SUDS for Roads. Design Tools in new guidance targeted at roads engineers. Chris Jefferies, Taye Akinrelere & Frank Guz University of Abertay Dundee

Transcription

1 SUDS for Roads Design Tools in new guidance targeted at roads engineers Chris Jefferies, Taye Akinrelere & Frank Guz University of Abertay Dundee

2 What s in my talk? The context behind SUDS for Roads Overview of Design Tool SUDS Selection Flowchart Site Factor Scoring Table Worked Examples Conclusion SUDS for Roads Training delivered through EU funded Interreg IIIb Project SKINT A pond roadside as swale soft as they still soft come Pervious Bioretention Serious paving underground not as much part green! of storage the road SUDS for Roads New guidance targeted at roads engineers in the language of roads engineers 2

3 What s in the overview Functions volume for attenuation. Function treatment. SUDS Options Treatment Train. The SUDS Triangle Design Considerations SUDS Overview Good detailing is much more critical than good design Rules are relatively simple What is continuation flow? How much storage is needed to control to the above flow? How many levels of treatment are provided? 3

4 SUDS Design information CIRIA C697 The SUDS Manual Comprehensive guidance on most SUDS types Covers general principles And design guidance for specific SUDS components. Not good on hard SUDS for small sites Sewers for Scotland Addresses what Scottish Water will adopt; Basins and ponds. Source control preferred. Seeking integrated solutions Most principles likely to apply in England following new legislation. SUDS for Roads Currently at consultation available at 4

5 SUDS Overview Functions Volume for Flow Control A volume of storage is required to attenuate flows. Location of this volume is relatively unimportant although local control is desirable. Configuration of this volume is relatively unimportant. External requirements will justify the continuation flow specified. A flow control device or pipe is essential to achieve the control required. 5

6 SUDS Overview Functions Treatment SUDS are not SUDS if there is no treatment. Some types target more and different pollutants from others. e.g. a pond will remove nutrients but a swale will not. In general a SUDS component should not be pollutant specific. Critical pollutants in the context of hard and soft SUDS; Sediment Hydrocarbons Heavy metals Treatment - excellent Treatment -good Treatment almost none 6

7 SUDS Overview SUDS Options SUDS are required to meet EU Water Framework Directive actions 7

8 SUDS Overview First and second level SUDS There can be a number of levels of treatment in SUDS, 1 st, 2 nd, 3 rd etc. 1 st level effectively storage only for roof drainage or discharge to combined sewer. 2 nd level good for most applications with roads, car parking etc. 3 rd level needed for larger sites or where special environmental protection is needed. Most SUDS under consideration here require 2 nd level treatment. Could be provided by; Permeable paving Detention basin with under-drain. Filter drain and swale Equivalent proprietary SUDS. 8

9 Overview of SUDS for Roads Design Tools The road is at the centre of the design tools. Level of treatment is the most significant new aspect. Compatible with hydrologic criteria. Technical, financial and other issues addressed. Flowchart represents an iterative process. Scoring approach to to facilitate resolution of of conflicts. Worked examples - demonstrate adoptable best practice. 9

10 SUDS Selection Full Flowchart Three processes; Scoping Evaluation Final selection Six stages for details; a. Description b. Characterisation c. Applicable options d. Preliminary design e. Financial considerations f. Final selection 10

11 SUDS Selection Flowchart Stage 1 - Scoping Characterise site Levels of treatment Space available Slopes Soils/ geology Integration Options identification 11

12 SUDS Selection Flowchart Stage 2 - Evaluation Social criteria? Technical drivers O & M. Outline design. Financial. Capital cost. Whole life cost. 12

13 SUDS Selection Flowchart Stage 3 - Final Selection Final selection made after full consideration of all options and criteria. Including financial criteria. 13

14 Site factor scoring table Purpose of scoring; To enable identification of priorities. To address key constraints. It is for ranking purposes, not for design numbers. Binary scoring one or zero. Relatively subjective. Provides a basis for conflict resolution. 14

15 Site factor scoring table Data from Worked Example 1 Wauchope Square Permeable Block pavements Land / Space requirement Contributing Drained area Porous Asphalt Bioretention area Sand filter Modular Storage System Site Gradient Groundwater level Soil Type Not acceptable Acceptable Contaminated land Underlying geology Surface Water abstractions Integration with existing road Infrastructure Integration With Utilities and other Infrastructure Functional requirements* Level of treatment required Flow attenuation SITE FACTOR SCORE

16 SUDS for Roads Matrices To assist in making the correct choices. Three matrices Options Performance Maintenance 16

17 SUDS for Roads Options matrix 17

18 SUDS for Roads Performance matrix 18

19 SUDS for Roads Maintenance matrix 19

20 The guidance includes four worked examples 1. Wauchope Square - Permeable Paving in the City of Edinburgh (Next talk). 2. Calderglen High School - Detention basin and permeable paving serving roads at a school in South Lanarkshire. 3. J4M8 - Filter strip roadside and swale on an access road to a distribution hub in West Lothian. The SUDS are part of a three level treatment train. 4. Whiteness Nursery - Permeable paving in a small development. 20

21 Worked Example 2 Calderglen High School Permeable paving at disabled parking spaces Detention basin with school to right and public road to left Drainage of access and hard standing at a school. Two levels of treatment required. Permeable paving within car parks and detention basin. Site drainage had to address runoff from the full development including buildings and recreational areas. Example relates specifically to the vehicular accesses at the school. All details to adoptable standard. 21

22 Worked Example 3 J4M8 Swale with gully inlets Filter Strip and Swale Adopted link road to a distribution centre Roadside filter strip and swale. Three levels of treatment. Two of which are provided in the filter strip. Third is provided by a pond. Pond storage incorporates attenuation storage. 22

23 Worked Example 4 WHITENESS NURSERY DUNDEE Permeable adoptable road. Infiltration and no point outlet. Two levels of treatment. Small, high quality housing development. The SUDS in the road drain; The adoptable road. Housing and associated parking/ driveways. The impermeable access road. Infiltration is good; Soil and rock is highly satisfactory Infiltration SUDS have been designed. 23

24 Conclusion SUDS for Roads design tools have been presented. They are modified from existing guidance. The tools focus specifically on Roads. Experience is needed to improve the design tools. More case studies and worked examples needed. Please use the consultation to improve the guidance. Available at Thank You 24

25 SUDS Design information CIRIA C697 The SUDS Manual Comprehensive guidance on most SUDS types Covers general principles And design guidance for specific SUDS components. Not good on hard SUDS for small sites Sewers for Scotland Addresses what Scottish Water will adopt; Basins and ponds. Source control preferred. Seeking integrated solutions Most principles likely to apply in England following new legislation. SUDS for Roads Currently at consultation available at 25