in preparedness and the development of emergency response plans has catalyzed a flurry of activity. In coordination with the U.S. Environmental Protection Agency (EPA) and the American Water Works Association Research Foundation (AwwaRF), Sandia National Laboratory is developing a security risk assessment methodology for the nation's water infrastructure (Danneels, 2001). The American Water Works Association (AWWA) has presented seminars in six different locations sponsored by the EPA on "Counter Terrorism and Security in the Water Industry." In December 2001, water industry professionals from around the world convened in Hartford, Conn., for the first annual Water Security Summit sponsored by Haestad Methods, a manufacturer of software for the design and analysis of water resource systems. The Water Security Summit focused on evaluating possible terrorism scenarios, addressed topics such as financing infrastructure, detecting exposure to attacks, identifying and mitigating physical, chemical and biological threats, and developing emergency management plans.

Water quality modeling of distribution systems can be an integral component of emergency preparedness and has become a widely accepted tool in support of water supply planning, operations and research. This renewed interest in security has highlighted additional applications of models in general and water quality models in particular.

Assessing Water Vulnerability

Contamination is generally viewed as the most serious potential terrorist threat to water systems (Grayman, 2001). Chemical or biological agents could spread throughout a water distribution system and result in sickness and death amongst drinking water consumers. These include biological agents (protozoa, bacteria and viruses) and biological toxins. Diseases such as Cholera, Salmonella, Hepatitis A and Cryptosporidiosis are familiar to those who monitor water, so there is a high level of confidence in the ability of current treatment practices to protect the public from these agents. However, little is know about the ability of agents such as Bacillus anthracis, Staphylococcusavreus enterotoxins and aflatoxin to survive chlorination or the ability of current technology to detect these agents in water.

The most difficult aspect of dealing with contamination is detection.

A procedure for conducting a vulnerability assessment for a water utility has been developed by AWWA (AWWA, 2001). Highlights of this procedure as they pertain to threats of contamination are

Identify major system components. The components, which are vulnerable to contaminating agents, are the supply reservoirs or wells, transmission pipelines, treatment plants, storage tanks, pumping stations and distribution pipes. Theoretically any water tap is a point of entry. Each component should be identified and described, and potential points of access should also be identified.

Determine effects of probable disaster hazards on system components. Even if a component of the water system has been contaminated, its structural and operational integrity will probably remain intact. In fact, the most difficult aspect of dealing with contamination is detection. Ironically, the continued operation of a water distribution system may serve as the terrorists' delivery system.

Establish performance goals and acceptable levels of service for the system. A utility should develop specific goals and acceptable levels of service under emergency conditions. Examples of specific goals include

  • Life safety;
  • Fire suppression;
  • Public health needs; and
  • Commercial and business uses.

These goals will help to define the appropriate response during an emergency. For example, if a system is contaminated with coliform, a boil-water-notice will protect human health but allow the utility to supply water for other needs, such as fighting fires. Normal water use will then remove the contaminant. If a contaminant is to be flushed from the system, it must be determined if this release to the environment of a toxic substance is prudent.

Identify critical components. Critical components are those that are most vulnerable to failure or partial failure because of a disaster hazard. In terms of water quality, a critical component is one that if contaminated will impact a large fraction of the distribution system. Obviously, contaminated water leaving the treatment plant will impact the entire system. On the other hand, a small storage tank may only impact a small portion of the system.

Water quality models evaluate system performance and identify critical components. Calibrating the model for the existing distribution network and operating procedures is the first step. Then, extended period simulation of the network in response to a variety of hypothetical terrorist actions will reveal which regions are impacted, the duration of the impact and the help to identify the most critical components of the system.

Developing Strategies

After the critical components have been identified, the next step is to develop and implement strategies that will reduce the potential for a terrorist to compromise the system and mitigate the impact if it does occur. Historically, disinfection has been the best defense against biological contamination of drinking water. The operation of a well-maintained and well-equipped disinfection system by a properly trained staff will continue to provide this first line of defense.

Protection of the distribution system from access of unauthorized personnel is essential. The use of fencing, locks, cameras and security sensors will reduce the potential for unauthorized entry into tanks, reservoirs and pumping stations. Back-flow preventors will help to reduce movement of contaminants through the system.

