Constructing Rain Gardens & Bioswales (Keynote)

ConstructingRain Gardens& BioswalesBy Tom BarrettGreen Water Infrastructure, Inc.www.ThinkGWI.comTom.Barrett@ThinkGWI.com Follow us on Twitter @TomBarrett_GWI

The GREENEconomy

How Much Rain Falls in St. Louis?January - 1.83" Image of Rain FallingFebruary - 1.85"March - 2.88"April - 3.58"May - 4.10"June - 4.72"July - 3.56"August - 3.51"September - 3.17"October - 2.96"November - 2.35"December - 1.85"Total 36.36"

How Much Water Falls in St. Louis? 2,500 sq. ft. RoofJanuary - ,852 gallons 2 Image of Rain FallingFebruary - ,883 2March - ,488 4April - 5,579May - ,390 6June - 7,356July - ,548 5August - ,470 5September- ,940 4October - ,613 4November - 3,662December - 2,883Total 6,664 5

How Much Water Falls in St. Louis? 3 Acre Commercial PropertyJanuary - 49,075 gallons 1 Image of Rain FallingFebruary - 50,705 1March - 34,611 2April - 291,634May - 33,994 3June - 384,501July - 90,005 2August - 85,932 2September - 58,235 2October - 41,128 2November - 191,436December - 150,705Total 2,961,961

How Much Water Falls in St. Louis? City Block (5 acres)January - 48,459 gallons 2February - 51,176 2March - 91,018 3April - 486,057May - 56,657 5June - 640,834July - 83,341 4August - 476,553September - 30,391 4October - 01,879 4November - 319,061December - 251,176Total 4,936,602

LOW IMPACT SITE DEVELOPMENT

Stormwater MitigationStormwater MitigationStormwater MitigationStormwater MitigationStormwater Mitigation

Image of Rain Falling

PESTICIDE ISSUESATRAZINE, NITROGEN, PHOSPHOROUS

Peak Flow (1 Acre Site) Grass Field Roof1 Year Storm 1.4 cfs 4.3 cfs2 Year Storm 2.1 cfs 5.4 cfs10 Year Storm 4.3 cfs 8.0 cfs25 Year Storm 5.7 cfs 9.5 cfs100 Year Storm 8.0 cfs 12.0 cfs cfs – cubic feet per second

Peak Flow (1 Acre Site) Grass Field Roof1 Year Storm 10.5 gps 32.2 gps2 Year Storm 15.7 gps 40.4 gps10 Year Storm 32.2 gps 59.8 gps25 Year Storm 42.6 gps 71.1 gps100 Year Storm 59.8 gps 89.8 gps gps – gallons per second

Peak Flow (1 Acre Site) Grass Field Roof1 Year Storm 630 gpm 1,932 gpm2 Year Storm 942 gpm 2,424 gpm10 Year Storm 1,932 gpm 3,588 gpm25 Year Storm 2,556 gpm 4,266 gpm100 Year Storm 3,588 gpm 5,388 gpm gpm – gallons per minute

Peak Flow (2,500 sq. ft. Roof) Grass Field Roof1 Year Storm 0.08 cfs 0.25 cfs2 Year Storm 0.12 cfs 0.31 cfs10 Year Storm 0.25 cfs 0.46 cfs25 Year Storm 0.33 cfs 0.55 cfs100 Year Storm 0.46 cfs 0.69 cfs cfs – cubic feet per second

Peak Flow (2,500 sq. ft. Roof) Grass Field Roof1 Year Storm 0.60 gps 1.85 gps2 Year Storm 0.90 gps 2.32 gps10 Year Storm 1.85 gps 3.43 gps25 Year Storm 2.44 gps 4.08 gps100 Year Storm 3.43 gps 5.15 gps gps – gallons per second

Peak Flow (2,500 ft. sq. Roof) Grass Field Roof1 Year Storm 36 gpm 111 gpm2 Year Storm 54 gpm 139 gpm10 Year Storm 111 gpm 206 gpm25 Year Storm 147 gpm 245 gpm100 Year Storm 206 gpm 309 gpm gpm – gallons per minute

Change in Peak Runoff Flow Before and after Development 300% 225% 150% 75% 0% 1 Year Storm Year Storm Year Storm Year Storm Year Storm 2 10 25 100 Stormwater Effects of Urbanization

PLANTING TREES

Stormwater Mitigation– Collection runoff near the source– Slow it down– Soak it in– Filter it– Apply it to the landscape– Create habitats

Rain GardenA Low SpotCatches StormwaterDeep Rooted Plants

SIMPLE RAIN GARDEN

Bioswales Engineered Soils Underdrain

Location Rain gardens are Plant Choices often located at the end of a roof or Choose plants based drain spout. on the need for light and soil type. Depth Size Soil A Rain Garden usually A tpical mix is 65% A typical Rain Garden five to ten percent sand, 15% top soil, is between four to of the impervious 25% organic matter. eight inches deep. surface area.RAIN GARDENS

RAIN GARDEN

BIOSWALESBURNSVILLE, MINNESOTA

NATIVE VEGETATIONWWW.EPA.GOV/GREENACRES/ WWW.FOR-WILD.ORG

Street Edges& Medians

Parking LotEdges

Parking LotIslands

DrivewayEdge

Downspout

NEIGHBORHOODS

CriteriaMeet Stormwater Utility ClearanceRegulations Soil InvestigationDetention Volume Percolation TestFix Drainage IssueFix Erosion Issue

CriteriaNear the Rainwater Distributed EvenlySource Across the SiteAvoid “End-of Pipe” Small Tributary Areasbecause of (usually 1 acre or less)Sedimentation IssuesTypically 10’ to 20’from Buildings

SoilInvestigation •Soil Proﬁle to Five Feet•Soil Compaction Level•Depth to Groundwater andBedrock

PercolationTest •Soil Inﬁltration Rate•Key Design Parameter•Percolates water in 24Hours

SizingDetermine Design Native vs. EngineeredGoals Soil AssessmentCalculate RunoffVolumeDetermine AllowableDepthCalculate SurfaceArea

SizingRunoffVolume =Precipitation xDrainage Area x RunoffCoefficientRV=Pr x D(area) x C(un

DepthBased UponInfiltration RateInfiltration in One DayAvoid MisquotesMaximum Depth 18”for Safety

Surface AreaArea of Rain Garden(ft2) = Runoff CaptureVolume (ft3) / AverageDepth (ft)A=V/D(average)

Engineered SoilsBioretentionSpace AvailableVolume of StormwaterDrain Faster(the garden can bedeeper and not aswide)

Plants -BottomPalm SedgeSoft RushTussock SedgeMarsh Milkweed Blue Flag IrisJoe-Pye Weed

Plants -SidesPurple ConeﬂowerShowy GoldenrodSmooth Phlox

Plants -EdgesButterﬂy MilkweedLittle BluestemAromatic Aster

Inlets

Outlets

Curb Cut &Filter StripControls Sedimentation

SplashBlocksPrevents Erosion and Gullies

FUNCTIONAL LANDSCAPES

Green • Water • InfrastructureGreen • Water • InfrastructureGreen • Water • InfrastructureGreen • Water • InfrastructureGreen • Water • Infrastructure

Thank You

Constructing Rain Gardens & Bioswales (Keynote)

by Tom Barrett on Jan 04, 2011

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Constructing Rain Gardens & Bioswales (Keynote) — Presentation Transcript