Designing LID Treatment Systems

Low Impact Development SystemsLow Impact Development SystemsSitingSiting, Design and Installation for , Design and Installation for Maximum Environmental Benefit. Maximum Environmental Benefit.

What are the aesthetic, What are the aesthetic, maintenance, & financialmaintenance, & financial

considerations?considerations?

AIA, Committee on the Environment AIA, Committee on the Environment Sustainable Sites ProgramSustainable Sites Program

New Haven, ConnecticutNew Haven, Connecticut

12/16/2010 Copyright Trinkaus Engineering

Presenter BackgroundPresenter Background

�� Nationally recognized expert in Low Impact Nationally recognized expert in Low Impact Development (Regulations and Applications)Development (Regulations and Applications)

�� Licensed Professional Engineer (CT)Licensed Professional Engineer (CT)

�� Holds IECA certifications as CPESC & Holds IECA certifications as CPESC & CPSWQCPSWQ

�� Over 27 years in the Land Development Field Over 27 years in the Land Development Field and 11 years working with Low Impact and 11 years working with Low Impact DevelopmentDevelopment


Stormwater ManagementStormwater ManagementOld Way to New WayOld Way to New Way

University of Arkansas Community Design Center


Types of LID Treatment System Types of LID Treatment System (Dry)(Dry)

� Bioretention

� Dry Swales

� Infiltration Basins & Trenches

� Sand Filters

� Permeable Pavement & Porous Concrete

� Filter Strips


Types of LID Treatment System Types of LID Treatment System (Wet)(Wet)

� Wet Swales

� Constructed Wetlands & Ponds

� Subsurface Gravel Wetlands

� Organic Filters


How they workHow they work

�� All “Dry” LID systems function by All “Dry” LID systems function by infiltrating runoff into the underlying infiltrating runoff into the underlying native soils where physical, chemical native soils where physical, chemical and biological processes treat and and biological processes treat and reduce pollutant loadsreduce pollutant loads


How they workHow they work

�� All “Wet” LID systems function by All “Wet” LID systems function by creating an anaerobic environment creating an anaerobic environment when bacteria can reduce pollutant when bacteria can reduce pollutant loads. Additional pollutant removal loads. Additional pollutant removal occurs by physical settlement and occurs by physical settlement and vegetative uptakevegetative uptake


SitingSiting of LID Systems on the of LID Systems on the LandscapeLandscape

� Site Considerations:

� Soil Class & Infiltrative Capacity

� Depth to Groundwater

� Slope of Land

� Hydrologic Conditions


Soil ClassesSoil Classes

� Four Main Soil Classifications (NRCS)�� “A” “A” –– Excessively well drained (Sands & Excessively well drained (Sands & GravelsGravels

�� “B” “B” –– Well drained (Sandy Loams)Well drained (Sandy Loams)

�� “C” “C” –– Moderately well drained (Fine Moderately well drained (Fine Sandy Loams to Silt Loams)Sandy Loams to Silt Loams)

�� “D” “D” –– Poorly drained (soils with high silt, Poorly drained (soils with high silt, clay content [wetland soils]clay content [wetland soils]


Soil Textural ClassesSoil Textural Classes


Soils: Get your hands Dirty!!!Soils: Get your hands Dirty!!!Test Pit: Best way to see the dirt. OK, you don’t need 14 people to log a test pit

Mason Jar Test: Simple test to determine type & amount of soil particles


““A” SoilsA” Soils


““B” and “C” SoilsB” and “C” Soils


““D” SoilsD” Soils


Average Infiltrative CapacityAverage Infiltrative Capacity

� “A” Soils: 10 – 200 feet/day

� “B” Soils: 3- 12 feet/day

� “C” Soils: 1 – 3 feet/day

� “D” Soils: NONE


Average Depth to GroundwaterAverage Depth to Groundwater

� “A” Soils: > 10 feet on average, but can be less depending upon position on landscape

