Texas; Innovative Stormwater Controls - Austin Energy

Environmental Criteria Manual Environmental Criteria Manual Updates:Updates:

Innovative Stormwater Innovative Stormwater ControlsControls

Michael Kelly, P.E.John Gleason, Landscape Architect

Watershed Protection Watershed Protection and Development and Development Review DepartmentReview Department

ECM 1.6.7 Innovative Water Quality ECM 1.6.7 Innovative Water Quality ControlsControls

•• Vegetative Filter Strips (VFS)/ VFS Vegetative Filter Strips (VFS)/ VFS –– Disconnection of Imp. CoverDisconnection of Imp. Cover

•• BiofiltrationBiofiltration

•• Rainwater HarvestingRainwater Harvesting

•• Porous Pavement for Pedestrian UsePorous Pavement for Pedestrian Use

•• Rain GardensRain Gardens

Presenter�

Presentation Notes�

The City of Austin uses a multiple solutions approach toward watershed protection. We create and implement regulations such as water quality ordinances that require land developers to build stormwater runoff ponds whenever they build. The SOS Save Our Springs Ordinance is the strictest of those, and it takes a ‘no degradation’ approach to water quality. We require stream setbacks and water quality zones for all of our local streams and rivers. Programs include a community education program called “Grow Green”, which is a partnership between the City of Austin and the Texas Cooperative Extension Service of Travis County. This program provides integrated pest management (IPM) information at the various local stores that sell landscape chemicals. Other programs include monitoring of water chemistry and biology in our creeks, a spills response program, and so on. The third primary technique we use for watershed protection is the use of CIP’s, or Capital Improvement Projects. And that is what I’d like to explain in some detail. �

OnOn--site Stormwater Treatmentsite Stormwater TreatmentSedimentation/Filtration: standard water quality treatment pondSedimentation/Filtration: standard water quality treatment pond

Presenter�


Land developers are required to build a sedimentation/filtration pond (aka sand filter) for stormwater runoff in the City of Austin. A potential substitute for the sand filter is a wet pond. A wet pond is a stormwater pond with a permanent pool of water. One advantage that a wet pond has over a sand filter is apparent at first glance… they look better!�

Vegetated Filter Strip/Disconnected Vegetated Filter Strip/Disconnected Impervious CoverImpervious Cover

Presenter�


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Vegetative Filter StripsVegetative Filter Strips

Vegetated Filter Strip Credit/Vegetated Filter Strip Credit/ Disconnected Impervious CoverDisconnected 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.

Vegetative Filter Vegetative Filter StripsStrips

(acres of VFS per acre (acres of VFS per acre of impervious cover)of impervious cover)

Contributing Contributing Area Imp. Area Imp. CvrCvr.. SOSSOS

Sand Filtration Sand Filtration EquivalencyEquivalency

15%15% 0.280.28 NANA

25%25% .45.45 .40.40

50%50% 1.041.04 .91.91

75%75% 1.841.84 1.611.61

100%100% 2.852.85 2.492.49

Vegetative Filter Strip DesignVegetative Filter Strip DesignAllowable in the BSZAllowable in the BSZ

May be natural or engineeredMay be natural or engineered

Size: Requires relatively large land Size: Requires relatively large land areaarea

Maintain sheet flowMaintain sheet flow

Do not exceed max. Do not exceed max. velocities/hydraulic loading ratesvelocities/hydraulic loading rates

Width: as wide as the contributing drainage areaWidth: as wide as the contributing drainage area

Leng

th

Min

. 25’

Pavement

L e v e l s p r e a d e r c r e a t e s s h e e t f l o w

Vegetated Filter Strip

Vegetative Filter Strip DesignVegetative Filter Strip Design

Primary pollutant removal mechanism Primary pollutant removal mechanism is infiltration is infiltration

Bunchgrass: min. ht. 18Bunchgrass: min. ht. 18””Turf: min. ht. 3Turf: min. ht. 3””

