Texas; Innovative Stormwater Controls - Austin Energy

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Texas; Innovative Stormwater Controls - Austin Energy

  1. 1. Watershed Protectionand DevelopmentReview DepartmentEnvironmental Criteria Manual Updates: Innovative Stormwater Controls Michael Kelly, P.E. John Gleason, Landscape Architect
  2. 2. ECM 1.6.7 Innovative Water Quality Controls • Vegetative Filter Strips (VFS)/ VFS – Disconnection of Imp. Cover • Biofiltration • Rainwater Harvesting • Porous Pavement for Pedestrian Use • Rain Gardens
  3. 3. On-site Stormwater TreatmentSedimentation/Filtration: standard water quality treatment pond
  4. 4. Vegetated Filter Strip/Disconnected Impervious Cover
  5. 5. Vegetative Filter Strips
  6. 6. Vegetated Filter Strip Credit/Disconnected Impervious Cover 1. Same as existing vegetated filter strip, except allow for smaller sizing to receive proportionately reduced credit. 2. Directs water over vegetated area. 3. Requires adequate soil quality & depth, slope, hydraulic loading rate.
  7. 7. Vegetative Filter Strips (acres of VFS per acre of impervious cover) Contributing Sand FiltrationArea Imp. Cvr. SOS Equivalency 15% 0.28 NA 25% .45 .40 50% 1.04 .91 75% 1.84 1.61 100% 2.85 2.49
  8. 8. Vegetative Filter Strip DesignAllowable in the BSZMay be natural or engineeredSize: Requires relatively large land areaMaintain sheet flowDo not exceed max. velocities/hydraulic loading rates Width: as wide as the contributing drainage area Pavement Level spreader creates sheet flow Min. 25’Length Vegetated Filter Strip
  9. 9. Vegetative Filter Strip Design Min. 3” drop Primary pollutant removal mechanismPavement is infiltration 6” min. soil depth Water depth may not exceed the height of vegetation Bunchgrass: min. ht. 18” Turf: min. ht. 3”
  10. 10. BiofiltrationOld Dominion Freight (near Lake Walter Long)
  11. 11. Biofiltration1. Same design procedures as sedimentation/filtration.2. Key differences: 1. Addition of organic material into sand medium. 2. Plants provide key functional component to remove additional dissolved nutrients and enhance aesthetics
  12. 12. Biofiltration: Vegetated Flow Spreader vs. Gabion
  13. 13. Diagram of Biofiltration Pond Cross-Section – Conceptual Design Sedimentation Filtration OutletInletSplitterBox Separator Element Outlet Pipe Filtration Media Filter Fabric Vegetation Gravel Flood spillway
  14. 14. Biofiltration – Landscape Design • Plants must tolerate wide variations in moisture • Total Plants: Surface area (s.f.) of pond bottom x 0.1 • Sedimentation basin: Min. 20% of total plants • Trees are allowed • Filtration basin: Min. 50% of total plants • Min. 20% tall herbaceous • No more than 30% medium herbaceous • No trees are allowed
  15. 15. Biofiltration Plants - Grasses
  16. 16. Biofiltration at TechRidge
  17. 17. Rainwater Harvesting HEB Brodie Lane
  18. 18. Rainwater Harvesting: Option ACaptured Runoff discharged to a VFS for infiltration (<72 hr)
  19. 19. Rainwater Harvesting1. Captures runoff to be used for other beneficial purposes.2. Capture volume can be sized to meet watershed specific requirements (e.g. Urban vs. SOS); requires adequate infiltration or irrigation field for ultimate disposal of stormwater3. May be upsized to provide water conservation function.
  20. 20. Rainwater Harvesting: Option ACaptured Runoff discharged to a VFS for infiltration (<72 hr)
  21. 21. Rainwater Harvesting: Option A
  22. 22. Rainwater Harvesting: Option B Captured Runoff Used to Irrigate Vegetated Area • Max. 72 hr. drawdown time • Use retentio/irrigation criteria (ECM 1.6.7A) • Allowable in the Barton Springs Zone Conveyance system
  23. 23. Rainwater Harvesting: Option B Captured Runoff Used to Irrigate Vegetated Area Tank Sprinkler system (per retention/irrigation criteria)
  24. 24. Porous Pavement for Pedestrian Use Pervious Concrete Permeable Pavers
  25. 25. Porous Pavement1. Retains & infiltrates water underneath pavement used for pedestrian use only.2. Criteria will allow for Impervious Cover (IC) credit.
  26. 26. Porous PavementPossibilities include:• porous concrete• reinforced turf• gravel
  27. 27. Rain Gardens
  28. 28. Rain Gardens• Filtration or Infiltration system for small (<1 acre) drainage areas• Allows for dispersed, small-scale treatment systems integrated into site landscaping
  29. 29. Rain Garden Info: Grow Green
  30. 30. Rain Gardens Plan Plan View Section Section
  31. 31. Contact InformationMichael Kelly, P.E. John Gleason(512) 974-6591 (512) 974-3543mike.kelly@ci.austin.tx.us john.gleason@ci.austin.tx.usEnvironmental Resource ManagementWatershed Protection and Development Review Department505 Barton Springs RoadAustin, Texas 78704

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