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
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)