Construction of Gonna Flood Retention Basin

Construction of the Gonna flood retention basin: 180 m long and up to 6 m high dam with internal sealing, reinforced concrete culvert structure on deep foundation. Earthworks include topsoil removal/application of 20,000 m², 5,000 m³ excavation, and installation of 10,000 m³ supplied soil. Drilling works involve 50 m drilling template for overlapping bored pile wall d=88 cm, 50 m drilling template for overlapping bored pile wall d=120 cm, approx. 70 units bored piles d=88 cm (6 m length), approx. 50 units bored piles d=120 cm (10 m length), and 1,000 units bar anchors for back-anchored facing shells. Piling works include 1,500 m² sheet piling as internal sealing, up to 12 m embedment depth. Dewatering works involve creating a bypass channel and open dewatering in construction pits. Pressure pipeline works outside water bodies: renewal of 60 m drinking water pipeline (incl. connection and ventilation at high point) and 60 m wastewater pressure pipeline (incl. connection and ventilation at high point). Securing works on water bodies: 600 m² riprap from hydraulic engineering stones, 1,000 m² hydraulic engineering stone fill. Road construction works: 1,000 m² sub-base without binder. Concrete works: 800 m³ reinforced concrete for culvert structure, 520 m³ underwater concrete, 850 m³ bored pile concrete. Steel and metal construction works: slide gate 2.0 m x 2.0 m clear opening, service walkway with 8 m span, spatial rake, 100 m handrail, 350 m wildlife fence. Disposal: 3,000 t soil, stones up to and including Z 1.2; 1,000 t soil, stones over Z 1.2 up to and including Z2. Unexploded ordnance (UXO) reconnaissance: 6,000 m² computer-aided surface probing and 1,700 m auger drilling.

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