Development of LID Design Guidein Edmonton

Xiangfei Li and Fayi Zhou, the City of EdmontonDan Healy, AMEC Earth and Environmental

Philadelphia LID SymposiumSeptember 26, 2011

1Drainage Planning

Outline

• Why LID

• Why develop LID Design Guide

• Development of LID Design Guide

• Lessons learned

• Next steps

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Where is Edmonton

• 6th largest city in Canada, population ~ 780 thousand (2009)

• Located within a cold climate zone (53° 33' 0" N / 113° 30' 0" W)

• Soil predominately are silt loam and silty clay loam

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Why LID?

• Corporate strategic direction– The Way We Green

• Regulatory requirements– Municipal Policies and Procedures Manual (Alberta Environment 2001)

• 85% removal for TSS >75 μm– City of Edmonton Drainage Approval-to-Operate

• Total Loading Plan– AENV Water for Life Strategy

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LID Applications

Green roof

(Terwillegar Rec Centre, Edmonton, AB)

Bioswale

(Terwillegar Rec Centre, Edmonton, AB)

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LID Applications

Rain garden(Trumpeter Neighbourhood, Edmonton, AB)

Rain water harvesting for plant irrigation at green house

(Enjoy Centre, St. Alberta, AB)

Bioswale(Trumpeter Neighbourhood, Edmonton, AB)

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Why Develop LID Design Guide

• Technical guidance is needed– LID application continuously increasing

• Local challenges– Cold climate

– Tight soils

– Suitable vegetations

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Key Project Components

Data Collection &

Review

Community Model Comparison

Stakeholder Engagement

Cost-Benefit AnalysisLID Research

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Community Model Comparison

• Compare LID neighbourhood design with conventional neighbourhood design

• Assess benefits of LID neighbourhood design

• Illustrate how a “community” of LID features function together

• Provide an hydrologic modelling example

Conventional LID

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Stakeholder Engagement

… towards a “made in Edmonton” solution.

• Stakeholder identification

• Advocacy sessions– Objective: to educate, inform and gather information from

stakeholders

• Roundtables– Objective: to gather technical inputs into LID Design Guide

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General Guidelines

• Relevant regulatory requirements

• Overview of LID BMPs– Description and performance

– Facility selection

– Cost, benefit, cost-benefit analysis

– Monitoring and maintenance

• Local characteristics and considerations– Physical and climatic conditions, hydrology

– Size for cold climate, manage and design for salt/sand application etc.

• Site planning and design

Bioretention

Bioswale

Green roof

Permeable pavement

Box planters

Naturalized drainage way

Rainwater harvesting

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Hydrological design

~90% events (duration ≤ 5 hr) are less than 26mm

Rainfall capture distribution for 26mm capture volume

Rain point diagram for Edmonton area rainfall

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7 LID BMPs

• Application• Design considerations

– Design parameters and guidelines– Deign drawing requirements

• Operation and maintenance scheduling

Cross section view of a basic bioretention area

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Reported Parameters Description

Sub-Soil Infiltration Rate >13 mm/hr, under-drain required in tighter soils; for design and modeling, use 50% of specified or measured rate

Inlet design 0.5 m to 3 m grass filter buffer for non-point source inlet; erosion control at point source inlet; filter strips to buffer salt impacts are required as follows: 3-5 m width along collectors (may use sidewalk) and 5-35 m width along arterials

Design Discharge Max overflow or under-drain flow rate in design events (2-year, 5-year, 10-year, 25-year and 100-year)

Surface Area 3%-30% of contributing impervious area, several small facilities provide better treatment than one large facility; facilities to be sized by designer based on snowmelt volumes and salt loadings as required

Contributing Impervious Area <4 ha; pretreatment (grass filter with level spreader, etc) to facility required if imperviousness <75%

Facility Flow Velocity <0.3 m/s in planted areas and <0.9 m/s in mulched zones, to prevent erosion

Outlet Release Rate From under-drain or catchbasin lead; less than or equal to on-site release rates defined in Master Stormwater Drainage Plan

Ponding Depth < 0.3 m during a 2 year design event; max. 0.35 m depth per City of Edmonton standards

WSE1 in Design Storms Show that HWL during 5-year, 10-year and 100-year design events does not compromise adjacent structures

Captured Volume Volume of water retained through ponding and surface infiltration during the 2 year design event; additional volume captured during larger events if applicable

