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Waikato stormwater management guideline

TR 2018/01

Report: TR 2018/01

Author: Earl Shaver (Aqua Terra International Limited)

About this report

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This is one of two guidelines that address stormwater management:

The Waikato Stormwater Management Guideline is based on Auckland Council’s Technical Publication 10 (TP10) Stormwater Management Devices Design Guidelines Manual (Auckland Regional Council, 1992 and 2003) and replaces use of this guideline in the Waikato region.

This guideline also builds on other guidance including the New Zealand Transport Agency’s ‘Stormwater Treatment Standards’, Bay of Plenty Regional Council’s ‘Stormwater Management Guidelines for the Bay of Plenty Region’, Hawkes Bay Regional Council’s ‘Waterway Guidelines Stormwater Management’ and Tauranga City Council’s ‘Stormwater Management Guidelines’. 

Read or download the report

Waikato stormwater management guideline [PDF, 9.9 MB]

Contents

Part I:Stormwater management overview and orientation
1 Introduction
1.1 Overview
1.2 Principles of stormwater management
1.3 Best practicable option
1.4 How to use this guideline
2 Impacts associated with stormwater runoff
2.1 Hydrological cycle
2.2 Stormwater quantity
2.2.1 Flood effects
2.2.2 Case study – water quantity effects
2.3 Stormwater quality
2.3.1 Contaminant types
2.3.2 Contaminant sources
2.3.3 First flush
2.4 Stream morphology and aquatic resource
2.4.1 Bankfull discharge
2.4.2 Stream channel dimensions
2.4.3 Stream channel patterns
2.4.4 Stream channel profile
2.4.5 Stream ecology
2.4.6 Physical habitat
2.4.7 Ecological stress factors
2.4.8 Importance of first and second order streams
2.5 Cumulative effects
3 Waikato context
3.1 The Waikato Region
3.2 Regulatory framework
3.2.1 The Vision and Strategy
3.2.2 Waikato Regional Policy Statement
3.2.3 Relevant WRPS Policy Provisions
3.2.4 Waikato Regional Plan
3.2.5 Healthy Rivers Wai Ora: Plan for Change He Rautaki Whakapaipai
4 Receiving environments
4.1 Streams and rivers
4.1.1 Examples of impacted aquatic resources
4.2 Floodplains
4.2.1 Catchment size and slope
4.2.2 Surface conditions and land use
4.2.3 Floodplain topography
4.2.4 Floodplain values
4.3 Wetlands
4.4 Ground
4.4.1 Soil compaction
4.4.2 Contamination of soils
4.4.3 Migration of contaminants to groundwater
4.5 Karst geology
4.6 Estuaries
4.7 Harbours
4.8 Open coasts
4.9 Lakes
4.10 Geothermal areas
4.11 Stormwater management and receiving environments
5 Stormwater management concepts
5.1 Avoid, remedy or mitigate
5.1.1 Avoid
5.1.2 Remedy
5.1.3 Mitigate
5.2 Low impact design
5.2.1 Achieve multiple objectives
5.2.2 Integrate stormwater design early in the process
5.2.3 Avoid rather than mitigate
5.2.4 Manage stormwater at-source
5.2.5 Rely on natural soil and plant processes
5.3 Approaches and techniques
5.3.1 Low impact design approaches
5.3.2 Low impact design devices
5.3.3 Clustering and alternative lot configuration
5.3.4 Reduce imperviousness
5.3.5 Minimise site disturbance
5.4 Cost of low impact design approach
5.5 Stormwater treatment processes 
5.5.1 Sedimentation
5.5.2 Aerobic and anaerobic decomposition
5.5.3 Filtration and adsorption to filter material
5.5.4 Biological uptake
5.5.6 Biofiltration
5.5.6 Flocculation 
5.6 Summary
Part II: Stormwater design approach, device design and sample design calculations
6 Choosing a stormwater management approach
6.1 Regulatory and design requirements