Pavement

66”” min. soil depthmin. soil depth

Min. 3Min. 3”” drop drop

Water depth may not exceed the Water depth may not exceed the height of vegetation height of vegetation

BiofiltrationBiofiltration

Old Dominion Freight (near Lake Walter Long)

BiofiltrationBiofiltration1. 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

BiofiltrationBiofiltration: Vegetated Flow : Vegetated Flow Spreader vs. GabionSpreader vs. Gabion

Diagram of Biofiltration PondDiagram of Biofiltration PondCrossCross--Section Section –– Conceptual DesignConceptual Design

InletInlet

Splitter Splitter BoxBox Separator ElementSeparator Element

Filtration MediaFiltration Media

Filter FabricFilter Fabric

GravelGravel VegetationVegetation

Flood spillwayFlood spillway

FiltrationFiltrationSedimentationSedimentation OutletOutlet

Outlet PipeOutlet Pipe

BiofiltrationBiofiltration –– Landscape Design Landscape Design

•• Plants must tolerate wide variations in moisturePlants must tolerate wide variations in moisture•• Total Plants: Surface area (Total Plants: Surface area (s.fs.f.) of pond bottom .) of pond bottom

x 0.1x 0.1•• Sedimentation basin: Min. 20% of total plantsSedimentation basin: Min. 20% of total plants

•• Trees are allowedTrees are allowed•• Filtration basin: Min. 50% of total plantsFiltration basin: Min. 50% of total plants

•• Min. 20% tall herbaceousMin. 20% tall herbaceous•• No more than 30% medium herbaceousNo more than 30% medium herbaceous•• No trees are allowedNo trees are allowed

Biofiltration Plants Biofiltration Plants -- GrassesGrasses

BiofiltrationBiofiltration at at TechRidgeTechRidge

Rainwater HarvestingRainwater Harvesting

HEB Brodie Lane

Rainwater Harvesting: Option ARainwater Harvesting: Option ACaptured Runoff discharged to a VFS for infiltration (<72 hr)Captured Runoff discharged to a VFS for infiltration (<72 hr)

Rainwater HarvestingRainwater 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 stormwater

3. May be upsized to provide water conservation function.

Rainwater Harvesting: Option ARainwater Harvesting: Option ACaptured Runoff discharged to a VFS for infiltration (<72 hr)Captured Runoff discharged to a VFS for infiltration (<72 hr)

Rainwater Harvesting:Rainwater Harvesting: Option AOption A

Rainwater Harvesting: Option BRainwater Harvesting: Option BCaptured Runoff Used to Irrigate Vegetated AreaCaptured Runoff Used to Irrigate Vegetated Area

Conveyance system

• Max. 72 hr. drawdown time

• Use retentio/irrigation criteria (ECM 1.6.7A)

• Allowable in the Barton Springs Zone

Rainwater Harvesting: Option BRainwater Harvesting: Option BCaptured Runoff Used to Irrigate Vegetated AreaCaptured Runoff Used to Irrigate Vegetated Area

Tank

Sprinkler system (per retention/irrigation criteria)

Porous Pavement for Pedestrian Use Porous Pavement for Pedestrian Use

Pervious ConcretePervious Concrete Permeable PaversPermeable Pavers

Porous PavementPorous Pavement

1. Retains & infiltrates water underneath pavement used for pedestrian use only.

2. Criteria will allow for Impervious Cover (IC) credit.

Porous PavementPorous PavementPossibilities include: Possibilities include: •• porous concreteporous concrete•• reinforced turfreinforced turf•• gravelgravel

Rain GardensRain Gardens


• Filtration or Infiltration system for small (<1 acre) drainage areas

• Allows for dispersed, small-scale treatment systems integrated into site landscaping

Rain Garden Info: Grow GreenRain Garden Info: Grow Green


Plan View

Section

PlanPlan

SectionSection

Contact InformationContact 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

Presenter�


Question:What is Corps doing for sust.? �

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Texas; Innovative Stormwater Controls - Austin Energy