module 2: bioretention area siting and design andy rowe, pe, leed ap, qsd cannon
TRANSCRIPT
Module 2: Bioretention Area Siting and Design
Andy Rowe, PE, LEED AP, QSD Cannon
Siting and Design Topics
• Site Assessment• Constraints• Opportunities• Site Layout Strategies• Case Study – 21st Street, Paso Robles
Site Assessment
• Develop a series of site assessment maps– Natural features– Built features– Non-physical characteristics
Source: LID Technical Guidance Manual for Puget Sound
Natural Site Features
• Topography– Site visits– As-builts– USGS maps– Topographic
surveys
Source: United States Geological Survey
Natural Site Features
• Hydrologic Features– Floodplains (FEMA)– Wetlands– Watercourses– Seeps or springs
• Sensitive and Restricted Areas– Army Corps– Department of Fish
and GameSource: Federal Emergency Management Agency
Natural Site Features
• Existing Drainage Area Delineation
Natural Site Features• NRCS Maps
– Soil types– Hydrologic soil groups
Source: National Resources Conservation Service
Natural Site Features
• Geotechnical Assessment– Soil profile– Depth to impervious layer such as bedrock– Depth to groundwater– Geotechnical hazards including landslides– Infiltration rates
• EPA– Soil contamination– Groundwater contamination
Natural Site Features• Vegetative and Tree Cover
– Site visits– Aerial photography– Topographic surveys– Arborist reports
Source: Google Earth
Built Site Features
• Sources– GIS– As-builts– Topographic surveys– USA dig
• Drainage Infrastructure• Buildings and Walls• Impervious Areas• Landscape Areas• Utilities• Groundwater Wells for Drinking Water
Non-Physical Characteristics
• Easements• Covenants• Zoning/Land Use• Development Code• Setbacks from Buildings and Property
Lines• Open Space and Landscaping
Requirements• Historical Designations• Other Pertinent Overlays
Bioretention Constraints• Impermeable Soils• Groundwater Pollution or Contaminated Soils• High Groundwater• Impervious Soil Layer• Vector Issues• Geotechnical Instability• Steep Slopes• Coastal Bluffs
When should an underdrain be used?
Bioretention Constraints
• Infill, Redevelopment and High Density Land
• Buildings to Remain• Utility Locations
Bioretention Constraints
• Incompatibility with Surrounding Drainage System
• Flooding and Overflow Routes• Tree Preservation• ADA Considerations• Safety• Hydrologic Features• Sensitive Areas• Drinking Water Wells
Bioretention Opportunities
• Permeable Soils• Uncompacted Soils (Undeveloped Areas)• Mild Slopes and Depressions
Bioretention Opportunities• Intersection Bulb-Outs
Source: LID Technical Guidance Manual for Puget Sound
Bioretention Opportunities• Cul-de-Sacs and Loop Roads• Roadway Medians
Source: LID Technical Guidance Manual for Puget Sound
Bioretention Opportunities• Buffer Between Curb and Sidewalk
Source: LID Technical Guidance Manual for Puget Sound
Bioretention Opportunities• Required Landscaping and Open Space• Setbacks and Easements
Source: bluegreenbldg.org
Bioretention Opportunities• Combine Conveyance
with Bioretention– Sinuosity
Bioretention Opportunities• Distribute Bioretention Areas Across the
Site
Site Layout Strategies• Identify the Development Envelope and
Protected Areas• Limit Clearing and Grading of Native
Vegetation– Incorporate established trees
• Prevent Disturbance of Natural Drainage Features
• Concentrate Development on Least Permeable Soils
• Plan Construction to Minimize Compaction of Permeable Soils
• Iterate Design
Site Layout Strategies• Cluster Development
Source: LID Technical Guidance Manual for Puget Sound
Site Layout Strategies• Dispersal of Runoff to Pervious Areas
– Direct runoff from impervious to pervious areas– Disconnect downspouts
Source: bluegreenbldg.org
Source: LID Manual for Southern California
Site Layout Strategies• Measures to Limit Imperviousness and
Create Space for Bioretention– Compact, taller structures– Cluster development– Narrower streets and lanes– Reduce number of cross streets– Smaller parking lots (fewer stalls, smaller stalls, more
efficient lanes)– Shared driveways
Site Layout Strategies• Other Considerations
– Locate bioretention areas away from high pedestrian traffic or provide elevated walkways
– Sight distance– Accessibility for maintenance– Separate clean and dirty water– Complete streets
• Pedestrian and ADA considerations• Bicycles• Parking• Traffic Calming
Case Study: 21st St, Paso Robles
Source: City of Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles• Project Goals
Improve stormwater quality reaching the Salinas River
Reduce street flooding
Recharge the groundwater table
Replace aging utilities
Improve safety and mobility for pedestrians and bicycles
Shade the street with trees
Promote infill and redevelopment
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles
Case Study: 21st St, Paso Robles