Low Impact DevelopmentLow Impact Developmentfor for

Prince William Prince William Advanced Master GardenersAdvanced Master Gardeners

Frank ReillyFrank Reilly

Why Me?Why Me?

Army Engineers Waterways Army Engineers Waterways Experiment StationExperiment Station

9 Years of Wetlands Workshops9 Years of Wetlands Workshops www.WetlandsWorkGroup.orgwww.WetlandsWorkGroup.org

Green Highways InitiativeGreen Highways Initiative www.GreenHighways.orgwww.GreenHighways.org

ReviewReview

PrecipitationPrecipitation RunoffRunoff InfiltrationInfiltration EvaporationEvaporation

Natural ConditionsNatural Conditions

Developed ConditionsDeveloped Conditions

More impervious surface = more More impervious surface = more runoffrunoff

So What?So What?

Degraded habitatDegraded habitat bacteria, sediments, bacteria, sediments,

nutrients, and petroleum nutrients, and petroleum productsproducts

Impaired watersheds Impaired watersheds Loss of habitatLoss of habitat

Silting in wetlandsSilting in wetlands Destruction of SAVDestruction of SAV Oyster reefOyster reef

Increased regulationIncreased regulation TMDLsTMDLs Rain tax Rain tax

So what for me?So what for me?

FloodingFlooding stormwater Taxstormwater Tax stormwater stormwater

maintenancemaintenance

Q

T

Developed Condition, Conventional CN(Higher Peak, More Volume, and Earlier Peak Time)

Existing Condition

HydrographHydrograph

Washington, DC - Reagan National

2001 Daily RainfallFrequency (inches)

90%

4%4% 2%

0.25

0.5

1

> 1

How can we make residential How can we make residential developmentsdevelopments

function hydrologically like natural function hydrologically like natural systems?systems?

Challenges of traditional stormwater Challenges of traditional stormwater management include:management include:

Engineering, design and infrastructure can be Engineering, design and infrastructure can be more costly than mimicking natural systemsmore costly than mimicking natural systems

Maintenance can be more expensiveMaintenance can be more expensive Significant space required for detention pondsSignificant space required for detention ponds Flow and volume of stormwater may not be Flow and volume of stormwater may not be

adequately controlled, leading to:adequately controlled, leading to: ErosionErosion FloodingFlooding Slope destabilizationSlope destabilization

LID, as an alternative emphasizes:LID, as an alternative emphasizes:

Using natural hydrologic functions as the Using natural hydrologic functions as the design frameworkdesign framework

Relying on natural features and processesRelying on natural features and processes Integrating stormwater management early Integrating stormwater management early

in site planning activitiesin site planning activities Applying simple, nonstructural and low Applying simple, nonstructural and low

cost methodscost methods Distributing small-scale practices Distributing small-scale practices

throughout the landscapethroughout the landscape

Low Impact Development (LID)Low Impact Development (LID)

stormwater Management stormwater Management

Ecosystem Based Functional DesignEcosystem Based Functional Design

““Uniformly Distributed Small-scale Controls”Uniformly Distributed Small-scale Controls”

““Integration of Controls with Sites, Streets and Integration of Controls with Sites, Streets and Architecture ”Architecture ”

What is LID?What is LID? A stormwater Management Strategy Concerned With:A stormwater Management Strategy Concerned With:

Maintaining or Restoring the Natural Hydrologic Functions of a Maintaining or Restoring the Natural Hydrologic Functions of a SiteSite

Helps Meet Construction (New & Retrofit) stormwater Helps Meet Construction (New & Retrofit) stormwater Management GoalsManagement Goals

Fulfilling Environmental Regulatory RequirementsFulfilling Environmental Regulatory Requirements Helps Reach NPDES Permit Limits & TMDL GoalsHelps Reach NPDES Permit Limits & TMDL Goals

Meeting Natural Resource Protection ObjectivesMeeting Natural Resource Protection Objectives Using Low Maintenance & Native VegetationUsing Low Maintenance & Native Vegetation Protection of WatershedsProtection of Watersheds

LID Employs Natural & Built Features that:LID Employs Natural & Built Features that: Reduce RunoffReduce Runoff Filter Out PollutantsFilter Out Pollutants Facilitate Water InfiltrationFacilitate Water Infiltration

Thanks, Larry Coffman

Where can LID apply?Where can LID apply?