� “B” Soils: 6 – 3 feet

� “C” Soils: 1 – 2 feet

� “D” Soils: On Surface


Land SlopeLand Slope


LID Slope IssuesLID Slope Issues

�� Ideal slope for Bioretention systems is 2 Ideal slope for Bioretention systems is 2 ––10%10%

�� Ideal slope for Vegetated Filter Strips < 6%Ideal slope for Vegetated Filter Strips < 6%

�� Ideal slope for Infiltration Basin < 6%Ideal slope for Infiltration Basin < 6%


Primary LID System:Primary LID System:BIORETENTIONBIORETENTION


BIORETENTION SYSTEMSBIORETENTION SYSTEMS

� Functionality:�� Settling of coarse & fine sediments on Settling of coarse & fine sediments on surfacesurface

�� Removal of pollutants by physical, chemical Removal of pollutants by physical, chemical and biological processesand biological processes

�� Infiltration of runoff into underlying soilsInfiltration of runoff into underlying soils


BIORETENTION SYSTEMSBIORETENTION SYSTEMS

� Design Requirements:�� Maintain specified separation to seasonally high Maintain specified separation to seasonally high groundwater levelgroundwater level

�� Surface storage must contain required Water Surface storage must contain required Water Quality Volume (fixed volume)Quality Volume (fixed volume)

�� Depth of Depth of PondingPonding (vary per natural soil type)(vary per natural soil type)

�� Specific Soil Media (Enhance pollutant removal)Specific Soil Media (Enhance pollutant removal)

�� Appropriate PlantsAppropriate Plants

�� PondedPonded water shall drain in 24 hours, no more than water shall drain in 24 hours, no more than 48 hours48 hours


BIORETENTIONBIORETENTION

1. Facility handles 1,900 sq.ft. of residential roof

2. Has not overtopped in 3 years

3. Located in “B” soils

Newtown, CT – Trinkaus Engineering



1. Facility handles 2,800 sq.ft. of road runoff

2. Facility is 4’ x 9’ x 10” deep

3. Never overtopped in 2 years

4. Located in “B” soils

5. Soil media is 50% sand & 50% leaf compost

6. Ponded surface drains down in less than 4 hours after rainfall

Southbury, CT – Trinkaus Engineering



� Field Investigation:� Deep Test Pit at least 6’ deep

� Type & Description of each soil layer

� Sample Soil Description:� 0 – 4” Topsoil (Organic layer)

� 4 – 33” Orange brown fine sandy loam

� 33 – 48” Orange brown fine sand to silt loam

� 48 – 84” Brown grey lightly compact sand & gravel, No ledge, no mottling, no water, roots to 48”



� Field Investigation:� Percolation Test:

� Depth of test shall be approximately equal to anticipated depth of soil media for Bioretention

� Shall be above season high groundwater level

� Provides reasonable estimate of soil infiltrative capacity


Location, Location, LocationLocation, Location, Location

1. Bioretention are infiltration systems – do the soils next to a wetland infiltrate?

2. Bottom of system is 6” above observed seasonal high groundwater level

3. Bottom of system is 2’ below ex. grade in wetlands

4. Treating parking lot runoff – require 3’ vertical separation to groundwater


This looks easy, what can go This looks easy, what can go wrong???wrong???

1. Pondingmore than 3 days AFTER a rainfall event

2. Very few plants

3. Site was not fully stabilized prior to installation of facility

Trinkaus Engineering



1. Use outdated detail for construction,

2. Inappropriate soil media (too much topsoil)

3. Use of filter fabric (causes clogging, reduced or no infiltration



1. Overflow grate set flush to soil surface – NO STORAGE VOLUME

2. Questionable soil media, visual inspection shows large silt component

3. One tree (outside of low point of facility




1. Overflow grate set flush to soil surface, NO STORAGE VOLUME

2. Notch on left side has no function, parking pitches away from facility

3. 24” of soil media on top of Structural fill with no underdrains (Where would the water go if it could infiltrate?)