Emptying Time Duration of ponded water following a 2-year design event is <48 hrs

Media Layers

Mulch: 70-80 mm depth

Growing media: (amended topsoil with infiltration rate 15-50 mm/hr) 500-1000 mm depth

Filter layer: (16-25 mm washed rock <0.1% silt) 100 mm depth

Drainage / infiltration: (>40 mm washed rock <0.1% silt) 300-1000 mm depth

Surface Geometry Flat bottom, recommended length / width = 2:1

Side Slopes 4:1 (H:V) preferred (max 2:1)

Infiltration Trench (optional) 0.5 m to 1 m depth (dependent on native soils infiltration rate); 1 m to 6 m width, through length of facility; bottom slope 0%

Groundwater Buffer Groundwater must be >1.8 m below final surface grade; facility base must be 0.6 m to 1 m above groundwater level

Structural Buffer Facility located 3 m (significant clay content) to 5 m (heavy clay soils) from building foundations

Vegetation Species selected for contaminant removal, aesthetics and inundation / drought resistance (see Appendix A)

Parameter Plan Detail Profile Description

Location x Areal extent shown on plan view (bump-outs, municipal reserves, private lots, parks)

Surface area x Outlined on plan view drawings and stated in report

Inlet x x Shown on plan view and typical detail provided (curb cut, flow spreader, ribbon curb)

Materials x x Material specs (soil, drainage layer), depth, hydraulic conductivity, porosity

Vegetation x x Planting plan and vegetation details (species, mature density, succession plan)

Outlet x x Under-drain spec & slope, spill elevation, catchbasin type and grate, weir type and location, inlet control device details

Catchment x Delineated catchment area directed to bioretention facility

Flow Arrows xFrom contributing area and overflow route

Water Depth x Ponding depth and water surface elevation during design storm and maximum prior to spill

Inundation x Extent of inundation during design storms

Erosion control x x Located at inlet, outlet if overland spill

Operation Activities Scheduling

Inspect for sedimentation, erosion, plant health, mulch condition Semi-annually (spring, fall), quarterly during establishment (2 yrs)

Avoid use as snow storage facility unless specifically designed for this purpose Winter

Strategic application of de-icing and anti-skid material on roadways contributing to facility Winter

Street sweeping to prevent sedimentation Semi-annually (spring, fall)Soil contamination testing in areas with high levels of contaminants AnnuallySoil infiltration (empty time <36hrs) and pH (5.2-7.0) testing Bi-annually

Maintenance Activities

Weed control MonthlyMow grass and remove clippings, minimum length (50-250 mm) no shorter than maximum flow depth Monthly (May-October)

Prune vegetation when access or operation limited AnnuallyLitter and debris removal from inlets, outlets, vegetation and flow paths Bi-monthlyTilling or deep raking Bi-annually, prior to infiltration testing

Sand and sediment removal Annually (spring) or when sediment depth >100 mm

Under-drain flush Annually (spring)

Erosion repair of soils, mulch, splash pad, rip rap As indicated by inspection, annually (spring)

Replacement Activities

Grass/plants (unhealthy or dead >10%) As indicated in inspection (1-10 years)Mulch, replenish or replace As indicated by inspection (1-3 years)

Soils As indicated by contaminant / infiltration testing (2-20 years)

Gravel drainage layer As indicated by infiltration testing (25-50 years)

Under-drain When flushing indicates irreparable clogging (25-50 years)

Design Parameters and Guidelines

Drawing Detail Requirements

Operation, Maintenance, and Replacement Schedule

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Tools & Examples

• Recommended native and ornamental plants

• Soil amendment tools

• Cold climate facility sizing example

• Salt application example

• LID modelling example

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Lessons Learned

• Local considerations– The Guide is tailored for its local climate and geographical conditions

– Update of the Guide requires further research

• Stakeholder engagement – Prepare user-oriented LID BMP fact sheets, approval checklists etc.

– Use demonstration projects

• Team collaboration

• Education– Home owners, government staff, and private industry should all be educated

on the benefits along with the development Design Guide

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Next Steps

• LID research– Cold climate issues: snowmelt runoff treatment etc.

– Pollutant mass balance study

• Develop and implement long term monitoring program

• Develop local project database

• Develop LID implementation plan

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Thank You

Questions?