Presentation on theme: "SUDS Retrofits in Scotland Barbara Barbarito Environmental Quality Advisor Scottish Water."— Presentation transcript:
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
Lyne Burn Tower Burn Calais Burn Dunfemline Town & Iron Mill Bay Iron Mill Bay Desk based study investigating Dunfermline and Iron Mill Bay
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 Objectives
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
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. Aim 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
Phase 2 – Detailed design, construction, monitoring, cost comparison, reporting Method 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 flow enters the pond through a culvert (A= 891 m 2 d=60 mm) The system includes a main settlement pond and a vegetated overland flow zone (wetland) 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, Caw Burn wetland and Catchment Improvements Stage 1) Storage volume (m 3 ) Retention times (days) All Caw Burn SUDS Average CIRIA guidelines for detention basins/wetlands All Caw Burn SUDS as % of CIRIA guidelines
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
Flooding of entire valley floor Construction of additional offline SUDS Proposed options 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