1. At low point is flush catch basin grate directly connected to hydrodynamic separator

2. No available storage for runoff

3. Balance of island is raised, not depressed

1. Runoff can only enter near low end of sloping facility

2. Runoff must make 90 degree turn into facility

3. Minimal storage around overflow grate

CT NEMO CT NEMO



1. How does runoff enter this facility? (Forgot to cut notches thru curb

CT NEMO


BioretentionBioretention InstallationInstallation

�� Excavate to required Excavate to required subgradesubgrade

�� Scarify with hand rake; bottom and Scarify with hand rake; bottom and sides of facility to remove soil smearingsides of facility to remove soil smearing

�� Place 1Place 1--1/41/4”” crushed stone (storage crushed stone (storage layer) layer) w/underdrainw/underdrain & overflow pipe& overflow pipe

�� Place pea gravel filter layerPlace pea gravel filter layer

�� Mix and place soil media layerMix and place soil media layer

�� Install plantsInstall plants


Scarification of Native SoilsScarification of Native Soils

Harwinton Sports Complex – Trinkaus Engineering


Scarification and Placement of Scarification and Placement of Reservoir LayerReservoir Layer



Installation of Installation of underdrainunderdrain/overflow /overflow pipe & Pea Gravelpipe & Pea Gravel



Bioretention ConstructionBioretention Construction

�� Protect area from construction traffic Protect area from construction traffic and stockpiling during site workand stockpiling during site work

�� Fully stabilize surface around Fully stabilize surface around bioretentionbioretention area, such as pavementarea, such as pavement

�� Do not install when soils are wet (will Do not install when soils are wet (will adversely affect infiltration capacity)adversely affect infiltration capacity)


Erosion/Sediment IssueErosion/Sediment Issue

Unstabilized site surrounding Bioretention Area Silt layer from gravel parking

base material - clogged Bioretention soil surface

North Carolina State University – Bioengineering Group


Result from prior slideResult from prior slide

North Carolina State University – Bioengineering Group


Bioretention MaintenanceBioretention Maintenance

�� Mulch around plant stems onlyMulch around plant stems only

�� Stabilize inlet of runoff with stones to Stabilize inlet of runoff with stones to encourage overland flowencourage overland flow

�� Weed basin annually for first two yearsWeed basin annually for first two years

�� Prune vegetation as neededPrune vegetation as needed

�� Remove accumulated sediment at inlet by Remove accumulated sediment at inlet by handhand


SwalesSwales

�� BioswalesBioswales (Dry) Swales:(Dry) Swales:�� Linear applicationsLinear applications

�� Max. slope = 4.0%Max. slope = 4.0%

�� 3’ vertical separation from top of soil to 3’ vertical separation from top of soil to shallow groundwatershallow groundwater

�� Bioretention soil media Bioretention soil media –– 30” in depth30” in depth


SwalesSwales

�� Wet Swales:Wet Swales:�� Max. slope = 4.0%Max. slope = 4.0%

�� Bottom of swale must intercept shallow Bottom of swale must intercept shallow groundwater level (necessary to create & groundwater level (necessary to create & maintain hydrologic condition)maintain hydrologic condition)

�� Plant with wetland speciesPlant with wetland species


Dry & Wet SwalesDry & Wet Swales

Dry Swale Wet Swale

CT NEMO Dr. Bill Hunt, PE (NCSU)


Dry SwalesDry Swales

High Point – Seattle, WA SEA Street Retrofit – Seattle, WA


Dry Swale ConstructionDry Swale Construction

�� Protect area from construction traffic and Protect area from construction traffic and stockpiling during site work, do not want to compact stockpiling during site work, do not want to compact underlying soilsunderlying soils

�� Fully stabilize contributing drainage area above swale. Fully stabilize contributing drainage area above swale. Prevent silt from entering the systemPrevent silt from entering the system

�� Do not install when soils are wet (will adversely affect Do not install when soils are wet (will adversely affect infiltration capacity)infiltration capacity)

�� Vegetation must be fully established before receiving Vegetation must be fully established before receiving runoffrunoff


