WATER SENSITIVE URBAN DESIGN TECHNICAL …

1 W A TER SEN SI TI V E U RB A N D ESI GN TECH N I CA L GU I D EL I N ES FO R W ESTERN SYD N EY D R A F T F OR C OMME NT 7 November 2003 Draft Prepared by: Supported by: Document Management Version Manager Date Final Draft URS Australia 7 October 2003 Revised Final Draft UPRCT 7 November 2003 Contents i 1 Introduction---------------------------- ---------------------------------------- ----------------------------- 1-1 Background 1-1 What is WSUD 1-2 Proponent of the TECHNICAL Guidelines 1-3 Purpose and Use of the TECHNICAL Guidelines 1-3 Australian Runoff Quality 1-4 Document Structure 1-4 2 Key Physical Characteristics Affecting WSUD in Western sydney ----------------------2-1 Climate 2-1 Geology and Soils 2-2 Groundwater/Salinity 2-3 Stormwater Management Objectives 2-5 Objectives for New

2 Developments 2-5 Construction Phase 2-5 Post-Construction Phase 2-6 3 WSUD Measures and Application----------------------------- --------------------------------------3- 1 WSUD Measures 3-1 Relationship between WSUD Measures 3-2 Description of WSUD Measures and Implementation Issues 3-3 Vegetated Swales 3-3 Vegetated Filter Strips 3-5 Sand Filters 3-6 Bioretention Systems 3-7 Permeable Pavement 3-9 Infiltration Trenches 3-12 Infiltration Basins 3-15 Rainwater Tanks 3-18 Landscape Developments 3-20 4 WSUD Planning and Selection Guide----------------------------------- ---------------------------4-1 WSUD Planning Process 4-1 Applicability and Function of WSUD Measures 4-2 WSUD Selection and Treatment Train 4-4 Incorporation of WSUD Measures in Streetscapes 4-5 5 WSUD DESIGN Specification--------------------------- ---------------------------------------- --------5-1 Introduction 5-1 DESIGN Process 5-2 DESIGN Specification DS1 Vegetated Swales 5-3 DESIGN Specification DS2 Vegetated Filter Strips 5-10 DESIGN Specification DS3 Sand Filters 5-15 DESIGN Specification DS4 Bioretention Systems 5-20 DESIGN Specification DS5 Permeable Pavements 5-28 DESIGN Specification DS6 Infiltration Trenches 5-33 DESIGN Specification DS7 Infiltration Basins 5-38

3 Contents ii DESIGN Specification DS8 Rainwater Tanks 5-43 DESIGN Specification DS9 - Landscape Developments 5-49 6 WSUD Operation and Maintenance----------------------------- ------------------------------------ 6-1 Introduction 6-1 Vegetated Swales 6-2 Vegetated Filter Strips 6-4 Sand Filters 6-6 Bioretention Systems 6-8 Permeable Pavements 6-10 Infiltration Trenches 6-12 Infiltration Basins 6-14 Rainwater Tanks 6-16 Landscape Developments 6-18 7 Life Cycle Costs for WSUD Measures-------------------------------- ------------------------------7-1 Introduction 7-1 Vegetated Swales 7-1 Vegetated Filter Strips 7-2 Sand Filters 7-3 Bioretention Systems 7-3 Permeable Pavements 7-4 Infiltration Trenches 7-4 Infiltration Basins 7-5 Rainwater Tanks 7-5 8 References------------------------------ ---------------------------------------- ---------------------------- 8-1 List of Tables, Figures, Plates & Appendices iii Tables Table Average Monthly Rainfall in the Western sydney Area Table Average Evaporation Rates in Western sydney Table Rainfall Statistics Mean Inter-Event Dry Period (hrs) for sydney Table Rainfall Statistics Mean Storm Duration (hrs)

4 For sydney Table Ranking of Objectives for New Development Table Treatable Flow Rates and Runoff Depths (Blacktown City Council) Table WSUD Measures Included in the DESIGN Specifications Table WSUD Treatment Measure Categories Table Control Levels in the URBAN Hydrological System Table Minimum Clearances for Infiltration Systems Table Site Assessment for Infiltration Systems Table Scale of WSUD Application in URBAN Catchments Table Role and Function of WSUD Measures Table Site Constraints for WSUD Elements Table Maximum Flow Velocities in Channels Table Selection of Flow Retardance Class Table Maximum Acceptable Flow Velocities in Channels Table Selection of Flow Retardance Class Table Sand Filter Particle Grading Specification Table Maximum Flow