Finally, it should be noted that the customers may be the best water quality monitors. The customers should be informed that any usual changes in the taste, odor or appearance of the water should be brought to the immediate attention of the water utility. Such notices should be taken seriously and responded to appropriately.

Response strategies to specific terrorist actions are developed in concert with model simulations. For example, if the contamination is isolated to one section of the network, and flushing is the proposed response action, the model will show the rate and duration of flushing required to reduce contamination to safe levels. Model simulations should be conducted for the entire range of anticipated attacks. For each scenario, the model can be used to

  • Identify the potential extent and level of exposure to the infectious agent;
  • Evaluate the effectiveness of response actions; and
  • Determine when the water is safe again.

Emergency Management Plans

A water utility will have only one emergency response plan that addresses all types of emergencies. Elements of a plan that are specific to contamination include

Mission, Goals, Objectives

The water utility's philosophy regarding emergency planning and response should be clearly stated. This will guide personnel in making the rapid decisions that are often required during an emergency response. For a water utility, the mission typically involves the provision of safe drinking water to the public.

Plan Activation

The emergency response plan should be activated when there is knowledge or a reasonable suspicion of contamination to the water system. The person who makes this determination (or alternate) should be identified. The criteria for making this determination should be clearly defined.

During the emergency, it may not be possible to run the model. However, the decision-makers should have a summary of model results available to them. Essentially, this would be a summary of answers to the "what-if" questions.

Communications Chart

Upon activation, the emergency response plan can only be implemented through clear and continued communication with all appropriate organizations. A communications chart should list all utility staff (and alternatives) who will lead in the implementation of the emergency response plan. The chart should include job titles, contact information and responsibilities. Others that should be included in the communications list are

  • Local and regional law enforcement;
  • Local government officials;
  • Regulatory agencies;
  • Public health agencies; and
  • Media.

Communication with the local medical community will assist in rapidly identifying any affected individuals. In the event of a terrorist attack on the public water system, it is important to keep utility communications to the public via a single, well-articulated voice. The information provided to the public should include

  • What is known;
  • What is being done;
  • What is the risk to the public; and
  • What the public should do.

Applications of Water Quality Models

To date, there are no examples of the use of models in response to a terrorist attack on a water distribution system. However, the following examples of the applications of models in forensic analysis demonstrate their effectiveness as a tool for protecting public health.

The continued operation of a water distribution system may serve as the delivery system for the terrorists.

Dover Township, N.J.

Maslia et al (2000) reported on the use of a water quality model to assist in the epidemiologic study of childhood leukemia and central nervous system cancers in Dover Township, N.J. At the end of 1997, the distribution system served 44,510 customers and consisted of 785.7 kilometers (km) of mains, three elevated and six ground-level storage tanks, 23 groundwater wells and 17 high service or booster pumps. The model was developed from databases supplied by the water utility and was calibrated on the basis of hydraulic and operational data collected during two tests. The water quality component of the model was verified against the measured concentrations of a natural tracer (barium) through the system. The model was used to simulate the operation of the system during the period from 1962 to 1996. These results will be used by epidemiologists to quantify the percent of water-received from each of the points of entry by the consumers.

Gideon, Mo.

An outbreak of Salmonella in Gideon, Mo., resulted in 31 confirmed cases and seven deaths in December 1993. Although the disease was considered to be waterborne, the source of the contamination was not known. A hydraulic model of the distribution system was developed using the waterworks system distribution map and was calibrated with the results of several pressure studies previously conducted on the systems (Clark et al, 1996). The model was used to simulate the flushing program that was implemented during the outbreak. A map showing the locations of the earliest confirmed cases of Salmonella showed correlation with the area of greatest influence of a suspected water storage tank. An inspection of the tank revealed the tank was covered with bird feathers, dirt and droppings. It was also observed that the vents were designed in a way as to allow for the entry of contaminants.

Scottsdale, Ariz.

