…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…

• 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

Filter Drain with filter strip

Filter Drain with filter strip

Filter Drain with filter strip

Grassed Swale

Grassed Swale

Infiltration Detention Basin

Detention Basin

Permeable Carpark

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.

Ballyshannon Model Village

FKL Architects

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

Streetscape room walk, grow and drive

Streetscape shaping topography to drain without pipes

Natural Effluent Treatment Systems

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.

Reed Bed Wastewater Treatment Systems

Primary Treatment – Settlement Tank

Secondary Treatment – Horizontal Flow Reed BedThe 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.

Very Low Maintenance

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

The Village,Cloughjordan

Solearth Ecological Architects

Layout

Boreens and meandering streams

SOAKAWAYS

Filter Drains

Swales and Detention Ponds

Paving over soft ground

(‘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

Sustainable Drainage Systems (SuDS), or, Sustainable Urban Drainage Systems (SUDS)

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)

• 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

SuDS Techniques

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

Opportunities from SuDS

• 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.