5 Velocities in Vegetated Channels Table Infiltration Rates for Homogeneous Soils Table Factors of Safety for Infiltration (Bettess, 1996) Table Infiltration Rates for Homogeneous Soils Table Factors of Safety (f) for Infiltration (Bettess, 1996) Table DESIGN Roof Area and Number of Occupants for a given Lot Size Table DESIGN Demand for Rainwater Tank (kL/year) Table Average Efficiency of Rainwater Tank for 250 m2 Lot Table Average Efficiency of Rainwater Tank for 350 m2 Lot Table Average Efficiency of Rainwater Tank for 450 m2 Lot Table Average Efficiency of Rainwater Tank for 1000 m2 Lot Table Average Available Detention Volume for 250 m2 Lot Table Average Available Detention Volume for 350 m2 Lot Table Average Available Detention Volume for 450 m2 Lot Table Average Available Detention Volume for 1000 m2 Lot Table Estimated Unit Rate Construction Cost for Vegetated Swale Table Estimated Swale Maintenance Costs Model Farms High School Table Estimated Unit Rate Construction Cost for

6 Bioretention Trench List of Tables, Figures, Plates & Appendices iv Figures Figure WSUD Planning Process Figure Streetscape View Zone with Development Both Sides Figure Streetscape View Zone with Development One Side Figure Existing Road with Car Parking One Side Figure Existing Road with Car Parking Two Sides Figure 2 m Wide Median Figure 4 m Wide Median Figure 6 m Wide Median Figure 2 m Median with Car Parking, Permeable pavement and Street Trees Figure 4 m Median with Car Parking, Permeable pavement and Street Trees Figure 6 m Median with Car Parking, Permeable pavement and Street Trees Figure Open Space Edge Median with Car Parking, Permeable pavement and Street Trees SECTION 1 Introduction 1-1 1 Introduction Background WATER SENSITIVE URBAN DESIGN (WSUD) is a relatively new approach to WATER management in URBAN areas.

7 The objective of WSUD is to maintain or replicate the pre-development WATER cycle through the use of DESIGN techniques to create a functionally equivalent hydrological landscape. When URBAN development occurs, the natural WATER cycle is altered to the extent that stormwater runoff from individual properties and roads intensify, flows usually increase and potential contaminants from residential and commercial activity and associated vehicle use flow into the streams and watercourses. Traditionally stormwater generated from URBAN areas is conveyed efficiently to designed trunk drainage systems to reduce stormwater ponding and flooding risk. The effect of this type of WATER management approach on natural systems has in the past included: the intensification of flows in watercourses potentially resulting in stream bank erosion and sedimentation; and an increase in contamination of receiving aquatic environments resulting in generally adverse impacts on aquatic ecosystems.

8 An increase in the use of WATER resources for domestic, commercial/industrial uses as well as outdoor irrigation of gardens and open space areas; an increased tendency for more severe flooding and increased areas of flooding; Much of the Western sydney area has recently been converted from a peri- URBAN and rural landuse to residential development. The implementation of WSUD in these areas can therefore be used to counteract disruptions to the natural WATER cycle. The importance of increasing the use of WSUD has be recognised by local councils across sydney with growing acceptances of the longer-term environmental benefits of the application of WSUD principles.

9 However, implementation of WSUD has been limited in the past due to the lack of understanding of WSUD measures available and suitable to Western sydney as well as a lack of established procedures, standards and approvals within councils. This creates a perception that there are unacceptable risks involved in approving alternative approaches to WATER management. In order to encourage WSUD implementation in Western sydney this document aims to provide WSUD best management practice DESIGN specifications for a diverse range of WSUD measures at the subdivision and allotment scales. The WSUD measures provided in this document are based upon innovative WSUD methods that have proven environmental, aesthetic and economic outcomes and are applicable to the local environment of Western sydney .

10 It should be noted however that the WSUD DESIGN specifications provided is not an exhaustive list of all possible WSUD measures that could be used in URBAN development. However, they do include those measures that are most likely to be used in the Western sydney region. SECTION 1 Introduction 1-2 The appropriate WSUD measures, procedures and products are generally well known, even though ongoing research is providing additional information. The challenge is to gain broad-based acceptance and application of WSUD. This requires a greatly increased level of awareness and understanding of the techniques involved. This document is aimed at achieving broad application of WSUD measures by providing best practice DESIGN specifications for a number of those measures.