Around 8.30 pm during a maintenance operation on a fire foam production device of a unit in a power station, the technicians inadvertently disconnected the emulsifier suction valve thinking of the automatic shutdown due to under voltage. Since the valve was a fail-safe type, it remained open allowing the aspiration of the product. The technicians then proceeded to testing the water pipe without the foam supply after manually opening the water valve and closing the valve at the foot of the emulsifier tank that retained the emulsifier in the tank. Further to this concluding test, the two valves were returned to their original position. Moreover, during a previous operation, the technicians had forgotten to close the valve draining the water from the fire circuit of the same unit. The supply pipes were consequently emptied of the water resulting in the siphoning of 1,000 l of the A3F emulsifier (agent forming a floating film) in the effluents retention drain. The product was then diluted in the last 390 m³ settling tank before being disposed off in the SALIVE river. The time that the 95% biodegradable product diluted in the decantation system of the plant crosses all the tanks allows the slowing down of the propagation speed of the product until its release into the river.
A dam has been built on the SALIVE and traces of foam have been recovered with adapted absorbents. The release of industrial water in the river has been stopped and the COD is measured in the settling tanks (1280 mg/l) and water bodies (326 mg/l). The SALIVE river passing through the plant and is channelled in a cup shaped civil engineering structure where the initial waste is stored. This allowed about 28 m³ of waste to be pumped as of 10/11/2006 and released into the sewage networks after obtaining permission from the city water authority. A treatment system using activated carbon from the COD was set up at the outlet of the flocculation system of the plant on 21/11 and 22/11. The release of industrial water in the SALIVE river was resumed and that of sewage was stopped.
For beginning 2007, the operator has planned to draft a procedure to de-commission the emulsifier network, to conduct training on the test mode requirements and operation of solenoid valves and launch a corporate campaign on the need to refurbish the facilities back to the original state as required by the test mode. The inspection authorities of classified facilities were informed on the how the accident was managed by reports dated 10/11/2006, 14/11/2006 and 21/11/2006.