Inside a drinking water production plant, an empty bottle of chlorine (Cl2) was not replaced subsequent to a sensor malfunction. An abnormally high quantity of faecal coliform was detected during a routine inspection on samples extracted 1st June. The magnitude of this contamination could not be quickly assessed right after a flaw detected in the operator’s monitoring system; it would take 48 hours to confirm the initial analyses performed. The facility’s health services informed the municipality of Champagnole (the department seat) of this pollution incident on 4th June around 7 pm, and Champagnole officials then alerted the local population (4,075 recipients of plant drinking water) within 30 min thereafter: using the city’s electronic display panels, by microphone announcements, and at the end of a fashion show staged in front of the city hall that same evening. The operator of the water extraction site issued its own press release during the televised regional newscast. Ultimately, a total of 7,000 water customers spread over 61 towns and villages, i.e. 20,000 people in all, were cautioned to avoid consuming tap water.

The extraction site operator proceeded with an extensive manual chlorination programme in order to eliminate any bacteriological risk. Pipelines were cleaned by bleeding. On 5th June, some one dozen inspection samplings were conducted at various points on the network. A campaign of water bottle distribution was organised. Area hospitals and retirement homes for the elderly were supplied in priority, then the rest of the population with 2 bottles / day / person as of 5th June, 11 am. The Red Cross participated in this distribution effort and the local member of parliament visited the site. It was intended to supply school cafeterias by Monday 7th June, if necessary. A meeting scheduled at city hall was attended by prefecture representatives, health services and the operator; the consumption of water from the distribution network remained prohibited at least until obtaining the results of all analyses performed, which were expected on 6th June.

The results of the microbiological analyses were certified on 7th June, and the water consumption ban lifted at noon the same day. The population was informed by both telephone calls and a press release. The situation was restored to normal by 3:30 pm.