stormwater management - precast concrete

LEED Reference GuideFor Precast Concrete Products

STORMWATER MANAGEMENT

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LEED Reference Guide for Precast Concrete Products • www.precast.org

National Precast Concrete Association 1320 City Center Dr. Suite 200, Carmel, IN 46032 (800) 366-7731 | www.precast.org

This publication is designed to provide accurate and authoritative information in regard to the subject matter covered; however, National Precast Concrete Association acts as a mediator without approving, disapproving or guaranteeing the validity or accuracy of any data, claim or opinion appearing herein. Information is provided and disseminated with the understanding that the National Precast Concrete Association is not engaged in rendering engineering, legal or any other professional services. If engineering, legal or other professional assistance is required, the services of a competent professional should be obtained. The National Precast Concrete Association does not assume and hereby disclaims liability to any person for any loss or damage caused by errors or omissions in the material contained herein, regardless of whether such errors result from negligence, accident or any other cause whatsoever.

The Credit Requirements listed in this document are contained within the Leadership in Energy and Environmental Design Green Building Rating System developed by the United States Green Building Council. For more information on the LEED Green Building Rating System, please visit www.usgbc.org.

For additional information about using precast concrete within the LEED system, please visit www.precast.org

Bring on the RainQuick and efficient, precast concrete underground stormwater systems are sized to channel large discharges in case of heavy rain to nearby bodies of water. Precast concrete withstands not only the volumes of water flowing inside them, but extreme loading conditions on the outside as well. And in both cases, they must stand up to corrosive elements. Precast concrete steps up to these challenges.

Advantages of Precast Concrete Stormwater Management ................................................................ 3

LEED 2009 New Construction• SS5.1–SiteDevelopment–ProtectOrRestoreHabitat ................................................................ 4• SS6.1–StormwaterDesign:QuantityControl ................................................................................ 5• SS6.2–StormwaterDesign:QualityControl .................................................................................. 6• SS7.1–SustainableSites:HeatIslandEffect-NewRoof ............................................................... 7• MR4–RecycledContent ................................................................................................................ 8• MR5–RegionalMaterials................................................................................................................ 9• WE1–WaterEfficientLandscaping .............................................................................................. 10• WE2–InnovativeWastewaterTechnologies ...................................................................................11

LEED 2009 Neighborhood Development• GIB4–WaterEfficientLandscaping .............................................................................................. 12• GIB7–MinimizeSiteDisturbanceinDesignandConstruction ..................................................... 13.• GIB8–StormwaterManagement.................................................................................................. 14• GIB9–HeatIslandReduction ........................................................................................................ 15• GIB15–RecycledContentinInfrastructure ................................................................................... 16

LEED 2008 Homes • SS1.2–MinimizeDisturbedAreaofSite ....................................................................................... 17• SS3.–LocalHeatIslandEffects ..................................................................................................... 18• SS4.1–SurfaceWaterManagement:PermeableLot ................................................................... 19• SS4.3.–ManagementofRunofffromRoof .................................................................................. 20• WE1.1–RainwaterHarvestingSystem ......................................................................................... 21• WE1.2–GraywaterReuseSystem ................................................................................................ 22• MR3.–ConstructionWasteManagement ..................................................................................... 23.

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Rough and toughThe strength of precast concrete gradually increases overtime.Othermaterialscandeteriorate,experience creep and stress relaxation, lose strength and/ordeflectovertime.Theload-carryingcapacityof precast concrete is derived from its own structural qualities and does not rely on the strength or quality of the surrounding backfill materials. Studies have shown that precast concrete products can provide aservicelifeinexcessof100years.Insevereconditions, additional design options are available to extend the life of precast concrete products.

We’re talking quality hereBecause precast concrete products typically are made in a controlled plant environment, they exhibit high quality and uniformity. Problems affecting qualitytypicallyfoundonajobsite–temperature,curing conditions, poor craftsmanship and material quality–arenearlyeliminatedinaplantenvironment.Precastconcreteproductsmanufacturedinaquality-controlledenvironmentandinstalledwithhigh-qualitysealants offer a superior solution to watertightness requirements. Standard watertight sealants are specially formulated to adhere to precast concrete, makingwatertightmultiple-seamprecastconcretestructures possible.

