Sustainability: Drainage systems | Features

The following are indicative costs for commercial schemes located in south-east England, current in first quarter 2006.
Infiltration systems
Standard pavings, 150 mm thick sub-base (not SUDS, comparison only)	拢35-40/尘2
Permeable pavings, 250 mm crushed rock sub-base, disposal of spoil on site	拢40-45/尘2
Permeable pavings, 350 mm crushed rock sub-base, disposal of spoil off site	拢50-55/尘2
Land drainage, perforated pipes in trenches, granular fill	拢30-45/尘
Soakaways, crushed rock soakaway, cover and cover slab, geotextile membrane and granular surround, excavation and disposal of soil off-site	拢150-275/尘3
Swales; excavation and formation of swale channel to fall, 1m wide by 750 mm average deep; geo-textile membrane; vegetation	拢75-100/尘
Retention systems
Geocellular storage system; 500 mm thick storage blocks, perforated land drains in granular surround; sub-base; impermeable membrane; excavation and disposal of spoil off site (surface costs excluded)	拢100-140/尘2
Vortex control valves
Supply cost of valve and chamber ring only	拢200
Total cost of valve and inspection chamber	拢2,000-2,700
Control systems	听
Bypass separator, about 7,000-litre capacity	拢9,000-10,000
Full retention separator, about 7,000-litre capacity	拢15,000

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