module 12 - construction site management · 2015. 1. 5. · same site, different stages, very...
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12 ‐ Construction Site Management
Mary Halley
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Module Content
ImportanceofconstructionsitemanagementtoRunoffReduction
CommonConstructionMistakesAvoidingGIPfailure
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Time to Wake Up!
Themostimportantfactor determiningthesuccessorfailureofinfiltrationGIPSis
ConstructionSiteManagement.
InfiltrationGIPS willfail iftheyarecompactedorsedimentdischargestothem.
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Same Site, Different Stages, Very Different Runoff
StageofDevelopment TotalSuspected Sediment (TSS)Concentration(mg/L) DataSource
Open Land(Urban) 70 (median) NURP, 1983
During Construction 20,000to 160,000 McCaleb etal,2008
PostConstruction 69 to100(median) NURP, 1983
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Post‐Construction BMP Mechanisms
Infiltration:Runoffreduction&pollutantremoval(allpollutants)Evapotranspiration:Runoffreduction&pollutantremoval(nutrients)Settling:Pollutantremoval(TSS,Phosphorus,Metals)Filtration:Pollutantremoval(TSS,P,N,Metals)
Evapotranspiration
Settling
Filtration
Underdrain to Surface
Infiltration Filtration
Filtration
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Sediment Impacts to BMP Mechanisms
Infiltration:ClogsvoidspacesinporoussoilsandpermeablepavementsEvapotranspiration:Preventsinfiltrationandwateruptakethroughroots,killingthevegetationSettling:DestroysthesettlingcapabilityandcauseuncontrolledsedimentdischargesifleftunmaintainedFiltration:Coversforestlitterandvegetation,clogsvoidspacesinporoussoilsandinunderdrains
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Approved GIP – Bioretention
From Design Approval to Operation
Actual GIP – Sediment Basin
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Different Stages, Similar Goals
DuringConstruction•Minimizetheextentanddurationofdisturbance
• Nodischargeofsedimentandconstructionmaterials
• Protectstreams,wetlandsandothernaturalfeatures
• InspectandmaintainBMPs• Stabilizedisturbedareas
PostConstruction• AvoidsoildisturbanceandcompactioninGIPareas
• Nodischargeoffirst1‐inchofrainfall(nopollutants)
• Protectstreams,wetlandsandothernaturalfeatures
• InspectandmaintainBMPs• Keepopenspacestabilized
The transition from construction to post-construction is the most critical time to ensure Green Infrastructure success!
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Montgomery County, MDBioretention
GIPs are typically installed in final phases
of construction, primarily to protect them from sediment
discharges
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GIPs look different from traditional BMPs.
Subcontractors may not realize these are
stormwater controls!
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Final stage subcontractors, (home subcontractors,
landscapers) need to have full knowledge of site GIPs too!
Vehicles, equipment or activities in the wrong area can
cause failure.
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The Top 10 List of Poor Construction Site Practices1. Pooron‐sitecommunicationbetweencontractorand
subcontractors,vendors,landscapers2. Failingtofollowtheapprovedconstructionsequencing
andsitephasingpracticesshownonEPSCplans3. InstallingPermanentStormwaterBMPstooearly4. FailingtostabilizeareasupstreamofPermanent
StormwaterBMPsbeforeinstallation5. FailingtoprotectareaswhereBMPswillbeinstalled6. Failingtoprotectnativevegetationorsoilareas7. Failingtoclean‐outtemporaryBMPsbeforeinstallationof
GIPs8. Massgrading9. FailingtoinstallandmaintaintheproperEPSCBMPs10. Failingtorepairerosionareasquicklyafterexposure
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Communication Modes
Signs,fencingandtape!! Morningtailgatemeetings Subcontractorcheck‐ins On‐siteplanupdates On‐siteplanbillboards Siteinspectiondocuments Tandeminspections
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Communication Needs
PermitHolder
SiteDesigner
Contractor
CountyInspector
Subcontractor
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Construction Phasing & Sequencing MostGIPsrelyonuncompacted soil and/orhealthyvegetation,so
consider:• AdjustmentstootherconstructionactivitiestoaccommodatetheGIP(parkingareas,equipmentstorage,materialsstockpiles,etc.)
• Performinginspectionsduringlandscapeinstallation• Thetimeofyear,anticipatedweather,andneedforwateringplants• Ashort‐termandlong‐termplantwateringplan
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Construction Phasing & Sequencing
BeforeGIPinstallation:• ContributingdrainageareastoGIPsmustbestabilized• UnprotectedGIPareasmayrequiresoilamendments• ThepotentialforGIPcompactionmustbeeliminated• Post‐installationprotectionmustbeplannedandready
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Clean GIP Installations
Source: www.lid-stormwater.net
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Final Thoughts
Designplansshouldincludephasing,sequencing,protection,andvegetationplanningandmaintenance.
CountySitePlanReviewersandSiteInspectorswillbemorediligentabouttheseelements– soyoushouldtoo!
Correctiveactionswillberequiredifthereisevidenceofsoilcompaction,sedimentdischargestoGIPs,orunhealthyvegetation.
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Module Topic Summary
ImportanceofconstructionsitemanagementtoRunoffReduction
CommonConstructionMistakesAvoidingGIPfailure
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Questions?
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