Transcript SUDS Retrofits

SUDS Retrofits in Scotland
Barbara Barbarito
Environmental Quality Advisor
Scottish Water
Summary
• SUDS retrofits in Dunfermline
• SUDS retrofits for Bathing Waters
improvements
• Caw Burn wetland
Retrofitting Sustainable Urban
Drainage Systems- Dunfermline
Case Study
Scottish Executive
Scottish Water
SEPA
Hyder Consulting
Desk based study investigating Dunfermline
and Iron Mill Bay
Tower Burn
Calais Burn
Lyne Burn
Iron Mill Bay
Dunfemline Town & Iron Mill Bay
Objectives

Identify and rank in order of importance areas
contributing to the flow in the sewer system

Establish runoff generated by the subcatchment
targeted for investigation

Identify areas where SUDS could be retrofitted

Assess costs and benefits of SUDS vs
conventional approaches

Quantify water quality improvements that can be
provided by introducing SUDS
Results
 Road and roof area contributes the highest
percentage of runoff to the combined system.
 Suds retrofits in isolation will not solve problems with
the sewerage system-need strategic approach.
SUDS Retrofit Research Project –
Ayrshire study
Scottish Executive
Scottish water
SEPA
WS Atkins
Aim
To pilot SUDS techniques to minimise CSO spills
impacting onto identified bathing waters by limiting the
entry of surface water into the combined sewer
system.
Study area: Ayrshire
Objectives
 Identify sites suitable for retrofitting SUDS facilities
 Design and construct SUD schemes
 Undertake pre and post construction monitoring
 Compare the cost and benefit of the constructed scheme to
conventional alternatives
 Develop methodologies for the adoption of SUDS retrofitting,
to assist the incorporation of retrofitting into Water Industry
capital investment programmes
Method
Phase 1 – Site identification, feasibility and selection of sites
for SUDS implementation
Method
Phase 2 – Detailed design, construction, monitoring, cost
comparison, reporting
 Irvine industrial estate - combination of conventional
drainage network and feature pond
 Girvan residential area - filter drains to intercept land
and roads drainage, with underground infiltration device.
Results
 Retrofitting in isolated areas across a given catchment is
unlikely to significantly reduce the frequency and volume of
sewage discharges to receiving waters
 SUDS may be retrofitted for similar costs to those
estimated for conventional solutions.
 Retrofit SUDS can offer longer term benefits in comparison
to conventional practice, through reduced maintenance and
operational expenditure.
Caw Burn Wetland &
Catchment Improvements
(Stage 1)
SEPA
Scottish Water
University of Edinburgh (Dr Kate Heal & Dr Miklas Scholtz)
 Stirling University (Dr Nigel Willby)
Caw Burn Wetland
Constructed in 1996 to treat diffuse pollution entering the
Caw Burn (West Lothian) from the Houston Industrial
Estate, Livingston
Overflow to SUDS
SUD system
The system includes a main settlement pond and a
vegetated overland flow zone (wetland)
The flow enters the pond through
a culvert (A= 891 m2 d=60 mm)
Is then directed to the wetland
(A= 4060 m2 d=800 mm)
Benefits
 Effective in removing sediments, oil,
detergents and other pollutants
Increase in diversity of aquatic life in 2Km of
Caw Burn downstream
 Caw Burn class improved from River
Quality Class D (seriously polluted) to C
(poor)
Problems
System is considerably undersized
Comparison of design treatment volume and retention time of
the different components of the Caw Burn SUDS with the
CIRIA manual guidelines (from; Heal K and Sholz M, 2004.
Caw Burn wetland and Catchment Improvements Stage 1)
Storage volume
(m3)
Retention times
(days)
All Caw Burn SUDS
3858
0.025
Average CIRIA guidelines for
detention basins/wetlands
30219
14
All Caw Burn SUDS as % of
CIRIA guidelines
12.8
0.2
Problems ..cont
 25% of pond volume has been in filled by
sediments since construction = reduction in
water retention time
 Preferential flow and short circuiting
 Evidence of increased erosion over time
 Algae also appear to increase
Proposed options
• Flooding of entire valley floor
• Construction of additional offline SUDS
Likely to raise
water quality
to class B
• Repair gaps in hearth bank where short circuits occur
• Block preferential flow pathways
• Remove sediments from settlement pond
For More Info please contact
[email protected]
[email protected]