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�� 11 SIERRA SES STANDARD OPERATING PROCEDURE GROUND WATER SAMPLING The following describes sampling procedures used by SES field personnel to collect and handle ground water samples Before samples are collected, careful consideration is given to the type of analysts to be performed so that precautions are taken to prevent loss of volatile components or contamination of the sample, and to preserve the sample for subsequent analysis Wells will be sampled no less than 24 hours after well development Collection methods specific to giound water sampling are presented below Prior to sampling, each well is checked for the presence of free-phase hydrocarbons using an MMC flexi-dip interface probe Product thickness (measured to the nearest 0 01 foot) is noted on the sampling form Water level measurements ale also rade using either a water Ievel meter or the interface probe The water level measurements ale also noted on the sampling form Prior to sampling each well is purged of a minimum of three well casing volumes of watei using a steam-cleaned PVC bailer, or a pre-cleaned pump Temperatuie pH and electrical conductivit\ are measured at least thiee times during puiging Purging is continued until these parameters have stabilized (i e , changes in temperature, pH or conductivity do not exceed ±0 5`F, 0 1 or 5%, respectively) The purge watei is taken to Chev.on s Richmond Refinery for disposal Ground water samples are collected from the wells with steam-cleaned Teflon bailers I'lne water samples are decanted into the appropriate container for the analysis to be pe±formed Pre- preserved sample containers may be used or the analytic laboratory may add preservative to the sample upon arrival Duplicate samples are collected from each well as a back-up sample and/or to provide quality control The samples are labeled to include the project number, sample ID date, preservative and the field person's initials The samples arc placed in polyethylene bags and in an ice chest (maintained at 4°C) for transpoi t under chain of custody to the laboratory The chain of custody form includes the pioject number, analysis iequested, sample, ID, date analysis and the SES field person's name The fol ni is signed and dated (with the transfer time) by each person who yields or receives the samples beginning with the field personnel and ending with the laboratory personnel A trip blank and bailer blank accompanies each Sampling set or 5%trip blanks and 5%bailei blanks are included for sets of greater than 20 samples The bailer blank is piepared by pouiing previously boiled watei into a steam-cleaned ']'Olon bailer pi ioi to sampling a well The ti ip and bailer blanks are analyzed foi some or all of the -<1211e rompotind5 as tht' ground v atei samples cws uu 2$01,