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a SIERRA SES STANDARD OPERATING PROCEDURE GROUND WATER SAMPLING HI( fclllmmino &,�Cnbcs sampling ploccclul(� 11gcd In 91_S rield ]personnel to collect '111(l handle ground water samples Before samples are collected careful consideration is given to the type of analysis to be performed so that precautions are taken to prevent loss of volatile components or contarrunation 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 specidic Lo ground water sampling are presented below Prior to sampling each well is checked for the presence of free-phase hydrocarbons using an MMC flexr-dip interface probe Product thickness (measured to the nearest 0 01 foot) is noted o« the sampling form Water level measurements are also made using either a water level meter or the interface probe The water level measurements are also noted on the sampling form Pryor to sampling, each well is purged of a minimum of four well casing volumes of water using a steam-cleaned PVC bailer, or a pre-cleaned pump Temperature, pH and electrical conductivity are measured at least three times during purging Purging is continued until these parameters have stabilized (i e , changes iri temperature, pH or conductivity do not exceed±0 5'F, 0 1 or 5%, respectively) The purge water is taken to Chevron's Richmond Refinery for disposal Ground water samples are collected from the wells with steam-cleaned Teflon bailers The water samples are decanted into the appropriate container for the analysis to be performed 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 are placed in polyethylene bags and in an ice chest (maintained at 4°C with blue ice or ice) for transport under chain of custody to the laboratory