12 ‐ Construction Site Management

Mary Halley

Module Content

ImportanceofconstructionsitemanagementtoRunoffReduction

CommonConstructionMistakesAvoidingGIPfailure

Time to Wake Up!

Themostimportantfactor determiningthesuccessorfailureofinfiltrationGIPSis

ConstructionSiteManagement.

InfiltrationGIPS willfail iftheyarecompactedorsedimentdischargestothem.

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

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

Sediment Impacts to BMP Mechanisms

Infiltration:ClogsvoidspacesinporoussoilsandpermeablepavementsEvapotranspiration:Preventsinfiltrationandwateruptakethroughroots,killingthevegetationSettling:DestroysthesettlingcapabilityandcauseuncontrolledsedimentdischargesifleftunmaintainedFiltration:Coversforestlitterandvegetation,clogsvoidspacesinporoussoilsandinunderdrains

Approved GIP – Bioretention

From Design Approval to Operation

Actual GIP – Sediment Basin

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!

Montgomery County, MDBioretention

GIPs are typically installed in final phases 

of construction, primarily to protect them from sediment 

discharges

GIPs look different from traditional BMPs.  

Subcontractors may not realize these are 

stormwater controls!

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.

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

Communication Modes

Signs,fencingandtape!! Morningtailgatemeetings Subcontractorcheck‐ins On‐siteplanupdates On‐siteplanbillboards Siteinspectiondocuments Tandeminspections

Communication Needs

PermitHolder

SiteDesigner

Contractor

CountyInspector

Subcontractor

Construction Phasing & Sequencing MostGIPsrelyonuncompacted soil and/orhealthyvegetation,so

consider:• AdjustmentstootherconstructionactivitiestoaccommodatetheGIP(parkingareas,equipmentstorage,materialsstockpiles,etc.)

• Performinginspectionsduringlandscapeinstallation• Thetimeofyear,anticipatedweather,andneedforwateringplants• Ashort‐termandlong‐termplantwateringplan

Construction Phasing & Sequencing

BeforeGIPinstallation:• ContributingdrainageareastoGIPsmustbestabilized• UnprotectedGIPareasmayrequiresoilamendments• ThepotentialforGIPcompactionmustbeeliminated• Post‐installationprotectionmustbeplannedandready

Clean GIP Installations

Source: www.lid-stormwater.net

Final Thoughts

Designplansshouldincludephasing,sequencing,protection,andvegetationplanningandmaintenance.

CountySitePlanReviewersandSiteInspectorswillbemorediligentabouttheseelements– soyoushouldtoo!

Correctiveactionswillberequiredifthereisevidenceofsoilcompaction,sedimentdischargestoGIPs,orunhealthyvegetation.

Module Topic Summary

ImportanceofconstructionsitemanagementtoRunoffReduction

CommonConstructionMistakesAvoidingGIPfailure

Questions?