Cooperation crucial in large-scale repair job weir Linne

Damage to at least four yokes-the steel uprights that are part of the weir structure-which meant that the stability of the weir could no longer be guaranteed.

Ensuring stability permanently

Immediately after the incident, the maintenance contractor Combinatie Mourik-Dynniq arrived on site on behalf of Rijkswaterstaat and Mourik Infra was added to the crisis team. "We wanted to continuously monitor the stability of the weir, and Mourik Infra set up a real-time monitoring system for this purpose," says Jens op het Veld, technical manager of Rijkswaterstaat. "To ensure the stability of the weir and to be able to inspect and repair the damage, Paans Van Oord was approached by Mourik Infra to construct a temporary fracture stone dam in the Meuse. Building a fracture stone dam is almost an everyday job for Paans Van Oord. But building a dam at high flow velocities, upstream four meters from a weir? "That can rightly be called a challenge," says Peter Brand, work planner at Paans Van Oord. "It was a battle against the clock and the water. But thanks to the intensive effort by all involved, fantastic cooperation and our high-quality equipment, a water-safe situation was back in place within a short period of time." The dam takes over the water-retaining function of the weir that allows the water level to be maintained properly, even when the water supply decreases.

A huge job

"The repair to weir Linne is a huge job, which normally requires about two years of preparation time," explained Op het Veld. Roel van Oudheusden, project manager at Combination Mourik-Dynniq adds: "Many technical challenges and that under the necessary time pressure, that only works if there is extremely good cooperation between Rijkswaterstaat and the contractor. In good mutual consultation and after careful consideration, it was decided to also construct a crushed stone dam downstream to create a dry construction pit." Op het Veld: "Because the renovation of this weir was already scheduled at the Department of Public Works, sometime within the next five years, we decided to replace all the yokes. Inspection of the remaining yokes that had sustained no visible damage is quite time-consuming and, of course, we want to ensure the stability of the whole thing."

Critical sizing

Engineering firm Boorsma, commissioned by Mourik Infra, took charge of the complete design of the entire weir renovation, including the yokes. The entire design was realized in close consultation with Rijkswaterstaat, with Rijkswaterstaat responsible for the design choices for the sake of time. Jan Wessels, consultant at Boorsma, explains that the yokes are similar in geometry to the old ones, but have a different shape and meet the current standard. It is a great advantage in a job like this that the design and engineering for the disciplines of hydraulic engineering (fracture dam), geotechnics, concrete and steel construction and mechanical engineering are all handled in one house. For Boorsma, Linne was the third major weir renovation; the Sambeek and Belfeld weirs had been done earlier, both also commissioned by Mourik Infra. Wessels points out that it is certainly not routine work: "In Linne, too, there were plenty of design challenges for our specialists."

The yokes were manufactured at Mourik Infra, location Echt. Due to the critical dimensions and the special combination of materials to be welded together, all the craftsmanship that Mourik Infra has in house was required. Van Oudheusden explains, "Because of the tight schedule, you are designing and fabricating at the same time. So you start first on the most time-critical components. During the work you encounter technical challenges, but thanks to short lines between the project teams and quick decision-making from Rijkswaterstaat, you get it done."

Sublime cooperation

Inge Beckers, project manager at Mourik Infra cites as an example that reinforcement was needed in the rear pivot point of the yokes. "The weir must of course meet current standards and last another 20 years. By modifying the design of the yokes, we brought the weir up to current standards." New bridge sections were also designed and a winch structure was installed. Says Op het Veld, "Because the yokes are interconnected with cables, a 65-ton winch can simultaneously lower and set the yokes at the push of a button." After a busy period of design, fabrication and preparations, assembly of the first of the weir's fourteen yokes began at the end of August. Construction of the weir continued unabated, with the weir able to turn the water back into the Meuse fully independently by November 1, 2020. Just in time for the start of the flood season. 

Let's be clear: thanks to the problem-solving ability of the project teams and the good mutual trust, it is possible to complete a job of this magnitude without a defined contract within such a tight timeframe. "Even in corona time and, of course, with the desired and required quality," concludes a satisfied Op het Veld.