6.1.1

 Design responsibility 

6.1.2

 Information requirements

6.1.3

 Low impact design scoring approach

6.2

 Individual device suitability

6.2.1

 Site considerations

6.2.2

 General constraints

6.2.3

 Contaminant generation 

6.2.4

 Contaminant removal processes

6.2.5

 Device selection

6.2.6

 Treatment train approach

7

 Design criteria

7.1

 Water quantity design

7.1.1

 Preventing existing flooding problems from getting worse

7.1.2

 Controlling intermediate storms
7.1.3 Catchment location 
7.1.4 Design rainfall
7.1.5 Hydrologic design method
7.1.6 Effects of climate change
7.1.7 Peak flow control criteria
7.2 Stream channel erosion
7.2.1 Runoff volume control
7.2.2 Detention time control
7.2.3 General discussion
7.2.4 What criteria should be established?
7.2.5 Where the criteria should be applied
7.2.6 Water quality credit for extended detention
7.2.7 Erosion control criteria
7.2.8 Lands within and draining into Hamilton City Council jurisdiction
7.3 Water quality design
7.3.1 General sizing requirements
7.3.2 Effluent limits versus best practicable option
7.3.3 Water quality treatment criteria

7.4

 Summary of recommendations

7.4.1

 Peak flow control

7.4.2

 Stream erosion control

7.4.3

 Water quality treatment

8

 Stormwater management device design

8.1

 Introduction

8.2

 Source control

8.3

 Designing for ease of operation and maintenance

8.3.1

 Spend a year at the practice

8.3.2

 Maintenance questions

8.3.3

 Uniform materials or components

8.4

 Designing for safety

8.5

 Specific design guidance for stormwater management devices

8.5.1

 Swales

8.5.2

 Filter strips

8.5.3

 Sand filters

8.5.4

 Bioretention

8.5.5

 Infiltration

8.5.6

 Stormwater pond

8.5.7

 Wetlands

8.5.8

 Green roofs

8.5.9

 Bush revegetation
8.5.10 Water tanks
8.5.11 Compacted soil remediation
8.5.12 Oil/water separators
9 Outlet design
9.1 Introduction
9.2 Objective
9.3 Design approach
9.3.1 Pipe or channel grade
9.3.2 Inlet and outlet velocities
9.3.3 Riprap aprons
9.3.4 Engineered energy dissipators
9.3.5 Outfalls to freshwater receiving environments
9.3.6 Outfalls in coastal receiving environments 
9.4 Detailed design
9.5 Construction
9.6 Operation and maintenance
10 Landscaping
10.1 Introduction
100.2 Objective
10.2.1 Aesthetic appeal of stormwater devices
10.2.2 Water quality and ecological function
10.2.3 Economic value of the site
10.3 Native vegetation
10.4 General landscape guidance
10.4.1 Stormwater device area
10.4.2 Landscape screening
10.4.3 Soils
10.4.4 Site preparation
10.4.5 Planting
10.4.6 General guidance
10.5 Specific landscape provisions for individual devices
10.5.1 Ponds and wetlands
10.5.2 Infiltration and filter devices
10.5.3 Swales and filter strips
10.5.4 Green roofs 
11 Proprietary devices and innovative products 
11.1 Introduction
11.2 Approval options
11.2.1 Approval through another certification process
11.2.2 Information submission to Waikato Regional Council
11.3 Information requirements
11.4 Information required to determine adequacy of monitoring data
11.4.1  Catchment parameters
11.4.2 Device design parameters
11.4.3 Water quality analysis
11.5 Discussion 
12 Contaminant loads
12.1 Introduction
12.2 Determining water quality loads 
12.2.1 Auckland Council’s contaminant load model
12.2.2 Tweed Catchment, New South Wales 
12.2.3 Nutrient export coefficient model
12.2.4 Unit loadings for nutrients based on MfE guidance
12.3 Recommended approach
12.3.1 Rainfall differences
12.3.2 Local soils
12.3.3 Case study – Contaminant load mode
13 Bringing the elements together
13.1 Introduction
13.2 Criteria detailed for the various elements 
13.2.1 Receiving environments and stormwater issues
13.2.2 Low impact design scoring matrix
13.2.3 Peak flow management and erosion potential
13.3 The overall process
Part III: Different site applications for stormwater management
14 Industrial site management
14.1