New developmentNew development: residential & commercial: residential & commercial Zoning: Zoning: applying impervious surface ceilings applying impervious surface ceilings

to sensitive watersheds or basinsto sensitive watersheds or basins Land-use planning: Land-use planning: selecting appropriate selecting appropriate

watersheds, soils and hydrology for new watersheds, soils and hydrology for new development; minimizing road and utility development; minimizing road and utility distances to serve new developmentdistances to serve new development

Watershed planning: Watershed planning: integrating LID with integrating LID with other management practicesother management practices

Renovation/retro-fit: Renovation/retro-fit: building remodels, building remodels, road repair/paving, updating stormwater road repair/paving, updating stormwater systemssystems

LID Practices (No Limit!)LID Practices (No Limit!)

Bioretention / Rain GardensBioretention / Rain Gardens Strategic Grading Strategic Grading Site Finger PrintingSite Finger Printing Resource Conservation Resource Conservation Flatter Wider Swales Flatter Wider Swales Flatter SlopesFlatter Slopes Long Flow PathsLong Flow Paths Tree / Shrub Depression Tree / Shrub Depression Turf DepressionTurf Depression Landscape Island Storage Landscape Island Storage Rooftop Detention /Retention Rooftop Detention /Retention Roof Leader (Gutter) Roof Leader (Gutter)

DisconnectionDisconnection Parking Lot / Street Storage Parking Lot / Street Storage Smaller Culverts, Pipes & InletsSmaller Culverts, Pipes & Inlets

Alternative SurfacesAlternative Surfaces Reduce Impervious SurfaceReduce Impervious Surface Surface Roughness Technology Surface Roughness Technology Rain Barrels / Cisterns / Water UseRain Barrels / Cisterns / Water Use Catch Basins / Seepage PitsCatch Basins / Seepage Pits Sidewalk StorageSidewalk Storage Vegetative Swales, Buffers & Vegetative Swales, Buffers &

Strips Strips Infiltration Swales & TrenchesInfiltration Swales & Trenches Eliminate Curb and GutterEliminate Curb and Gutter Shoulder Vegetation Shoulder Vegetation Maximize Sheet flow Maximize Sheet flow Maintain Drainage PatternsMaintain Drainage Patterns Reforestation……………….. Reforestation……………….. Pollution Prevention…………..Pollution Prevention…………..

““Creative Techniques to Treat,Use, Store, Retain, Detain and Recharge”

LID PRACTICESLID PRACTICES

Compact DesignCompact Design Distributed Subsurface Storage Distributed Subsurface Storage Pervious PavementPervious Pavement Dispersion of Runoff Dispersion of Runoff Bioretention Cells/Rain GardensBioretention Cells/Rain Gardens Amended SoilsAmended Soils Green RoofsGreen Roofs Rooftop Rainwater HarvestingRooftop Rainwater Harvesting

Compact DesignCompact DesignDescriptionDescription::

An approach to site design that clusters An approach to site design that clusters buildings and infrastructure in designated, buildings and infrastructure in designated, compact areas of a development site.compact areas of a development site.

Benefits:Benefits: Leaves larger percentage of development site in natural Leaves larger percentage of development site in natural

conditions (preserving native vegetation, topsoils and hydrology)conditions (preserving native vegetation, topsoils and hydrology) Reduces the infrastructure needed to service the area (roads, Reduces the infrastructure needed to service the area (roads,

utilities, stormwater)utilities, stormwater) Enables larger and more effective buffers between development Enables larger and more effective buffers between development

and critical areas (streams, wetlands, steep slopes)and critical areas (streams, wetlands, steep slopes) Enhances property value and aesthetic by preserving open space Enhances property value and aesthetic by preserving open space

and viewscapesand viewscapes

But you have to keep the But you have to keep the “promise”“promise”

Golf Courses soldGolf Courses sold

Bash and BuildBash and Build

Compact Design is “retrofit-Compact Design is “retrofit-able”able”

Distributed Subsurface Distributed Subsurface StorageStorageDescription:Description:

Underground stormwater storage in Underground stormwater storage in decentralized areas using rock matrix, decentralized areas using rock matrix, cellular storage media and underdrainscellular storage media and underdrains

Benefits:Benefits: Can be carried out under parking Can be carried out under parking

lots, sports fields etc. in a shallow lots, sports fields etc. in a shallow depth, levering large areas of often depth, levering large areas of often unused spaceunused space

Eliminates the need for surface Eliminates the need for surface ponds or large vaults.ponds or large vaults.

