Sewer Approved Method Statement - Ribble Valley · PDF fileMethod statement and ... Promoter...
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SewerApprovedMethodStatementMittonRoad,
Whalley
ExistingSewerNetworkThereare3existingsewercrossthesite;
150mmcombinedsewerservingpropertiesfacingontoMittonRoad.
450mmcombinedsewercrossingthesitefromnorthtosouth.
675mmcombinedsewerfollowingRidingLane
ProposedScheme;Theproposedschemeistoconstruct137residentialunitswithassociatedinfrastructure.SeeappendixA.Thereareanumberofinteractionsbetweentheexistingsewernetworkandtheproposedscheme,therisksarehighlightedbelow;
150mmSewerShallow,closetofoundationsandshareddrive,groundlevelsneedtobereviewed.Proposedlevelsareelevatedabovecurrentlevelsbycirca300mm.Highriskofcontact.
450mmCombinedSewerCirca2.5mbelowexistinggroundlevel,multiplepointsofconnectionfornewsewernetwork.Proposedlevelsareelevatedabovecurrentlevelsbycirca300mm.Moderateriskofcontact.
675mmCombinedSewerDeepandremotefromallproposedconstruction.Lowriskofcontact.
DiscussionandMitigationofrisks;Priortocommencementonsitethedepthandlocationofallexistingsewerswillbeconfirmedandtheirlocationclearlymarkedonthesurfaceat20mcentresandaCCTVsurveywillbeundertakentorecordthecurrentcondition.
Allfoundationswilldesigntopreventloadstransferringontothesewers,duetotheproximityofthe150mmsewertotheproposedhousingitisatrisk.Asproposedplotsarelocated65mawayforthesewerandthefoundingdepthsareatasimilarleveltotheinvertofthesewer,thereisnoriskofloadingthesewer.SeefoundationscheduleinAppendixB.
The450mmsewersitsdirectlybeneaththesiteaccessroadsotheconstructionoftheroadneedstobeconsidered.SeeAppendixCLongsectionshowingproposedroadandsewersalongwithexistingsewer.ThesectionofsewertohavearoadconstructedaboveitrunsfromUU6508(EGL46.10,ProposedCL46.40,IL43.40)toUU6401(EGL45.034,PCL45.76,IL43.13),alongthisentirelengththeproposedfinishedroadlevelisabovethecurrentgroundlevelthusincreasingcovertothepipeandensuringthatexcavationabovethepipeislimited.
Theproposedroadconstructionisgenerally600mmbutthiscouldincreaseto900mm,sothisexcavationfortheroadcappinglayerwillbeinexcessof2.5mabovethesewer.Intermofprocessthetopsoilwillberemovedandtheroadfootprintexcavatedtoformationlevelwhereuponitwillbebackfilledwithsuitablecrushedstoneorconcrete,thusprotectingtheexistingsewer.
Installationofproposedsewerstheproposedsewersdonotunderminetheexistingnetworkandthereforeriskoflateralmovementislimited,irrespectivethiscorrectuseoftrenchsupportsandshoringwouldpreventthisforoccurring.
Methodstatementandriskassessmentforinstallationofnewsewersandcrossingoftheexistingsewers;AppendixDcontainsthecontractorsriskassessmentfortheinstallationofnewsewersdiscussingthemethodsforconnectingontoandcrossingtheexistingnetwork.
WithregardtotheexistingnetworkUnitedUtilitiesstandardmethodswillbeadopted,theseareasfollows:
Demolition,piling,tunnelingoranyotherconstructiontechniquewhichinducessignificantvibration(notexceedingapeakparticlevelocityof5mm/s)shallbepermittedupto10metresawayfromthePipeline(s).PermissionwillbegrantedbyUUprovidedthatthePromoterhasaccuratelyestablishedthepositionofthePipeline(s)andthishasbeenverifiedbyUUandawrittenstatementoftheprecautionstobetakentoensurethesafetyofthePipeline(s)hasbeensubmittedbythePromoterandreceivedandconsentedtobyUUpriortoworksbeingundertaken.
Shoulddemolition,piling,tunnelingoranyotherconstructiontechniquewhichinducessignificantvibrationbeproposedwithin3.510metresofthePipeline(s)thisshallbesubjecttoseismicmonitoringinordertopreventdamagetothePipeline(s).ThePromotershallaccuratelyestablishthepositionofthePipeline(s).SeismographreadingsshallbetakenbythePromoter'sspecialistorganisationonthelineofthePipelineatlocationstobeagreedwithUU.Vibrationmonitoringshallbedoneunderthesupervisionofaspecialistorganisationwhichhassignificantexperienceofsimilarmonitoringwork.TheidentityofthespecialistorganisationshallbeproposedbythePromoterandapprovedbyUU.Thisapprovalshouldnotbeunreasonablywithheldordelayed.ThecostoftheseismicmonitoringshallbebornebythePromoter.Vibrationshallbemeasuredintermsofpeakparticlevelocity(PPV)andthePromotershallemploysuitablemethodsofconstructionincarryingoutitsworkssuchthatthePPVdoesnotexceed5mm/s.IfthemeasuredPPVdoesexceed5mm/sthenworkshallceaseimmediatelyandareviewofthemonitoringdatashallbeundertakenbetweenthePromoterandUUEngineeringstaff.IfnecessaryUUshallnotifythePromoterofanyreasonablemitigationmeasurestoprotectthePipeline(s)thatitrequiresthePromotertocarryout.ThePromotershallcomplywiththesereasonablemitigationmeasuresincarryingoutitsworks.AwrittenstatementoftheprecautionstobetakentoensurethesafetyofthePipeline(s)shallbesubmittedbythePromoterandreceivedandapprovedbyUUpriortoworksbeingundertaken.
