environmental site design

Low Impact DevelopmentLow Impact DevelopmentWhat is a What is a

Sustainable Site?Sustainable Site?How do you create a Sustainable How do you create a Sustainable

Site?Site?

AIA, Committee on the AIA, Committee on the Environment Environment –– Sustainable Sustainable

Sites ProgramSites Program

New Haven, ConnecticutNew Haven, Connecticut

9/8/2010 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 10 years working with Low Impact and 10 years working with Low Impact DevelopmentDevelopment


What are problems with current What are problems with current development philosophy?development philosophy?

� Developments not respecting the natural land form, forcing the site to “fit” the development program� Excessive land clearing,

� Massive amounts of earthwork,

� Significant erosion & sedimentation issues,

� Difficulty stabilizing the site,


What are problems with current What are problems with current development philosophy?development philosophy?

� Stormwater Issues� Large, interconnected impervious areas,

� Handling of stormwater is an “afterthought” in the design process,

� Excessive use of structural systems,

� Analyze for changes in peak rate only,

� Emphasis on large, infrequent storm events,

� No consideration of water quality impacts


What constitutes a Sustainable What constitutes a Sustainable Site?Site?

� Preservation of Natural Resources

� Development which respects the Natural Land Form

� Minimize site clearing & grading

� Rainfall is a resource to be embraced and reused

� Stormwater management is an integral part of the site design


What constitutes a Sustainable What constitutes a Sustainable Site?Site?

� Focus of stormwater management:� Groundwater Recharge (Volumetric Reduction)

� Water Quality (Remove Pollutants from the stormwater)

� Source Control (Treat runoff where it is first generated)

� Implement “Treatment Train” approach to stormwater


How do we create a Sustainable How do we create a Sustainable Site?Site?

Implement Low Impact Implement Low Impact Development Development

Design StrategiesDesign Strategies


What is Low Impact Development?What is Low Impact Development?

LID is an ecologically friendly approach to site development and storm water management that aims to mitigate development impacts to land, water, and air. The approach emphasizes the integration of site design and planning techniques that conserve natural systems and hydrologic functions on a site.


How does Low Impact Development How does Low Impact Development work?work?

To manage rainfall at the source using uniformly distributed decentralized micro-scale controls. LID’s goal is to mimic a site’s predevelopment hydrology by using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source

HYDROLOGIC TRANSPARENCYHYDROLOGIC TRANSPARENCY


What is Hydrologic Transparency?What is Hydrologic Transparency?

The use of LID design strategies and The use of LID design strategies and storm water treatment systems for a storm water treatment systems for a development scenario which yields development scenario which yields hydrologic conditions matching or in hydrologic conditions matching or in extremely close proximity to the extremely close proximity to the hydrologic conditions of the natural site hydrologic conditions of the natural site prior to development.prior to development.


Low Impact DevelopmentLow Impact DevelopmentFive Basic ToolsFive Basic Tools

�� Encourage Conservation MeasuresEncourage Conservation Measures

�� Reduce Impervious AreasReduce Impervious Areas

�� Slow Runoff by using landscape featuresSlow Runoff by using landscape features

�� Use Multiple measures to reduce and cleanse Use Multiple measures to reduce and cleanse runoffrunoff

�� Pollution PreventionPollution Prevention


Regulatory Requirements (sample site)Regulatory Requirements (sample site)Open Space SubdivisionOpen Space Subdivision

�� Total Site Area = Total Site Area = 104.50 acres104.50 acres

�� 15% site area (roads) = 15% site area (roads) = --15.67 acres15.67 acres

�� Utility Easement = Utility Easement = --5.12 acres5.12 acres

�� 50% of Wetlands = 50% of Wetlands = --10.83 acres10.83 acres

�� 50% of 25% slopes = 50% of 25% slopes = --6.12 acres6.12 acres�� NET AREA = 66.76 acresNET AREA = 66.76 acres

�� Allowable Density = 66.76/1.9513 = 34.2 lotsAllowable Density = 66.76/1.9513 = 34.2 lots

(85,000 (85,000 sq.ftsq.ft. = 1.9513 acres). = 1.9513 acres)


A Typical LayoutA Typical LayoutIs this realistic?Is this realistic?


What is Environmental Site Design?What is Environmental Site Design?

