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` 2.2.10 Sample Filtration: Samples requiring on-site filtration will be <br />J filtered using a barrel filter apparatus, which filters through a <br />0.45-micron membrane. Alternatively, disposable 0.45-micron filter <br />cartridges may be attached directly to the pump discharge. <br />_~ <br />Samples will be preserved directly following filtration. <br />Filter apparatus will be cleaned by having the solutions "pulled" <br />J through the apparatus prior to, and after, each use in the <br />following manner: <br />J (1) mild non-phosphatic detergent wash; <br />(2) tap water rinse. <br />J <br />Following a filtration series of no more than 20 samples, a rinse <br />blank will be collected from the cleaned apparatus or, if <br />applicable, through an un-used filter cartridge, by running <br />J laboratory-provided deionized, distilled water throughout the <br />entire filtering apparatus. Analysis of this rinse blank will be <br />used to validate cleaning procedures. <br />2.3 Field Quality Control <br />2.3.1 Field Duplicates: Field duplicates (splits) will be collected to <br />evaluate the precision of the analytical technique. One field <br />duplicate will be collected for every ten samples collected. <br />Field duplicates shall be obtained by either compositing the entire <br />1 sample, then filling the appropriate bottles, or by wing a flow <br />splitter on the pump discharge so duplicate samples can be obtained <br />i simultaneously. <br />j The duplicate sample will be submitted to a second independent <br />laboratory that is U.S. EPA-certified for Safe Drinking Water Act <br />1 <br />-17- <br /> <br />