In a complex distribution system, use of average or even hourly peak flows in a model will result in the inability of the model to simulate the variations in water quality that occur within a distribution system. In support of litigation, Harding and Walski (2000) reconstructed the historical record of contaminant concentrations in a public water system in Scottsdale, Ariz. The researchers modified the EPANET (a computer program that performs extended period simulation of hydraulics and water quality behavior) code to accept time series data files, provide continuous simulation over an extended duration and reduce data in output files. Five diurnal patterns were used to determine demands associated with land use. Their results showed that the operation of booster pumps and changes in water levels in storage tanks impacted the Trichloroethylene (TCE) concentrations at the point of use. Simulations as long as one year were required to accurately determine "average" levels of TCE exposure to water consumers.

What is Needed?

In order to integrate a model into an emergency response action, the water utility must have a working, calibrated model in place at the time of the terrorist threat. Calibration requires extensive input of the pipe network, operating schemes and field measurements. The establishment of a calibrated model will provide a utility with value beyond the terrorist threat and be a tool for cost-efficient management of the distribution system.

The following questions should be asked while selecting the most appropriate model for a specific distribution system:

  • Can the model accurately simulate the fluctuating demands and operating characteristics of a system?
  • Can the model simulate a variety of operational and control scenarios?
  • Can the model perform a multiple-day extended period simulation of the system?
  • Can the model produce easily interpreted graphic output?

Of course, the ultimate application of a water distribution model is when it is updated with near real-time data from the water distribution system. Technology currently exists that can provide feedback of pump operations data, flow and/or pressure readings and reservoir levels to a running model. The features may be incorporated into a supervisory control and data acquisition (SCADA) system. Unfortunately, near real-time monitors for biohazards and most toxic substances do not exist today. Sobsey (1998) presents a review of the latest techniques for detection of microbial contamination in drinking water. A commercial device for detecting Escherichia Coli and a DNA chip for sensing microbial pathogens are currently in development (Betts, 1999a,b).


American Water Works Association, 2001, Emergency Planning for Water Utility Management, Manual of Water Supply Practices - M19, Fourth Edition, American Water Works Association, Denver, OC.

Betts, K.S., 1999, "'DNA Chip Technology Could Revolutionize Water Testing," Environmental Science and Technology, 33(15): 300A-301A.

Betts, K.S., 1999, "Testing the Waters for New Beach Technology," Environmental Science and Technology, 33(17): 353A-354A.

Brosnan, T. M. (ed), 1999, "Early Warning Monitoring to Detect Hazardous Events in Water Supplies, An ILSI Risk Science Workshop Report," ILSI Risk Science Institute, Washington, DC.

Clark, R.M., Geldreich, E.E., Fox, K.R., Rice, E.W., Johnson, C.H., Goodrich et al, 1996, "Tracking a Salmonella servar typhimurium Outbreak in Gideon, Missouri: Role of Contaminate Propagation Modeling," J. Water SRT - Aqua, 45(4): 171-183.

Danneels, J.J., 2001, Testimony before U.S. House of Representatives, Committee on Science, Hearing on H.R. 3178 and the Development of Anti-Terrorism Tools for Water Infrastructure.

Grayman, W.M., 2001, "Vulnerability of water supply systems to terrorists activities," in: Presented at The Water Security Summit, Hartford, Conn., Haestad Press, Waterbury, CT.

Harding, B, Walski, T.M., 2000,"Long time-series Simulation of Water Quality in Distribution Systems," J. Water Resources Planning and Management, 126(4): 199-209.

Hickman, D.D., 1999, "A Chemical and Biological Warfare Threat: USAF Water Systems at Risk, Counterpoliferation paper No. 3," Maxwell Air Force Base, AL: USAF Counterproliferation Center.

Maslina, M.L., Suatner, J.B., Aral, M.M, Reyes, J.J., Abraham, J.E., Williams, R.C., 2000, "Using Water-distribution System Modeling to Assist Epidemiologic Investigations," J. Water Resources Planning and Management, 126(4): 180-198.

Sobsey, M.D., 1999, "Methods to Identify and Detect Contaminants in Drinking Water," in: Identifying Future Drinking Water Contaminates, National Academy Press, Washington, D.C.

This article originally appeared in the March/April 2002 issue of Water & Wastewater Products, Volume 2, Number 2, page 10.

This article originally appeared in the 03/01/2002 issue of Environmental Protection.

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