Dry Swale MaintenanceDry Swale Maintenance

�� Maintain grass at 4” heightMaintain grass at 4” height

�� Weed swale annually for first two yearsWeed swale annually for first two years

�� Prune vegetation as neededPrune vegetation as needed


�� Remove accumulated sediment at inlet Remove accumulated sediment at inlet by handby hand


Wet Swale ConstructionWet Swale Construction

�� Protect area from construction traffic and Protect area from construction traffic and stockpiling during site workstockpiling during site work

�� Fully stabilize contributing drainage area above swale. Fully stabilize contributing drainage area above swale. Prevent silt from entering the systemPrevent silt from entering the system

�� If soils are a little wet, it is OK If soils are a little wet, it is OK –– we want a we want a siltysilty, wet , wet environmentenvironment

�� Vegetation must be fully established before receiving Vegetation must be fully established before receiving runoffrunoff


Wet Swale MaintenanceWet Swale Maintenance

�� DO NOT MOW OR CUT VEGETATIONDO NOT MOW OR CUT VEGETATION

�� Remove any invasive speciesRemove any invasive species

�� Do not prune vegetation, denser is Do not prune vegetation, denser is betterbetter


�� Accumulated sediment can actually helpAccumulated sediment can actually help


Vegetated Filter StripsVegetated Filter Strips

Maximum slope = 6%

Stone trench or raised concrete lip – very important to achieve overland flow

Generally –berms are not needed or desired as concentration flow can develop


Vegetated Filter StripsVegetated Filter Strips

Ledgebrook Lane – Trinkaus Engineering


Filter Strip ConstructionFilter Strip Construction

�� Prevent compaction of soilsPrevent compaction of soils

�� If soils get compacted, perform deep If soils get compacted, perform deep tillage (12tillage (12--18”) to restore infiltrative 18”) to restore infiltrative capacity.capacity.

�� Protect area with erosion control Protect area with erosion control measures above filter strip to prevent measures above filter strip to prevent erosionerosion


Filter Strip ConstructionFilter Strip Construction

�� Grade uniform cross slope to ensure Grade uniform cross slope to ensure overland flow will occuroverland flow will occur

�� HydroseedHydroseed filter strip areafilter strip area

�� ONLY allow runoff onto filter strip ONLY allow runoff onto filter strip after fully vegetatedafter fully vegetated

�� A hardened edge must be installed A hardened edge must be installed above the filter strip to achieve above the filter strip to achieve overland flowoverland flow


Filter Strip MaintenanceFilter Strip Maintenance

�� Inspect annually and remove Inspect annually and remove accumulated sediment from upper edge accumulated sediment from upper edge of filter stripof filter strip

�� Maintain vegetation at an appropriate Maintain vegetation at an appropriate heightheight


Why a Slope Limitation and Why a Slope Limitation and Minimum Width Requirement?Minimum Width Requirement?

�� Filter strips on unreinforced slopes > Filter strips on unreinforced slopes > 6% are susceptible to small 6% are susceptible to small rivletsrivlets of of concentrated flow, leading to erosionconcentrated flow, leading to erosion

�� Flow widths < 25’ will not adequately Flow widths < 25’ will not adequately disperse concentrated flow to overland disperse concentrated flow to overland flowflow


Infiltration BasinInfiltration Basin

�� OffOff--line design:line design:

�� Treat and fully infiltrate Water Quality Treat and fully infiltrate Water Quality VolumeVolume

�� ByBy--pass larger flowspass larger flows


Infiltration BasinInfiltration Basin

-3’ separation from bottom of system to SHGW

- Native soils must have < 20% & 20-40% silt/clay

- Native soils must have in-situ infiltration rate of 0.5”/hr

- 25% of WQv to be provided by pretreatment

- Must be installed “off-line)

- Install on slopes < 6%

- Basin to fully infiltrate WQvthrough bottom of basin only


Infiltration BasinsInfiltration Basins

Design Infiltration Rates for Soil TexturesDesign Infiltration Rates for Soil Textures

