At the beginning of the 60s, in connection with the construction of the Colbitz II waterworks, a weighable lysimeter station was planned and erected on the current site of the infiltration plant in the Colbitz-Letzlinger Heide. This has been in operation since October 1968 and is managed by the State Agency for Flood Protection and Water Management Saxony-Anhalt (LHW). It comprises 12 weighable soil monoliths, each with a surface area of 1 m² and a usable depth of 2 m, which are planted with vegetation typical of the heath. Two lysimeter vessels each stand on a total of 6 switching weight scales. Furthermore, there are several precipitation collectors, a bulk collector for recording atmospheric deposition and a weather station with various meteorological sensors on the system. The facility collects basic data for water balance and substance input considerations of open heathland and makes it available for scientific evaluation. Since the mid-90s, the previously purely manual data collection has been gradually supplemented

as a forward value through continuous digital recording and an extension with regard to the collection of meteorological data. Due to the almost uninterrupted monitoring since the existence of the plant, a scientifically very valuable data pool has been created, which will continue to exist and be expanded. After more than 40 years of operation, minor concrete spalling occurred on the structure, which was treated accordingly. In recent years, there has been increasing damage to the concrete body. In addition to the spalling of the area, cracks now also appeared in the columns and beams up to the steel reinforcement. In order to clarify the causes of the structural damage and as a basis for the development of renovation options, an analysis of the state of the construction including the necessary chemical, mechanical, static and other test and laboratory tests was commissioned in 2015. As a result, the building fabric had to be evaluated. Here it had to be determined that due to the structural unity of beams and building ceiling, a separate demolition of the beams and new construction is not feasible and a renovation as a more cost-effective variant is not feasible. To ensure that the plant continues to operate without danger, safety measures were carried out on the structure at short notice. As part of a feasibility study from 2021, the possibilities for a partial or complete new construction of the lysimeter system were examined and variants for its implementation were developed. Furthermore, the expediency of continued operation was examined. The feasibility study serves as the basis for a fundamental decision on the future of the lysimeter facility. As part of the study, the following 5 project variants were developed:

Variant 1: 0 variant (no measures)

Variant 2: Refurbishment of existing building envelopes and technical systems

Variant 3: Replacement building with old experimental set-up

Variant 4: Replacement building with new test arrangement

Variant 5: Dismantling without replacement

For the two variants for the replacement new building, a further comparison of the construction method as a reinforced concrete basement or PE-HD container system was subsequently carried out. Taking into account the expected cost framework of the preferred variants and the scientific value of the measurement series, the tendency towards their continuation and new construction of the plant is clearly recognizable and justifiable. The preferred variant is variant 4: a new replacement building with a new test arrangement in PE-HD projector design. The new and old system are to be operated in parallel for an initial period of 4 years in order to compare recorded measured values. After that, the old plant will be dismantled. The dismantling of the lysimeter system and the replacement building are to be planned in compliance with the above-mentioned objectives.

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The order is placed in two service levels. In stage 1, the basic determination, preliminary planning, design and approval planning are commissioned.

In stage 2, the services for the production of execution readiness, the awarding of services as well as construction and property management are to be commissioned.

Optional special and additional services are also called up and commissioned in accordance with the service levels if necessary.