Rehabilitation of the historic dam wall, Kerspe dam

The PORR Specialised Civil Engineering team was deployed at the Kerspetalsperre dam for the rehabilitation and cleaning of the approx. 2,800 m2 listed dam wall as well as the bottom of the stilling basin. With their own bricklayers and concrete repairers, the refurbishment specialists brought extensive in-house expertise with them. They also have all the necessary qualifications, e.g. for dry and wet spraying methods and the inspection of scaffolding. 

25,000 quarry stones made from Bergisch greywacke

Built between 1909 and 1912, the hydraulic structure has a capacity of 15.5 million cubic metres and is used to supply drinking water to the city of Wuppertal. Like many other dams, the Kerspetalsperre was built more than 100 years ago according to the Intze principle. Its unmistakable feature is the dam, constructed as a gravity dam with a curvature towards the water side as well as a triangular cross-section. Otto Intze, the Aachen professor and pioneer of dam construction, specified coarse quarry stone and trass mortar as the construction material. 

Flushing with HDW jets

During a survey of the air side of the dam wall, flaking of the quarry stones, washed-out joints and intensive plant growth were discovered.

For the rehabilitation, the damaged joints were rinsed out using high-pressure water jets, around 5,000 damaged stones were replaced with new stones and the masonry was finally spray-pointed.

New reinforced concrete stilling basin floor

The bottom of the stilling basin was also originally built with quarry stones. Drill core analyses revealed masonry damage down to a depth of 50 cm. The masonry was therefore dismantled and the base rebuilt with 450 m2 of reinforced concrete.

The rehabilitation of the wall, up to a height of 34 metres from the scaffolding and below the spillway, was challenging for both man and material. During a heavy rainfall event like the one in July 2021, which brought with it the devastating flood of the century, the spillway had to be opened and the water poured over the special scaffolding.