USDA Soil TextureUSDA Soil Texture Design Infiltration Rate (Design Infiltration Rate (fcfc))

SandSand 8.27 8.27 ““/hr/hr

Loamy SandLoamy Sand 2.41 2.41 ““/hr/hr

Sandy LoamSandy Loam 1.02 1.02 ““/hr/hr

LoamLoam 0.52 0.52 ““/hr/hr

Silt LoamSilt Loam 0.27 0.27 ““/hr/hr


Infiltration BasinInfiltration BasinMulvaney Subdivision – Ridgefield, CT

1. Very sandy soils –has never discharged via overflow pipe

2. System is not off-line, yet fully infiltrates all runoff

3. Designed & Constructed in 2000 prior to State Design specifications

Mulvaney Subdivision – Trinkaus Engineering


Infiltration Basin ConstructionInfiltration Basin Construction

�� Prevent ALL vehicular movement over Prevent ALL vehicular movement over area of infiltration basinarea of infiltration basin

�� Construct preConstruct pre--treatment facility treatment facility ((forebayforebay) and basin (off) and basin (off--line facility)line facility)

�� Vegetated as soon as grading is doneVegetated as soon as grading is done

�� No runoff allowed until dense vegetated No runoff allowed until dense vegetated cover has been establishedcover has been established


Infiltration Basin MaintenanceInfiltration Basin Maintenance

�� Inspect Inspect forebayforebay and remove and remove accumulated sediment on annual basisaccumulated sediment on annual basis

�� Remove leaves from bottom of basin Remove leaves from bottom of basin annuallyannually

�� Mow grass on regular basis to maintain Mow grass on regular basis to maintain 4” height (+/4” height (+/--))


Permeable Pavement Design & Permeable Pavement Design & MaintenanceMaintenance

�� Maintain required vertical separation to Maintain required vertical separation to shallow groundwatershallow groundwater

�� Do not overly compact native soils, Do not overly compact native soils, reservoir course and filter course of reservoir course and filter course of pavement systempavement system

�� No application of sandNo application of sand

�� Minimal applications of salt (75% less Minimal applications of salt (75% less than normal)than normal)


Permeable Pavement/Porous Permeable Pavement/Porous ConcreteConcrete


Porous Concrete Design & Porous Concrete Design & MaintenanceMaintenance

�� Maintain required vertical separation to Maintain required vertical separation to shallow groundwatershallow groundwater

�� DO NOT USE SALT ON SURFACE DO NOT USE SALT ON SURFACE UNTIL IT HAS CURED 12 MONTHSUNTIL IT HAS CURED 12 MONTHS

�� Can use sand in first winter, but must Can use sand in first winter, but must use vacuum sweeper to remove fines use vacuum sweeper to remove fines from surfacefrom surface


Construction CostsConstruction Costs

�� Bioretention: Bioretention: �� $14,000 per acre treated$14,000 per acre treated

�� Permeable Pavement:Permeable Pavement:�� $ 6$ 6--8/sq.ft., does not include site prep.8/sq.ft., does not include site prep.

�� Porous Concrete:Porous Concrete:�� $ 8$ 8--11/sq.ft., does not include site prep11/sq.ft., does not include site prep

Surface materials are approximately +20% Surface materials are approximately +20% than standard surface materialsthan standard surface materials


Construction CostsConstruction Costs

�� Subsurface Gravel Wetlands: Subsurface Gravel Wetlands: �� $26,000 per acre treated$26,000 per acre treated

�� Permanent Wet Pond:Permanent Wet Pond:�� $15,000 per acre treated$15,000 per acre treated

�� Wet Swale:Wet Swale:�� $3,500 per acre treated$3,500 per acre treated

�� Dry Swale:Dry Swale:�� $5,500 per acre treated$5,500 per acre treated


Placement on the LandscapePlacement on the Landscape

24 Lots – 64+ acres of preserved Open Space

Site Fingerprinting –defined clearing area as percentage of lot area

Bioretention systems for roof drains

Meadow filter strip with Micro-berm at edge of development envelope

Impervious area disconnection –driveway runoff as overland flow across 75’ of vegetated surface


