Full alert

By Dan Kroll

Dan Kroll examines vulnerabilities in drinking water supplies, highlighting recent breakthroughs that may prevent or detect a potentially fatal attack.

The vulnerability of our distribution systems to disruption and contamination by potential terrorist or malicious acts has been well documented. These potential attack scenarios have the ability to produce casualties on a massive scale. Studies conducted by personnel at Hach Homeland Security Technologies, Colorado State University and the US Army Corps of Engineers among others have shown that attacks on drinking water supplies could be mounted for between $0.05 and $5.00 per death, using rudimentary techniques, and could amass casualties in the thousands over a period of hours.

The most likely scenario for such an attack, in which the goal is to inflict mass casualties, is to orchestrate a simple backflow contamination event. A backflow attack occurs when a pump is used to overcome the pressure gradient that is present in the distribution system’s pipes. This is usually around 80 lbs/in and can be easily achieved by using pumps available for rent at most home improvement stores. After the pressure gradient present in the system has been overcome and a contaminant introduced, siphoning effects act to pull the contaminant into the flowing system. Once the contaminant is present in the pipes, the normal movement of water in the system acts to disseminate the contaminant throughout the network effecting areas surrounding the introduction point. The introduction point can be anywhere in the system such as a fire hydrant, commercial building or residence.

Backflows occur via accident on a regular basis and are of great concern to the water industry. Accidental backflow events have been found to be responsible for many incidents of water borne illness and even death in the United States. According to the USEPA, backflow events caused 57 disease outbreaks and 9734 cases of water borne disease between 1981 and 1998.

Intentional dissemination of contaminants through a backflow event is in fact a very critical vulnerability. Studies conducted by the US Air Force and CSU have shown this to be a highly effective means of contaminating a system. These studies show a few gallons of highly toxic material was enough, if injected at a strategic location via the proper method, to contaminate an entire system supplying a population of 100,000 people in a matter of a few hours. Using computer simulations, when a military nerve agent material was used over 20 percent of the population received a dose adequate to result in death and when a common chemical was used in place of the warfare agent the result was a casualty rate of over 10 percent. Thousands of deaths could result from this very inexpensive and low-tech mode of attack. It would cause mass casualties, be inexpensive, and actually offer the terrorists a good chance of avoiding apprehension. Unfortunately, because monitoring for contamination in the distribution system typically is limited to infrequent grab samples, the first indications of such an attack are likely to be casualties showing up at local hospitals. 

These sorts of attacks can occur from any access point to the water system. Wherever water can be drawn out, material can be forced back into the system. Access points near high flow areas and larger pipes would be favored because they would disseminate the material to a wider area more quickly, however, any access point except for those at the very end of long deadhead lines could be used to effectively access the system. 

It should be obvious from the large number of accidental backflows that occur and the fact that terrorist organizations have shown an interest in attacking water, the distribution system is a prime candidate for such an attack. Protecting against and/or detecting such an attack is difficult.

Recent breakthroughs in the online detection of contaminants have made the deployment of a cost effective early warning system capable of detecting and categorizing such events a reality. 

Biography

Dan Kroll is Chief Scientist at Hach Homeland Security Technologies and Principal Investigator for the Hach Advanced Technology Group. Kroll has developed both advanced and simplified methods for a variety of crucial water quality parameters.  He is also the author of the book Securing Our Water Supplies; Protecting a Vulnerable Resource.