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COSTING 1. Swales The works and the quantities of the materials used for the construction of the first type of swales are presented in the following table. The presented unit cost values are based on actual prices in Greece Figure 1.1: Schematic of a swale The considered swale is of trapezoidal cross section with bottom width 1.00 m, depth 0.30m and bank inclination 1:1. Table 1.1: Direct cost for the construction of 1 m of swale 1 2 Unit cost Direct cost [€] [€/m] 0.39 12.00 4.68 1.95 0.50 0.98 TOTAL 5.66 €/m Works / materials Unit Quantity Excavation m3/m m3.km/m Transportation and deposition of excavations at a distance of 5 km The direct cost that has been estimated above includes materials and labour. In order to convert direct cost into total cost, taxes, overhead and financial charges, bonds, etc have to be added. These additional charges are typically estimated between 60-100% of the direct cost. Accordingly, the total cost for the construction of a swale is considered to be between 1.6 × 5.66 – 2.0 × 5.66 €/m = 9.0 – 11.3 €/m. 2. Enhanced dry swales (or trough-trenches) The works and the quantities of the construction materials are calculated per meter in the following table. The presented unit cost values are based on actual prices in Greece. In the system of trough-trench the considered trough is of trapezoidal cross section with bottom width 1.00 m, depth 0.30m and bank inclination 1:1. The trench has rectangular cross section with bottom width 1.00 m, depth 1.00 m Τhe bed between the trough and the trench has rectangular cross section with width 1.00 m and depth 0.30 m. Figure 2.1: Schematic of a trough-trench Table 2.1: Direct cost for the construction of 1 m of trough-trench 1 2 Unit cost Direct cost [€] [€/m] 1.40 12.00 16.80 m3.km/m 7.00 0.50 3.50 Works / materials Unit Quantity Excavation m3/m Transportation and deposition of excavations at a distance of 5 km 3 Coarse aggregate m3/m 1.00 11.00 11.00 4 Supply and installation of the pipe m/m 1.00 12.00 12.00 5 Geotextile kg/m 0.20 6.00 1.20 6 Overflow 5.00 5.00 TOTAL 49.50 €/m In order to convert direct cost into total cost, the additional charges have to be added. These additional charges are typically estimated between 60-100% of the direct cost. Accordingly, the total cost for the construction of a swale is considered to be between 1.6 × 49.50– 2.0 × 49.50 €/m = 79.00 – 100.00 €/m. According to data obtained from Germany, the construction cost for a trough-trench is around 150 €/m. 3. Wet swales The costing of a wet swale is similar to that of a constructed stormwater wetland.