The Kachlet barrage is located north of Passau on the Danube river and was built between 1922 and 1927. It consists of a double lock on the northern side, a power plant in the middle section and a weir system with an adjacent bank wall on the southern side. After almost 90 years of operation, the individual structures show considerable damage and stability deficiencies, requiring a major overhaul necessary

The project will start with the 230 m long locks (north and south locks). The repair work will be carried out on each lock while maintaining the operation of the other lock and under the protection of watertight construction pit enclosures (braced and anchored). The existing structure must be largely dismantled and rebuilt. An 80 cm thick lining anchored back into the rock will be constructed inside the chambers. The lock heads will be almost completely dismantled and rebuilt, and the upper head will be moved around 27 m into the outer harbour.

As an early measure to upgrade the weir system, the bank wall will be repaired in two construction phases. The southern bank wall with a length of around 260 m upstream and 13.5 m downstream consists of a heavyweight concrete wall. A back-anchored combined sheet pile wall will be constructed in front of this. In addition, the associated weir fore-court and the drainage pipes will be renewed.

As part of the planned major overhaul of the weir, the solid structure of the weir base and the weir piers are to be strengthened locally. The basic structure is to be preserved in its existing state. The existing weir superstructure will be replaced by a new structure and the existing double-hook gates will be replaced by new elements. The existing inspection gate upstream will be fitted with a new lock, to be used in future as well as an emergency gate. A new landing stage is planned to replace the existing one.

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