Installation is easySetting precast concrete structures into place is easier because they do not require special rigging (such as fabric slings) to avoid structural damage. Othermaterialssuchasfiberglasscansufferstructural damage during compaction.In contrast, precast concrete is less susceptible to vibratory damage while the surrounding soil is backfilled. Consequently, backfilling operations can usually proceed much faster around precast concrete structures.

Heavyweight championWithaspecificgravityof2.40,precastconcretestructures resist the buoyant forces associated with underground construction. In comparison, fiberglass hasaspecificgravityof1.86,andhigh-densitypolyethylene(HDPE)hasaspecificgravityof0.97.

Ready for anythingWhilenomaterialiscompletelyimmunetochemical attack, the mix designs used to produce precast concrete can be adjusted to help withstand anticipated corrosive agents. Materials such as steel and other metals quickly deteriorate in the presence of corrosive agents, some in the presence of water alone.

To better protect reinforcement from corrosion, the precast concrete strength should be designed to 4,000psiormore.

Looks good in “Green”Besides water, concrete is the most used material on earth. It is nontoxic and environmentally safe. As environmental laws heighten, especially those that prohibit pollutant discharge into rivers and lakes, precast concrete is additionally beneficial because it is made from natural materials. Precast concrete products are buried throughout the world as part of the stormwater management systems of nearly every modern city but do not themselves contribute to poor water quality.

Precast concrete is the choice material for products used in stormwater management systems. Precast structures are modular, can fit any design situation, areproducedinaquality-controlledenvironmentandare ready to install immediately upon arrival at the job site. Precast stormwater management components are easily produced to be watertight, durable during storage and transportation, easy to install, less vulnerable than competing products to damage during backfill, and are environmentally safe during operation.

Advantages of Precast Concrete Stormwater Management

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Credit Requirement Max. Points: 1 Precast Contribution

STORMWATER MGT. LEED New Construction

SS 5.1Sustainable Sites

Site DevelopmentProtect or Restore Habitat

Site Development – Protect or Restore Habitat Case 1 – Greenfield SitesLimitallsitedisturbancestothefollowingparameters: • 40feetbeyondthebuildingperimeter • 10feetbeyondsurfacewalkways,patios,surfaceparkingand utilitieslessthan12inchesindiameter • 15feetbeyondprimaryroadwaycurbsandmainutilitybranch trenches • 25feetbeyondconstructedareaswithpermeablesurfaces (such as pervious paving areas, stormwater detention facilities and playing fields) that require additional staging areas to limit compaction in the constructed area, or

Case 2 – Previously Developed AreasRestoreorprotectaminimumor50%ofthesite(excludingthebuildingfootprint)or20%ofthetotalsitearea(includingbuildingfootprint area), whichever is greater, with native or adapted vegetation.

See the LEED Canada guide for information on Canada’s credit requirements.

Precast concrete products are cast and cured in the plant and delivered to the site ready to set so they reduce the staging area required, which can reduce the overall site disturbance.

The impact on the construction site is also reduced because there is no additional formwork, which often requires more construction area for above-groundproductsandlargerexcavation areas for underground products.

Less impact on sites can reduce construction waste, shorten the construction schedule and require fewer laborerson-site.

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Stormwater DesignQuantity Control


Stormwater Design – Quantity Control Case 1 – Sites with existing imperviousness 50% or less

Option 1Implement a stormwater management plan that prevents the postdevelopment peak discharge rate and quantity from exceeding the predevelopment peak discharge rate and quantity forthe1and2-year24-hourdesignstormsmor

Option 2Implement a stormwater management plan that protects receiving stream channels from excessive erosion. The stormwater management plan must include a stream channel protection and quantity control strategies.

Case 2 – Sites with existing imperviousness greater than 50%Implementastormwatermanagementplanthatresultsina25%decreaseinthevolumeofstormwaterrunofffromthe2-year24-hour design storm.

Precast concrete is an excellent choice to help control the quantity of stormwater runoff with a wide variety of products that can contribute to a proper stormwater management plan.

Precast concrete mats are a superior choice for stormwater quantity control in high velocity channels. The precast mats prevent massive soil erosion while creating spaces for water infiltration and vegetation growth.

Precast products such as rainwater cisterns can also contribute to this credit because they can capture runoff and can be emptied after each storm or used as graywater or landscape irrigation.

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Stormwater DesignQuality Control

Quality Control Implement a stormwater management plan that reduces impervious cover, promotes infiltration and captures and treats the stormwaterrunofffrom90%oftheaverageannualrainfallusingacceptable best management practices (BMPs).

