Discussion Topics Brief history of structural stormwater management The Low Impact Development (LID)...
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Transcript of Discussion Topics Brief history of structural stormwater management The Low Impact Development (LID)...
![Page 1: Discussion Topics Brief history of structural stormwater management The Low Impact Development (LID) alternative to ponds, ponds, ponds… LID for Hydromodification.](https://reader030.fdocuments.net/reader030/viewer/2022032517/56649ca45503460f94964a15/html5/thumbnails/1.jpg)
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Discussion TopicsDiscussion Topics
• Brief history of structural stormwater management
• The Low Impact Development (LID) alternative to ponds, ponds, ponds…
• LID for Hydromodification Management:– State of Washington– City of Portland, Oregon– Prince George’s County, Maryland
• Contra Costa approach builds on the best ideas from these programs
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Brief HistoryBrief History
• Pre-1990’s – Northwest:
Detention ponds for peak rate control
– California: Emphasis on conveyance to regional channel systems
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Brief History (Cont’d)Brief History (Cont’d)
• 1990’s (NPDES Triggers New Thinking )– Northwest:
Treatment and hydromodification added, new analytical tools, salmon also a driver
– California: Structural controls appear for stormwater treatment
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Brief HistoryBrief History
• Late 1990’s to Now (Convergence)
– LID gains traction
– Guidance Manuals proliferate! (Start at the Source 1999, Prince George’s County 1999)
– Numerous “pilot studies”
– California: NPDES flow control req’ts kick-in
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So what do we mean by LID…So what do we mean by LID…
Low impact development is a stormwater management strategy that emphasizes conservation and use of existing natural site features integrated with distributed, small-scale stormwater controls to more closely mimic natural hydrologic patterns in residential, commercial, and industrial settings.
Source: (Puget Sound Action Team 2005)
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Why is LID so popular?Why is LID so popular?
• Minimizes changes to natural hydrology• Controls pollutants at the source• Soil contact optimal for pollutant removal
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Why is LID so popular?Why is LID so popular?
• Aesthetics and public acceptance• Vectors (e.g., mosquitos)• Reuse potential
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So what does LID look like?...So what does LID look like?...
• Site assessment
• Site planning and layout
• Vegetation protection and maintenance
• Clearing and grading
• Distributed and integrated management practices (IMPs)
• Maintenance and Education
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Today’s Emphasis…Today’s Emphasis…
• Site planning and layout – Hydrology as the “organizing principle”– Road, driveway and parking layouts– Street trees– Lot Layout– Building design– Collection system with…
• Distributed and integrated management practices (IMPs)
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Integrated Management Practices
Integrated Management Practices
• Examples (Yes, people are really building these things…)– Highly urban environment (Growing Vine)– Road runoff (SEA Streets, Viewlands)– Parking lots (Auburn Library)– College campus (Olympic College)
• Spokane – LID since 1979
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Growing Vine StreetGrowing Vine Street
Cistern & CascadeBio downspoutBio downspout
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SEA Street BeforeSEA Street Before
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SEA Street AfterSEA Street After
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SEA StreetsSEA Streets
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SEA-StreetSEA-Street
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SEA-Streets SEA-Streets
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SEA-Streets Initial PerformanceSEA-Streets Initial Performance
• Monitoring showed 98% reduction in runoff for small storms
• Commensurate water quality benefits
• Traffic calming
• Neighborhood enhancement
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Viewlands CascadeViewlands Cascade
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Viewlands CascadeViewlands Cascade
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Auburn Library Auburn Library
“Stacked” system: Lined bioswale overflows into underlying infiltration pipe
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Olympic CollegeOlympic College
Lined Bioswale
Sheet flow into swale
Infiltration basin
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Spokane Has Successfully Used Bio-Infiltration Since 1979
Spokane Has Successfully Used Bio-Infiltration Since 1979
>8,000 Bio-infiltration facilities installed to protect Sole Source Aquifer
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Improve design standards and integrate with other codes
Improve design standards and integrate with other codes
• Fine tune standards over time
• Address conflicts with building code
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Aesthetics increase public acceptance and success
Aesthetics increase public acceptance and success
Attractive landscape features less likely to be filled in by property owner
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Educate Contractors and Facility Owners
Educate Contractors and Facility Owners
• Intended function and proper design
• Installation procedures
• Proper maintenance
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Inspect facilities during and after construction
Inspect facilities during and after construction
• Full time staff person hired for inspections
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Provide regulatory authority to ensure long-term performanceProvide regulatory authority to ensure long-term performance
• City ordinance requires owners to maintain swales• Allows City to maintain facilities and charge owners
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IMPs for Flow ControlIMPs for Flow Control
• Existing Stormwater Programs with emphasis on LID for flow control– State of Washington– City of Portland, Oregon– Prince George’s County, Maryland
• Contra Costa Clean Water Program
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State of WashingtonState of Washington
• Continuous hydrology volume/duration control
• Challenge: extending modeling tool to dozens of distributed IMPs
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City of Portland, OregonCity of Portland, Oregon
• Easy to use tool encourages LID
• Hydromod control assumed, no continuous analysis to support
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Prince George’s County, MarylandPrince George’s County, Maryland
• Event based• Cumbersome
calculations steps• No continuous,
duration analyses
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Contra Costa Clean Water Program
Contra Costa Clean Water Program
Total: SF
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Dimension: Units
Total Drainage Area (SF):Number of Drainage Management Areas (DMAs):
Mean Annual Precipitation at Site:
Units
Units
Units
Units
Units
Units
Select IMP TypeIMP Dimensions IMP Size
Units
Surrounding Soil Group
Units
Underdrain Discharge Limit
Units
Units
Post-project
Select IMP ID to Manage Runoff
SFTotal:
Units
Units
Units
Units
Units
Units
Units
Units
Units
Units
IMP ID
Pre-project
Project Name:
DMA ID
Hydrologic Soil Group
Land CoverArea of
DMA (SF)
No. of Identical
Areas
Total Area (SF)
• Challenge: – Rapidly develop
technically rigorous method and easy to use tools
• Approach:– Hybrid of WA/OR– Continuous
hydrology, duration analysis
– User friendly