Introduction
14.2 Source control and housekeeping
14.2.1 Importance of having site plans
14.2.2 Stormwater pipes, their inlets and outlets
14.2.3 Outdoor areas
14.2.4 Stormwater and wastewater systems
14.2.5 Housekeeping 
14.3 Industries, contaminants and treatment devices
14.4 Stormwater management devices
14.4.1 Stormwater management ponds
14.4.2 Constructed wetlands
14.4.3 Sand and sand/peat filters
14.4.4 Bioretention 
14.4.5 Infiltration devices
14.4.6 Swales and filter strips
14.4.7 Oil and water separators 
14.4.8 Oxidation
14.5 Conclusion
15 Rural residential development 
15.1 Introduction
15.2 Key objectives
15.3 General principles
15.4 Source, flowpaths and receiving environments 
15.4.1 Source
15.4.2 Pathway
15.4.3 Receiving environment
15.5 Hydrology
15.5.1 An individual residence
15.5.2 Rural residential subdivision
15.5.3 Device capability to detain flows
15.6 Stormwater management device design
16 Waikato Regional Council administered drainage areas
16.1 Introduction 
16.2 Drainage standards 
16.3 Problem identification
16.4 Urban development issues
16.5 Land use change and drainage areas
16.5.1 Introduction
16.5.2 Site specific criteria
16.5.3 Information requirements
16.5.4 Information requirements for small scale subdivision
16.5.5 Information requirements for larger scale development
16.5.6 Funding
16.5.7 Land ownership
16.6 Conclusion
17 Retrofitting stormwater management
17.1 Introduction
17.2 Retrofit process
17.3 Prioritisation of projects
17.4  Magnitude of impact
17.4.1 Public safety
17.4.2 Collaborative projects
17.4.3 Water quality retrofits 
17.4.4 Stream erosion reduction
17.5 Device availability
17.5.1 Downstream flooding impacts
17.5.2 Downstream channel erosion effects 
17.5.3 Stormwater quality
17.6 Space availability
17.7 Positive drainage
17.8 Magnitude of benefit
17.9 Cost 
17.9.1 Cost benefit analysis
17.9.2 Total cost
17.9.3 Total cost for the maintenance programme
17.10 Taking advantage of opportunities
17.10.1 Retrofitting existing stormwater quantity control structures 
17.10.2 Using existing road crossings to impound stormwater
17.10.3 Demonstration projects
17.10.4 Use of new consenting to exceed individual project benefits
17.10.5 Retrofitting through education
Part IV: Construction, operations and maintenance 
18 Construction related issues
18.1 Introduction
18.2 Responsibility for construction 
18.3 Pre-construction activities 
18.4 Device construction
18.4.1 Swale and filter strip construction
18.4.2 Sand filters
18.4.3 Bioretention devices
18.4.4 Infiltration
18.4.5 Ponds and wetlands 
18.4.6 Green roofs
18.4.7 Water tanks
18.4.8 Bush revegetation
18.4.9 Oil/water separators
18.5 Final acceptance 
18.6 Inspection reports and construction notes
18.7 Construction inspection checklists
19  Operation and maintenance
19.1 Introduction
19.2 Inspection and maintenance
19.2.1 Device inspection frequencies
19.2.2 Timing of device maintenance
19.3 Documenting inspection and maintenance
19.4 Prioritising maintenance tasks
19.4.1 Corrective maintenance
19.4.2 Preventive maintenance
19.4.3 Aesthetic maintenance
19.5 Disposal of removed contaminants
19.6 Safety issues
19.7 Inspection reports and operational notes
19.8 As-built certification
References 
Appendix A: Glossary of terms
Appendix B: Low impact design scoring matrix
Appendix C: Forms for construction and operation