BMPsusedtotreatrunoffmustbecapableofremoving80%ofthe average annual postdevelopment total suspended solids (TSS) load based on existing monitoring reports.

BMPsareconsideredtomeetthesecriteriaif: • Theyaredesignedinaccordancewithstandardsand specifications from state or local program that has adopted these performance standards, or

• Thereexistsinfieldperformancemonitoringdata demonstrating compliance with the criteria. Data must conform to accepted protocol for BMP monitoring.

Credit Requirement Max. Points: 1

Precast Contribution

Natural Treatment Precast concrete can contribute to helping reduce pervious cover through components such as grid pavers. These open grid pavers allow runoff water to be absorbed into the surrounding soil which helps eliminate the need for additional stormwater treatment.

Mechanical TreatmentPrecast products such as rainwater cisterns can also contribute to this credit as a component of a rainwater recycling system. The natural weight of precast makes it an excellent choice for underground applications in high water table areas.

Precast inlet structures with drain inserts can filter sediment and debris, which helps limit pollution of the stormwater runoff.

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Heat Island Effect – Non-Roof

Option 1Useanycombinationofthefollowingstrategiesfor50%ofthesite hardscape (including roads, sidewalks, courtyards and parking lots):

• Provideshadefromtheexistingtreecanopyorwithinfive years of landscape installation. Landscaping (trees) must be in place at the time of occupancy.• Provideshadefromstructurescoveredbysolarpanelsthat produce energy used to offset some nonrenewable resource use.• Provideshadefromarchitecturaldevicesorstructuresthat haveasolarreflectanceindex(SRI)ofatleast29.• UsehardscapematerialswithanSRIofatleast29.• Useanopengridpavementsystem(atleast50%pervious), or

Option 2Placeaminimumof50%ofparkingspacesundercover.AnyroofusedtoshadeorcoverparkingmusthaveanSRIofatleast20,bea vegetated green roof or be covered by solar panels that produce energy used to offset some nonrenewable resource use.


Precast concrete products are generally light in color and have a solar reflectanceindex(SRI)ofatleast29.Precast open grid pavers, precast pavers and other site hardscape features help reflect the sun’s rays, which helps reduce the heat island effect.

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MR 4Materials and Resources

Recycled Content


Precast concrete products may contain supplementary cementitious materials such as fly ash and blast furnace slag which will add to the project’s recycled content goals.

Precast products may also contain rebar and welded wire mesh which is often made from recycled steel.

Otherlessfrequentlyusedrecycledcontent components include various fiber reinforcements, glass aggregates, silica fume, and recycled crushed concrete.

The NPCA LEED calculator helps members respond with the proper documentation required for this credit. Simply input the Zip Code/Postal Code and weight for each component to generateapdffilethatcanbee-maileddirectly to the LEED AP, contractor or architect.

Recycled Content Points

10% 1

20% 2

Recycled Content RequirementsUse materials with recycled content such that the sum of postconsumerrecycledcontentplus1/2thepreconsumercontentconstitutesatleast10%or20%(basedoncost)ofthetotalvalueof the materials in the project. The minimum percentage materials recycledforeachpointthresholdis:

The recycled content value of a material assembly is determined by weight. The recycled fraction of the assembly is then multiplied by the cost of the assembly to determine the recycled content value.

Mechanical, electrical and plumbing components and specialty items such as elevators cannot be included in this calculation. Include only materials permanently installed in the project. Furniture may be included if it is included consistently in MR Credit3.:MaterialsReusethroughMRCredit7:CertifiedWood.

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Regional Materials


Because concrete uses plentiful and natural raw materials, concrete components can be extracted, harvestedandmanufacturedwithin500miles of the project site. Using locally obtained raw materials helps reduce transportation distances which reduces the environmental impact of carbon emissions.

If shipping is done by rail or water, LEEDCanadaallowsupto2,400km(1,500miles)fromboththemanufacturing site to the project site and the location where building materials are extracted, harvested, recovered and processed to the manufacturing site.

The NPCA LEED Calculator helps provide the proper documentation required for this credit. Simply input the Zip code where each raw material originates and the weight of each material to generate a printable file thatcanbee-mailedtotheLEEDAP,contractor or architect.

Regional Materials

Use materials or products that have been extracted, harvested, andmanufacturedwithin500milesoftheprojectsite.

