The city of Alamosa's public water system that supplies drinking water to the community became contaminated with Salmonella bacteria. Alamosa's population is about 8,900 people. The outbreak resulted in 442 reported illnesses, 122 of which were laboratory-confirmed, and one death. In general, the city was historically in compliance with all health-based drinking water standards, with the exception of the arsenic standard. Although there were several possible causes of the outbreak, our conclusion is that an animal source of fecal contamination entered the Weber Reservoir, and then spread throughout the entire system.