Movementofvehiclesandplantwithatotalweightexceeding6tonnesacrosstheunprotectedPipelineisforbidden.TherepetitivemovementofvehiclesorplantofanyweightovertheunprotectedPipelineinthesamepositionisforbidden.Wheretemporaryorpermanentaccessisrequired,thePromotermustconsultwithUUpriortogainingaccess.
EachproposedtemporarycrossingpointofaPipelineshallbeconsideredonanindividualbasis.ThePromotershallsubmitthedesignoftheproposedcrossingpointtoUUforacceptance.WorktoconstructthetemporarycrossingpointshallnotcommencewithoutpriorwrittenconsentfromUU.
ThePromotershalldesignanytemporarycrossingpointsuchthattheloadfromanyvehicleoranyitemofconstructionplantthatwillusethecrossingpointcreatesasuitablyfactoredbearingpressureofnotmorethan8.5kN/m2atthecrownoftheUUPipeline.(N.B.ThisloadisapproximatelyequivalenttotheloadingonaPipelinewith900mmofcoverwhena6tonneexcavatorcrossesaboveit.)Inordertoachievethis,thePromotermayusesubstantialtimberbaulks,reinforcedconcreteslabsorproprietarygroundprotectionsystems(e.g.EveTrakway).Whereitisnotpossibletodistributethesurchargeloadfromtheplanttolessthan8.5kN/m2atthecrownofthePipeline,thenthedesignofthetemporarycrossingpointshallconsistofasuspendedcrossingwhichbridgesoverthePipeline.
TemporarycrossingpointsshallonlybeusedtoallowvehiclesandplanttotraverseacrossaPipeline.Temporarycrossingpointsarenottobeusedasworkingplatformsforconstructionplant.PlantshallnotbeallowedtooperateaboveaUUPipelineunlessspecificwrittenconsentisgivenbyUU.Any
requestbyaPromoterforthemtositeworkingplantaboveaUUPipelinemustdemonstratethattheplatformwhichtheirplantistobesitedonhasbeendesignedasaworkingplatformandwillensurethatthemaximumsurchargeloadfromthatplantisdistributedtolessthan8.5kN/m2atthecrownofthePipeline,orbridgesoverthePipeline.
Allpartsofatemporarycrossingpointmustberemovedwhentheworkiscomplete,unlesswrittenconsentisobtainedfromUUforthecrossingtobeleftinplace.Thedesignandconstructionofthetemporarycrossingpointshallbesuchthatitpermitsforitsremoval(andthereinstatementofthegroundbeneathit)withoutexposingthePipelinetoundueloading,vibrationorrisk
PondConstruction;Theproposedpondistobeconstructedadjacenttotheexisting450mmcombinedsewer,thepondislocatedoutsideoftheUnitedUtilitiessewereasementandisgenerallybetween5m(minimum)and10mtotheeastofthesewer.Thebedlevelofthepondisbetween41.863mAODand42.163mAOD,theinvertofthesewer42.51mAOD(worstcase).Theedgeofthepondwillbesituatedsome5mfromthesewer,thedeepestbedpointwillbesome11mfromthesewer,themaximumleveldifferenceis0.68mgivingagradientof1:16whichisstableisallsoilconditions.
Thepondwillbeformerbyremovingthetopsoil,excavatingthesubsoilandthenliningthebasinwithpuddleclaytoformanimpermeablelining.Thesidesofthepondsaretobebatteredat1:3toensureslopestability.
Uponreviewingtheproximityofthepondtothesewerandtherelativeinvertlevels,itisclearthatthesewerhighlyunlikelytobeimpactedbytheconstructionofthepond.Howevertoensurethatthereisnochanceofthesewerbeingimpactedduringtheconstructionphase,insitugeotechnicaltestingwouldbeundertakentoensureslopestabilitycanbeensuredandifnecessarysheetpilingwillbeinstalled.GeotechnicalreviewanddetaileddesigntobeagreedwithUnitedUtilitiespriortoconstruction.
AppendixAMainDrainagePlanDWH133101_DRAINAGE_LAYOUT_P3
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