�� Environmental Site Design (ESD) is considered part Environmental Site Design (ESD) is considered part of Low Impact Development Design Toolsof Low Impact Development Design Tools

�� It was development in Maryland to complement the It was development in Maryland to complement the 2000 Stormwater Management Design Manual for the 2000 Stormwater Management Design Manual for the State of MarylandState of Maryland

�� The ESD approach is to design a site which protects The ESD approach is to design a site which protects the natural resources on a site and maintains the the natural resources on a site and maintains the hydrologic characteristics of the site.hydrologic characteristics of the site.


Environmental Site DesignEnvironmental Site Design�� The largest benefit of LID can be The largest benefit of LID can be achieved by implementing achieved by implementing Environmental Site Design ConceptsEnvironmental Site Design Concepts

�� Preservation of critical natural resourcesPreservation of critical natural resources

�� Places development on land most suitable Places development on land most suitable for developmentfor development

�� Helps match preHelps match pre--development hydrologydevelopment hydrology


ESD Site Assessment ESD Site Assessment –– Primary Primary Conservation AreasConservation Areas

�� Inland Wetlands & WatercoursesInland Wetlands & Watercourses

�� Vernal PoolsVernal Pools

�� Steep Slopes (Steep Slopes (>>25%) 25%)

�� 100100--year Floodway and Floodplainyear Floodway and Floodplain

�� Upland Soil Types with Moderate to High Upland Soil Types with Moderate to High infiltration rates (Class A & B Soils)infiltration rates (Class A & B Soils)


ESD Site Assessment ESD Site Assessment ––Secondary Conservation AreasSecondary Conservation Areas

�� Upland areas adjacent to wetlands, watercourses, & Upland areas adjacent to wetlands, watercourses, & vernal pools (variable distance vernal pools (variable distance –– suggested min. 25suggested min. 25--50’)50’)

�� Habitat for sensitive speciesHabitat for sensitive species

�� Scenic views and areasScenic views and areas

�� Vegetation systems, unusual tree speciesVegetation systems, unusual tree species

�� Existing drainage patternsExisting drainage patterns


Why should we protect these Why should we protect these resources?resources?

�� Undisturbed woodlands provide great filtering Undisturbed woodlands provide great filtering of overland flow, reduces runoff by rainfall of overland flow, reduces runoff by rainfall interception by canopy, provides interception by canopy, provides evapotranspiration, carbon storageevapotranspiration, carbon storage

�� Wetlands provide trapping of TSS, and Wetlands provide trapping of TSS, and attenuation of nutrients attenuation of nutrients –– provide provide denitrificationdenitrification of Nitrogen, recharge of Nitrogen, recharge groundwatergroundwater



�� Restricting construction on Steep Slopes Restricting construction on Steep Slopes reduces soil disturbance, reduces or reduces soil disturbance, reduces or eliminates erosion & sedimentation issues, eliminates erosion & sedimentation issues, does not create stabilization issues does not create stabilization issues

�� Well Drained soils have the ability to Well Drained soils have the ability to infiltrate large amounts of runoff infiltrate large amounts of runoff –– dense dense development on them should be minimizeddevelopment on them should be minimized



�� Significant trees and unusual portions Significant trees and unusual portions of the site topography all provide of the site topography all provide natural (habitat) and aesthetic benefits natural (habitat) and aesthetic benefits to the end users and should be to the end users and should be preservedpreserved


ESD Site Assessment ProcessESD Site Assessment Process

�� Obtain Accurate Topographic informationObtain Accurate Topographic information

�� Obtain delineation of inland wetlands & Obtain delineation of inland wetlands & watercourses by soil scientistwatercourses by soil scientist

�� Determine presence of vernal pools or other Determine presence of vernal pools or other sensitive environmental areas (swamps, sensitive environmental areas (swamps, marshes, ponds, flood prone areas, etc.)marshes, ponds, flood prone areas, etc.)