The calculation is based on the overall materials cost. Materials costs include all expenses to deliver the material to the project site. Materials costs should account for all taxes and transportation costs incurred by the contractor but exclude any cost for labor and equipment once the material has been delivered to the site.

Regional Materials of 10% = 1 point

Regional Materials of 20% = 2 points

See the NPCA LEED Calculator at www.precast.org/leed for help with this credit.


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WE 1Water Efficiency

Water Efficient Landscaping


The intent of this credit is to eliminate the need to use potable water for landscape irrigation. Precast rainwater capturingsystemsandon-sitewastewater systems can contribute toward this goal.

Precast concrete cisterns help capture rainwater from building roofs for reuse. Captured rainwater can be used for landscape irrigation or to reduce dependency on the municipal facility while reducing personal water costs.

Precast wastewater tanks and wastewater systems can also contribute toward this credit when the treatedwaterisusedforwater-efficientlandscape irrigation.

Water Efficient LandscapingOption 1: Reduce by 50% (2 points)Reducepotablewaterconsumptionforirrigationby50%fromacalculatedmid-summerbasewatercase.Reductionsmustbeattributedtoanycombinationofthefollowingitems: • Plantspecies,densityandmicroclimatefilter • Irrigationefficiency • Useofcapturedrainwater • Useofrecycledwastewater • Useofwatertreatedandconveyedbyapublicagency specifically for nonpotable usesGroundwater seepage that is pumped away from the immediate vicinity of building slabs and foundations may be used for landscapeirrigationtomeettheintentofthiscredit.However,theproject team must demonstrate that doing so does not affect site stormwater management systems.

Option 2: No Potable Water Use or Irrigation (4 points)MeettherequirementsforOption1,andPath 1Use only captured rainwater, recycled wastewater, recycled graywater or water treated and conveyed by a public agency specifically for nonpotable uses for irrigation, orPath 2Install landscaping that does not require permanent irrigation systems. Temporary irrigation systems used for plant establishment are allowed only if removed within one year of installation.

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WE 2Water Efficiency

Innovative Wastewater Technologies


The intent of this credit is to eliminate the need to use potable water used in building sewage. Precast wastewater systems and rainwater cisterns can contribute toward this credit when the treated water is used to help flush water-conservingfixtures.

Innovative Wastewater TechnologiesOption 1Reduce potable water use for building sewage conveyance by 50%throughtheuseofwater-conservingfixtures(suchaswaterclosets, urinals) or nonpotable water (for example, captured rainwater,recycledgraywater,on-siteormunicipallytreatedwastewater), or

Option 2Treat50%ofwastewatertotertiarystandards.Treatedwatermustbeinfiltratedorusedon-site.

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STORMWATER MGT. LEED Neighborhood

Development

GIB 4Green Infrastructure

and Buildings

Water Efficient Landscaping

Water Efficient Landscaping Reduce water consumption for outdoor landscape irrigation by 50%fromacalculatedmidsummerbaselinecase.Reductionsmay be attributed to any combination of the following strategies, amongothers: a. Plant species, plant density and microclimate factor

b. Irrigation efficiency

c. Use of captured rainwater

d. Use of recycled wastewater

e. Use of water treated and conveyed by a public agency specifically for nonpotable uses

f. Use of other nonpotable water sources, such as stormwater, air conditioning condensate and foundation drain water.

Projects with no new or existing landscape irrigation requirements automatically meet the credit requirements.

Groundwater seepage that is pumped away from the immediate vicinity of building slabs and foundations can be used for landscapeirrigationandmeettheintentofthiscredit.However,it must be demonstrated that doing so does not affect site stormwater management systems.


Precast concrete cisterns help capture rainwater from building roofs or graywater (wastewater from laundry, dishes, bathing, etc.) for reuse.

Captured rainwater can be used for landscape irrigation or to reduce dependency on municipal water sources, lessening the burden on the municipal facility while reducing personal water costs. The natural weight of precast makes it an excellent choice for underground applications in high water table areas.

Precast wastewater tanks can also contribute toward this credit when the treatedwaterisusedforwater-efficientlandscape irrigation.

