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…Pretty Nice Looking Drains Is civil engineering a necessary encumbrance involving considerable cost but no visible or tangible benefit?Because it goes largely unseen, engineering tends to matter to people only when things go wrong and fail to function properly. A tendency exists to commit the minimum required resource to obtain the minimum required result. As a consequence, marginal infrastructure can result. We believe the way to avoid costly and marginal infrastructure is to aim for a result that people can appreciate, like…
Filter Drain with filter strip • Surface runoff from road drains to median • Runoff passes through grass vegetation planted on edge of filter drain, removing pollutants • Stone medium slows and filters the water • Larger rocks and variety planting adds to the aesthetic value while slowing the flow of water
Permeable Carpark • Surface runoff from impermeable carpark surface drains over grass to filter drain • Infiltration only achievable for small carpark areas or if highly permeable soils exist on site • Otherwise, filter drain will treat and attenuate surface water before discharge
The following slides illustrate the application of SuDS principles to civil engineering designs carried out by Chris Bakkala’s team at Buro Happold.
A new Place Place = Location + Identity
1 x 5 classroom primary school 1 crèche Village hall 4 commercial units Enterprise units 9 Office/ work units 1 stables building 128 houses Accommodation = Place for Living • Allotments • Football pitch • Age-specific playgrounds • Bridle path • Wetlands, ponds – biodiversity habitats • Kick around space • Open green space
A Proposed Reed Bed and Wetland System To provide full treatment for 500P.E from the Ballyshannon Model Village and tertiary treatment to ~1000P.E from surrounding developments in Calverstown. It is proposed to achieve this through the use of a gravity fed natural treatment system having the benefit of increasing biodiversity habitats for many bird, animal and invertebrate species, in keeping with the rural aspect of the development. Natural Effluent Treatment Systems • Primary Treatment– Settlement Tank • Secondary Treatment– Horizontal Flow Reed Bed • The primary and secondary systems have been designed according to the EPA Wastewater Treatment Manuals, “Treatment Systems for Small Communities, Business, Leisure Centres and Hotels” • Secondary and Tertiary Treatment– Integrated Constructed Wetland (ICW) • The tertiary system has been designed according to the ICW concept developed by the National Parks and Wildlife Service, Department of Environment, Heritage and Local Government. Reed Bed Wastewater Treatment Systems
Horizontal Flow Reed Bed and Integrated Constructed Wetlands Weekly - Log flow rates from continuous flow monitor to and from the wetland - Examine distribution pipes for blockages - Water level management and flow maintenance - Visual monitoring of final effluent, vegetation progress and initial fencing Monthly - Surface water quality monitoring of influent, effluent and receiving water course - Ground water monitoring Yearly - Maintenance of embankments - Sediment/sludge management Very Low Maintenance
(‘Traditional’ is a word whose meaning will change in the future) Aims: Remove surface water from streetscape (conveyance) Reduce potential downstream flooding (storage) Remove heavy particulates and hydrocarbons – more recent addition (treatment) Methods: Road Gully Traps connected to an underground pipe network Attenuate stormwater on-site – via underground tanks or ponds – with discharge from site restricted via a hydrobrake or orifice plate etc Surface water from carparks and large road areas passing through a Catchpit and Petrol and Oil Interceptor Traditional Drainage Systems
Focuses decisions about drainage on the environment and on people Takes account of the quantity AND quality of runoff Takes account of the amenity value of surface water in the urban environment (work with Landscape Architects) Requires a philosophy shift from previous design techniques used Aim to mimic natural (greenfield) drainage processes, albeit in a controlled, engineered manner - Infiltration; volume of infiltration should ideally match greenfield rates - Slow runoff - Runoff to pass through vegetation - Good water quality Sustainable Drainage Systems (SuDS),or, Sustainable Urban Drainage Systems (SUDS)
Surface Water Management Train - Source Control (street level) - Site Control (estate/developed site) - Regional Control (receiving waters – local authorities) SuDS features also achieve the three main aims of the traditional drainage system, broadly summarised as: Conveyance Storage Treatment Sustainable Drainage Systems (SuDS)
Filter Strips and Swales Mimics natural drainage patterns; surface flow Surface Runoff passes through vegetation, slowing and filtering the flow Can be designed to achieve conveyance, infiltration, storage and treatment Suitable for roads, carparks and small residential developments Very economical, however flow path may be easily blocked by parked cars, construction materials etc Filter Drains and Permeable Surfaces Encourages subsurface flow Contains permeable material below ground to convey and store surface water Provides treatment by slowing, filtering and storing the flow SuDS Techniques
Infiltration Devices Subsurface – Soakaways, infiltration trenches/filter drains Surface – Swales, landscaped basins/fields Remain dry (except during heavy rainfall periods) allowing public use, such as playing fields, recreational areas, public open space etc Help to recharge groundwater, thereby mitigating development impacts on rivers and streams by maintaining base flows Detention Basins and Retention Ponds Basins are utilised during heavy rainfall to provide flood attenuation and can be incorporated to fulfill a number of SuDS aims such as treatment and infiltration Ponds retain water in dry weather, providing treatment and amenity value (with an allowance for flood attenuation) and include wetlands and lagoons SuDS Techniques
Many engineers are used to treating surface water as a ‘nuisance’ Chance to be seen as leading thinkers and designers for holistic drainage design – quantity, quality and amenity Work closely with Landscape Architects: - SuDS can play a vital role in the landscaping of a development. It is highly advantageous to work together early in the planning/design phase to understand the possibility of achieving common goals through SUDS. Opportunities from SuDS
