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BIORETENTION Considerations and Case Studies SCVURPPP GSI Details Workshop #2 April 24, 2018 Shauna Dunton, P.E. Lotus Water
BIORETENTIONConsiderations and Case Studies
SCVURPPP GSI Details Workshop #2April 24, 2018
Shauna Dunton, P.E. Lotus Water
Lotus Water – Who we are
Local community infrastructure and water resourcesengineering firm Civil infrastructure planning and design Technical specialty in water management and wet
infrastructure Integrated and collaborative design, planning, and
engagement process Green Infrastructure Expertise Assisted SFPUC with development of their GI Typical
Details and Specifications 2013-2016 Led the development of BASMAA’s typical bulbout
bioretention details in 2017 Currently working on the Santa Clara SWRP and the San
Jose GI Plan
How the refinement of bioretention details can improve: Aesthetics Performance Constructability Cost-effectiveness
Case studies that demonstrate how lessons learned were incorporated into the development of typical details and construction guidance. Common challenges Design solutions Construction oversight Additional considerations
Today’s Presentation
Focus on the following key components: 1. Inlets2. Roadway/Bioretention Planter Interface3. Sidewalk/Bioretention Planter Interface
Today’s Presentation
INLETS
Water bypassing inlets due to: Lack of adequate depression in
gutter or sidewalk drainage notch Poor micro-grading along bulbout Change of flowline trajectory
Inlets – Common Challenges
Newcomb Avenue, SF Wiggle Neighborhood Green Corridor, SF
Erosion at inlet due to: Lack of or inadequately sized splash pad/cobbles Poor maintenance
Inlets – Common Challenges
Source: Minnesota Stormwater ManualSource: City of Portland BES
Difficulty in keeping inlets clear of debris and sediment due to: Trash and sediment getting stuck in narrow inlet openings and within
cobbles Vegetation blocking inlets
Inlets – Common Challenges
Cesar Chavez Streetscape Improvements, SFSource: Contech
Modified gutters at curb cut inlets
Inlets – Design Solutions
MODIFIED GUTTER
1-2” GUTTER DEPRESSION
DESIGN PONDING ELEVATION
GUTTER UPSLOPE AND DOWNSLOPE OF INLET
Holloway Avenue Green Street, SF
Provide inline inlet to bulbout planters where feasible
Inlets – Design Solutions
Holloway Avenue Green Street, SF
Rounding/chamfering vertical corners of curbs Sharp edges can direct water away from inlet opening
Inlets – Design Solutions
ANGLE BACK FACE OF CURB
Holloway Avenue Green Street, SF
Slope bottom of sidewalk drainage notches and provide at adequate intervals
Inlets – Design Solutions
SIDEWALK NOTCH SLOPED TOWARD PLANTER
DESIGN PONDING ELEVATION
SIDEWALK
Cesar Chavez Streetscape Improvements, SF
Splash apron pad + cobbles Flat pad allows for easy removal of sediment & debris Cobbles provide energy dissipation
Inlets – Design Solutions
FOREBAY / SPLASH PAD
Cesar Chavez Streetscape Improvements, SFHolloway Ave Green Street, SF
Ensure contractor understands how water is designed to move through planter
Encourage contractor to install formwork for gutter depression Prevents need to grind down
concrete later
Inlets – Construction Oversight
Mission Valencia Green Gateway, SF
Flow tests after completion Grind down inlet and corner of curb if necessary
Inlets – Construction Oversight
Holloway Avenue Green Street, SFHolloway Avenue Green Street, SF
ROADWAY/BIORETENTION PLANTER INTERFACE
Trash and sediment accumulation at corners of bulbouts
Roadway Interface – Common Challenges
Santa Fe, NM, Credit: Nelson Nygaard
Edge restraint structure that: Meets traffic loading, pedestrian and traffic safety, and other code
requirements Maintains maximum infiltrative footprint Integrates into project’s landscape design Is cost-effective
Roadway Interface – Common Challenges
Source: City of Portland BES
Vehicular and pedestrian safety Especially important in retrofit
projects Temporary and/or permanent
visual warnings may be necessary in addition to physical barriers
Roadway Interface – Common Challenges
Mission Valencia Green Gateway, SF
Bulbout transition alignments that can be maneuvered by city street sweeping vehicles
Roadway Interface – Design Solutions
Holloway Avenue Green Street, SF
Edge restraint details and designer guidance that addresses all of the overlapping requirements and project goals Coordinated with Public Works,
Transportation Agency, and ADA director Consider compacted soil benches under
walls and lateral bracing
Roadway Interface – Design Solutions
Lateral Bracing Construction, SF
Vehicular safety Standard curb and gutter at roadside edge 1-foot setback curb face to edge of travel or bike lane Red painted curbs in urban settings to prevent parking along bulbouts
and alert drivers Limit vegetation height where maintaining sight distance is an issue Reflectors within bulbouts on high-traffic corners
Roadway Interface – Design Solutions
Cesar Chavez Streetscape Improvements, SF
Vehicular safety Courtesy strips and trench drain
inlets adjacent to parallel parking
Roadway Interface – Design Solutions
12th Street, Portland
SIDEWALK/BIORETENTION PLANTER INTERFACE
Meeting ADA requirements and pedestrian safety concerns due to large drop-off
Sidewalk Interface – Common Challenges
San Diego, CA
General aesthetics and integration into streetscape design
Sidewalk Interface – Common Challenges
Wiggle Neighborhood Green Corridor, SF
Reduce elevation drop-off wherever feasible
Provide sloped sides
Sidewalk Interface – Design Solutions
Los Altos, CAMission Bay, SF
Provide flat buffers at edges to eliminate need for raised curbs
Sidewalk Interface – Design Solutions
ADA solutions Use check dams on sloped sites to
limit vertical drop from sidewalk 30” max but 12” or less preferred
Sidewalk Interface – Design Solutions
Cesar Chavez Streetscape Improvements SF
ADA solutions Integrate raised perimeter curb or short decorative fence/rail that
meets ADA requirements Taper end of raised curb back down to street curb Seat walls and other landscape features can provide barriers
Sidewalk Interface – Design Solutions
Wiggle Neighborhood Green Corridor, SFBay Meadows
Aesthetic considerations Minimize “bathtub” effect by
reducing overall drop down to planter soil
Make sure ADA compliance is considered in typical details and design and not an after-thought
Provide clear and easy-to-navigate details that designers and contractors can follow
Sidewalk Interface – Design Solutions
Mission Valencia Green Gateway, SF
ADDITIONAL CONSIDERATIONS
Overflow Structure Design Discourage oversized structures Research feasibility of finding local
available grate products to meet requirements
Address maintainability and durability
Additional Considerations
Wiggle Neighborhood Green Corridor, SF
18” – 24”
Irrigation Backflow Preventers If irrigation system is included,
need to consider how backflows will be accommodated
If within planter, account for impact to infiltrative capacity
Additional Considerations
Wiggle Neighborhood Green Corridor, SF
CONCLUSION
Conclusion
Lessons learned from local bioretention construction projects should be incorporated into typical details and designer guidelines
Typical bioretention details are not a plug and play solution – site specific conditions and needs have to be addressed by the designer
To find out how Lotus Water can help on your next project, contact us at:
215 Kearny StreetSuite BSan Francisco, CA [email protected]
THANK YOU