�� Determination of upland soil types in Determination of upland soil types in the field by soil scientistthe field by soil scientist

�� Determine the general infiltration rates Determine the general infiltration rates of the soils (NRCS data)of the soils (NRCS data)

�� Define steep slopes (>25%)Define steep slopes (>25%)



�� Determine generalized types of Determine generalized types of vegetation (meadows, brush, deciduous vegetation (meadows, brush, deciduous woods, evergreen woods, etc)woods, evergreen woods, etc)

�� Determine existing drainage patterns on Determine existing drainage patterns on the sitethe site


Site Analysis ProcessSite Analysis Process

�� Remove wetland/watercourse/vernal Remove wetland/watercourse/vernal pools from potential development areapools from potential development area

�� Remove the upland area immediately Remove the upland area immediately adjacent to wetland/watercourse adjacent to wetland/watercourse systems to preserve the biological systems to preserve the biological integrity (width of area will vary, integrity (width of area will vary, suggested 25 suggested 25 -- 5050’’, could be larger , could be larger depending upon quality of wetland)depending upon quality of wetland)


Wetlands, Soils & Watershed Wetlands, Soils & Watershed BoundariesBoundaries


Site Analysis ProcessSite Analysis Process

�� Remove 25% slopes from development areaRemove 25% slopes from development area

�� Highlight those soil areas with moderate to Highlight those soil areas with moderate to fast infiltration rates (Soil Class A and B)fast infiltration rates (Soil Class A and B)

�� Highlight unusual vegetative features on the Highlight unusual vegetative features on the sitesite

(i.e. 200 yr old Oak tree in the middle of a field, (i.e. 200 yr old Oak tree in the middle of a field, Ridge line, unusual scenic vista)Ridge line, unusual scenic vista)


Slopes and VegetationSlopes and Vegetation


Results of Site AnalysisResults of Site Analysis

�� Through the protection of the Through the protection of the environmentally sensitive features environmentally sensitive features noted previously, you will have noted previously, you will have determined the optimum area for determined the optimum area for developmentdevelopment

NEXT STEPNEXT STEP�� Evaluate hydrologic patterns and think Evaluate hydrologic patterns and think about how storm water will be handled about how storm water will be handled on the site as part of the site designon the site as part of the site design


Developable AreaDevelopable Area


LID Design Strategies AppliedLID Design Strategies Applied

�� Preserve Large Portions of SitePreserve Large Portions of Site

�� Reduce Connected Impervious AreasReduce Connected Impervious Areas

�� Increase Time of Concentration by using landscape Increase Time of Concentration by using landscape featuresfeatures

�� Use Multiple measures to reduce and cleanse runoff Use Multiple measures to reduce and cleanse runoff at the sourceat the source

�� Remove Pollutants from Storm WaterRemove Pollutants from Storm Water


LID TechniquesLID Techniques

�� Apply Open Space or Cluster Development to preserve large Apply Open Space or Cluster Development to preserve large contiguous portions of the sitecontiguous portions of the site

�� Layout the geometry of the road to follow the existing contoursLayout the geometry of the road to follow the existing contours

�� How you will convey stormwater to the discharge point?How you will convey stormwater to the discharge point?

�� How will you meet Groundwater Recharge & Water Quality How will you meet Groundwater Recharge & Water Quality requirements?requirements?

�� What treatment systems are available to meet these What treatment systems are available to meet these requirements that will work on the site?requirements that will work on the site?


Road & Lot LayoutRoad & Lot Layout

24 Lots – 64+ acres of preserved Open Space

Road layout follows ex. contours, lots are located within “developable area”

Large extents of property protected as Open SpaceDensity is

concentrated on Class C soils, minimal density on Class B soils


Stormwater Discharge PointsStormwater Discharge Points


Stormwater discharge points to maintain pre-development drainage patterns

Intermittent stream

Intermittent stream


Stormwater ConveyanceStormwater Conveyance


Vegetated swales along both sides of road

Conventional curb & gutter


LID TechniquesLID Techniques

�� Minimize direct impacts to wetlands & watercoursesMinimize direct impacts to wetlands & watercourses

�� Can you disconnect proposed impervious areas on the site?Can you disconnect proposed impervious areas on the site?

