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C LEARWATER G r, U U P I ` C Ouaht,y A urance Procedures To prevent contamination of the samples, CGI personnel adhere to the following procedures in the field • A new, clean pair of latex gloves are put on prior to sampling each well • Wells are gauged, purged and groundwater samples are collected in the expected order of increasing degree of contamination based on historical analytical results • All purging equipment will be thoroughly decontaminated between each well, using the procedures previously described at the beginning of this section • During sample collection for volatile organic analysis, the amount of air passing through the sample is minimized This helps prevent the air from stripping the volatiles from the water Sample bottles are filled by slowly running the sample down the side of the bottle until there is a convex meniscus over the mouth of the bottle The lid is carefully screwed onto the bottle such that no air bubbles are present within the bottle If a bubble is present, the cap is removed and additional water is added to the sample container After resealing the sample container, if bubbles still are present inside, the sample container is discarded and the procedure is repeated with a new container Laboratory and field handling procedures may be monitored, if required by the client or regulators, by including quality control (QC) samples for analysis with the groundwater samples Examples of different types of QC samples are as follows • Trip blanks are prepared at the analytical laboratory by laboratory personnel to check field handling procedures Trip blanks are transported to the project site in the same manner as the laboratory-supplied sample containers to be filled They are not opened, and are returned to the laboratory with the samples collected Trip blanks are analyzed for purgable organic compounds o Equipment blanks are prepared in the field to determine if decontamination of field sampling equipment has been effective The sampling equipment used to collect the groundwater samples is rinsed with distilled water which is then decanted into laboratory-supplied containers The equipment blanks are transported to the laboratory, and are analyzed for the same chemical constituents as the samples collected at the site • Duplicates are collected at the same tune that the standard groundwater samples are being collected and are analyzed for the same compounds in order to check the reproducibility of laboratory data They are typically only collected from one well per sampling event The duplicate is assigned an identification number that will not associate it with the source well Generally, trip blanks and field blanks check field handling and transportation procedures Duplicates check laboratory procedures The configuration of QC samples is determined by CGI depending on site conditions and regulatory requirements CLEARWATER GROUP, INC August 26, 1996