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SvR High Point presentation


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A presentation by SvR on the natural drainage system and green infrastructure aspects of the High Point redevelopment.

A presentation by SvR on the natural drainage system and green infrastructure aspects of the High Point redevelopment.

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  • 1. Civil Engineering Landscape Architecture Environmental Restoration Planning High Point Redevelopment & Natural Drainage System Kathryn Gwilym, PE, LEED ® AP Tom von Schrader, PE, LEED ® AP
  • 2. High Point Revitalization Project
    • Developer: Seattle Housing Authority
    • 120-acre mixed income housing redevelopment
    • 34 blocks of new streets with new utilities, street trees, sidewalks, parks and open space
    • Up to 1,600 housing units, neighborhood center, library and mixed-use block
    Mithun Architects + Planners High Point Prior to Redevelopment
    • Density ranges from 16 to 30 units/acre of ground-related housing
  • 3. Priority Watershed- Longfellow Creek
    • High Point Subbasin: 8% of Longfellow Creek Watershed
    • High-priority, salmon-bearing watershed that has been identified by “the community and the City as a significant and valuable resource” (Seattle Public Utilities)
    • Urban Watershed that drains to Puget Sound
    Longfellow Creek Longfellow Creek watershed High Point basin
  • 4. Natural Drainage System (NDS) Strategies – where we started in 2002
    • Partnership of Seattle Housing Authority & Seattle Public Utilities
    • Design Charrette with City Departments
    • Vegetated, shallow grass and grass conveyance swales along 15,000 lf streets
    • Traditional storm drain conveyance pipe for large storm events
    • Stormwater pond for Flood Control
    • Reduce Impervious Surfacing
    • Disperse Runoff at Source
  • 5. Drainage Criteria & Goals for High Point
    • Water quality treatment: 6 month Seattle storm
    • Conveyance sizing for 25-year Seattle storm
    • Peak flow control for 2, 25 and 100 year Seattle storm events
    • Conveyance of dam safety flows downstream of stormwater pond
    • NDS combined with the stormwater pond detain and match duration up to the 2 year , 24-hour storm assuming pasture conditions
  • 6. Challenges for Developing Street Section: Having space for all users & infrastructure in ROW ↑ Drainage Swale Concept ↑ Electrical & Franchise Utilities
  • 7. ROW Street Section with NDS Swale
    • The cross sections for the NDS swales were developed through discussions with various City of Seattle departments (decisions by inches)
    • Street widths: 25 feet/56 right of way; 28 feet/56 ft rw; 32 feet/60 ft rw
    • Curb height, swale width, street tree locations, berm locations, side slopes, bottom width, etc. were established
    • Porous sidewalks on the swale side
  • 8. Developing Cross Section & Swale Length in ROW
    • Vegetated swale
    • 5’+/- compost gravelly soil
    • 18” deep, 10” ponding
    • Grass-lined swale
    • 5’ +/- compost gravelly soil
    • 8” deep, 2” ponding
  • 9. High Point Swales
    • Vegetated
    • Grass-lined
    • Conveyance
    • Amended soils
  • 10. Seattle Public Utilities’ First Public Porous Cement Concrete Pavement Street at 32 nd Ave SW
    • Integration between redevelopment and adjacent single family neighborhood
    • Road: 8” porous concrete over 18” gravel storage subbase
    • Collaboration between suppliers, designers, City Inspectors, Contractors, Neighbors and Seattle Housing Authority
    • Being Monitored by Seattle Public Utilities
  • 11. 32nd Avenue SW Porous Cement Concrete Street Prior to Construction Post Construction Placing Concrete
  • 12. Natural Drainage Strategies – Housing Block-level Design
    • High Point Drainage Technical Standards and requirements for each lot per the plat
    • Examples of Methods to use:
      • Porous pavement
      • Conveyance furrow
      • Dispersal trench
      • Rain garden
      • Pop-up emitter
      • Downspout Disconnect
      • Reduce Impervious footprint
  • 13. Housing Sites Drainage Dispersion, Splashblocks, Rain Gardens & Art Splash Blocks by Myersculpture
  • 14. Stormwater Pond
    • Receives 130 acres of run-off
    • Flow control for 100-year storm event
    • Water Quality Treatment in combination with NDS swales
    • Depth 15.5’, Storage 22 ac-ft
    • Dam Safety
    • Park Amenity & Art
  • 15. How High Point Works & Informing the Community
  • 16. High Point has
    • … proven installations that are now being applied across the country
      • Low Impact Design/Site Drainage Technical Standards
      • Reduced impervious footprints
      • Mature tree protection techniques
      • Site fully integrated with Low Impact Development techniques
      • Reduced road widths
      • Site-wide pedestrian circulation and safety enhancements
      • Use of porous paving applications for walks, road and parking lots
  • 17. High Point has
    • … proven installations that are now being applied across the country
      • Multifunctional stormwater park
      • Menu driven low impact development approach
      • Defined permitting review process
      • Interagency collaboration
      • Community education
      • Resident education
      • Maintenance and operation standards
      • Art integration
      • Aesthetic treatment of drainage swales
    Sandblasting by Myersculpture
  • 18. Recognition: Seattle Housing Authority Seattle Public Utilities Other agencies: Washington State Department of Ecology US Department of HUD Seattle Department of Planning and Development Seattle Department of Transportation Seattle City Light Seattle Parks Department Artist: Myers Sculpture For more information: and Seattle Public Utilities had a vision for a neighborhood with a naturalistic drainage approach. Seattle Housing Authority had a vision for a diverse, sustainable neighborhood. These two public agencies have worked hard to implement these visions. Consultants: SvR Design Company Mithun Architects and Planners Resource consultants: Shannon and Wilson RW Beck & Herrera Nakano Associates Stoneway Concrete Cedar Grove Composting NW ACPA Ph I Natural Drainage System Contractors: Gary Merlino Construction T. Yorozu Gardening Co. Absher Construction Fardig Ph II Natural Drainage System Contractors: Tri-State Construction Inc. T. Yorozu Gardening Co.