SUDS and Sustainability

Kate Heal, University of Edinburgh

Neil McLean, SEPA

Brian D’Arcy, SEPA

SUDS and Sustainability

• Sustainability - Neil– Economic Issues– Social Issues– Environmental Issues

• SUDS – Kate– Are SUDS Sustainable?– Pollutants and Ecology– Limits and Effects– Increasing the

Sustainability of SUDS

?

Sustainable Development• Quote from the Brundtland report -

'development which meets the needs of the present without compromising the ability of future generations to meet their own needs'.

Environmental

SocialEconomic

The Sustainability Triangle

Economic Issues (i)

• River restoration/flood control schemes may face major costs due to the legacy of contamination in stream sediments & hydrological impacts.

• Can SUDS avoid the need for future flood control schemes if used at outset of major urbanisation projects in stream headwaters?

• Can SUDS reduce costs by better management of the fate of persistent pollutants?

Economic Issues (ii)• There has been a progressive increase

in sales of permeable surface systems in England – yet no regulatory driver: cost effectiveness drives uptake.

•Formpave report that a permeable surface car park is about 15% cheaper than a conventionally drained one since no gullies or oil interceptor and fewer pipes (P Hart)

Economic Issues (iii)• Can cost savings be achieved for SUDS

technology ?– Motorway service areas M40 & M42 (R Bray Assoc.)– Schools Projects & Stroud College (R Bray Assoc.)

• Savings are achievable when SUDS are an

alternative, not an add-on• Challenge for public bodies

is to allow developers to

realise potential cost-savings

The SUDS Triangle

• Water Quality– SEPA

• Water Quantity– Local Authority

• Habitat/Amenity– SNH

Wat

er Q

ualit

y Water Q

uantity

Habitat/Amenity

Social issues (i)• Abertay studies: questionnaires, door-to-door,

focus groups (Apostalaki)• Community Engagement projects (e.g. DEX

and SE Wedge)• Just look around the DEX site: ad hoc

footpaths around every pond… people like water.

Social Issues (ii)

– Tree with raised kerbed plot

– Stops water draining from pavement

– Keeping water out of tree’s root system

– Tripping hazard!

Wet day in Perth with no permeable paving– Puddles to be negotiated

Environmental Issues• 16 fold increase in car/taxi mileage in last 50 years• 500km downgraded due to urban runoff• SEPA’s “Pressures & Impacts on Scotland’s Water

Environment” Report & Consultation– Over 6,000 km of waterbodies

“at, or probably at, significant risk”

from diffuse pollution

– Urban runoff

– Bathing waters

• SUDS can help !

Source; Campbell et al, 2004

Environmental Issues & SUDS

• Protect aquatic environment using the SUDS treatment train– prevent deterioration

• SUDS retrofits for river & bathing water quality and combined sewers – Restoration

• SUDS as habitats where possible• Most important: need action to reduce traffic volume, &

develop cleaner technology for construction & motor industries –

• Are the drainage systems unsustainable? It’s the inputs of persistent pollutants that are not sustainable

• SUDS – Lose the “S” for sustainable• UDS - Unsustainable Drained Substances!!

Are SUDS sustainable?

• Maintenance requirement

• Fate of pollutants– Redistribution of pollutants– Groundwater pollution– Disposal of SUDS sediments

• Impoverished ecology– Exotic species, monoculture planting

• SUDS failures

Estimated relative mass flow (%) of copper in different urban drainage systems for Sankt Gallen, Switzerland,

(75,000 inhabitants) (after Boller, 1997)

Combined sewer

Separate sewer

Separate stormwater infiltration

Treatment plant 5 2 2

Agriculture/deposit 71 23 23

Soil 0 0 68

Surface water 24 75 7

Groundwater 0 0 ?

0

5

10

Zn Pb Cu

g m

-2

Infiltration area

Reference area

Scottish urban rivers sediment study (SEPA, 2003)– 23/26 sites: at least 1 metal exceeded

lowest effect level– 4/26 sites: sediment classified as

Special Waste

Anthropogenic metal accumulation in top 5 cm soil over 8 years, Göteborg, Sweden (Lind & Karro, 1995)

Introductions with planting (Lancaster, 2003)

99 00 01 02 99 00 01 02 99 00 01 02 99 00 01 02

Ab

und

ance

(N

o/s

am

ple

)

Halbeath Linburn Wetland Pond 7

QuickTime™ and aGraphics decompressorare needed to see this picture.

0

500

1000

1500 Macroinvertebrates- immature snails

0

1000

11000

12000Immature snails

Limits to SUDS

• SUDS designed for specific circumstances– e.g. 10-year, 60 minute storm– e.g. treat runoff from 90% annual storms

• Poor design, construction and maintenance• Treatment facility ≠ pristine ecosystem• No one correct solution: in some situations

conventional drainage techniques (or mixture) is most sustainable option

• SUDS only one part of solution to urban drainage problems

Poor design, construction & maintenance

•Blocked & broken inlets

•Inlet to perforated pipe covered with sediment

(Images: Wolfram Schluter, Ewan Associates)

Inlet to trench

BypassInlet

Groundwater inputs to Linburn Pond (Morgan, 2004)

• Data from UWTC, University of Abertay: – Continuous rainfall for DEX catchment

– Continuous outflow for Linburn Pond

Total inflow (10% impermeable

surface)

Max possible inflow (100% impermeable

surface)

Total observed outflow

5.33 x 107 l 5.33 x 108 l 6.36 x 108 l

• Outflow > maximum possible inflow

Inflow v Observed Outflow for Linburn Pond May 2000-2001

0

50

100

150

200

250

300

350

400

450

May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00 Dec-00

Time (months)

Flo

w (l

/s)

Inflow Observed Outflow

Simulated Inflow v Observed and Modelled Outflow for Linburn Pond May 2000-2001

0

50

100

150

200

250

300

350

400

450

May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00 Dec-00

Time (months)

Flo

w (

l/s

)

Inflow Observed Outflow Modelled Outflow

Increasing the sustainability of SUDS

• Surface water management train• Improved design at all scales:

– Design with development– Design for maintenance– Design detailing

• Community engagement from start

• Multi-disciplinary approach

Construction swale, Waterside Gardens

Swale, Waterside Gardens

Sustainable development is “a journey and not a destination”

development is an opportunity…

“SUDS: Sustainable urban drainage system: a sequence of management practices and

control structures designed to drain surface water in a more sustainable fashion than

some conventional techniques” (CIRIA C521, design manual for Scotland & Northern

Ireland)