EN 
DE DIBAG Industriebau AG from Munich is planning to develop the "Obere Walke" construction area in Backnang with mixed residential and commercial use. Contamination in the soil and groundwater has been identified due to the area's previous use as a leather factory.
In the event of a 100-year flood according to the flood hazard map, the planned construction project lies partly within the floodplain of the neighbouring Murr. The planning therefore envisaged the construction of a retention basin and an additional retaining wall between the future residential area and the Murr watercourse. MuP Umwelttechnik GmbH from Heidelberg was commissioned with the expert supervision of the earthworks and all work relating to the waste classification of excavated material.
To ensure the harmless infiltration of rainwater in the retention area, the official requirement was to excavate all fillings in the retention area. In order to achieve the planned base height of the retention basin, the potentially contaminated fillings were removed in layers. The disposal costs could be significantly optimised by excavating and temporarily storing organoleptically conspicuous areas separately from inconspicuous areas under the expert supervision of MuP Umwelttechnik.
A total of approx. 30,000 m³ of soil material was excavated from the entire retention area covering an area of around 9,500 m². After completion of the excavation work, the retention area was divided into grids of 1,000 m² each. Excavator trenches were made in the grid areas up to the groundwater interface and samples were taken. The samples were analysed for the parameters of the Federal Soil Protection Ordinance (soil - groundwater impact pathway) in order to ensure the success of the remediation.
After a six-month construction period, including the construction of the retaining wall and ensuring the success of the renovation, the retention area was handed over to the next trade.
