There are about 168,000 public-water systems in the United States, some serving 8 million people and some serving 25. To thwart a repeat of the Milwaukee poisoning, security has been stepped up around the country’s water supplies. Since Sept. 11, the local Coast Guard has been patrolling the area of Lake Michigan where Chicago’s water intake is located. New York City has increased the number of daily samples it takes at 900 sites from 2,060 to nearly 2,500, blocked off some roads that traverse reservoirs and stationed armed guards at “critical sites” (authorities prefer not to be specific). Helicopter surveillance, including the use of night-vision goggles, has been stepped up in New York’s 2,000-square-mile watershed, where hunting, fishing and hiking permits have been suspended, says Charles Sturcken of the city’s Department of Environmental Protection.
If security at the water supply fails to deter terrorists, the next line of defense involves not technology or security, but simple dilution. “Approximately four dump-truck-loads of sodium cyanide mixed into a 1 million-gallon reservoir are required to yield a lethal dose to users,” says Jeffrey Danneels of Sandia National Laboratories. Large systems typically draw on stores of 3 million to 30 million gallons, making a high-casualty chemical attack very unlikely. Although giardia, cholera and crypto all survive in open water, exposure to the ultraviolet radiation in sunlight kills salmonella and some other pathogens.
If contaminated water reaches the treatment plant, disinfection is the next line of defense. Chlorination, used in most every municipal system, kills or inactivates viruses as well as bacteria like E. coli and salmonella. It does not kill anthrax spores. Some plants also treat water with ozone, which is more effective in killing protozoans like crypto. Ultraviolet light of sufficient intensity destroys the DNA of living organisms, including anthrax spores, but very few water systems use the expensive devices. In most facilities, the water is also filtered. Removing particles larger than 1 micron catches anthrax and botulinum spores, but some of the nation’s largest systems do not filter. And many waterworks officials are not even sure which treatments in which doses kill or inactivate which pathogens.
Security at purification plants is arguably even more important than at reservoirs. The Milwaukee Water Works, which has always tested its bulk chemical deliveries, has therefore also begun checking drivers’ names and truck serial numbers, says superintendent Carrie Lewis.
Once the processing is complete, the water is sometimes held in tanks, either on the plant’s grounds or off-site. “That’s what I put at the top of the list” of risks, says Danneels: few tanks have 24/7 security. “Money is the No. 1 reason,” says Milwaukee’s Lewis. Tanks are much smaller than reservoirs, so contamination there would be harder to thwart by dilution. They do, however, contain residual chlorination, which should kill newly arriving pathogens. The next safety net is sampling, but water systems test for only a limited number of common impurities, not exotic stuff like botulinum toxin. And the results can take days: real-time monitoring, to catch problems within hours, is at least four years away.
The distribution system of underground pipes and connections poses high obstacles to terrorism. A saboteur would not only have to get under a street to reach the pipes but would also need “some pretty sophisticated equipment,” says Jack Hoffbuhr, executive director of the American Water Works Association. “He’d have to pump the contaminant in against pressure in the pipe.” That pressure can reach 120 pounds per square inch.
FIRST STEPS: Filter all water. Adopt ultraviolet disinfection. Increase studies of exotic pathogens.
