The aim of the weir reconstruction is to lower the weir sill by 1.5 m while retaining the dam objective. The old weir will be demolished except for the lateral abutments and the stilling basin and replaced by a new structure consisting of three weir spans, each 10 m wide and 2.8 m high. As part of the reconstruction measures, a new fish pass (slotted pass with 21 basins) will also be integrated into the weir to create ecological passability and the weir bridge will be renewed.
The purpose of the Papierwehr is the water supply of the Bergstrom above the weir, which has to be maintained as far as possible during the entire construction work. This, in combination with the confined space conditions on site, presented a particular challenge for the planning and implementation of the measure. Directly adjacent to the Papierwehr are an open-air swimming pool, water supply facilities of ThüWa GmbH and a sophisticated park, so that there was no space available for a bypass channel during construction. In order to allow the watercourse to flow during the construction phase, the construction measure will be divided into two construction sections with separate construction pits, so that half the flow cross-section will be preserved for the discharge of the water.
An initial award of construction services was cancelled in 2019 due to excessive prices. Price drivers were found to be, among other things, insufficient space for on-site construction facilities, the costly dewatering for feeding the Bergstrom, and the tight order situation prior to the start of the BUGA 2021 (due to the BUGA, the construction period was set very tightly at the request of the city under agreement of a contractual penalty). In the fall of 2021, a new invitation to tender was issued under optimized boundary conditions. The tender was held at the end of November. Four bids were submitted, three of which differed by less than 3% from the cost calculation updated in 2021. Thus, the award to the most economc bidder is scheduled for January 2022. Construction will start on February 1, 2022, and completion of the weir rebuild is planned by the end of 2024. The client is the Thuringian State Office for the Environment, Mining and Nature Protection. The project is part of the state programme for flood protection and is financed by European subsidies (EFRE), federal and state funds.
Andreas Obry – Weimar