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t r STANDARD OPERATING PROCEDURE - GROUNDWATER SAMPLING t Gettler-Ryan ]nc field personnel adhere to the following procedures for the collection and handling of groundwater samples prior to analysis by the analytical laboratory. Prior to sample collection, the type of analysis to be performed is determined. Loss prevention of volatile compounds is controlled and sample preservation for subsequent analysts is maintained. Pnor to sampling, the presence or absence of free-phase hydrocarbons is determined using an interface probe Product thickness,if present, is measured to the nearest 0 01 foot and is noted in the field notes. In addition, static water level measurements are collected with the interface probe and are also recorded in the field notes. After water levels are collected and prior to sampling, each well is purged a minimum of three well casing volumes of water using pre-cleaned pumps (stack, suction, Grundfos), or polyvinyl chloride bailers Temperature,pH and electrical conductivity are measured a minimum of three times during the purging Purging continues until these parameters stabilize Groundwater samples are collected using Chevron-designated disposable bailers. The water samples are transferred from the bailer into appropriate containers. Pre-preserved containers, supplied by analytical laboratories, are used when possible When pre-preserved containers are not available, the laboratory is instructed to preserve the sample as appropriate. Duplicate samples are collected for the laboratory to use in maintaining Quality assurance/quality control standards The samples are labeled to include the ,lob number, sample identification, collection date and time, analysis, preservation (if any), and the sample collector's initials. The water samples are placed in a cooler,maintained at OC for transport to the laboratory. Once collected in the field, all samples are maintained under chain of custody until delivered to the laboratory. The chain of custody document includes the,lob number, type of preservation, if any, analysis requested, sample identification, date and time collected, and the sample collector's name. The chain of custody is signed and dated (including time of transfer) by each person who receives or surrenders the samples, beginning with the field personnel and ending with the laboratory personnel A laboratory supplied trip blank accompanies each sampling set For sampling sets greater than 20 samples, S% trip blanks are included. The trip blank is analyzed for some or all of the same compounds as the groundwater samples. As requested by Chevron Products Company, the purge water and decontamination water generated during sampling activities is transported by ]WM to McKittrick Waste Management located in McKittnck, California. NX-Abf0moxfomakhevroo-sop 30M