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
93-102
V
V
V
V
V
V
V
V
CE1
CE2
CE3
CE2
CE1
CE1
CE1
CE1
CE1
CE1
CE1
93
94
95
96
97
98
99
100
101
102
O
PP
A
S
O
P
P
A
S
O
P
P
O
P
P
O
P
P
O
P
P
A
S
A
S
A
S
A
S
A
S
O
P
P
O
P
P
A
S
A
S
O
P
P
O
P
P
A
S
A
S
O
P
P
O
P
P
O
P
P
A
S
O
P
P
A
S
AS
OPP
A
S
O
P
P
A
S
A
S
A
S
A
S
A
S
O
P
P
O
P
P
O
P
P
O
P
P
A
S
A
S
O
P
P
A
S
O
P
P
A
S
A
S
O
P
P
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
18
19
17
20
21
22
23
24
25
31
32
33
34
35
36
37
38
49
50
51
52
53
5455
56
57
58
59
60
61
62
63
64
65
73
74
75
76
77
78
80
81
82
83
84
85
86
87
88
89
90
91
92
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117118
119
120
121
122