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Development


and Buildings

Minimized Site Disturbance in Design

and Construction

Minimized Site Disturbance in Design and Construction

Option 1 – Development Footprint on Previously Developed Land:Locate100%ofthedevelopmentfootprintonareaspreviouslydeveloped, or

Option 2 – Undeveloped Portion of Project Left Undisturbed:Limitdisturbanceto:• 40feetbeyondthebuildingperimeter• 10feetbeyondsurfacewalkways,patios,surfaceparkingandutilitieslessthan12inchesindiameter• 15feetbeyondstreetcurbsandmainutilitybranchtrenches• 25feetbeyondconstructedareaswithpermeablesurfacesthat require additional staging areas to limit compaction in the constructed zone.

Note: This is a condensed version of the credit. The full credit may be downloaded from USGBG’s Neighborhood Development Guide.


Precast concrete products are plant cast and delivered to the site ready to set so they reduce the staging area required which can reduce the overall site disturbance.

The impact on the construction site is also reduced because there is no additional formwork, which often requires more construction area for above-groundproductsandlargerexcavation areas for underground products.

Less impact on sites can reduce construction waste, shorten the construction schedule and require fewer laborerson-site.

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Development


and Buildings

Stormwater Management

Precast ContributionPrecast concrete is an excellent choice to help control the quantity of stormwater runoff, with a wide variety of products that can contribute to a proper stormwater management plan.

Precast concrete mats are a superior choice for stormwater quantity control in high velocity channels, for example. The precast mats prevent massive soil erosion, while spaces between the mats allow for water infiltration and vegitation growth.

Precast products such as rainwater cisterns can also contribute to this credit because they capture runoff and can be used for landscape irrigation.

Precast concrete underground stormwater systems are sized to channel large discharges in case of heavy rain to nearby bodies of water. Precast concrete withstands not only the volume of water flowing inside the system, but extreme loading conditions on the outside as well.

Credit Requirement Max. Points 4

Stormwater Management Implement a comprehensive stormwater management planfortheprojectthatretainson-site,throughinfiltration,evapotranspiration, and/or reuse, the rainfall volumes listed below. Rainfall volume is based on the project’s development footprint, any other areas that have been graded so as to be effectively impervious,andanypollution-generatingpervioussurfaces,such as landscaping, that will receive treatments of fertilizers or pesticides.

Percentile rainfall event

Total volume to be retained Points 80% 1 85% 2 90% 3. 95% 4

Note: This is a condensed version of the credit. The full credit may be downloaded from USGBG’s Neighborhood Development Guide.

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Development


and Buildings

Heat Island Reduction

Precast ContributionPrecast concrete products are generally light in color and have a solar reflectanceindex(SRI)ofleast29.

Precast open grid pavers, precast pavers and other site hardscape features help reflect the sun’s rays, which reduces the heat island effect.

Credit Requirement Max. Points 1

Heat Island ReductionOPTION 1: Nonroof Measures

Useanycombinationofthefollowingstrategiesfor50%ofthenonroof site hardscape (including roads, sidewalks, courtyards, parkinglots,parkingstructuresanddriveways):

a) Provide shade from open structures, such as those supporting solar photovoltaic panels, canopied walkways, and vine pergolas, all with a solar reflectance index (SRI) of at least29.

b)UsepavingmaterialswithanSRIofatleast29.

c)Installanopen-gridpavementsystemthatisatleast50% pervious.

d) Provide shade from tree canopy (within ten years of landscape installation), or

OPTION 2: High-Reflectance and Vegetated Roofs

Use roofing materials that have an SRI equal to or greater than the valuesinTable1foraminimumof75%oftheroofareaofallnewbuildings within the project; or install a vegetated (“green”) roof foratleast50%oftheroofareaofallnewbuildingswithintheproject.

CombinationsofSRI-compliantandvegetatedroofscanbeusedprovidedtheysatisfytheequationinOption3..

Roof slope SRI

Low (≤2:12) 78Steep(>2:12) 29

Table 1. Minimum solar reflectance index value, by roof slope

OPTION 3: Mixed Nonroof and Roof MeasuresUseanyofthestrategieslistedunderOptions1and2thatincombinationmeetthefollowingcriteria:

Area of Nonroof Area of SRI Area of Measures Roof Vegetated Roof

0.5 0.75 0.5

Total Site Hardscape

Area

Total RoofArea+ + +>

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Development


and Buildings

Recycled Content in Infrastructure


Recycled Content in Infrastructure Use materials for new infrastructure such that the sum of postconsumerrecycledcontent,in-placereclaimedmaterialsandone-halfofthepreconsumerrecycledcontentconstitutesatleast50%ofthetotalmassofinfrastructurematerials.