�� Layout building lots to have construction (House, driveway, wellLayout building lots to have construction (House, driveway, well, , sewage disposal system) on land most suitable for developmentsewage disposal system) on land most suitable for development

�� Implement Implement ““Site FingerprintingSite Fingerprinting”” to minimize land clearing & soil to minimize land clearing & soil disturbancedisturbance

�� Minimize soil compaction by limiting the area of grading. Minimize soil compaction by limiting the area of grading. Consider specifying measures to address soil compaction, if Consider specifying measures to address soil compaction, if unavoidableunavoidable


Site Layout Site Layout –– LID Source ControlsLID Source Controls


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


Hydrologic IssuesHydrologic Issues

Groundwater RechargeGroundwater Recharge�� Bioretention for roof drainsBioretention for roof drains

�� Infiltration TrenchesInfiltration Trenches

�� Impervious Area DisconnectionImpervious Area Disconnection

Water QualityWater Quality�� Constructed WetlandConstructed Wetland

�� Subsurface Gravel WetlandsSubsurface Gravel Wetlands

�� Vegetated swales & Level SpreaderVegetated swales & Level Spreader


LID Treatment SystemsLID Treatment Systems


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


LID Treatment SystemsLID Treatment Systems


What Does the Project Look Like?What Does the Project Look Like?

60% of the site preserved as Open Space

Ridge top is part of Open Space in center of loop road


What Does the Project Look Like?What Does the Project Look Like?When you consider the woods which remain on the lots, over 76% of the site remains undisturbed


Actual DesignActual Design

Defined tree clearing limits (site fingerprinting)

Meadow filter strip Rain Garden for

roof drains



Storm Water Controls for lots:Storm Water Controls for lots:�� Utilize “site fingerprinting” to minimize the Utilize “site fingerprinting” to minimize the extent of clearing on each lotextent of clearing on each lot

�� Utilize rain gardens for roof drains on Utilize rain gardens for roof drains on every lot (sized for Water Quality Volume)every lot (sized for Water Quality Volume)

�� Utilize a “meadow” filter strip with a 3” Utilize a “meadow” filter strip with a 3” ‘micro‘micro--bermberm’ below the lawn area on each ’ below the lawn area on each lot to filter overland runoff & encourage lot to filter overland runoff & encourage infiltrationinfiltration



Limit development to mild & moderate slope areas

Preserve steep slopes


Hydrologic Issues ConclusionHydrologic Issues Conclusion

�� PrePre--development infiltration rates are metdevelopment infiltration rates are met

�� Water quality goal of 80% TSS removal will Water quality goal of 80% TSS removal will be met, other pollutants also reducedbe met, other pollutants also reduced

�� PrePre--development development TcTc is closely approximated is closely approximated by the use of vegetated swales and treatment by the use of vegetated swales and treatment systems that will increase systems that will increase TcTc (gravel (gravel wetlands, level spreader)wetlands, level spreader)

�� PrePre--development peak rates are matched for development peak rates are matched for postpost--development conditionsdevelopment conditions


Other Sustainable Benefits of ESDOther Sustainable Benefits of ESD

�� A resource for reductions of A resource for reductions of atmospheric carbon dioxideatmospheric carbon dioxide

�� A resource for the long term storage of A resource for the long term storage of carbon carbon


The Carbon CycleThe Carbon Cycle


Mixed Northern Hardwood ForestsMixed Northern Hardwood Forests


Where is Carbon stored?Where is Carbon stored?

�� Forest Forest –– all above & below ground portions of live all above & below ground portions of live treestrees

�� Soils Soils –– mineral horizons to a depth of 1 metermineral horizons to a depth of 1 meter

�� Forest Floor Forest Floor –– all dead organic matter above all dead organic matter above mineral/sod horizons, including litter humus & coarse mineral/sod horizons, including litter humus & coarse woody debriswoody debris

�� UnderstoryUnderstory Vegetation Vegetation –– all live vegetation which are all live vegetation which are not tree (shrubs, herbaceous species)not tree (shrubs, herbaceous species)


Well Established Forest Well Established Forest w/understoryw/understory layerslayers


Carbon Dioxide Storage in TreesCarbon Dioxide Storage in Trees

�� Green WT above Green WT above gndgnd: : WgWg=(0.25)(D)(D)H=(0.25)(D)(D)H

�� Green WT (total w/roots): Green WT (total w/roots): WgtWgt=120%*=120%*WgWg

�� Dry WT: Wd=72.5%*Dry WT: Wd=72.5%*WgtWgt

�� Weight of Carbon Stored: Weight of Carbon Stored: WcWc=Wd * 50%=Wd * 50%

�� Weight of Carbon Dioxide stored: Weight of Carbon Dioxide stored: WcoWco=Wd*3.6663=Wd*3.6663

