UVM-AWRA CHARRETTE: designing an alternative

stormwater treatment technique

W h a t I s a C h a r r e t t e?

A Charrette is a cross-disciplinary workshop to create designs for complicated problems

in a brief time window.

THE PROBLEM: StormwaterTHE PROBLEM: Stormwater Runoff from impervious surfacesRunoff from impervious surfaces 17 streams and rivers in VT 17 streams and rivers in VT

impaired by stormwaterimpaired by stormwater UVM’s 5 new treatment pondsUVM’s 5 new treatment ponds Centralized treatment – Centralized treatment –

undersized? over-worked?undersized? over-worked?

Centralized Stormwater TreatmentCentralized Stormwater Treatment

Reduces rate of Reduces rate of runoff for selected runoff for selected design stormsdesign storms

Fails to control Fails to control volume of runoffvolume of runoff

Water quality Water quality treatment???treatment???

Commonly no Commonly no recharge to recharge to groundwatergroundwater

Decentralized ApproachesDecentralized Approaches

Small-scale approachSmall-scale approach Treat close to sourceTreat close to source Encourage infiltration, Encourage infiltration,

evapotranspirationevapotranspiration Examples:Examples:

Filter/buffer stripsFilter/buffer strips BioswalesBioswales Infiltration trenchesInfiltration trenches Permeable pavementPermeable pavement RoofgardensRoofgardens

THE PROJECTTHE PROJECT

Design for Design for demonstration projectdemonstration project

Votey parking lot, Votey parking lot, 4820 m4820 m2 2 drainage drainage area, 85% TIAarea, 85% TIA

Stormwater Stormwater monitoring datamonitoring data Lead and trace metalsLead and trace metals 2 Fall storm events2 Fall storm events

Mission & GoalsMission & Goals

Minimize the ecological footprintMinimize the ecological footprint Increase environmental consciousnessIncrease environmental consciousness ““Greening the campus”Greening the campus” Promote excellence in environmental academicsPromote excellence in environmental academics

Decentralized PracticesDecentralized Practices

BioretentionBioretention Dry WellsDry Wells Filter StripsFilter Strips SwalesSwales Rain BarrelsRain Barrels CisternsCisterns Infiltration TrenchesInfiltration Trenches Tree Box FilterTree Box Filter

BioretentionBioretention

Landscaped areasLandscaped areas Conditioned soilConditioned soil Detains and infiltratesDetains and infiltrates Components:Components:

Pretreatment areaPretreatment area Ponding areaPonding area Ground coverGround cover Planting soilPlanting soil PlantsPlants Inlet and outlet controlsInlet and outlet controls

Dry Wells & Infiltration TrenchesDry Wells & Infiltration Trenches

Excavated trenchesExcavated trenches Backfill with stone or gravelBackfill with stone or gravel Detains and infiltratesDetains and infiltrates Components:Components:

Pretreatment - filteringPretreatment - filtering Backfill materialBackfill material Filter fabric liningFilter fabric lining Inflow and outflow controlsInflow and outflow controls Observation wellObservation well

Filter StripsFilter Strips

Grassy vegetation between runoff source and receiving Grassy vegetation between runoff source and receiving waterbodywaterbody

Level spreader for sheet flowLevel spreader for sheet flow Components:Components:

Flow distributionFlow distribution Planting materialPlanting material

• BermBerm• Outlet ControlsOutlet Controls

SwalesSwales Dry or wet swales to slow runoff and promote Dry or wet swales to slow runoff and promote

infiltrationinfiltration Typical along roadways Typical along roadways ComponentsComponents

PretreatmentPretreatment Check damsCheck dams UnderdrainUnderdrain

• Planting materialPlanting material• Conditioned soilConditioned soil

Rain Barrels & CisternsRain Barrels & Cisterns

Small-scale, low-cost Small-scale, low-cost devicesdevices

Detention and re-useDetention and re-use Above or below groundAbove or below ground Components:Components:

Screen or filterScreen or filter ContainerContainer Sighting gaugeSighting gauge Inlet, outlet, overflowInlet, outlet, overflow

Tree Box FiltersTree Box Filters

In-ground containers In-ground containers with street treeswith street trees

Detains, infiltrates, Detains, infiltrates, evapotranspiratesevapotranspirates

Components:Components: Open-bottom vaultOpen-bottom vault Porous soil mediaPorous soil media UnderdrainUnderdrain Salt- and water-Salt- and water-

tolerant treestolerant trees

CONSTRAINTSCONSTRAINTS

Physical Characteristics of SitePhysical Characteristics of Site CostCost Maintenance RequirementsMaintenance Requirements