Can be combined with filtration and Can be combined with filtration and ground water rechargeground water recharge

Distributed Subsurface Distributed Subsurface StorageStorage

Pervious PavementPervious Pavement

Description:Description:

Special types of porous pavement that enable Special types of porous pavement that enable water to flow or pass through it, made from a water to flow or pass through it, made from a variety of materials (cement, aggregate, fly ash, variety of materials (cement, aggregate, fly ash, asphalt).asphalt).

Benefits:Benefits: Many different options enable variety of applications and Many different options enable variety of applications and

uses (grass blocks, pavers, porous asphalt).uses (grass blocks, pavers, porous asphalt). Enables water to infiltrate, recharging groundwater and Enables water to infiltrate, recharging groundwater and

reducing total volume of runoff from a site.reducing total volume of runoff from a site. Provides filtration and can enable treatment of pollutants.Provides filtration and can enable treatment of pollutants.

Pervious PavementPervious Pavement Here is how well some Here is how well some

of of thisthis works works Here is how good Here is how good

some of this lookssome of this looks

Dispersion of RunoffDispersion of Runoff

DescriptionDescription::

Stormwater is dispersed evenly and Stormwater is dispersed evenly and uniformly, across a wide area, uniformly, across a wide area, using outlets designed to spread using outlets designed to spread concentrated flow into sheet flow.concentrated flow into sheet flow.

Benefits:Benefits: Helps restore natural sheet flows Helps restore natural sheet flows

to existing drainage has been to existing drainage has been altered by development.altered by development.

Reduces velocity of flows, Reduces velocity of flows, preventing scouring and erosion.preventing scouring and erosion.

Disconnecting the flow from Disconnecting the flow from other drainpipes reduces overall other drainpipes reduces overall quantity of water that must be quantity of water that must be treated.treated.

Bioretention Cells/Rain Bioretention Cells/Rain GardensGardensDescription:Description:

Shallow, landscaped areas that use porous Shallow, landscaped areas that use porous soils and vegetation to store and treat soils and vegetation to store and treat runoff. Sometimes called rain gardens.runoff. Sometimes called rain gardens.

Benefits:Benefits: Can promote groundwater recharging through infiltration.Can promote groundwater recharging through infiltration. May enable greater evapotranspiration, reducing runoff from site.May enable greater evapotranspiration, reducing runoff from site. Helps maintain pre-development discharge rates and timing, more Helps maintain pre-development discharge rates and timing, more

closely replicating natural watershed conditions.closely replicating natural watershed conditions. Filters and treats pollutants, such as heavy metals, petroleum Filters and treats pollutants, such as heavy metals, petroleum

products, nutrients and fertilizers.products, nutrients and fertilizers.

Amended SoilsAmended Soils

Description:Description:

Soil amendments are needed when development Soil amendments are needed when development removes top layers of soil and compacts removes top layers of soil and compacts subsurface layers, thereby reducing ability of soils subsurface layers, thereby reducing ability of soils to store and treat runoff.to store and treat runoff.

Benefits:Benefits: Increases soil permeability, enabling greater storage capacity Increases soil permeability, enabling greater storage capacity

and infiltration, reducing overall runoff from development site.and infiltration, reducing overall runoff from development site. Can effectively filter and treat. pollutants.Can effectively filter and treat. pollutants. Reduces the need for extensive use of irrigation and fertilizers.Reduces the need for extensive use of irrigation and fertilizers.

Green RoofsGreen Roofs

Description:Description:

Lightweight vegetated surface laid over an Lightweight vegetated surface laid over an impervious roof area.impervious roof area.

