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April 20, 1990 <br /> i . <br /> 1 <br /> Laboratory' y - <br /> and field hand-ling .procedures of :=samples are ..monitored by <br /> I including QC _samples for. analysis ' with every.::submitted sample lot from <br />{! a project site. ; ' QC samples may include any combination of the <br /> following: <br /> A. Trip Blank- Used for purgeable organic- compounds only; QC <br /> samples `..are collected in 40 milliliter (ml=) sample vials <br /> filled' in the analyticallaboratory with organic-free water. <br /> .Trip blanks are sent 't', the project site, and . travel with. <br /> project site .',samples. Trip blanks are no opened, and .are <br /> returned from a ,project site with. the _project -site =samples for <br /> analysis..., <br /> B. Field Blank: Prepared in 'the field -using organic-free <br /> water. ' These, QC samples, accompany project site samples to the <br /> laboratory and are analyzed for specific chemical parameters. <br /> unique'to the.project site where, hey. were prepared. <br /> y <br /> C. Duolicates: " Duplicated;, samples. are, collected _ "second <br /> -samples" from a selected well and. project site: They .are <br /> collected as;, either split samples or second-run samples <br /> collected from-the,same well. <br /> D.. Eauinment Blank: Periodic. QC sample collected from field . <br /> 1. equipment rinsate to verify decontamination procedures. <br /> The number and types of:QC samples are determined°as°follows: <br /> A. Up .to 2 wells`- Trip Blank-;Only <br /> r B. ­2 to S Well .1.Field Blank and 1 Trip Blank . <br /> C.. 5 to 10 Wells l-Field"blank, 1 Trip. Blank, and 1 Duplicate <br /> D. 4 More than 10 Wells'- i Field Blank, 1'Trip Blank,and 1 . <br /> Duplicate per each .12 wells <br /> 'E. . If sampling extends •.beyond one :day;. quality control samples <br /> will be:collected 4or each day. <br /> +t,r Additional QC' is performed through ongoing and. random reviews of <br /> duplicate samples. to evaluate. the .;precision of the field sampling <br />! procedures. and analytical laboratory. Precision of QC data- is <br /> - accomplished` by calculating the . Relative :Percent Difference (RPD). <br /> The RPD is evaluated to assess whether values are %within an acceptable <br /> range (typically + 20% of duplicate.-sam,ple): <br /> Page ll• <br /> j jeHler ryan. nc. dais}iss�soo <br /> general and environmental conlraclors <br />