A major leak of industrial water was detected at the end of November 2008 at a depth of 6 m below the research centre’s buildings. Some 65,000 m³ (i.e. 722 m³/day) of effluent from the site infiltrated into the soil and the wastewater disposal network during several weeks. The operator observed a generalised subsidence of the network over a 20-m length, with the industrial and wastewater effluents mixing upstream of the treatment plant at several points.

Once the leak had been detected, several measurements were taken: effluent transiting in the degraded industrial network adjacent to building 390 was isolated and deviated by 3 stiffening and pumping systems in December; pipelines around the periphery of building 388 were cleaned out; the deteriorated pipeline at the level of building 390 was replaced; and 14 boreholes were drilled.

A diagnosis of the state of repair of water networks had been performed in 2005; however, given access difficulties relative to this zone (low point of the research centre), this diagnostic mission using video equipment could not be conducted in an exhaustive manner (underground networks not inspected during the study). A diagnostic of collectors running in the gallery could nonetheless be completed before 2002 yet did not identify any malfunction in the underground networks as a result of insufficient indicators and criteria. The leak was caused by the ageing of underground pipelines, whose break was tied to the lack of supervision and maintenance due to their limited accessibility.

A modelling study of the consequences of a rupture to the industrial effluent network pipeline was carried out in order to determine the chemical and radiological impact on Fontainebleau sand groundwater since the site’s industrial effluents display an average tritium concentration of 100 Bq/l and in cesium 37, cobalt 60, strontium 90 and plutonium 239 of 0.01 Bq/l. This study concluded the presence of negligible radiological and chemical impacts.

In its detailed report, the operator also underscored: a diagnostic of parasite water, definition of a monitoring plan, description of missions for field actors involved in managing the water cycle, plus the drafting of an organisational memo indicating the various interfaces.