Placement on the LandscapePlacement on the Landscape

24 Lots – 64+ acres of preserved Open Space

Infiltration trenches for driveway runoff

Constructed Wetland System w/forebay & vegetated outlet swale to wetland

Subsurface flow gravel wetland w/forebay & vegetated outlet swale to wetland

Linear vegetated level spreader


Individual LotsIndividual Lots

Impervious area

disconnection

Meadow filter strip Bioretention for

roof runoff


Individual LotsIndividual Lots

Bioretention for roof drains

Meadow Filter Strip


Holland Joint Venture Holland Joint Venture -- CommercialCommercial

�� Conventional Stormwater Plan:Conventional Stormwater Plan:�� Catch Basins & PipeCatch Basins & Pipe

�� Two Dry Detention BasinsTwo Dry Detention Basins

�� Estimated Cost of Conventional: Estimated Cost of Conventional: $ 200,000.00$ 200,000.00


Holland Joint Venture Holland Joint Venture --CommercialCommercial

Bioretention in parking island & along perimeter of facility – sheet flow from building out to facilities


Holland Joint Venture Holland Joint Venture -- CommercialCommercial

�� LID Stormwater Plan:LID Stormwater Plan:�� Grade parking lot to use sheet flow, direct Grade parking lot to use sheet flow, direct runoff to treatment systemsrunoff to treatment systems

�� Construct four Bioretention systems to Construct four Bioretention systems to handle WQV for roof & parking areahandle WQV for roof & parking area

�� Construct Construct BiorentionBiorention system to handle system to handle WQV from access roadwayWQV from access roadway

�� Estimated Cost of LID: $ 110,000.00Estimated Cost of LID: $ 110,000.00


Harwinton Sports Center Harwinton Sports Center --CommercialCommercial

�� Conventional Stormwater Plan:Conventional Stormwater Plan:�� Catch Basins & PipeCatch Basins & Pipe

�� 600 lf 600 lf –– 24” Perforated HDPE in crushed 24” Perforated HDPE in crushed stone in select fillstone in select fill

�� Cost of Conventional System: $ 90,000.00Cost of Conventional System: $ 90,000.00


Harwinton Sports Center Harwinton Sports Center --CommercialCommercial

Bioretention System with Dry Conveyance Swale


Harwinton Sports CenterHarwinton Sports Center

�� LID Stormwater PlanLID Stormwater Plan�� Grade parking lot to two low points, Grade parking lot to two low points, eliminate all structural drainageeliminate all structural drainage

�� Construct two Dry Swales to convey runoffConstruct two Dry Swales to convey runoff

�� Construct two Bioretention systems to Construct two Bioretention systems to handle WQV for roof & parking areahandle WQV for roof & parking area

�� Cost Saving over Conventional Plan: Cost Saving over Conventional Plan: $ 40,000.00$ 40,000.00


Subsurface Gravel WetlandsSubsurface Gravel Wetlands

Subsurface Gravel Wetlands: siting OK, not designed per UNHSC specifications – WQV not provided per specs.


PseudoPseudo--LID at “End of the Pipe”LID at “End of the Pipe”

Proposed ponding depth = 3’ will kill plants in system due to excessive inundation

Bioretention in close proximity to wetland boundary – no sizing calculations


QUESTIONS??QUESTIONS??


Contact InformationContact Information

Steve Trinkaus, PE, CPESC, CPSWQSteve Trinkaus, PE, CPESC, CPSWQTrinkaus Engineering, LLCTrinkaus Engineering, LLC114 Hunters Ridge Road114 Hunters Ridge RoadSouthbury, CT 06488Southbury, CT 06488203203--264264--4558, Fax: 2034558, Fax: 203--264264--45594559Email: Email: [email protected]@earthlink.netWebsite: Website: http://http://www.trinkausengineering.comwww.trinkausengineering.com

mailto:[email protected]

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Technology

Designing LID Treatment Systems