Count materials in all of the following infrastructure items as applicabletotheproject: • Roadways,parkinglots,sidewalks,unitpaving,andcurbs • Waterretentiontanksandvaults • Baseandsubbasematerialsfortheabove • Stormwater,sanitarysewer,energydistribution,andwater piping

See the NPCA LEED Calculator at www.precast.org/leed for help with this credit.


Precast concrete products may contain supplementary cementitious materials such as fly ash and blast furnace slag which will add to the project’s recycled content goals.

Precast products may also contain rebar and welded wire mesh which oftencontainrecycledsteel.Otherless frequently used recycled content components include various fiber reinforcements, glass aggregates, silica fume, and recycled crushed concrete.

Beyond precast products themselves, recycled crushed concrete can also contribute to this credit when utilized as road fill base.

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Site Stewardship: Minimize Disturbed Area of Site Minimizedisturbancetothesitebymeetingthefollowing:

Where the site is developed: • Developatreeorplantpreservationplanwith“nodisturbance” zones clearly delineated on drawings and on the lot. • Leaveundisturbedatleast40%ofthebuildablelotarea,not includingareaundertheroof.Onlysoftscapescanbe counted toward this credit; projects cannot receive credit for preserving preexisting hardscapes, such as driveways, or

Where the site is previously developed: • Developatreeorplantpreservationplanwith“nodisturbance” zones clearly delineated on drawings and on the lot, and rehabilitate the lot by undoing any previous soil compaction, remove existing invasive plants, and meetingtherequirementsofSS2.2 • Buildonasitewithalotareaoflessthan1/7acre,orwith housing density for the project that is equal to or greater than7unitsperacre.Formultifamilybuildings,theaverage lot size shall be calculated as the total lot size divided by the number of units.

Note:Any“Nodisturbance”zonesmustalsobeprotectedfromparked construction vehicles and building material storage. Soils compacted by vehicles or stored materials can cause major difficulties in establishing any new landscaping.


Precast concrete products are plant cast and delivered to the site ready to set, so they reduce the staging area required, whick can reduce the overall site disturbance.

The impact on the construction site is also reduced because there is no additional formwork, which often requires more construction area for above-groundproductsandlargerexcavation areas for underground products. Less impact on the site includes reduced construction waste, less noise pollution, a shorter construction schedule and fewer laborersneededon-site.

STORMWATER MGT. LEED Homes


Site Stewardship Minimize Disturbed Area

of Site

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Reduce Local Heat Island Effects

Do one of the following: a) Locate trees or other plantings to provide shading for at least 50%ofsidewalks,patiosanddrivewayswithin50feetofthe home.ShadingshouldbecalculatedfornoononJune21, when the sun is directly overhead, based on five year’s growth.

b)Installlight-colored,high-albedomaterialsorvegetationforat least50%ofsidewalks,patiosanddrivewayswithing50feet ofthehome.Acceptablestrategiesincludethefollowing: •Whiteconcrete

•Grayconcrete

•Openpavers(countingonlythevegetation,notthe pavers)

•Anymaterialwithasolarreflectanceindex(SRI)ofat least29


Precast concrete products are generally light in color and have a solar reflectanceindex(SRI)ofleast29.

Precast open grid pavers, precast pavers and other site hardscape features help reflect the sun’s rays, which reduces the heat island effect.


SS 3Sustainable Sites

Local Heat Island Effects

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Surface Water Management – Permeable LotDesignthelotsuchthatatleast70%ofthebuiltenvironment,not including area under roof, is permeable or designed to capture waterrunoffforfiltrationon-site.Areathatcanbecountedtowardtheminimumincludesthefollowing:

a) Vegetative landscape (such as grass, trees, shrubs)

b) Permeable paving, installed by an experienced professional. Permeable paving must include porous above ground materials (such as open pavers, engineered products) and a 6-inchporoussub-base,andthebaselayermustbedesigned to ensure proper drainage away from the home.

c) Impermeable surfaces that are designed to direct all runoff toward an appropriate permanent infiltration feature (such as vegetatedswale,on-siteraingardenorrainwatercistern)


Precast concrete can contribute to helping reduce pervious cover through components such as grid pavers. These open grid pavers allow runoff water to be absorbed into the surrounding soil, which helps elimiinate the need for additional stormwater treatment. Pavers are an excellent choice for driveways and additional parking areas.

