A Colorado Department of Public Health and Environment recently released a report, Waterborne Salmonella Outbreak in Alamosa, Colorado – March and April 2008, which confirms earlier suspicions that an aging infrastructure and a waiver exempting some communities from treating their drinking water with chlorine allowed deadly bacteria from animals to invade Alamosa's 320,000-gallon Weber Reservoir.

In 2008, Alamosa, Colo., experienced a salmonella outbreak that caused 442 reported illnesses and one death. Epidemiological estimates suggest that up to 1,300 people may have been ill. Although several possible causes of the outbreak have been suspected, the conclusion is that an animal source of fecal contamination entered the Weber Reservoir – Alamosa’s main water source – and spread throughout the entire system.

According to the report, had the city used chlorine to disinfect its water supply, the bacteria might not have grown; however, Alamosa and 125 public-drinking water systems throughout the state had been exempted since 1974 from a state requirement to treat drinking water with chlorine, which kills salmonella bacteria. In addition to the chlorine waver, the report suggests poor maintenance, incorrect bacteria testing and inadequate supervision by a chronically short-staffed state drinking-water program combined to form "a perfect storm of multiple defects" in the city water system at the time of the outbreak.

When asked what could have prevented the epidemic, state drinking-water program manager Ron Falco, the report's co-author, answered, "Chlorination."

The findings in the report have now prompted the state to revoke waivers from 72 public drinking-water systems and require chlorine treatment of most public supplies as part of the response to Alamosa’s salmonella-poisoning epidemic. The city has also since installed advanced treatment processes and improved system operations.

The situation in Alamosa underscores why it's so important to have multiple ways to protect against an outbreak of disease from tainted water. Pipes and storage tanks can become contaminated but disinfection with chlorine will help protect the water, 24-7, in case of a failure in the system like Alamosa experienced. No waivers from disinfection is a good idea.

For more information on salmonella and safe drinking water, please visit the Water Quality & Health Council or the Centers for Disease Control.

(Chris J. Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.)

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