March: BiodefenseColorado city shuts down water supply because of salmonella poisoning

Published 27 March 2008

City orders shut down of water supply after many residents become ill; water supply to be treated for several days with concentrated chlorine, with residents restricted to bottled water and a no-shower regimen

Residents of the city of Alamosa, Colorado are in the midst of a salmonella-poisoning outbreak and were told to brace themselves for life without running water beginning yesterday. The city began to flush high concentrations of chlorine through fifty miles of municipal pipelines, and the chlorine will initially make the water unfit for anything but flushing toilets, said acting mayor and public works director Don Koskelin. The chemical will be introduced into the system at a level of 10 parts per million for 12 to 24 hours or 25 ppm for three hours. Normal chlorine levels used to treat drinking water are 1 to 2 ppm. High chlorine concentrations can cause skin, eye, and lung irritation.

The entire decontamination process could take ten to fourteen days, officials said, because even if successful the city must wait seven days for tests to confirm it has made the water safe to drink. Even before final confirmation, officials said, they will notify residents when the water is safe for short showers and other external uses. “We really don’t know how long any of this is going to take,” Koskelin said Monday afternoon. “This is an unprecedented event in this state.” Health officials received confirmation Monday that five of six water samples taken from the municipal water supply were positive for the bacteria. By late Monday afternoon, officials had reports of 219 people with symptoms — and lab confirmation of 68 cases. Ten people had been hospitalized. Last Wednesday, the Colorado Department of Public Health and Environment issued a bottled-water advisory for Alamosa, a southern Colorado town of about 8,500 people. Salmonella can cause diarrhea, fever, cramping and dehydration.

Koskelin said late Monday it was still unknown how the city supply became infected. The city’s water comes from five deep groundwater wells, generally presumed to be free of harmful bacteria and so not disinfected, state epidemiologist John Pape said. It is extremely rare to have this kind of outbreak, but there have been five cases across the United States in the past twenty years, Pape said. The city is building a treatment plant, expected to be in operation later this year, to remove natural arsenic from the water. Governor Bill Ritter on Monday asked for epidemiological and environmental expert help from the federal Department of Health and Human Services. “Local resources have become overburdened and may soon become exhausted,” Ritter said in a letter to Health and Human Services Secretary Michael Leavitt.