Benefits:Benefits: Improves a building’s energy performance (both heating and Improves a building’s energy performance (both heating and

cooling) by adding a thermal layer.cooling) by adding a thermal layer. Provides significant stormwater storage and evapotranspiration – Provides significant stormwater storage and evapotranspiration –

reducing need for other SW practices on site.reducing need for other SW practices on site. Improves air quality (filters large percentage of particulates in the Improves air quality (filters large percentage of particulates in the

air).air). Provides wildlife habitat.Provides wildlife habitat. Increases lifespan of conventional roof (can double lifespan of roof).Increases lifespan of conventional roof (can double lifespan of roof).

Two Main typesTwo Main types IntensiveIntensive

require deeper substrate layers require deeper substrate layers (usually > 10 cm (4 in))(usually > 10 cm (4 in))

are generally limited to flat roofsare generally limited to flat roofs require ‘intense’ maintenance, and require ‘intense’ maintenance, and are often park-like areas accessible are often park-like areas accessible

to the general publicto the general public variety of plant species that may variety of plant species that may

include trees and shrubsinclude trees and shrubs

ExtensiveExtensive Can have shallower substrate Can have shallower substrate

layers (usually < 10 cm (4 in))layers (usually < 10 cm (4 in)) require minimal maintenance, and require minimal maintenance, and are generally not accessible to the are generally not accessible to the

publicpublic limited to herbs, grasses, mosses, limited to herbs, grasses, mosses,

and drought tolerant succulents and drought tolerant succulents such as Sedumsuch as Sedum

Chicago City Hall after 18 months

33

Wetlands Mitigation?

34

Rooftop Rainwater Rooftop Rainwater HarvestingHarvesting

Description:Description:

Collection system designed to capture rainwater and Collection system designed to capture rainwater and store for dry-period irrigation or for graywater use store for dry-period irrigation or for graywater use within a building. Smaller systems referred to as within a building. Smaller systems referred to as “rain barrels”.“rain barrels”.

Benefits:Benefits: Use of graywater provides significant conservation Use of graywater provides significant conservation

water.water. Use of stored water enables inexpensive irrigation Use of stored water enables inexpensive irrigation

during dry periods.during dry periods. Reduce overall runoff from a development site.Reduce overall runoff from a development site.

There are many ways to go There are many ways to go herehere

Disconnect Disconnect

Benefits:Benefits: Retains water on site Retains water on site Available systems for almost any densityAvailable systems for almost any density Can be retrofittedCan be retrofitted Can help attain stormwater goals at lower costCan help attain stormwater goals at lower cost

Definition:Definition:

Interrupt the rapid flow of stormwater off Interrupt the rapid flow of stormwater off sitesite

Separation Plan in CSO 006 Area (Est. Cost =

$3,900/private property)

New Storm Sewer Connection

New Storm Sewer in Street

Roof Leader Disconnected and Rain Barrel (LID) Used*

*No Extension on Private Property Required (May Result in 10-50% savings).

Disconnects

Combined Sewer Converted to Sanitary Sewer

Splash Blocks by Splash Blocks by MyersculptureMyersculpture

Low Cost Alternatives

Moderate Cost AlternativesModerate Cost Alternatives

Flow-through PlanterFlow-through Planter

Reservoir, 12" min. depth

Reverse bend trap or hooded overflow

18" sandy loam, minimum infiltration rate 5" per hour

12" open-graded gravel, approx. ½" dia.

Perforated pipe

Downspout

Building exterior wall

Cobbles or splash block

Filter fabric

Concrete or other structural planter wall with waterproof membrane

Additional waterproofing on building as needed

Drain to storm drain or discharge; bottom-out or side-out options

““High” Cost AlternativesHigh” Cost Alternatives

Doing Nothing!Doing Nothing! Flood DamageFlood Damage County-wide re-plumbing to meet County-wide re-plumbing to meet

TMDLsTMDLs

Comparison of Conventional Comparison of Conventional and LID Site Conditionsand LID Site Conditions

Many LID tools are “retrofit-Many LID tools are “retrofit-able”able”

Next TimeNext Time

What can Master Gardeners do?What can Master Gardeners do? Specific Ideas for our clientsSpecific Ideas for our clients

Rain garden techniquesRain garden techniques Rain barrel techniquesRain barrel techniques Dis-connectivity techniquesDis-connectivity techniques