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Texas; Innovative Stormwater Controls - Austin Energy
This document summarizes updates to Austin's Environmental Criteria Manual regarding innovative stormwater controls. It describes vegetative filter strips, biofiltration, rainwater harvesting, porous pavement for pedestrian use, and rain gardens. Details are provided on the design and sizing criteria for each control, including graphics illustrating examples. Contact information is given for two city employees who can provide more information.
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Texas; Innovative Stormwater Controls - Austin Energy
- 1. Watershed Protection and Development ReviewDepartment Environmental Criteria Manual Updates: Innovative Stormwater Controls Michael Kelly, P.E. John Gleason, Landscape Architect
- 2. ECM 1.6.7 InnovativeWater Quality Controls • Vegetative Filter Strips (VFS)/ VFS – Disconnection of Imp. Cover • Biofiltration • Rainwater Harvesting • Porous Pavement for Pedestrian Use • Rain Gardens
- 3. On-site Stormwater Treatment Sedimentation/Filtration:standard water quality treatment pond
- 4. Vegetated Filter Strip/Disconnected Impervious Cover
- 5.
- 6. Vegetated Filter StripCredit/ 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. Vegetative Filter Strips (acres of VFS per acre of impervious cover) Contributing Sand Filtration Area 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. Vegetative Filter StripDesign Allowable in the BSZ May be natural or engineered Size: Requires relatively large land area Maintain sheet flow Do 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. Vegetative Filter StripDesign Min. 3” drop Primary pollutant removal mechanism Pavement is infiltration 6” min. soil depth Water depth may not exceed the height of vegetation Bunchgrass: min. ht. 18” Turf: min. ht. 3”
- 10. Biofiltration Old Dominion Freight(near Lake Walter Long)
- 11. Biofiltration 1. Same designprocedures 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. Biofiltration: Vegetated Flow Spreader vs. Gabion
- 13. Diagram of BiofiltrationPond Cross-Section – Conceptual Design Sedimentation Filtration Outlet Inlet Splitter Box Separator Element Outlet Pipe Filtration Media Filter Fabric Vegetation Gravel Flood spillway
- 14. Biofiltration – LandscapeDesign • 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. Biofiltration Plants -Grasses
- 16.
- 17. Rainwater Harvesting HEB Brodie Lane
- 18. Rainwater Harvesting: OptionA Captured Runoff discharged to a VFS for infiltration (<72 hr)
- 19. Rainwater Harvesting 1. Capturesrunoff 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 stormwater 3. May be upsized to provide water conservation function.
- 20. Rainwater Harvesting: OptionA Captured Runoff discharged to a VFS for infiltration (<72 hr)
- 21. Rainwater Harvesting: Option A
- 22. Rainwater Harvesting: OptionB 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. Rainwater Harvesting: OptionB Captured Runoff Used to Irrigate Vegetated Area Tank Sprinkler system (per retention/irrigation criteria)
- 24. Porous Pavement forPedestrian Use Pervious Concrete Permeable Pavers
- 25. Porous Pavement 1. Retains& infiltrates water underneath pavement used for pedestrian use only. 2. Criteria will allow for Impervious Cover (IC) credit.
- 26. Porous Pavement Possibilities include: •porous concrete • reinforced turf • gravel
- 27.
- 28. Rain Gardens • Filtrationor Infiltration system for small (<1 acre) drainage areas • Allows for dispersed, small-scale treatment systems integrated into site landscaping
- 29. Rain Garden Info:Grow Green
- 30. Rain Gardens Plan Plan View Section Section
- 31. Contact Information Michael Kelly,P.E. John Gleason (512) 974-6591 (512) 974-3543 [email protected] [email protected] Environmental Resource Management Watershed Protection and Development Review Department 505 Barton Springs Road Austin, Texas 78704