Development of LID Design Guide in Edmonton

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1 Development of LID Design Guide in Edmonton Xiangfei Li and Fayi Zhou, the City of Edmonton Dan Healy, AMEC Earth and Environmental Philadelphia LID Symposium September 26, 2011

2 Outline Why LID Why develop LID Design Guide Development of LID Design Guide Lessons learned Next steps 1

3 Where is Edmonton 6 th largest city in Canada, population ~ 780 thousand (2009) Located within a cold climate zone (53 33' 0" N / ' 0" W) Soil predominately are silt loam and silty clay loam 2

4 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 3

5 LID Applications Green roof (Terwillegar Rec Centre, Edmonton, AB) Bioswale (Terwillegar Rec Centre, Edmonton, AB) 4

6 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) 5

7 Why Develop LID Design Guide Technical guidance is needed LID application continuously increasing Local challenges Cold climate Tight soils Suitable vegetations 6

8 Key Project Components Community Model Comparison Data Collection & Review Stakeholder Engagement Cost-Benefit Analysis LID Research 7

neighbourhood design Illustrate how a community of LID features

9 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 8

10 Stakeholder Engagement Stakeholder identification Advocacy sessions Objective: to educate, inform and gather information from stakeholders Roundtables Objective: to gather technical inputs into LID Design Guide towards a made in Edmonton solution. 9

11 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 Bioretention Bioswale Green roof Permeable pavement Box planters Naturalized drainage way Rainwater harvesting Physical and climatic conditions, hydrology Size for cold climate, manage and design for salt/sand application etc. Site planning and design 10

12 Hydrological design ~90% events (duration 5 hr) are less than 26mm Rain point diagram for Edmonton area rainfall Rainfall capture distribution for 26mm capture volume 11

13 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 12

14 Reported Parameters Design Parameters and Guidelines Sub-Soil Infiltration Rate Description >13 mm/hr, under-drain required in tighter soils; for design and modeling, use 50% of specified or measured rate 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 Inlet design required as follows: 3-5 m width along collectors (may use sidewalk) and 5-35 m width along arterials Parameter Plan Detail Profile Description Design Discharge Max overflow or under-drain flow rate in design events (2-year, 5-year, 10-year, 25-year and 100-year) Location x Areal extent shown on plan view (bump-outs, municipal reserves, private lots, parks) 3%-30% of contributing impervious area, several small facilities provide better treatment than one large facility; facilities to be sized Surface AreaDrawing Detail Requirements by designer based on snowmelt volumes and salt loadings as required Surface area x Operation Activities Outlined on plan view drawings and stated in report Scheduling Contributing Impervious Area <4 ha; pretreatment (grass filter with level spreader, etc) to facility required if imperviousness <75% Semi-annually (spring, fall), Inspect for sedimentation, erosion, plant health, mulch condition Facility Inlet Flow Velocity x <0.3 m/s x in planted areas and Shown <0.9 m/s on plan in mulched view and zones, typical to prevent detail erosion provided quarterly (curb cut, during flow establishment spreader, ribbon (2 yrs) curb) Outlet Release Avoid Rate use as snow storage From facility under-drain unless or catchbasin specifically lead; designed less than for or this equal purpose to on-site release rates defined in Master Winter Stormwater Drainage Plan Ponding MaterialsOperation, Depth < 0.3 m x Maintenance, during a 2 year x design Material event; specs max (soil, m drainage and depth per layer), Replacement City of depth, Edmonton hydraulic standards conductivity, porosity Schedule Strategic application of de-icing and anti-skid material on roadways Winter contributing to facility WSE1 in Design Storms Show that HWL during 5-year, 10-year and 100-year design events does not compromise adjacent structures Vegetation Street sweeping to prevent x sedimentation x Planting plan and vegetation details (species, mature Semi-annually density, succession (spring, fall) plan) Soil contamination testing Volume in areas of water with retained high levels through of contaminants ponding and surface infiltration during the 2 year design event; Annually additional volume captured during Captured Volume larger events if applicable Outlet Soil infiltration (empty time <36hrs) x and ph x ( ) Under-drain testing spec & slope, spill elevation, catchbasin type Bi-annually and grate, weir type and location, inlet control device details Emptying Time Duration of ponded water following a 2-year design event is <48 hrs Maintenance Activities Catchment x Mulch: mm depth Delineated catchment area directed to bioretention facility Weed control Monthly Mow grass and remove Growing clippings, media: minimum (amended length topsoil ( with infiltration mm) no shorter rate mm/hr) mm depth Media Flow Layers Arrows x Monthly (May-October) than maximum flow depth Filter layer: (16-25 mm washed From rock contributing <0.1% silt) area 100 mm and depth overflow route Prune vegetation when access or operation limited Annually Water Depth Drainage x / infiltration: (>40Ponding mm washed depth rock and <0.1% water silt) surface elevation mm depth during design storm and maximum prior to spill Litter and debris removal from inlets, outlets, vegetation and flow paths Bi-monthly Surface Geometry Tilling or deep raking Flat bottom, recommended length / width = 2:1 Bi-annually, prior to infiltration testing Inundation x Extent of inundation during design storms Side Slopes 4:1 (H:V) preferred (max 2:1) Annually (spring) or Sand and sediment removal when sediment depth >100 mm Infiltration Erosion Trench Under-drain control (optional) flush x 0.5 m to x1 m depth (dependent Located on native inlet, soils outlet infiltration if overland rate); 1 m spill to 6 m width, through Annually length of (spring) facility; bottom slope 0% Groundwater Buffer Groundwater must be >1.8 m below final surface grade; facility base must be 0.6 m As to indicated 1 m above by groundwater inspection, level Erosion repair of soils, mulch, splash pad, rip rap annually (spring) Structural Buffer Facility located 3 m (significant clay content) to 5 m (heavy clay soils) from building foundations Vegetation Species Replacement selected for Activities contaminant removal, aesthetics and inundation / drought resistance (see Appendix A) 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 Under-drain As indicated by infiltration testing (25-50 years) When flushing indicates irreparable clogging (25-50 years) 13

15 Tools & Examples Recommended native and ornamental plants Soil amendment tools Cold climate facility sizing example Salt application example LID modelling example 14

16 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 15

17 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 16

18 Thank You Questions? 17

Inspection and Maintenance of Stormwater Best Management Practices

FAC T S H E E T Inspection and Maintenance of Stormwater Best Management Practices is a general term that refers to vegetated stormwater best management practices (BMPs) that temporarily store rainwater