During an extreme flood event in April 1994, severe flooding of inhabited areas and high property damage occurred in Hettstedt. As a result, the LHW commissioned several investigations to improve the flood protection situation along the rocker. As a result of the investigations, it was decided to build a flood retention pool above the local location of Wippra and to protect settlements through local measures. Preplanning for the measure was recorded in 2008. A variation discussion on possible measures was investigated and ultimately a preferential variant was developed, which was further considered in the draft. The flow cross-section of the rocker is to be expanded in the majority of the measure. For this purpose, the western shores are suitcase and the construction of a lane gutter road to manage the rivers take place. In areas with near borderline development, the use of sheet pile walls or the construction of a flood protection wall is carried out. The section under discussion in the area of responsibility of the Sangerhausen river area is approximately 1,260 m long and is located between wiper kilometers 37+750 and 39+200. Preliminary planning was developed in 2008 and design planning in 2015. As a result of the preliminary planning and design planning, a preferential variants were agreed, which must be updated up to the stage of execution in the following performance stages, to list the scope of construction services and to accompany the structural implementation up to acceptance.
The preferred option is divided into the following sub-sections:
— flood barrier with a total length of 114 m.
The flood barrier is designed to protect downtown Hettstedt from HQ100 and to achieve the level of protection in this area. As the flooding surfaces in this area are manageable, this measure only marginally affects the hydraulic conditions of the rocker.
— sheet pile wall approx. 80 m and 100 m
A sheet pile wall is planned between stations 0+610 and 0+700 as well as in the area of the Hettstedt employment office to ensure flood protection.
— profile extension with a total length of 900 m.
The planned profile expansion is to be started in critical areas where the water level of the HQ100 is heavily proliferated. The river profiles are adapted to the existing terrain with an overflowing berm with a width of 6 m and an embankment with a slope of 1:2. The berm must be designed in such a way that water maintenance from the berm is possible. The berm must also be manufactured in such a way that its upper edge is at least 0.4 m above the water level of the MQ. This prevents the MQ from spreading out. The sole and right bank of the rocker remains intact. As a result of profile expansion, the water level of the HQ100 is reduced to 0.51 m in the area of profile running expansion up to 0.51 m. The unfavorable flow rate of km 38+400 to 38+500 will also be optimised.
— replacement new building of bridge 69 AM Mühlgraben
In the area of water relocation at km 38+450, it is necessary to dismantle and replace the existing bridge. There is no planning for this yet. As a result, in the first performance stage for the new bridge construction, the performance phases 1-2 of object and structural engineering have to be developed.
The order is placed in 4 stages. In stage 1, the foundation determination and preliminary planning of object and structural engineering for the replacement new building of the bridge including special services and planning surveying Lph. 1 to 4 are commissioned.
In stage 2, building and structural engineering, the Lph. 3 and 4 for the replacement construction of the bridge as well as Lph. 4 for flood protection plants, LBP, optional basic services and additional services for the environmental impact study, the geotechnical report as well as special and additional services including the support of the approval procedures are commissioned.
Stage 3 includes commissioning property planning flood protection systems Lph. 5 to Lph. 7 and structural engineering Lph. 5 (prorated — the basic services of Lph. 5 b to d become part of the construction contract) and Lph. 6 for the replacement new bridge and flood protection systems as well as special and additional services and other freelance achievements.
Lph. 8 of the property planning replacement new bridge and flood protection systems including special and additional services and other freelance services are commissioned with level 4.
The detailed description of the services to be provided can be found in the procurement documents Part B — SOW.