Designation:D6771−21StandardPracticeforLow-FlowPurgingandSamplingUsedforGroundwaterMonitoring1ThisstandardisissuedunderthefixeddesignationD6771;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thispracticedescribesthemethodoflow-flowpurgingandsamplingusedtocollectgroundwatersamplesfromwellstoassessgroundwaterquality.1.2Thepurposeofthisprocedureistocollectgroundwatersamplesthatrepresentaflow-weightedaverageofsoluteandcolloidconcentrationstransportedthroughtheformationnearthewellscreenunderambientconditions.Samplescollectedusingthismethodcanbeanalyzedforgroundwatercontami-nantsand/ornaturallyoccurringanalytes.1.3Thispracticeisgenerallynotsuitableforuseinwellswithverylow-yieldsandcannotbeconductedusinggrabsamplingorinertialliftdevices.Thispracticeisnotsuitableforuseinwellswithnon-aqueousphaseliquids.1.4Units—ThevaluesstatedinSIunitsaretoberegardedasstandard.Thevaluesgiveninparenthesesareapproximatemathematicalconversionstoinch-poundunitsthatarepro-videdforinformationonlyandarenotconsideredstandard.1.5Thispracticeoffersasetofinstructionsforperformingoneormorespecificoperations.Thisdocumentcannotreplaceeducationorexperienceandshouldbeusedinconjunctionwithprofessionaljudgment.Notallaspectsofthispracticemaybeapplicableinallcircumstances.ThisASTMstandardisnotintendedtorepresentorreplacethestandardofcarebywhichtheadequacyofagivenprofessionalservicemustbejudged,norshouldthisdocumentbeappliedwithoutconsiderationofaproject’smanyuniqueaspects.Theword“standard”inthetitlemeansonlythatthedocumenthasbeenapprovedthroughtheASTMconsensusprocess.1.6Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilit...
