The French company SIBA (Syndicat Intercommunal du Bassin d’Arcachon) is investing more than 15 million euros over two years (2018 and 2019) to build a reservoir of 30,000 m³, which will store wastewater in the Lagrua region of La Teste de Buch. If a problem occurs in the sanitary network, the wastewater can be temporarily stored in this underground reservoir. This leaves enough time for the repair and the continuity of the wastewater collection remains guaranteed.
The two huge tanks with diameters of 60 m and 40 m and depths of 8.5 m are built in in-situ concrete. Walls and ceilings are lined with 9000 m² of co-extruded Sure Grip concrete protection liners in 3 mm and 5 mm thickness. This sealing is intended to protect the non-water-covered concrete surfaces against aggressive hydrogen sulfide gas. The construction team produces prefabricated elements with a height of 8.5 m with concrete protection liners and overlap joints cast in on one side. The team uses co-extruded Sure Grip liners for millimeter precision production. The white anchoring top side reduces expansion of the concrete protection liners before concreting.
After curing, these lined precast concrete elements are attached to the preconcreted circular wall and also cast with concrete. Due to the prefabricated parts with lap joints, the number of necessary weld beads is reduced to a minimum. In both tanks an additional 67 or 33 AGRULINE HDPE pipes in OD 500 mm are delivered as “lost” column formwork with simultaneous concrete protection function. The pipes serve as a casting mold for the in-situ concrete, but remain permanently in the tank even after the concrete has hardened, thus protecting the concrete columns like a second skin against corrosion by the aggressive hydrogen sulfide gas.
