SUDS and Sustainability Kate Heal, University of Edinburgh Neil McLean, SEPA Brian D’Arcy, SEPA.

transcript

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

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 ?

Zn Pb Cu

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

Halbeath Linburn Wetland Pond 7

QuickTime™ and aGraphics decompressorare needed to see this picture.

1500 Macroinvertebrates- immature snails

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

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

Time (months)

Inflow Observed Outflow

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

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

Time (months)

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)

SUDS and Sustainability Kate Heal, University of Edinburgh Neil McLean, SEPA Brian D’Arcy, SEPA.

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