KEMROC DMW Cutting Wheel Provides Economical Demolition of a Weir Wall
Published: 15/1
By late 2024, migrating fish will have free passage again when the weir system in Stadtilm, Germany, is dismantled. Once part of a hydropower system, the weir has been little more than an obstruction for more than half a century. With other system elements already dismantled, contractor JeFra Bauservice GmbH & Co. was tasked with removing, solid concrete weir wall, over which water flowed down into the downstream basin. Due to the wall’s dimensions—82 ft (25m) long and 6.5 ft (2m) high – and its composition of unreinforced concrete interspersed with wooden structures, it was decided that the KEMROC DMW 220 cutter wheel with a cutting depth of 3.2 ft (1m) on a 32t excavator would be the most suitable equipment for the job A 30t excavator with hammer and sorting grapple would support the operations.
Another important factor, according to Jens Frank, Managing Director of JeFra Bauservice, the weir system was directly integrated into bank reinforcement on both sides of the river.
“Vibration from an excavator using a hammer attachment could result in damage to the adjacent buildings,” Frank explains.
KEMROC’s DMW range of cutter attachments’ have benefits when refurbishing existing concrete structures where hammers or pulverizes could damage other remaining structures due to excessive vibration. The DMW range comprises models in four sizes for carriers from 14t to 60t operating weight. In addition, models in the DMW range from KEMROC are “watertight” to depths of 100 ft (30m), making them suitable for underwater trenching and demolition work.
Demolition work on the weir wall was carried out over a two-week period in July and August 2024. At predetermined intervals the operator of the large excavator cuts through the weir wall which effectively prevented transmission of any vibration in the direction of the riverbank. The smaller excavator then freed individual wall segments and transported them to the riverbank for transport away from the job site. Despite some interruptions due to heavy rainfall, the work was completed on schedule. “According to the values measured by the consultant’s office, we always remained far below the limit values set for vibration,” Frank adds.
Ecological hydraulic engineering
Overflow weirs like the one at Stadtilm are insurmountable barriers for aquatic life. They interrupt passage along the river for fish and other wildlife whose life cycle requires free movement in the water.
“Fish in this body of water have never passed upstream beyond this weir,” says Jens Görlach, a graduate fisheries engineer from the Thuringian State Office for Environment, Mining and Nature Conservation. The agency is replacing the weir with a so-called bottom slide to overcome the difference in height of the riverbed by building a relatively flat gradient over a length of about 330 ft (100m). An arrangement of stone bars across the entire width of the riverbed will create a number of basins through which the fish can swim upstream.
With at least a dozen other such weir systems remaining to be dismantled or demolished, Frank says a cutter wheel will prove to be a valuable solution.
“We have already had several applications which were successfully completed with the help of KEMROC attachments,” he says. “We trust that we will continue to find suitable solutions for special challenges together with the specialists from this manufacturer in the future.”
