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8) Designedtodischargeallstormwater(includingstormwaterinexcessofthewater <br />qualityvolume)routedtothesystemthroughtheuppermostsoilsurfaceorengineered <br />mediasurfacewithin48hours.Additionalflowsthatcannotinfiltratewithin48hours <br />mustbypassthesystemthroughastabilizeddischargepoint; <br />9) Mustprovideameanstovisuallyverifytheinfiltrationsystemisdischargingthroughthe <br />soilsurfaceorfiltermediasurfacewithin48hoursorless; <br />10) Mustprovideatleastonesoilboring,testpitorinfiltrometertestinthelocationofthe <br />infiltrationpracticefordetermininginfiltrationrates; <br />11) Fordesignpurposes,dividefieldmeasuredinfiltrationratesby2asasafetyfactoror <br />usesoilboringresultswiththeinfiltrationratechartintheMinnesotaStormwater <br />Manualtodeterminedesigninfiltrationrates.WhensoilboringsindicatetypeAsoils, <br />fieldmeasurementsshouldbeperformedtoverifytherateisnotabove8.3inchesper <br />hour. <br />12) Mustemployappropriateonsitetestingtoensureaminimumofthree(3)feetof <br />separationfromtheseasonallysaturatedsoils(orfrombedrock)andthebottomofthe <br />proposedinfiltrationsystem; <br />13) Mustdesignamaintenanceaccess,typicallyeight(8)feetwide; <br />14) InfiltrationSystemsareprohibitedinthefollowingareas(See"higherlevelof <br />engineeringreview"intheMinnesotaStormwaterManualformoreinformation):ΝLƷĻƒ <br />ЋЉ͵ВΞ <br />a) Areasthatthatreceiverunofffromvehiclefuelingandmaintenanceareas; <br />b) Areaswhereinfiltratingstormwatermaymobilizehighlevelsofcontaminantsin <br />soilorgroundwater; <br />c) Areaswheresoilinfiltrationratesarefieldmeasuredatmorethan8.3inchesper <br />hourunlessthesoilsareamendedtoslowtheinfiltrationratebelow8.3inches <br />perhour; <br />d) Areaswithlessthanthree(3)feetofseparationdistancefromthebottomofthe <br />infiltrationsystemtotheelevationoftheseasonallysaturatedsoilsorthetopof <br />bedrock; <br />e) AreasofpredominatelyHydrologicSoilGrouptypeDsoils(clay); <br />f) ThefollowingareaswithinaDrinkingWaterSupplyManagementArea(DWSMA)as <br />definedinMinn.R.4720.5100,subp.13: <br />i. InanEmergencyResponseArea(ERA)withinaDWSMAclassifiedas <br />havinghighorveryhighvulnerabilityasdefinedbytheMinnesota <br />DepartmentofHealth;or <br />ii. InanERAwithinaDWSMAclassifiedasmoderatevulnerabilityunlessa <br />higherlevelofengineeringreviewsufficienttoprovideafunctioning <br />treatmentsystemandtopreventadverseimpactstogroundwaterhas <br />beenapprovedbythe CityofCenterville;or <br />iii. OutsideofanERAwithinaDWSMAclassifiedashavinghighorveryhigh <br />vulnerabilityunlessahigherlevelofengineeringreviewsufficientto <br />provideafunctioningtreatmentsystemandtopreventadverseimpacts <br />togroundwaterhasbeenapprovedbythe CityofCenterville. <br />March2024|wqstrm498 <br />Page 19 of 23 <br /> <br />