Creation of rainwater retention in Frankfurt Oder: The implementation of the "Southeastern City Center" in Frankfurt Oder included the installation of a rainwater retention system. According to the limited pipe network, a volume of about 815 m³ was essential. In autumn 2009 the construction begann with the needed ground water lowering, later on, the excavation including the sheet piling was prepared. The lack of space or storage space allowed channels are still open stormwater retention basin. The required lowering of ground water required a possible short construction period of six Weeks.