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.