New LKA building in Hannover Mitte

At the location of the State Criminal Police Office of Lower Saxony at Waterlooplatz 11 in the centre of Hanover, the extension for the Forensic Institute (CTI) will be built starting this summer. For this purpose, part of the car park, which borders the existing office building at the rear, must be demolished. The former conference area and the old canteen extension have already had to make way.

A total of about 55,000 m³ of soil must be moved or disposed of as part of the construction excavation. These batches have to be declared and classified according to waste legislation before they can be removed, so that they can be sent to appropriately approved disposal facilities. Since there is not enough space on the construction site to place the excavated material on piles and then sample it, the entire cubic volume is to be sampled and analysed in advance in-situ via excavator trenches. Coordination on this had already taken place at the end of last year. Coordinated by M&P Ingenieurgesellschaft mbH (M&P), the type and scope of the preliminary investigation was agreed upon together with the lower waste authority of the Hanover region and the client's representative on site.

As a result, a total of 24 large excavator trenches will open up the soil and samples will be taken horizontally. Due to the large final depth of the excavation pit, the excavations have to take place in two levels. The first level, which extends to a depth of three metres below ground level, was already sampled in March of this year. The results will be given to the civil engineering company before construction begins. On the basis of the documents, concrete disposal facilities can be contracted even before the actual start of construction, because the quantity and load classes of the excavation batches are already known through the preliminary investigation. This means that the approx. 55,000 m³ can be transported to the disposal company immediately after excavation, which saves a lot of time, money and space throughout the project.

Nevertheless, a small partial area is kept as a staging area for the excavation. After all, the first two to two and a half metres are in typical Hanoverian fill, which dates back to the period after the Second World War. Surprises must always be expected here. This means that individual batches can also be made available in the construction field and, if necessary, examined more closely.

The entire excavation measure is also accompanied by M&P, always in close coordination with the waste authority of the region.

Last but not least, important new legal foundations must be taken into account in the project. For example, the so-called "Mantelverordnung" and the "Ersatzbaustoffverordnung" (Substitute Construction Materials Ordinance) included therein will come into force on 1 August 2023. This regulates the examination and waste-legal assessment of mineral waste, such as the excavated soil in this case, and replaces the previously valid Communication 20 (M20) of the Federal/State Working Group on Waste (LAGA). The date of entry into force of the ordinance coincides exactly with the start of construction of the project and also required precise consultation with the supervisory authority.