One of the storm water discharges of the A40 motorway, situated at the East of Nantua, is equipped with a constantly working device for hydrological supervision. This discharge collects the run-off coming from 2.9 km of road area. The supervision device installed in 2001 measures and records the following values: the discharged flows, the run-off conductivity before discharging, and the same parameters, below in the brook where the water is discharged. First of all, this study is a synthesis of all the data collected during two winter seasons: 2002/2003 and 2003/2004, and it analyses the effect of the water discharge on the surface water, as far as salinityis concerned. Secondly, the study explains the results and the variationsof the conductivity measured downstream, in terms of: weather conditions,road winter maintenance practices (periodicity and quantity of spread salt), water collection and treatment system (lowering and time-lag of the peaks in the collecting system, dilution and treatment in the settling tanks, …). Finally, the study suggests new practices for the use of the hydraulic system, aiming at reducing the effect of run-off in winter, while maintaining the hydrological capacity. For the covering abstract see ITRD E143097.
Abstract