Win-Win for People and Nature

The Lac du Jaunay is largely responsible for the supply of drinking water to the western Vendée region of France. However, its capacity proves to be insufficient at various times of year and surplus precipitation flows unused into the sea during the winter.

Climate change and its impact on precipitation in the region prompted the water utility Vendée Eau to look for additional storage capacity in good time. The company found what it was looking for in Les Clouzeaux, which has a disused quarry on its outskirts. Instead of building a dam to create a new lake, the water utility seized this ideal opportunity to use a derelict site.

Doubling storage capacity

The old granite quarry, which operated in Les Clouzeaux until 2018, will be able to store 2.5 million m³ of raw water, thus almost matching the capacity of the Lac du Jaunay. A pipeline about 25 km long will allow the water to be transmitted in both directions.

The installation of the new pipelines called for extensive preparations. But before the work could really get started, nature had already taken the lead. As a nest site, a pair of peregrine falcons had chosen, of all places, a spot on the rock face that had been earmarked for the installation of the water pipes.

Off to a late start

Without further ado, the installation work was suspended for six months until the offspring had fledged and the nest had been vacated by their parents. But then the work could finally begin. Industrial climbers abseiled down the 70 m high rock face and first fastened special brackets to precisely hold the three parallel pipe strings.

On completion of this preliminary task, a roughly 15-strong team was busy installing the pipes in February 2022. These had been welded into string sections and two heavy-duty cranes precisely positioned them at an angle of 67 degrees ready for installation. It was now the turn of the climbers again, who screwed the pipes with precision into the prepared sleeves. The next pipe strings were then pushed into the sleeves of the lower pipe ends, likewise fastened in the brackets and welded together.

Small quantity, big demands

Although the request from our long-standing business partner SPREAD for water pipes in this region involved only 156 m of DN 300 and 84 m of DN 400, the HFI-welded pipes have to satisfy very demanding requirements in the planned application.

First, they will be exposed to extreme temperatures in summer and, second, they will be in the water at fluctuating levels for prolonged periods. After consultation with the experienced technicians of Mannesmann Line Pipe, they were manufactured in grades P355 and B in lengths of 12 m with wall thicknesses of 5 and 5.6 mm and delivered by Capelle freight forwarders. The pipes were lined with drinking-water-standard Portland cement and given a special 'Interzone 954' outer coating resistant to heat, cold and water.

Second-hand recreation area

Following the spectacular installation and connection of the pipes, flooding of the quarry started at the end of March 2022 and is scheduled to be completed over the winter of 2022 by April 2023.

By then a roughly 10 hectare lake up to 55 m deep will have developed, providing a magnificent backdrop for running, horseback riding and walking. It will also become a new habitat for flora and fauna. 6,000 new trees have already been planted and five observation points have been set up. The Tinouze, a stream passing close to the quarry, has been renatured, and an educational trail for young and old explains the history of the quarry, the natural water cycle, and the topic of biodiversity. A natural stone grandstand with space for up to 500 visitors will also provide a natural setting for events for local residents, clubs and schools

Let's hope the peregrine falcons find a nice place to watch!