Wipperfürth
Kerspetalsperre
Oberbergischer Kreis, Germany / 03.2021 - 05.2022
Nestled in the heart of the Bergisch low mountain range lies the Kerspetal Dam, which has shaped the region’s water supply for over 100 years. Constructed between 1909 and 1912, the structure is one of the historic dams built according to the Intze principle and remains to this day a striking example of early hydraulic engineering in Germany. PORR special civil engineering was commissioned to carry out the necessary rehabilitation works for the rehabilitation of the listed dam wall and the stilling basin bed. The works involved the cleaning and rehabilitation of approximately 2,800 m² of masonry surface, as well as the renewal of the stilling basin bed.
Facts & Figures
Company
PORR Spezialtiefbau GmbH
Type
Rehabilitation
Runtime
03.2021 - 05.2022
Natural stone, hydraulic engineering and heritage conservation at the Kerspetal Dam
Historic hydraulic structure in the Bergisches Land
The Kerspetal Dam has a capacity of around 15.5 million m³ and supplies drinking water to the region. A characteristic feature of the structure is its gravity dam design, with its curved water-facing side and typical triangular cross-section. As with many dams of this era, rubble stone made of Bergisch greywacke as well as trass mortar were used as building materials. This historic construction method continues to shape the appearance of the dam wall to this day.
Masonry made of Bergisch grauwacke
During a condition survey, washed-out joints, damaged rubble stones as well as vegetation growth on the masonry were identified on the air-facing side of the dam. For the repair work, the damaged joints were flushed out using high-pressure water jets. Subsequently, around 5,000 damaged rubble stones were replaced with new stones made of Bergisch greywacke. Finally, the masonry was re-pointed. This preserved the characteristic natural stone surface of the historic dam wall, whilst at the same time ensuring the structure remains fit for continued use.
New stilling basin base below the dam
In addition to the dam, the stilling basin base was also repaired. Inspections of the existing masonry revealed damage extending to depths of around 50 cm. The existing masonry was therefore dismantled and replaced with a new reinforced concrete structure. A new stilling basin base, forming part of the hydraulic structure, was constructed over an area of around 450 m².
Work at heights of up to 34 m
The refurbishment work was carried out along the entire airside of the dam. To this end, a scaffolding system was erected over the full height of the structure. During the construction period, the work had to be adapted to the dam’s operational conditions. This was particularly evident in the summer of 2021, when heavy rainfall led to rising water levels and the flood spillway had to be opened. As this happened, water flowed over the dam and the scaffolding system whilst the repair work continued.
The foundation for preserving the dam
Even before the renovation work was visibly complete, the conditions necessary for preserving the historic structure were being established, stone by stone and joint by joint. With the restoration of the natural stone wall and the renewal of the stilling basin bed, another chapter in the Kerspetalsperre’s history – spanning over 100 years – has been written. The works help to preserve the dam and its distinctive construction as part of the history of hydraulic engineering in the Bergisches Land.