Precast products such as rainwater cisterns and storage tanks can also help contribute to this credit because they can capture stormwater runoff and can be emptied after each storm, or filtered to be used as graywater or for landscape irrigation.



Surface Water Management – Permeable Lot

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Surface Water Management –

Management of Runoff from Roof


Surface Water Management –Management of Runoff from Roof

Design and install one or more of the following runoff control measures: a) Install permanent stormwater controls (e.g. vegetated swales,on-siteraingarden,drywell,orrainwatercistern) designedtomanagerunofffromthehome(1point)

b)Installvegetatedrooftocover50%oftheroofarea (0.5point),or

c)Installvegetatedrooftocover100%oftheroofarea (1point)

d)Havethesitedesignedbyalicensedorcertifiedlandscape design or engineering professional such that all water runoff fromhomeismanagedthroughanon-sitedesignelement (2points).

Precast rainwater cisterns capture rainwater from building roofs for use in areas that receive little rainfall throughout the year. Captured rainwater can be used for landscape irrigation or to reduce dependency on municipal water sources, lessening the burden on the municipal facility while reducing personal water costs.

The natural weight of precast makes it an excellent choice for underground cisterns in high water table areas, while many styles of precast cisterns are also availableforabove-grounduse.

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WE 1.1Water Efficiency

Water Reuse – Rainwater Harvesting System


Water Reuse – Rainwater Harvesting System

≥50%ofRoofArea Indooronly 2points≥50%ofRoofArea Outdooronly 3.points≥75%ofRoofArea BothIndoorandOutdoor 4points

Design and install a rainwater harvesting and storage system (including surface runoff and/or roof runoff) for landscape irrigation use or indoor water use.

The storage system must be sized to hold all the water from a 1inchrainfallevent(equivalentto0.62gallonspersquarefootof roof area used for capture), taking into consideration the sizeoftheharvestsystem(i.e.,50%or75%oftotalroofarea,depending on the measure chosen from the table above)

Whileprecastdoesn’tdirectlycontributetoward earning this credit, precast cisterns help capture rainwater from building roofs or graywater for reuse.


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WE 1.2Water Efficiency

Water Reuse – Graywater Reuse System


Graywater Reuse System

Design and install a graywater reuse system for landscape irrigation use (i.e., not a septic system) or indoor water use. The system must include a tank or dosing basin that can be used as part of the irrigation system. Graywater must be collected from at leastoneofthefollowing:• Clotheswasher• Showers• Somecombinationoffaucetsandothersourcesestimatedtoexceed5,000gallonsperyear.

Precast concrete cisterns help capture rainwater from building roofs or graywater (wastewater from laundry, dishes, bathing, etc.) for reuse.


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Waste Management –Construction Waste

Management

Credit Requirement Max. Points: 3

Precast Contribution

Waste Management – Construction Waste Management3.1 Construction Waste Management Planning (Prerequisite)Investigate and document local options for diversion, then document the diversion rate for construction waste. (See LEED Homesguideforfullprerequisite)

3.2 Construction Waste ReductionReduce or divert waste generated from new construction activities from landfills and incinerators to a level below the industrynorm.Useeitherofthetwooptions: a)ReducedConstructionWaste.Generate2.5poundsor less of net waste (not including waste diverted reclamation or recycling) per square foot of conditioned floor area. Use the table to determine the score.

b)IncreasedWasteDiversion.Divert25%ofmoreofthe total materials taken off the construction site from landfills and incinerators. Use the table to determine the score. Calculate the percentage using either weight or volume.

Thiscreditallowsfor2.5poundsofconstruction waste per square foot of floor space. Precast concrete can contribute toward this credit because it is plant produced, which creates little to zeroon-siteconstructionwaste.

Lesson-sitewastemeanslesstransportationofwaste,lessclean-up time, and less time spent sorting recyclables. These savings can contribute to a quicker, cheaper project and a more efficient construction schedule.

AMOUNT TO LANDFILLS AND INCINERATORS

Reduced Construction Waste

Lbs./Ft.2

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

Increased Waste Diversion

Cubic Yds./1,000 Ft.2

25.5

22.3

19.1

15.9

12.8

9.6

6.4

3.2

% Waste

100.0%

88%

75%

63%

50%

38%

25%

13%

% Diverted

0%

13%

25%

38%

50%

63%

75%

88%

stormwater management - precast concrete

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