Sustainable Stormwater Retrofit Best Practices

Sustainable Stormwater Retrofit Best Practices

Presenter Zach Sample, PE Stormwater Products Manager XP Solutions

XP Solutions has a long history of Providing original, high-performing software solutions Leading the industry in customer service and support Educating our customers to be more successful in their work.

Agenda Thoughtful options Retrofit Background Considerations for each Assess exactly what will be built to ensure it all works!

State of (Stormwater) Affairs From EPA s Municipal Handbook - Green Infrastructure Retrofit Policies Existing development is responsible for degraded water quality 40%+ assessed waters fail 850 billion gallons untreated overflows Retrofits will be necessary $200 billion wastewater infrastructure $10 billion stormwater management $60 billion combined sewer overflows (CSOs) since we HAVE to make changes be smart about it! Cited: water.epa.gov https://www.epa.gov/sites/production/files/2015-10/documents/gi_munichandbook_retrofits.pdf

Back to Basics Stormwater Retrofit: Changing something that has already been built. Alterations during initial construction (oops!) Operational system capacity upgrades (volume, quality and/or flow rates) Aging system improvements cenews.com newarkohio.net njspotlight.com

Thoughtful Practices Pipes Network and Detention Ponds need work.. what do we do next? Just make the same system bigger? Nope: Peak Flow improvement; Volume and Quality not improved Incorporate Green and distributed treatment Get it all : Flow, Volume and Quality enhancements Target: 90-95 percentile events only (not for massive flood reduction) Potential issue: successful system lifecycle involves numerous (new) factors

Retrofit Options Bioretention/ Rain gardens Porous paving Swales Green roofs and Rainwater harvesting Ponds Underground tanks Infiltration Trenches Soakaways (UIC) Pipes, Channels and high-flow bypass

Raingarden/Bioretention Area Vegetated depressions that collect and treat runoff Typically include sand and washed gravel filter media zone Highly customizable (everything is optional) *Best* pollution treatment size of any BMP

Raingarden/Bioretention Area Thoughtful Retrofit Options: Existing inlet grate replacement bio/tree box Green Streets program Any surface interception imaginable

Raingarden/Bioretention Area Design Considerations: Actual flow behavior through media & high-flow outlet In-Situ soil capacity and slope stability Designer, planner, contractor and public understanding design intent

Permeable Pavement Porous Asphalt, Concrete and Permeable Pavers No Fines aggregate mix or spaced blocks Increases effective developable area Reduces runoff volume and reduce pollutants (temperature)

Permeable Pavement Thoughtful Retrofit Options: Parking lots, walkways and driveways!!! Main arterials and highways (great rain spray reduction) High sediment load areas worse than freeze-thaw

Permeable Pavement Design Considerations Hydraulic behavior through facility Site slopes (not a bathtub) Account for true layering of structural and filter material

Vegetated depressions that collect and treat runoff Either a ditch or a Bioretention system on a slope! Very common collection facility Can focus on runoff reduction, flow mitigation or both! Swales

Thoughtful Retrofit Options: Center island collection system Double duty Dry Swale Aesthetic corridor or walking path enhancement Swales

Design Considerations Storage capacity vs slope Storage capacity vs space Mowable side slopes and realistic filter zone Swales

Green Roofs and Rainwater Reuse Vegetated Roof Area and Runoff Storage Tanks Reduce total runoff volume and attenuate peak flows Excess rainwater flows through the medium and is drained Stored (non-potable) water used for: irrigating lawns and gardens, washing cars, or toilet flushing

Green Roofs and Rainwater Reuse Thoughtful Retrofit Options and Design Considerations: Any existing building public or private May be considered full for design purposes Draw rates, initial tank volume, tank overflow

Depressions that Collect and Mitigate Runoff Wet or Dry pond facilities Very common end of line facility Wide range of facility shape and outlet configurations Ponds

Thoughtful Retrofit Options: Feature ponds Tiered facilities and wildlife refuge Smaller dry version of existing wet facility Ponds

Design Considerations Wide range of volume sizing criteria and rainfall events Complex outlet structure Robust hydraulic assessment required Ponds

Storage Tank Above or Below Ground Collection Tank Corrugated plastic, steel, precast concrete or milk crate

Storage Tank Thoughtful Retrofit Options and Design Considerations: In place of detention pond - where parking space is needed! Void ratio (i.e. true storage) and base infiltration Hydraulic assessment of entire drainage system

Underground Injection Well or Dry Well Surface runoff directly introduced to water table without treatment Strictly regulated to protect groundwater and water supply Pre-treatment likely required Fill media and multiple soil infiltration rates critical to design Soakaways

Media filled trench High void media with underdrain Thoughtful Retrofits Dewatering or construction phase Edge or center of impervious area space saver! Pervious walking paths Infiltration Trench

Design Considerations: Underdrain configuration and in-situ soil capacity Hydraulics through system above and below Media void ratio and interception volume Infiltration Trench

Pipes, Channels and Bypass Plastic, metal, concrete, vegetated conveyance systems Pipes and channels aren t gone just thoughtfully placed Bypass structure or channel required with majority of Green Infrastructure

Pipes, Channels and Bypass Design Considerations: Distributed stormwater is complex comprehensive analysis Basic pipe sizing vs integrated design Need for as built level assessment

xpdrainage Design Needs for Retrofits - summary: Robust hydraulic analysis filter, ponding, channel flow Highly customizable facility configuration tie ins!!! Flexible control of infiltration and filtration Easy to report and communicate

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Questions? Comments? Thank you for joining this presentation, Sustainable Stormwater Retrofit Best Practices Zach Sample, PE Stormwater Products Manager Zach.Sample@xpsolutions.com Contact XP Solutions Americas: +1 888 554 5022 amsales@xpsolutions.com Asia Pacific: +61 7 3310 2302 ausales@xpsolutions.com EMEA: +44 0 1635 582555 uksales@xpsolutions.com www.xpsolutions.com