Subs above ground thomas geoghegan

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Sustainable Drainage Systems:

Above ground

attenuation

Thomas Geoghegan

Agenda

Background on Sustainable Drainage Systems (SUDS)

Selecting the best SUDS option

Above ground attenuation options

Case Study

Why choose above ground attenuation systems?

Questions

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Background on SUDS

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Background on SUDS

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• Drainage Design in the past has been simply using a rational method size pipes to ensure water is removed as quickly as possible

• Sustainable Drainage Systems: is a concept that includes long term environmental and social factors in

decisions about drainage.

• In rural areas 80% of rivers are below ground status

• Most pollution comes from:

- Underperforming small treatment plants

- Overloaded communal septic tanks

- Clusters of single unit septic tanks

- Farmyard runoff

• Over the past decade Ireland & the UK have been developing a more sustainable approach


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When selecting Sustainable drainage systems it important to consider Quality, Quantity Amenity Equally


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• There is no correct way in choosing the best SUDS option but these factors must be adhered to:

- Design techniques to meet design criteria

- There is no single correct solution: selection could result from

external factors

- The sustainable drainage system should be in accordance with

the original drainage system

- Decision must be on a wider context and not purely technical


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Basins and ponds Filter strips & swales


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Basins and ponds Basins are areas for storage of surface runoff & are free from water under dry

weather flow conditions. These include:

- Flood plains

- Detention basins

- Extended detention basins

Ponds contain water in dry weather and are designed to hold more when it

rains. They include:

- Attenuation ponds

- Flood storage reservoirs

- Lagoons

- Retention Ponds

- Wetlands


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Basins and pondsBasins and ponds store water at the ground surface as:

- Temporary flooding

- Flood plains

- Permanent ponds


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Basins and pondsQuantity

They store floodwater and release it slowly once the risk of flooding is over

Quality

Treat:

- Settlement of solids in still water

- Conditions and promotes settlement

- Adsorption by vegetation of soil

Amenity

Offer:

- Sports and recreation

- Wet ponds are great to store water for reuse


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Filters strips & swalesFilter strips and swales are vegetated surface features that drain water evenly

off impermeable areas. Swales are long shallow channels whilst filter strips

are gently sloping areas of ground.


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Filter strips & swalesThey work by imitating natural drainage patterns by allowing rainwater through

vegetation, slowing and filtering the flow.

Quantity

Swales & filter drains are designed for:

- Conveyance systems

- Infiltrations

- Reduce drained impermeable areas

Quality

Swales and filters remove polluting in the solids through filtration and

sedimentation


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Filter strips & swalesAmenity

Swales and filters trips are often interpreted into surrounding land use

Examples are:

- Public open space

- Road verges

- Grass and flowers can be planted for wildlife

Case Study

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Matchborough School

Case Study

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Location:

Redditch, Worcestershire, England

Description:

A school development was designed with conventional drainage that flowed to

a pump station from where it was pumped to a sewer

During construction one playground area could not be drained by gravity to the

pumping station.

Main suds used:

Swales

Detention basins

Case Study

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• The suds scheme was implemented & removed the need for the station

• Now follows the contour of the site and drains downhill to a ipsley stream

Initial proposal Sustainable drainage outline proposal

http://www.ciria.org.uk/suds/images/case%20studies/matchborough_initial_proposal.jpg

http://www.ciria.org.uk/suds/images/case%20studies/matchborough_sd_proposal.jpg

Case Study

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Swales collect overland flows from: - Adjacent site - Runoff from car park

- Playgrounds - Hence providing source of control

The retention basins drain the main driveway that is connected to a

constructed wetland (pond) which also takes runoff from the roof.

Car park Inlet

Case Study

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Benefits

The suds system has brought a valuable amenity and teaching resource for the

school

Why choose above ground attenuation systems?

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- Installed and maintained at a lower cost compared to more traditional

systems of drainage

- Problems can be observed and dealt with as they arise(swales)

- Can be incorporated into any terrain

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Any Questions?

Subs above ground thomas geoghegan

Education

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