�� Weight of Carbon Dioxide stored per year: Weight of Carbon Dioxide stored per year: W = Wco/20W = Wco/20


Example: 20yr old tree, 10Example: 20yr old tree, 10”” DBH, DBH, 3030’’ heightheight

�� Green WT above Green WT above gndgnd: : WgWg=(0.25)(10)(10)30 = 750 lb=(0.25)(10)(10)30 = 750 lb

�� Green WT (total w/roots): Green WT (total w/roots): WgtWgt=1.20 * 750 = 900 lb=1.20 * 750 = 900 lb

�� Dry WT: Wd=0.725 * 900 = 625.5 lbDry WT: Wd=0.725 * 900 = 625.5 lb

�� Weight of Carbon: Weight of Carbon: WcWc=625.5 *0.5 = 312.75 lb=625.5 *0.5 = 312.75 lb

�� Weight of Carbon Dioxide: Weight of Carbon Dioxide: WcoWco=312.75*3.6663 = 1146.6 lb=312.75*3.6663 = 1146.6 lb

�� Weight of Carbon Dioxide/year: W = 1146.6/20 = 57.3 lbs/yrWeight of Carbon Dioxide/year: W = 1146.6/20 = 57.3 lbs/yr


Actual Site ConditionsActual Site Conditions

�� In NE U.S. In NE U.S. –– Mixed Northern Hardwoods have an Mixed Northern Hardwoods have an average density of 100 trees/acreaverage density of 100 trees/acre

�� 100 * 57.33 lb = 5,733 lbs of carbon dioxide 100 * 57.33 lb = 5,733 lbs of carbon dioxide sequestered per acre/yr.sequestered per acre/yr.

�� 64 acres * 5,733 = 366,912 lbs per site area64 acres * 5,733 = 366,912 lbs per site area

�� Assume trees grow to 100 years, then a total of Assume trees grow to 100 years, then a total of 29,352,960 lbs (14,676 tons) of carbon dioxide will 29,352,960 lbs (14,676 tons) of carbon dioxide will be sequestered from this site in the trees within the be sequestered from this site in the trees within the Open SpaceOpen Space


Carbon Storage in the SoilsCarbon Storage in the Soils

�� Both Organic and Inorganic carbon will be Both Organic and Inorganic carbon will be stored in the soilsstored in the soils

�� Undisturbed soils will store more carbon than Undisturbed soils will store more carbon than disturbed soilsdisturbed soils

�� NE soils will store 144,703 lbs/acre of carbon NE soils will store 144,703 lbs/acre of carbon over the typical lifecycle of a mixed hardwood over the typical lifecycle of a mixed hardwood forestforest


Actual Site ConditionsActual Site Conditions

�� 64 acres * 144,703 lb/ac = 9,260,992 lbs 64 acres * 144,703 lb/ac = 9,260,992 lbs (4,630.5 tons)(4,630.5 tons)

�� Between storage in trees and soils, the open Between storage in trees and soils, the open space on this parcel will store 19,306 tons of space on this parcel will store 19,306 tons of carbon over the lifecycle of the forest (100 carbon over the lifecycle of the forest (100 years)years)


Vegetated LID Treatment SystemsVegetated LID Treatment Systems

�� Bioretention systems, constructed wetlands, Bioretention systems, constructed wetlands, and vegetated swales will provide additional and vegetated swales will provide additional sources to sequester carbonsources to sequester carbon

�� Plants have large stem or leaf areas, having Plants have large stem or leaf areas, having high rates of photosynthesis (retaining high rates of photosynthesis (retaining carbon in the plant material)carbon in the plant material)

�� Plants are fast growing, thus having high need Plants are fast growing, thus having high need for carbon (high capacity for sequestering)for carbon (high capacity for sequestering)


LID Vegetated SystemsLID Vegetated Systems


ConclusionConclusion

�� Preservation of large extents of undisturbed Preservation of large extents of undisturbed woodlands and native soils will continue to woodlands and native soils will continue to provide valuable resources for sequestering provide valuable resources for sequestering of carbon in the environmentof carbon in the environment

�� The utilization of vegetated LID treatment The utilization of vegetated LID treatment systems provide additional sources for the systems provide additional sources for the storage of carbonstorage of carbon


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]

http://www.trinkausengineering.com/


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